/* * Generic SSL/TLS messaging layer functions * (record layer + retransmission state machine) * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /* * http://www.ietf.org/rfc/rfc2246.txt * http://www.ietf.org/rfc/rfc4346.txt */ #include "common.h" #if defined(MBEDTLS_SSL_TLS_C) #if defined(MBEDTLS_PLATFORM_C) #include "mbedtls/platform.h" #else #include #define mbedtls_calloc calloc #define mbedtls_free free #endif #include "mbedtls/ssl.h" #include "ssl_misc.h" #include "mbedtls/debug.h" #include "mbedtls/error.h" #include "mbedtls/platform_util.h" #include "mbedtls/version.h" #include "ssl_invasive.h" #include #if defined(MBEDTLS_USE_PSA_CRYPTO) #include "mbedtls/psa_util.h" #include "psa/crypto.h" #endif #if defined(MBEDTLS_X509_CRT_PARSE_C) #include "mbedtls/oid.h" #endif static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl ); /* * Start a timer. * Passing millisecs = 0 cancels a running timer. */ void mbedtls_ssl_set_timer( mbedtls_ssl_context *ssl, uint32_t millisecs ) { if( ssl->f_set_timer == NULL ) return; MBEDTLS_SSL_DEBUG_MSG( 3, ( "set_timer to %d ms", (int) millisecs ) ); ssl->f_set_timer( ssl->p_timer, millisecs / 4, millisecs ); } /* * Return -1 is timer is expired, 0 if it isn't. */ int mbedtls_ssl_check_timer( mbedtls_ssl_context *ssl ) { if( ssl->f_get_timer == NULL ) return( 0 ); if( ssl->f_get_timer( ssl->p_timer ) == 2 ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "timer expired" ) ); return( -1 ); } return( 0 ); } static int ssl_parse_record_header( mbedtls_ssl_context const *ssl, unsigned char *buf, size_t len, mbedtls_record *rec ); int mbedtls_ssl_check_record( mbedtls_ssl_context const *ssl, unsigned char *buf, size_t buflen ) { int ret = 0; MBEDTLS_SSL_DEBUG_MSG( 1, ( "=> mbedtls_ssl_check_record" ) ); MBEDTLS_SSL_DEBUG_BUF( 3, "record buffer", buf, buflen ); /* We don't support record checking in TLS because * (a) there doesn't seem to be a usecase for it, and * (b) In TLS 1.0, CBC record decryption has state * and we'd need to backup the transform here. */ if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_STREAM ) { ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE; goto exit; } #if defined(MBEDTLS_SSL_PROTO_DTLS) else { mbedtls_record rec; ret = ssl_parse_record_header( ssl, buf, buflen, &rec ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 3, "ssl_parse_record_header", ret ); goto exit; } if( ssl->transform_in != NULL ) { ret = mbedtls_ssl_decrypt_buf( ssl, ssl->transform_in, &rec ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 3, "mbedtls_ssl_decrypt_buf", ret ); goto exit; } } } #endif /* MBEDTLS_SSL_PROTO_DTLS */ exit: /* On success, we have decrypted the buffer in-place, so make * sure we don't leak any plaintext data. */ mbedtls_platform_zeroize( buf, buflen ); /* For the purpose of this API, treat messages with unexpected CID * as well as such from future epochs as unexpected. */ if( ret == MBEDTLS_ERR_SSL_UNEXPECTED_CID || ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE ) { ret = MBEDTLS_ERR_SSL_UNEXPECTED_RECORD; } MBEDTLS_SSL_DEBUG_MSG( 1, ( "<= mbedtls_ssl_check_record" ) ); return( ret ); } #define SSL_DONT_FORCE_FLUSH 0 #define SSL_FORCE_FLUSH 1 #if defined(MBEDTLS_SSL_PROTO_DTLS) /* Forward declarations for functions related to message buffering. */ static void ssl_buffering_free_slot( mbedtls_ssl_context *ssl, uint8_t slot ); static void ssl_free_buffered_record( mbedtls_ssl_context *ssl ); static int ssl_load_buffered_message( mbedtls_ssl_context *ssl ); static int ssl_load_buffered_record( mbedtls_ssl_context *ssl ); static int ssl_buffer_message( mbedtls_ssl_context *ssl ); static int ssl_buffer_future_record( mbedtls_ssl_context *ssl, mbedtls_record const *rec ); static int ssl_next_record_is_in_datagram( mbedtls_ssl_context *ssl ); static size_t ssl_get_maximum_datagram_size( mbedtls_ssl_context const *ssl ) { size_t mtu = mbedtls_ssl_get_current_mtu( ssl ); #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH) size_t out_buf_len = ssl->out_buf_len; #else size_t out_buf_len = MBEDTLS_SSL_OUT_BUFFER_LEN; #endif if( mtu != 0 && mtu < out_buf_len ) return( mtu ); return( out_buf_len ); } static int ssl_get_remaining_space_in_datagram( mbedtls_ssl_context const *ssl ) { size_t const bytes_written = ssl->out_left; size_t const mtu = ssl_get_maximum_datagram_size( ssl ); /* Double-check that the write-index hasn't gone * past what we can transmit in a single datagram. */ if( bytes_written > mtu ) { /* Should never happen... */ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } return( (int) ( mtu - bytes_written ) ); } static int ssl_get_remaining_payload_in_datagram( mbedtls_ssl_context const *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t remaining, expansion; size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN; #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH) const size_t mfl = mbedtls_ssl_get_output_max_frag_len( ssl ); if( max_len > mfl ) max_len = mfl; /* By the standard (RFC 6066 Sect. 4), the MFL extension * only limits the maximum record payload size, so in theory * we would be allowed to pack multiple records of payload size * MFL into a single datagram. However, this would mean that there's * no way to explicitly communicate MTU restrictions to the peer. * * The following reduction of max_len makes sure that we never * write datagrams larger than MFL + Record Expansion Overhead. */ if( max_len <= ssl->out_left ) return( 0 ); max_len -= ssl->out_left; #endif ret = ssl_get_remaining_space_in_datagram( ssl ); if( ret < 0 ) return( ret ); remaining = (size_t) ret; ret = mbedtls_ssl_get_record_expansion( ssl ); if( ret < 0 ) return( ret ); expansion = (size_t) ret; if( remaining <= expansion ) return( 0 ); remaining -= expansion; if( remaining >= max_len ) remaining = max_len; return( (int) remaining ); } /* * Double the retransmit timeout value, within the allowed range, * returning -1 if the maximum value has already been reached. */ static int ssl_double_retransmit_timeout( mbedtls_ssl_context *ssl ) { uint32_t new_timeout; if( ssl->handshake->retransmit_timeout >= ssl->conf->hs_timeout_max ) return( -1 ); /* Implement the final paragraph of RFC 6347 section 4.1.1.1 * in the following way: after the initial transmission and a first * retransmission, back off to a temporary estimated MTU of 508 bytes. * This value is guaranteed to be deliverable (if not guaranteed to be * delivered) of any compliant IPv4 (and IPv6) network, and should work * on most non-IP stacks too. */ if( ssl->handshake->retransmit_timeout != ssl->conf->hs_timeout_min ) { ssl->handshake->mtu = 508; MBEDTLS_SSL_DEBUG_MSG( 2, ( "mtu autoreduction to %d bytes", ssl->handshake->mtu ) ); } new_timeout = 2 * ssl->handshake->retransmit_timeout; /* Avoid arithmetic overflow and range overflow */ if( new_timeout < ssl->handshake->retransmit_timeout || new_timeout > ssl->conf->hs_timeout_max ) { new_timeout = ssl->conf->hs_timeout_max; } ssl->handshake->retransmit_timeout = new_timeout; MBEDTLS_SSL_DEBUG_MSG( 3, ( "update timeout value to %lu millisecs", (unsigned long) ssl->handshake->retransmit_timeout ) ); return( 0 ); } static void ssl_reset_retransmit_timeout( mbedtls_ssl_context *ssl ) { ssl->handshake->retransmit_timeout = ssl->conf->hs_timeout_min; MBEDTLS_SSL_DEBUG_MSG( 3, ( "update timeout value to %lu millisecs", (unsigned long) ssl->handshake->retransmit_timeout ) ); } #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* * Encryption/decryption functions */ #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) || \ defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL) static size_t ssl_compute_padding_length( size_t len, size_t granularity ) { return( ( granularity - ( len + 1 ) % granularity ) % granularity ); } /* This functions transforms a (D)TLS plaintext fragment and a record content * type into an instance of the (D)TLSInnerPlaintext structure. This is used * in DTLS 1.2 + CID and within TLS 1.3 to allow flexible padding and to protect * a record's content type. * * struct { * opaque content[DTLSPlaintext.length]; * ContentType real_type; * uint8 zeros[length_of_padding]; * } (D)TLSInnerPlaintext; * * Input: * - `content`: The beginning of the buffer holding the * plaintext to be wrapped. * - `*content_size`: The length of the plaintext in Bytes. * - `max_len`: The number of Bytes available starting from * `content`. This must be `>= *content_size`. * - `rec_type`: The desired record content type. * * Output: * - `content`: The beginning of the resulting (D)TLSInnerPlaintext structure. * - `*content_size`: The length of the resulting (D)TLSInnerPlaintext structure. * * Returns: * - `0` on success. * - A negative error code if `max_len` didn't offer enough space * for the expansion. */ static int ssl_build_inner_plaintext( unsigned char *content, size_t *content_size, size_t remaining, uint8_t rec_type, size_t pad ) { size_t len = *content_size; /* Write real content type */ if( remaining == 0 ) return( -1 ); content[ len ] = rec_type; len++; remaining--; if( remaining < pad ) return( -1 ); memset( content + len, 0, pad ); len += pad; remaining -= pad; *content_size = len; return( 0 ); } /* This function parses a (D)TLSInnerPlaintext structure. * See ssl_build_inner_plaintext() for details. */ static int ssl_parse_inner_plaintext( unsigned char const *content, size_t *content_size, uint8_t *rec_type ) { size_t remaining = *content_size; /* Determine length of padding by skipping zeroes from the back. */ do { if( remaining == 0 ) return( -1 ); remaining--; } while( content[ remaining ] == 0 ); *content_size = remaining; *rec_type = content[ remaining ]; return( 0 ); } #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID || MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */ /* `add_data` must have size 13 Bytes if the CID extension is disabled, * and 13 + 1 + CID-length Bytes if the CID extension is enabled. */ static void ssl_extract_add_data_from_record( unsigned char* add_data, size_t *add_data_len, mbedtls_record *rec, unsigned minor_ver ) { /* Quoting RFC 5246 (TLS 1.2): * * additional_data = seq_num + TLSCompressed.type + * TLSCompressed.version + TLSCompressed.length; * * For the CID extension, this is extended as follows * (quoting draft-ietf-tls-dtls-connection-id-05, * https://tools.ietf.org/html/draft-ietf-tls-dtls-connection-id-05): * * additional_data = seq_num + DTLSPlaintext.type + * DTLSPlaintext.version + * cid + * cid_length + * length_of_DTLSInnerPlaintext; * * For TLS 1.3, the record sequence number is dropped from the AAD * and encoded within the nonce of the AEAD operation instead. */ unsigned char *cur = add_data; #if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL) if( minor_ver != MBEDTLS_SSL_MINOR_VERSION_4 ) #endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */ { ((void) minor_ver); memcpy( cur, rec->ctr, sizeof( rec->ctr ) ); cur += sizeof( rec->ctr ); } *cur = rec->type; cur++; memcpy( cur, rec->ver, sizeof( rec->ver ) ); cur += sizeof( rec->ver ); #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) if( rec->cid_len != 0 ) { memcpy( cur, rec->cid, rec->cid_len ); cur += rec->cid_len; *cur = rec->cid_len; cur++; cur[0] = ( rec->data_len >> 8 ) & 0xFF; cur[1] = ( rec->data_len >> 0 ) & 0xFF; cur += 2; } else #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ { cur[0] = ( rec->data_len >> 8 ) & 0xFF; cur[1] = ( rec->data_len >> 0 ) & 0xFF; cur += 2; } *add_data_len = cur - add_data; } #if defined(MBEDTLS_GCM_C) || \ defined(MBEDTLS_CCM_C) || \ defined(MBEDTLS_CHACHAPOLY_C) static int ssl_transform_aead_dynamic_iv_is_explicit( mbedtls_ssl_transform const *transform ) { return( transform->ivlen != transform->fixed_ivlen ); } /* Compute IV := ( fixed_iv || 0 ) XOR ( 0 || dynamic_IV ) * * Concretely, this occurs in two variants: * * a) Fixed and dynamic IV lengths add up to total IV length, giving * IV = fixed_iv || dynamic_iv * * This variant is used in TLS 1.2 when used with GCM or CCM. * * b) Fixed IV lengths matches total IV length, giving * IV = fixed_iv XOR ( 0 || dynamic_iv ) * * This variant occurs in TLS 1.3 and for TLS 1.2 when using ChaChaPoly. * * See also the documentation of mbedtls_ssl_transform. * * This function has the precondition that * * dst_iv_len >= max( fixed_iv_len, dynamic_iv_len ) * * which has to be ensured by the caller. If this precondition * violated, the behavior of this function is undefined. */ static void ssl_build_record_nonce( unsigned char *dst_iv, size_t dst_iv_len, unsigned char const *fixed_iv, size_t fixed_iv_len, unsigned char const *dynamic_iv, size_t dynamic_iv_len ) { size_t i; /* Start with Fixed IV || 0 */ memset( dst_iv, 0, dst_iv_len ); memcpy( dst_iv, fixed_iv, fixed_iv_len ); dst_iv += dst_iv_len - dynamic_iv_len; for( i = 0; i < dynamic_iv_len; i++ ) dst_iv[i] ^= dynamic_iv[i]; } #endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C || MBEDTLS_CHACHAPOLY_C */ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl, mbedtls_ssl_transform *transform, mbedtls_record *rec, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { mbedtls_cipher_mode_t mode; int auth_done = 0; unsigned char * data; unsigned char add_data[13 + 1 + MBEDTLS_SSL_CID_OUT_LEN_MAX ]; size_t add_data_len; size_t post_avail; /* The SSL context is only used for debugging purposes! */ #if !defined(MBEDTLS_DEBUG_C) ssl = NULL; /* make sure we don't use it except for debug */ ((void) ssl); #endif /* The PRNG is used for dynamic IV generation that's used * for CBC transformations in TLS 1.2. */ #if !( defined(MBEDTLS_SSL_SOME_SUITES_USE_CBC) && \ defined(MBEDTLS_SSL_PROTO_TLS1_2) ) ((void) f_rng); ((void) p_rng); #endif MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> encrypt buf" ) ); if( transform == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "no transform provided to encrypt_buf" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } if( rec == NULL || rec->buf == NULL || rec->buf_len < rec->data_offset || rec->buf_len - rec->data_offset < rec->data_len #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) || rec->cid_len != 0 #endif ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad record structure provided to encrypt_buf" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } data = rec->buf + rec->data_offset; post_avail = rec->buf_len - ( rec->data_len + rec->data_offset ); MBEDTLS_SSL_DEBUG_BUF( 4, "before encrypt: output payload", data, rec->data_len ); mode = mbedtls_cipher_get_cipher_mode( &transform->cipher_ctx_enc ); if( rec->data_len > MBEDTLS_SSL_OUT_CONTENT_LEN ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Record content %" MBEDTLS_PRINTF_SIZET " too large, maximum %" MBEDTLS_PRINTF_SIZET, rec->data_len, (size_t) MBEDTLS_SSL_OUT_CONTENT_LEN ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } /* The following two code paths implement the (D)TLSInnerPlaintext * structure present in TLS 1.3 and DTLS 1.2 + CID. * * See ssl_build_inner_plaintext() for more information. * * Note that this changes `rec->data_len`, and hence * `post_avail` needs to be recalculated afterwards. * * Note also that the two code paths cannot occur simultaneously * since they apply to different versions of the protocol. There * is hence no risk of double-addition of the inner plaintext. */ #if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL) if( transform->minor_ver == MBEDTLS_SSL_MINOR_VERSION_4 ) { size_t padding = ssl_compute_padding_length( rec->data_len, MBEDTLS_SSL_TLS1_3_PADDING_GRANULARITY ); if( ssl_build_inner_plaintext( data, &rec->data_len, post_avail, rec->type, padding ) != 0 ) { return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } rec->type = MBEDTLS_SSL_MSG_APPLICATION_DATA; } #endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */ #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) /* * Add CID information */ rec->cid_len = transform->out_cid_len; memcpy( rec->cid, transform->out_cid, transform->out_cid_len ); MBEDTLS_SSL_DEBUG_BUF( 3, "CID", rec->cid, rec->cid_len ); if( rec->cid_len != 0 ) { size_t padding = ssl_compute_padding_length( rec->data_len, MBEDTLS_SSL_CID_PADDING_GRANULARITY ); /* * Wrap plaintext into DTLSInnerPlaintext structure. * See ssl_build_inner_plaintext() for more information. * * Note that this changes `rec->data_len`, and hence * `post_avail` needs to be recalculated afterwards. */ if( ssl_build_inner_plaintext( data, &rec->data_len, post_avail, rec->type, padding ) != 0 ) { return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } rec->type = MBEDTLS_SSL_MSG_CID; } #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ post_avail = rec->buf_len - ( rec->data_len + rec->data_offset ); /* * Add MAC before if needed */ #if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) if( mode == MBEDTLS_MODE_STREAM || ( mode == MBEDTLS_MODE_CBC #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC) && transform->encrypt_then_mac == MBEDTLS_SSL_ETM_DISABLED #endif ) ) { if( post_avail < transform->maclen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Buffer provided for encrypted record not large enough" ) ); return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if( transform->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 ) { unsigned char mac[MBEDTLS_SSL_MAC_ADD]; ssl_extract_add_data_from_record( add_data, &add_data_len, rec, transform->minor_ver ); mbedtls_md_hmac_update( &transform->md_ctx_enc, add_data, add_data_len ); mbedtls_md_hmac_update( &transform->md_ctx_enc, data, rec->data_len ); mbedtls_md_hmac_finish( &transform->md_ctx_enc, mac ); mbedtls_md_hmac_reset( &transform->md_ctx_enc ); memcpy( data + rec->data_len, mac, transform->maclen ); } else #endif { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } MBEDTLS_SSL_DEBUG_BUF( 4, "computed mac", data + rec->data_len, transform->maclen ); rec->data_len += transform->maclen; post_avail -= transform->maclen; auth_done++; } #endif /* MBEDTLS_SSL_SOME_SUITES_USE_MAC */ /* * Encrypt */ #if defined(MBEDTLS_SSL_SOME_SUITES_USE_STREAM) if( mode == MBEDTLS_MODE_STREAM ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t olen; MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %" MBEDTLS_PRINTF_SIZET ", " "including %d bytes of padding", rec->data_len, 0 ) ); if( ( ret = mbedtls_cipher_crypt( &transform->cipher_ctx_enc, transform->iv_enc, transform->ivlen, data, rec->data_len, data, &olen ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret ); return( ret ); } if( rec->data_len != olen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } } else #endif /* MBEDTLS_SSL_SOME_SUITES_USE_STREAM */ #if defined(MBEDTLS_GCM_C) || \ defined(MBEDTLS_CCM_C) || \ defined(MBEDTLS_CHACHAPOLY_C) if( mode == MBEDTLS_MODE_GCM || mode == MBEDTLS_MODE_CCM || mode == MBEDTLS_MODE_CHACHAPOLY ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char iv[12]; unsigned char *dynamic_iv; size_t dynamic_iv_len; int dynamic_iv_is_explicit = ssl_transform_aead_dynamic_iv_is_explicit( transform ); /* Check that there's space for the authentication tag. */ if( post_avail < transform->taglen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Buffer provided for encrypted record not large enough" ) ); return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } /* * Build nonce for AEAD encryption. * * Note: In the case of CCM and GCM in TLS 1.2, the dynamic * part of the IV is prepended to the ciphertext and * can be chosen freely - in particular, it need not * agree with the record sequence number. * However, since ChaChaPoly as well as all AEAD modes * in TLS 1.3 use the record sequence number as the * dynamic part of the nonce, we uniformly use the * record sequence number here in all cases. */ dynamic_iv = rec->ctr; dynamic_iv_len = sizeof( rec->ctr ); ssl_build_record_nonce( iv, sizeof( iv ), transform->iv_enc, transform->fixed_ivlen, dynamic_iv, dynamic_iv_len ); /* * Build additional data for AEAD encryption. * This depends on the TLS version. */ ssl_extract_add_data_from_record( add_data, &add_data_len, rec, transform->minor_ver ); MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (internal)", iv, transform->ivlen ); MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (transmitted)", dynamic_iv, dynamic_iv_is_explicit ? dynamic_iv_len : 0 ); MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD", add_data, add_data_len ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %" MBEDTLS_PRINTF_SIZET ", " "including 0 bytes of padding", rec->data_len ) ); /* * Encrypt and authenticate */ if( ( ret = mbedtls_cipher_auth_encrypt_ext( &transform->cipher_ctx_enc, iv, transform->ivlen, add_data, add_data_len, data, rec->data_len, /* src */ data, rec->buf_len - (data - rec->buf), /* dst */ &rec->data_len, transform->taglen ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_auth_encrypt_ext", ret ); return( ret ); } MBEDTLS_SSL_DEBUG_BUF( 4, "after encrypt: tag", data + rec->data_len - transform->taglen, transform->taglen ); /* Account for authentication tag. */ post_avail -= transform->taglen; /* * Prefix record content with dynamic IV in case it is explicit. */ if( dynamic_iv_is_explicit != 0 ) { if( rec->data_offset < dynamic_iv_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Buffer provided for encrypted record not large enough" ) ); return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } memcpy( data - dynamic_iv_len, dynamic_iv, dynamic_iv_len ); rec->data_offset -= dynamic_iv_len; rec->data_len += dynamic_iv_len; } auth_done++; } else #endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C || MBEDTLS_CHACHAPOLY_C */ #if defined(MBEDTLS_SSL_SOME_SUITES_USE_CBC) if( mode == MBEDTLS_MODE_CBC ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t padlen, i; size_t olen; /* Currently we're always using minimal padding * (up to 255 bytes would be allowed). */ padlen = transform->ivlen - ( rec->data_len + 1 ) % transform->ivlen; if( padlen == transform->ivlen ) padlen = 0; /* Check there's enough space in the buffer for the padding. */ if( post_avail < padlen + 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Buffer provided for encrypted record not large enough" ) ); return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } for( i = 0; i <= padlen; i++ ) data[rec->data_len + i] = (unsigned char) padlen; rec->data_len += padlen + 1; post_avail -= padlen + 1; #if defined(MBEDTLS_SSL_PROTO_TLS1_2) /* * Prepend per-record IV for block cipher in TLS v1.2 as per * Method 1 (6.2.3.2. in RFC4346 and RFC5246) */ if( transform->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_3 ) { if( f_rng == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "No PRNG provided to encrypt_record routine" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } if( rec->data_offset < transform->ivlen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Buffer provided for encrypted record not large enough" ) ); return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } /* * Generate IV */ ret = f_rng( p_rng, transform->iv_enc, transform->ivlen ); if( ret != 0 ) return( ret ); memcpy( data - transform->ivlen, transform->iv_enc, transform->ivlen ); } #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ MBEDTLS_SSL_DEBUG_MSG( 3, ( "before encrypt: msglen = %" MBEDTLS_PRINTF_SIZET ", " "including %" MBEDTLS_PRINTF_SIZET " bytes of IV and %" MBEDTLS_PRINTF_SIZET " bytes of padding", rec->data_len, transform->ivlen, padlen + 1 ) ); if( ( ret = mbedtls_cipher_crypt( &transform->cipher_ctx_enc, transform->iv_enc, transform->ivlen, data, rec->data_len, data, &olen ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret ); return( ret ); } if( rec->data_len != olen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } data -= transform->ivlen; rec->data_offset -= transform->ivlen; rec->data_len += transform->ivlen; #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC) if( auth_done == 0 ) { unsigned char mac[MBEDTLS_SSL_MAC_ADD]; /* * MAC(MAC_write_key, seq_num + * TLSCipherText.type + * TLSCipherText.version + * length_of( (IV +) ENC(...) ) + * IV + // except for TLS 1.0 * ENC(content + padding + padding_length)); */ if( post_avail < transform->maclen) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Buffer provided for encrypted record not large enough" ) ); return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); } ssl_extract_add_data_from_record( add_data, &add_data_len, rec, transform->minor_ver ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) ); MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data, add_data_len ); mbedtls_md_hmac_update( &transform->md_ctx_enc, add_data, add_data_len ); mbedtls_md_hmac_update( &transform->md_ctx_enc, data, rec->data_len ); mbedtls_md_hmac_finish( &transform->md_ctx_enc, mac ); mbedtls_md_hmac_reset( &transform->md_ctx_enc ); memcpy( data + rec->data_len, mac, transform->maclen ); rec->data_len += transform->maclen; post_avail -= transform->maclen; auth_done++; } #endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC */ } else #endif /* MBEDTLS_SSL_SOME_SUITES_USE_CBC) */ { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* Make extra sure authentication was performed, exactly once */ if( auth_done != 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= encrypt buf" ) ); return( 0 ); } #if defined(MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC) /* * Turn a bit into a mask: * - if bit == 1, return the all-bits 1 mask, aka (size_t) -1 * - if bit == 0, return the all-bits 0 mask, aka 0 * * This function can be used to write constant-time code by replacing branches * with bit operations using masks. * * This function is implemented without using comparison operators, as those * might be translated to branches by some compilers on some platforms. */ static size_t mbedtls_ssl_cf_mask_from_bit( size_t bit ) { /* MSVC has a warning about unary minus on unsigned integer types, * but this is well-defined and precisely what we want to do here. */ #if defined(_MSC_VER) #pragma warning( push ) #pragma warning( disable : 4146 ) #endif return -bit; #if defined(_MSC_VER) #pragma warning( pop ) #endif } /* * Constant-flow mask generation for "less than" comparison: * - if x < y, return all bits 1, that is (size_t) -1 * - otherwise, return all bits 0, that is 0 * * This function can be used to write constant-time code by replacing branches * with bit operations using masks. * * This function is implemented without using comparison operators, as those * might be translated to branches by some compilers on some platforms. */ static size_t mbedtls_ssl_cf_mask_lt( size_t x, size_t y ) { /* This has the most significant bit set if and only if x < y */ const size_t sub = x - y; /* sub1 = (x < y) ? 1 : 0 */ const size_t sub1 = sub >> ( sizeof( sub ) * 8 - 1 ); /* mask = (x < y) ? 0xff... : 0x00... */ const size_t mask = mbedtls_ssl_cf_mask_from_bit( sub1 ); return( mask ); } /* * Constant-flow mask generation for "greater or equal" comparison: * - if x >= y, return all bits 1, that is (size_t) -1 * - otherwise, return all bits 0, that is 0 * * This function can be used to write constant-time code by replacing branches * with bit operations using masks. * * This function is implemented without using comparison operators, as those * might be translated to branches by some compilers on some platforms. */ static size_t mbedtls_ssl_cf_mask_ge( size_t x, size_t y ) { return( ~mbedtls_ssl_cf_mask_lt( x, y ) ); } /* * Constant-flow boolean "equal" comparison: * return x == y * * This function can be used to write constant-time code by replacing branches * with bit operations - it can be used in conjunction with * mbedtls_ssl_cf_mask_from_bit(). * * This function is implemented without using comparison operators, as those * might be translated to branches by some compilers on some platforms. */ static size_t mbedtls_ssl_cf_bool_eq( size_t x, size_t y ) { /* diff = 0 if x == y, non-zero otherwise */ const size_t diff = x ^ y; /* MSVC has a warning about unary minus on unsigned integer types, * but this is well-defined and precisely what we want to do here. */ #if defined(_MSC_VER) #pragma warning( push ) #pragma warning( disable : 4146 ) #endif /* diff_msb's most significant bit is equal to x != y */ const size_t diff_msb = ( diff | -diff ); #if defined(_MSC_VER) #pragma warning( pop ) #endif /* diff1 = (x != y) ? 1 : 0 */ const size_t diff1 = diff_msb >> ( sizeof( diff_msb ) * 8 - 1 ); return( 1 ^ diff1 ); } /* * Constant-flow conditional memcpy: * - if c1 == c2, equivalent to memcpy(dst, src, len), * - otherwise, a no-op, * but with execution flow independent of the values of c1 and c2. * * This function is implemented without using comparison operators, as those * might be translated to branches by some compilers on some platforms. */ static void mbedtls_ssl_cf_memcpy_if_eq( unsigned char *dst, const unsigned char *src, size_t len, size_t c1, size_t c2 ) { /* mask = c1 == c2 ? 0xff : 0x00 */ const size_t equal = mbedtls_ssl_cf_bool_eq( c1, c2 ); const unsigned char mask = (unsigned char) mbedtls_ssl_cf_mask_from_bit( equal ); /* dst[i] = c1 == c2 ? src[i] : dst[i] */ for( size_t i = 0; i < len; i++ ) dst[i] = ( src[i] & mask ) | ( dst[i] & ~mask ); } /* * Compute HMAC of variable-length data with constant flow. * * Only works with MD-5, SHA-1, SHA-256 and SHA-384. * (Otherwise, computation of block_size needs to be adapted.) */ MBEDTLS_STATIC_TESTABLE int mbedtls_ssl_cf_hmac( mbedtls_md_context_t *ctx, const unsigned char *add_data, size_t add_data_len, const unsigned char *data, size_t data_len_secret, size_t min_data_len, size_t max_data_len, unsigned char *output ) { /* * This function breaks the HMAC abstraction and uses the md_clone() * extension to the MD API in order to get constant-flow behaviour. * * HMAC(msg) is defined as HASH(okey + HASH(ikey + msg)) where + means * concatenation, and okey/ikey are the XOR of the key with some fixed bit * patterns (see RFC 2104, sec. 2), which are stored in ctx->hmac_ctx. * * We'll first compute inner_hash = HASH(ikey + msg) by hashing up to * minlen, then cloning the context, and for each byte up to maxlen * finishing up the hash computation, keeping only the correct result. * * Then we only need to compute HASH(okey + inner_hash) and we're done. */ const mbedtls_md_type_t md_alg = mbedtls_md_get_type( ctx->md_info ); /* TLS 1.0-1.2 only support SHA-384, SHA-256, SHA-1, MD-5, * all of which have the same block size except SHA-384. */ const size_t block_size = md_alg == MBEDTLS_MD_SHA384 ? 128 : 64; const unsigned char * const ikey = ctx->hmac_ctx; const unsigned char * const okey = ikey + block_size; const size_t hash_size = mbedtls_md_get_size( ctx->md_info ); unsigned char aux_out[MBEDTLS_MD_MAX_SIZE]; mbedtls_md_context_t aux; size_t offset; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_md_init( &aux ); #define MD_CHK( func_call ) \ do { \ ret = (func_call); \ if( ret != 0 ) \ goto cleanup; \ } while( 0 ) MD_CHK( mbedtls_md_setup( &aux, ctx->md_info, 0 ) ); /* After hmac_start() of hmac_reset(), ikey has already been hashed, * so we can start directly with the message */ MD_CHK( mbedtls_md_update( ctx, add_data, add_data_len ) ); MD_CHK( mbedtls_md_update( ctx, data, min_data_len ) ); /* For each possible length, compute the hash up to that point */ for( offset = min_data_len; offset <= max_data_len; offset++ ) { MD_CHK( mbedtls_md_clone( &aux, ctx ) ); MD_CHK( mbedtls_md_finish( &aux, aux_out ) ); /* Keep only the correct inner_hash in the output buffer */ mbedtls_ssl_cf_memcpy_if_eq( output, aux_out, hash_size, offset, data_len_secret ); if( offset < max_data_len ) MD_CHK( mbedtls_md_update( ctx, data + offset, 1 ) ); } /* Now compute HASH(okey + inner_hash) */ MD_CHK( mbedtls_md_starts( ctx ) ); MD_CHK( mbedtls_md_update( ctx, okey, block_size ) ); MD_CHK( mbedtls_md_update( ctx, output, hash_size ) ); MD_CHK( mbedtls_md_finish( ctx, output ) ); /* Done, get ready for next time */ MD_CHK( mbedtls_md_hmac_reset( ctx ) ); #undef MD_CHK cleanup: mbedtls_md_free( &aux ); return( ret ); } /* * Constant-flow memcpy from variable position in buffer. * - functionally equivalent to memcpy(dst, src + offset_secret, len) * - but with execution flow independent from the value of offset_secret. */ MBEDTLS_STATIC_TESTABLE void mbedtls_ssl_cf_memcpy_offset( unsigned char *dst, const unsigned char *src_base, size_t offset_secret, size_t offset_min, size_t offset_max, size_t len ) { size_t offset; for( offset = offset_min; offset <= offset_max; offset++ ) { mbedtls_ssl_cf_memcpy_if_eq( dst, src_base + offset, len, offset, offset_secret ); } } #endif /* MBEDTLS_SSL_SOME_SUITES_USE_TLS_CBC */ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context const *ssl, mbedtls_ssl_transform *transform, mbedtls_record *rec ) { size_t olen; mbedtls_cipher_mode_t mode; int ret, auth_done = 0; #if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) size_t padlen = 0, correct = 1; #endif unsigned char* data; unsigned char add_data[13 + 1 + MBEDTLS_SSL_CID_IN_LEN_MAX ]; size_t add_data_len; #if !defined(MBEDTLS_DEBUG_C) ssl = NULL; /* make sure we don't use it except for debug */ ((void) ssl); #endif MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> decrypt buf" ) ); if( rec == NULL || rec->buf == NULL || rec->buf_len < rec->data_offset || rec->buf_len - rec->data_offset < rec->data_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad record structure provided to decrypt_buf" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } data = rec->buf + rec->data_offset; mode = mbedtls_cipher_get_cipher_mode( &transform->cipher_ctx_dec ); #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) /* * Match record's CID with incoming CID. */ if( rec->cid_len != transform->in_cid_len || memcmp( rec->cid, transform->in_cid, rec->cid_len ) != 0 ) { return( MBEDTLS_ERR_SSL_UNEXPECTED_CID ); } #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ #if defined(MBEDTLS_SSL_SOME_SUITES_USE_STREAM) if( mode == MBEDTLS_MODE_STREAM ) { padlen = 0; if( ( ret = mbedtls_cipher_crypt( &transform->cipher_ctx_dec, transform->iv_dec, transform->ivlen, data, rec->data_len, data, &olen ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret ); return( ret ); } if( rec->data_len != olen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } } else #endif /* MBEDTLS_SSL_SOME_SUITES_USE_STREAM */ #if defined(MBEDTLS_GCM_C) || \ defined(MBEDTLS_CCM_C) || \ defined(MBEDTLS_CHACHAPOLY_C) if( mode == MBEDTLS_MODE_GCM || mode == MBEDTLS_MODE_CCM || mode == MBEDTLS_MODE_CHACHAPOLY ) { unsigned char iv[12]; unsigned char *dynamic_iv; size_t dynamic_iv_len; /* * Extract dynamic part of nonce for AEAD decryption. * * Note: In the case of CCM and GCM in TLS 1.2, the dynamic * part of the IV is prepended to the ciphertext and * can be chosen freely - in particular, it need not * agree with the record sequence number. */ dynamic_iv_len = sizeof( rec->ctr ); if( ssl_transform_aead_dynamic_iv_is_explicit( transform ) == 1 ) { if( rec->data_len < dynamic_iv_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%" MBEDTLS_PRINTF_SIZET " ) < explicit_iv_len (%" MBEDTLS_PRINTF_SIZET ") ", rec->data_len, dynamic_iv_len ) ); return( MBEDTLS_ERR_SSL_INVALID_MAC ); } dynamic_iv = data; data += dynamic_iv_len; rec->data_offset += dynamic_iv_len; rec->data_len -= dynamic_iv_len; } else { dynamic_iv = rec->ctr; } /* Check that there's space for the authentication tag. */ if( rec->data_len < transform->taglen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%" MBEDTLS_PRINTF_SIZET ") < taglen (%" MBEDTLS_PRINTF_SIZET ") ", rec->data_len, transform->taglen ) ); return( MBEDTLS_ERR_SSL_INVALID_MAC ); } rec->data_len -= transform->taglen; /* * Prepare nonce from dynamic and static parts. */ ssl_build_record_nonce( iv, sizeof( iv ), transform->iv_dec, transform->fixed_ivlen, dynamic_iv, dynamic_iv_len ); /* * Build additional data for AEAD encryption. * This depends on the TLS version. */ ssl_extract_add_data_from_record( add_data, &add_data_len, rec, transform->minor_ver ); MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD", add_data, add_data_len ); /* Because of the check above, we know that there are * explicit_iv_len Bytes preceeding data, and taglen * bytes following data + data_len. This justifies * the debug message and the invocation of * mbedtls_cipher_auth_decrypt_ext() below. */ MBEDTLS_SSL_DEBUG_BUF( 4, "IV used", iv, transform->ivlen ); MBEDTLS_SSL_DEBUG_BUF( 4, "TAG used", data + rec->data_len, transform->taglen ); /* * Decrypt and authenticate */ if( ( ret = mbedtls_cipher_auth_decrypt_ext( &transform->cipher_ctx_dec, iv, transform->ivlen, add_data, add_data_len, data, rec->data_len + transform->taglen, /* src */ data, rec->buf_len - (data - rec->buf), &olen, /* dst */ transform->taglen ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_auth_decrypt_ext", ret ); if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED ) return( MBEDTLS_ERR_SSL_INVALID_MAC ); return( ret ); } auth_done++; /* Double-check that AEAD decryption doesn't change content length. */ if( olen != rec->data_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } } else #endif /* MBEDTLS_GCM_C || MBEDTLS_CCM_C */ #if defined(MBEDTLS_SSL_SOME_SUITES_USE_CBC) if( mode == MBEDTLS_MODE_CBC ) { size_t minlen = 0; /* * Check immediate ciphertext sanity */ #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if( transform->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_3 ) { /* The ciphertext is prefixed with the CBC IV. */ minlen += transform->ivlen; } #endif /* Size considerations: * * - The CBC cipher text must not be empty and hence * at least of size transform->ivlen. * * Together with the potential IV-prefix, this explains * the first of the two checks below. * * - The record must contain a MAC, either in plain or * encrypted, depending on whether Encrypt-then-MAC * is used or not. * - If it is, the message contains the IV-prefix, * the CBC ciphertext, and the MAC. * - If it is not, the padded plaintext, and hence * the CBC ciphertext, has at least length maclen + 1 * because there is at least the padding length byte. * * As the CBC ciphertext is not empty, both cases give the * lower bound minlen + maclen + 1 on the record size, which * we test for in the second check below. */ if( rec->data_len < minlen + transform->ivlen || rec->data_len < minlen + transform->maclen + 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%" MBEDTLS_PRINTF_SIZET ") < max( ivlen(%" MBEDTLS_PRINTF_SIZET "), maclen (%" MBEDTLS_PRINTF_SIZET ") " "+ 1 ) ( + expl IV )", rec->data_len, transform->ivlen, transform->maclen ) ); return( MBEDTLS_ERR_SSL_INVALID_MAC ); } /* * Authenticate before decrypt if enabled */ #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC) if( transform->encrypt_then_mac == MBEDTLS_SSL_ETM_ENABLED ) { unsigned char mac_expect[MBEDTLS_SSL_MAC_ADD]; MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) ); /* Update data_len in tandem with add_data. * * The subtraction is safe because of the previous check * data_len >= minlen + maclen + 1. * * Afterwards, we know that data + data_len is followed by at * least maclen Bytes, which justifies the call to * mbedtls_ssl_safer_memcmp() below. * * Further, we still know that data_len > minlen */ rec->data_len -= transform->maclen; ssl_extract_add_data_from_record( add_data, &add_data_len, rec, transform->minor_ver ); /* Calculate expected MAC. */ MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data, add_data_len ); mbedtls_md_hmac_update( &transform->md_ctx_dec, add_data, add_data_len ); mbedtls_md_hmac_update( &transform->md_ctx_dec, data, rec->data_len ); mbedtls_md_hmac_finish( &transform->md_ctx_dec, mac_expect ); mbedtls_md_hmac_reset( &transform->md_ctx_dec ); MBEDTLS_SSL_DEBUG_BUF( 4, "message mac", data + rec->data_len, transform->maclen ); MBEDTLS_SSL_DEBUG_BUF( 4, "expected mac", mac_expect, transform->maclen ); /* Compare expected MAC with MAC at the end of the record. */ if( mbedtls_ssl_safer_memcmp( data + rec->data_len, mac_expect, transform->maclen ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "message mac does not match" ) ); return( MBEDTLS_ERR_SSL_INVALID_MAC ); } auth_done++; } #endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC */ /* * Check length sanity */ /* We know from above that data_len > minlen >= 0, * so the following check in particular implies that * data_len >= minlen + ivlen ( = minlen or 2 * minlen ). */ if( rec->data_len % transform->ivlen != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%" MBEDTLS_PRINTF_SIZET ") %% ivlen (%" MBEDTLS_PRINTF_SIZET ") != 0", rec->data_len, transform->ivlen ) ); return( MBEDTLS_ERR_SSL_INVALID_MAC ); } #if defined(MBEDTLS_SSL_PROTO_TLS1_2) /* * Initialize for prepended IV for block cipher in TLS v1.2 */ if( transform->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_3 ) { /* Safe because data_len >= minlen + ivlen = 2 * ivlen. */ memcpy( transform->iv_dec, data, transform->ivlen ); data += transform->ivlen; rec->data_offset += transform->ivlen; rec->data_len -= transform->ivlen; } #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ /* We still have data_len % ivlen == 0 and data_len >= ivlen here. */ if( ( ret = mbedtls_cipher_crypt( &transform->cipher_ctx_dec, transform->iv_dec, transform->ivlen, data, rec->data_len, data, &olen ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_crypt", ret ); return( ret ); } /* Double-check that length hasn't changed during decryption. */ if( rec->data_len != olen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* Safe since data_len >= minlen + maclen + 1, so after having * subtracted at most minlen and maclen up to this point, * data_len > 0 (because of data_len % ivlen == 0, it's actually * >= ivlen ). */ padlen = data[rec->data_len - 1]; if( auth_done == 1 ) { const size_t mask = mbedtls_ssl_cf_mask_ge( rec->data_len, padlen + 1 ); correct &= mask; padlen &= mask; } else { #if defined(MBEDTLS_SSL_DEBUG_ALL) if( rec->data_len < transform->maclen + padlen + 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "msglen (%" MBEDTLS_PRINTF_SIZET ") < maclen (%" MBEDTLS_PRINTF_SIZET ") + padlen (%" MBEDTLS_PRINTF_SIZET ")", rec->data_len, transform->maclen, padlen + 1 ) ); } #endif const size_t mask = mbedtls_ssl_cf_mask_ge( rec->data_len, transform->maclen + padlen + 1 ); correct &= mask; padlen &= mask; } padlen++; /* Regardless of the validity of the padding, * we have data_len >= padlen here. */ #if defined(MBEDTLS_SSL_PROTO_TLS1_2) /* The padding check involves a series of up to 256 * consecutive memory reads at the end of the record * plaintext buffer. In order to hide the length and * validity of the padding, always perform exactly * `min(256,plaintext_len)` reads (but take into account * only the last `padlen` bytes for the padding check). */ size_t pad_count = 0; volatile unsigned char* const check = data; /* Index of first padding byte; it has been ensured above * that the subtraction is safe. */ size_t const padding_idx = rec->data_len - padlen; size_t const num_checks = rec->data_len <= 256 ? rec->data_len : 256; size_t const start_idx = rec->data_len - num_checks; size_t idx; for( idx = start_idx; idx < rec->data_len; idx++ ) { /* pad_count += (idx >= padding_idx) && * (check[idx] == padlen - 1); */ const size_t mask = mbedtls_ssl_cf_mask_ge( idx, padding_idx ); const size_t equal = mbedtls_ssl_cf_bool_eq( check[idx], padlen - 1 ); pad_count += mask & equal; } correct &= mbedtls_ssl_cf_bool_eq( pad_count, padlen ); #if defined(MBEDTLS_SSL_DEBUG_ALL) if( padlen > 0 && correct == 0 ) MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad padding byte detected" ) ); #endif padlen &= mbedtls_ssl_cf_mask_from_bit( correct ); #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ /* If the padding was found to be invalid, padlen == 0 * and the subtraction is safe. If the padding was found valid, * padlen hasn't been changed and the previous assertion * data_len >= padlen still holds. */ rec->data_len -= padlen; } else #endif /* MBEDTLS_SSL_SOME_SUITES_USE_CBC */ { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } #if defined(MBEDTLS_SSL_DEBUG_ALL) MBEDTLS_SSL_DEBUG_BUF( 4, "raw buffer after decryption", data, rec->data_len ); #endif /* * Authenticate if not done yet. * Compute the MAC regardless of the padding result (RFC4346, CBCTIME). */ #if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) if( auth_done == 0 ) { unsigned char mac_expect[MBEDTLS_SSL_MAC_ADD]; unsigned char mac_peer[MBEDTLS_SSL_MAC_ADD]; /* If the initial value of padlen was such that * data_len < maclen + padlen + 1, then padlen * got reset to 1, and the initial check * data_len >= minlen + maclen + 1 * guarantees that at this point we still * have at least data_len >= maclen. * * If the initial value of padlen was such that * data_len >= maclen + padlen + 1, then we have * subtracted either padlen + 1 (if the padding was correct) * or 0 (if the padding was incorrect) since then, * hence data_len >= maclen in any case. */ rec->data_len -= transform->maclen; ssl_extract_add_data_from_record( add_data, &add_data_len, rec, transform->minor_ver ); #if defined(MBEDTLS_SSL_PROTO_TLS1_2) /* * The next two sizes are the minimum and maximum values of * data_len over all padlen values. * * They're independent of padlen, since we previously did * data_len -= padlen. * * Note that max_len + maclen is never more than the buffer * length, as we previously did in_msglen -= maclen too. */ const size_t max_len = rec->data_len + padlen; const size_t min_len = ( max_len > 256 ) ? max_len - 256 : 0; ret = mbedtls_ssl_cf_hmac( &transform->md_ctx_dec, add_data, add_data_len, data, rec->data_len, min_len, max_len, mac_expect ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_cf_hmac", ret ); return( ret ); } mbedtls_ssl_cf_memcpy_offset( mac_peer, data, rec->data_len, min_len, max_len, transform->maclen ); #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ #if defined(MBEDTLS_SSL_DEBUG_ALL) MBEDTLS_SSL_DEBUG_BUF( 4, "expected mac", mac_expect, transform->maclen ); MBEDTLS_SSL_DEBUG_BUF( 4, "message mac", mac_peer, transform->maclen ); #endif if( mbedtls_ssl_safer_memcmp( mac_peer, mac_expect, transform->maclen ) != 0 ) { #if defined(MBEDTLS_SSL_DEBUG_ALL) MBEDTLS_SSL_DEBUG_MSG( 1, ( "message mac does not match" ) ); #endif correct = 0; } auth_done++; } /* * Finally check the correct flag */ if( correct == 0 ) return( MBEDTLS_ERR_SSL_INVALID_MAC ); #endif /* MBEDTLS_SSL_SOME_SUITES_USE_MAC */ /* Make extra sure authentication was performed, exactly once */ if( auth_done != 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } #if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL) if( transform->minor_ver == MBEDTLS_SSL_MINOR_VERSION_4 ) { /* Remove inner padding and infer true content type. */ ret = ssl_parse_inner_plaintext( data, &rec->data_len, &rec->type ); if( ret != 0 ) return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } #endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */ #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) if( rec->cid_len != 0 ) { ret = ssl_parse_inner_plaintext( data, &rec->data_len, &rec->type ); if( ret != 0 ) return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= decrypt buf" ) ); return( 0 ); } #undef MAC_NONE #undef MAC_PLAINTEXT #undef MAC_CIPHERTEXT /* * Fill the input message buffer by appending data to it. * The amount of data already fetched is in ssl->in_left. * * If we return 0, is it guaranteed that (at least) nb_want bytes are * available (from this read and/or a previous one). Otherwise, an error code * is returned (possibly EOF or WANT_READ). * * With stream transport (TLS) on success ssl->in_left == nb_want, but * with datagram transport (DTLS) on success ssl->in_left >= nb_want, * since we always read a whole datagram at once. * * For DTLS, it is up to the caller to set ssl->next_record_offset when * they're done reading a record. */ int mbedtls_ssl_fetch_input( mbedtls_ssl_context *ssl, size_t nb_want ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t len; #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH) size_t in_buf_len = ssl->in_buf_len; #else size_t in_buf_len = MBEDTLS_SSL_IN_BUFFER_LEN; #endif MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> fetch input" ) ); if( ssl->f_recv == NULL && ssl->f_recv_timeout == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Bad usage of mbedtls_ssl_set_bio() " "or mbedtls_ssl_set_bio()" ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } if( nb_want > in_buf_len - (size_t)( ssl->in_hdr - ssl->in_buf ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "requesting more data than fits" ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { uint32_t timeout; /* * The point is, we need to always read a full datagram at once, so we * sometimes read more then requested, and handle the additional data. * It could be the rest of the current record (while fetching the * header) and/or some other records in the same datagram. */ /* * Move to the next record in the already read datagram if applicable */ if( ssl->next_record_offset != 0 ) { if( ssl->in_left < ssl->next_record_offset ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } ssl->in_left -= ssl->next_record_offset; if( ssl->in_left != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "next record in same datagram, offset: %" MBEDTLS_PRINTF_SIZET, ssl->next_record_offset ) ); memmove( ssl->in_hdr, ssl->in_hdr + ssl->next_record_offset, ssl->in_left ); } ssl->next_record_offset = 0; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "in_left: %" MBEDTLS_PRINTF_SIZET ", nb_want: %" MBEDTLS_PRINTF_SIZET, ssl->in_left, nb_want ) ); /* * Done if we already have enough data. */ if( nb_want <= ssl->in_left) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= fetch input" ) ); return( 0 ); } /* * A record can't be split across datagrams. If we need to read but * are not at the beginning of a new record, the caller did something * wrong. */ if( ssl->in_left != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* * Don't even try to read if time's out already. * This avoids by-passing the timer when repeatedly receiving messages * that will end up being dropped. */ if( mbedtls_ssl_check_timer( ssl ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "timer has expired" ) ); ret = MBEDTLS_ERR_SSL_TIMEOUT; } else { len = in_buf_len - ( ssl->in_hdr - ssl->in_buf ); if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER ) timeout = ssl->handshake->retransmit_timeout; else timeout = ssl->conf->read_timeout; MBEDTLS_SSL_DEBUG_MSG( 3, ( "f_recv_timeout: %lu ms", (unsigned long) timeout ) ); if( ssl->f_recv_timeout != NULL ) ret = ssl->f_recv_timeout( ssl->p_bio, ssl->in_hdr, len, timeout ); else ret = ssl->f_recv( ssl->p_bio, ssl->in_hdr, len ); MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_recv(_timeout)", ret ); if( ret == 0 ) return( MBEDTLS_ERR_SSL_CONN_EOF ); } if( ret == MBEDTLS_ERR_SSL_TIMEOUT ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "timeout" ) ); mbedtls_ssl_set_timer( ssl, 0 ); if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER ) { if( ssl_double_retransmit_timeout( ssl ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake timeout" ) ); return( MBEDTLS_ERR_SSL_TIMEOUT ); } if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_resend", ret ); return( ret ); } return( MBEDTLS_ERR_SSL_WANT_READ ); } #if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_RENEGOTIATION) else if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER && ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING ) { if( ( ret = mbedtls_ssl_resend_hello_request( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_resend_hello_request", ret ); return( ret ); } return( MBEDTLS_ERR_SSL_WANT_READ ); } #endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_RENEGOTIATION */ } if( ret < 0 ) return( ret ); ssl->in_left = ret; } else #endif { MBEDTLS_SSL_DEBUG_MSG( 2, ( "in_left: %" MBEDTLS_PRINTF_SIZET ", nb_want: %" MBEDTLS_PRINTF_SIZET, ssl->in_left, nb_want ) ); while( ssl->in_left < nb_want ) { len = nb_want - ssl->in_left; if( mbedtls_ssl_check_timer( ssl ) != 0 ) ret = MBEDTLS_ERR_SSL_TIMEOUT; else { if( ssl->f_recv_timeout != NULL ) { ret = ssl->f_recv_timeout( ssl->p_bio, ssl->in_hdr + ssl->in_left, len, ssl->conf->read_timeout ); } else { ret = ssl->f_recv( ssl->p_bio, ssl->in_hdr + ssl->in_left, len ); } } MBEDTLS_SSL_DEBUG_MSG( 2, ( "in_left: %" MBEDTLS_PRINTF_SIZET ", nb_want: %" MBEDTLS_PRINTF_SIZET, ssl->in_left, nb_want ) ); MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_recv(_timeout)", ret ); if( ret == 0 ) return( MBEDTLS_ERR_SSL_CONN_EOF ); if( ret < 0 ) return( ret ); if ( (size_t)ret > len || ( INT_MAX > SIZE_MAX && ret > (int)SIZE_MAX ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "f_recv returned %d bytes but only %" MBEDTLS_PRINTF_SIZET " were requested", ret, len ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } ssl->in_left += ret; } } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= fetch input" ) ); return( 0 ); } /* * Flush any data not yet written */ int mbedtls_ssl_flush_output( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *buf; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> flush output" ) ); if( ssl->f_send == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Bad usage of mbedtls_ssl_set_bio() " "or mbedtls_ssl_set_bio()" ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } /* Avoid incrementing counter if data is flushed */ if( ssl->out_left == 0 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= flush output" ) ); return( 0 ); } while( ssl->out_left > 0 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "message length: %" MBEDTLS_PRINTF_SIZET ", out_left: %" MBEDTLS_PRINTF_SIZET, mbedtls_ssl_out_hdr_len( ssl ) + ssl->out_msglen, ssl->out_left ) ); buf = ssl->out_hdr - ssl->out_left; ret = ssl->f_send( ssl->p_bio, buf, ssl->out_left ); MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_send", ret ); if( ret <= 0 ) return( ret ); if( (size_t)ret > ssl->out_left || ( INT_MAX > SIZE_MAX && ret > (int)SIZE_MAX ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "f_send returned %d bytes but only %" MBEDTLS_PRINTF_SIZET " bytes were sent", ret, ssl->out_left ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } ssl->out_left -= ret; } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { ssl->out_hdr = ssl->out_buf; } else #endif { ssl->out_hdr = ssl->out_buf + 8; } mbedtls_ssl_update_out_pointers( ssl, ssl->transform_out ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= flush output" ) ); return( 0 ); } /* * Functions to handle the DTLS retransmission state machine */ #if defined(MBEDTLS_SSL_PROTO_DTLS) /* * Append current handshake message to current outgoing flight */ static int ssl_flight_append( mbedtls_ssl_context *ssl ) { mbedtls_ssl_flight_item *msg; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_flight_append" ) ); MBEDTLS_SSL_DEBUG_BUF( 4, "message appended to flight", ssl->out_msg, ssl->out_msglen ); /* Allocate space for current message */ if( ( msg = mbedtls_calloc( 1, sizeof( mbedtls_ssl_flight_item ) ) ) == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc %" MBEDTLS_PRINTF_SIZET " bytes failed", sizeof( mbedtls_ssl_flight_item ) ) ); return( MBEDTLS_ERR_SSL_ALLOC_FAILED ); } if( ( msg->p = mbedtls_calloc( 1, ssl->out_msglen ) ) == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc %" MBEDTLS_PRINTF_SIZET " bytes failed", ssl->out_msglen ) ); mbedtls_free( msg ); return( MBEDTLS_ERR_SSL_ALLOC_FAILED ); } /* Copy current handshake message with headers */ memcpy( msg->p, ssl->out_msg, ssl->out_msglen ); msg->len = ssl->out_msglen; msg->type = ssl->out_msgtype; msg->next = NULL; /* Append to the current flight */ if( ssl->handshake->flight == NULL ) ssl->handshake->flight = msg; else { mbedtls_ssl_flight_item *cur = ssl->handshake->flight; while( cur->next != NULL ) cur = cur->next; cur->next = msg; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_flight_append" ) ); return( 0 ); } /* * Free the current flight of handshake messages */ void mbedtls_ssl_flight_free( mbedtls_ssl_flight_item *flight ) { mbedtls_ssl_flight_item *cur = flight; mbedtls_ssl_flight_item *next; while( cur != NULL ) { next = cur->next; mbedtls_free( cur->p ); mbedtls_free( cur ); cur = next; } } /* * Swap transform_out and out_ctr with the alternative ones */ static int ssl_swap_epochs( mbedtls_ssl_context *ssl ) { mbedtls_ssl_transform *tmp_transform; unsigned char tmp_out_ctr[8]; if( ssl->transform_out == ssl->handshake->alt_transform_out ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "skip swap epochs" ) ); return( 0 ); } MBEDTLS_SSL_DEBUG_MSG( 3, ( "swap epochs" ) ); /* Swap transforms */ tmp_transform = ssl->transform_out; ssl->transform_out = ssl->handshake->alt_transform_out; ssl->handshake->alt_transform_out = tmp_transform; /* Swap epoch + sequence_number */ memcpy( tmp_out_ctr, ssl->cur_out_ctr, 8 ); memcpy( ssl->cur_out_ctr, ssl->handshake->alt_out_ctr, 8 ); memcpy( ssl->handshake->alt_out_ctr, tmp_out_ctr, 8 ); /* Adjust to the newly activated transform */ mbedtls_ssl_update_out_pointers( ssl, ssl->transform_out ); return( 0 ); } /* * Retransmit the current flight of messages. */ int mbedtls_ssl_resend( mbedtls_ssl_context *ssl ) { int ret = 0; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_resend" ) ); ret = mbedtls_ssl_flight_transmit( ssl ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_resend" ) ); return( ret ); } /* * Transmit or retransmit the current flight of messages. * * Need to remember the current message in case flush_output returns * WANT_WRITE, causing us to exit this function and come back later. * This function must be called until state is no longer SENDING. */ int mbedtls_ssl_flight_transmit( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_flight_transmit" ) ); if( ssl->handshake->retransmit_state != MBEDTLS_SSL_RETRANS_SENDING ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialise flight transmission" ) ); ssl->handshake->cur_msg = ssl->handshake->flight; ssl->handshake->cur_msg_p = ssl->handshake->flight->p + 12; ret = ssl_swap_epochs( ssl ); if( ret != 0 ) return( ret ); ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_SENDING; } while( ssl->handshake->cur_msg != NULL ) { size_t max_frag_len; const mbedtls_ssl_flight_item * const cur = ssl->handshake->cur_msg; int const is_finished = ( cur->type == MBEDTLS_SSL_MSG_HANDSHAKE && cur->p[0] == MBEDTLS_SSL_HS_FINISHED ); uint8_t const force_flush = ssl->disable_datagram_packing == 1 ? SSL_FORCE_FLUSH : SSL_DONT_FORCE_FLUSH; /* Swap epochs before sending Finished: we can't do it after * sending ChangeCipherSpec, in case write returns WANT_READ. * Must be done before copying, may change out_msg pointer */ if( is_finished && ssl->handshake->cur_msg_p == ( cur->p + 12 ) ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "swap epochs to send finished message" ) ); ret = ssl_swap_epochs( ssl ); if( ret != 0 ) return( ret ); } ret = ssl_get_remaining_payload_in_datagram( ssl ); if( ret < 0 ) return( ret ); max_frag_len = (size_t) ret; /* CCS is copied as is, while HS messages may need fragmentation */ if( cur->type == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC ) { if( max_frag_len == 0 ) { if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) return( ret ); continue; } memcpy( ssl->out_msg, cur->p, cur->len ); ssl->out_msglen = cur->len; ssl->out_msgtype = cur->type; /* Update position inside current message */ ssl->handshake->cur_msg_p += cur->len; } else { const unsigned char * const p = ssl->handshake->cur_msg_p; const size_t hs_len = cur->len - 12; const size_t frag_off = p - ( cur->p + 12 ); const size_t rem_len = hs_len - frag_off; size_t cur_hs_frag_len, max_hs_frag_len; if( ( max_frag_len < 12 ) || ( max_frag_len == 12 && hs_len != 0 ) ) { if( is_finished ) { ret = ssl_swap_epochs( ssl ); if( ret != 0 ) return( ret ); } if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) return( ret ); continue; } max_hs_frag_len = max_frag_len - 12; cur_hs_frag_len = rem_len > max_hs_frag_len ? max_hs_frag_len : rem_len; if( frag_off == 0 && cur_hs_frag_len != hs_len ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "fragmenting handshake message (%u > %u)", (unsigned) cur_hs_frag_len, (unsigned) max_hs_frag_len ) ); } /* Messages are stored with handshake headers as if not fragmented, * copy beginning of headers then fill fragmentation fields. * Handshake headers: type(1) len(3) seq(2) f_off(3) f_len(3) */ memcpy( ssl->out_msg, cur->p, 6 ); ssl->out_msg[6] = ( ( frag_off >> 16 ) & 0xff ); ssl->out_msg[7] = ( ( frag_off >> 8 ) & 0xff ); ssl->out_msg[8] = ( ( frag_off ) & 0xff ); ssl->out_msg[ 9] = ( ( cur_hs_frag_len >> 16 ) & 0xff ); ssl->out_msg[10] = ( ( cur_hs_frag_len >> 8 ) & 0xff ); ssl->out_msg[11] = ( ( cur_hs_frag_len ) & 0xff ); MBEDTLS_SSL_DEBUG_BUF( 3, "handshake header", ssl->out_msg, 12 ); /* Copy the handshake message content and set records fields */ memcpy( ssl->out_msg + 12, p, cur_hs_frag_len ); ssl->out_msglen = cur_hs_frag_len + 12; ssl->out_msgtype = cur->type; /* Update position inside current message */ ssl->handshake->cur_msg_p += cur_hs_frag_len; } /* If done with the current message move to the next one if any */ if( ssl->handshake->cur_msg_p >= cur->p + cur->len ) { if( cur->next != NULL ) { ssl->handshake->cur_msg = cur->next; ssl->handshake->cur_msg_p = cur->next->p + 12; } else { ssl->handshake->cur_msg = NULL; ssl->handshake->cur_msg_p = NULL; } } /* Actually send the message out */ if( ( ret = mbedtls_ssl_write_record( ssl, force_flush ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret ); return( ret ); } } if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) return( ret ); /* Update state and set timer */ if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER ) ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_FINISHED; else { ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_WAITING; mbedtls_ssl_set_timer( ssl, ssl->handshake->retransmit_timeout ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_flight_transmit" ) ); return( 0 ); } /* * To be called when the last message of an incoming flight is received. */ void mbedtls_ssl_recv_flight_completed( mbedtls_ssl_context *ssl ) { /* We won't need to resend that one any more */ mbedtls_ssl_flight_free( ssl->handshake->flight ); ssl->handshake->flight = NULL; ssl->handshake->cur_msg = NULL; /* The next incoming flight will start with this msg_seq */ ssl->handshake->in_flight_start_seq = ssl->handshake->in_msg_seq; /* We don't want to remember CCS's across flight boundaries. */ ssl->handshake->buffering.seen_ccs = 0; /* Clear future message buffering structure. */ mbedtls_ssl_buffering_free( ssl ); /* Cancel timer */ mbedtls_ssl_set_timer( ssl, 0 ); if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE && ssl->in_msg[0] == MBEDTLS_SSL_HS_FINISHED ) { ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_FINISHED; } else ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_PREPARING; } /* * To be called when the last message of an outgoing flight is send. */ void mbedtls_ssl_send_flight_completed( mbedtls_ssl_context *ssl ) { ssl_reset_retransmit_timeout( ssl ); mbedtls_ssl_set_timer( ssl, ssl->handshake->retransmit_timeout ); if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE && ssl->in_msg[0] == MBEDTLS_SSL_HS_FINISHED ) { ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_FINISHED; } else ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_WAITING; } #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* * Handshake layer functions */ /* * Write (DTLS: or queue) current handshake (including CCS) message. * * - fill in handshake headers * - update handshake checksum * - DTLS: save message for resending * - then pass to the record layer * * DTLS: except for HelloRequest, messages are only queued, and will only be * actually sent when calling flight_transmit() or resend(). * * Inputs: * - ssl->out_msglen: 4 + actual handshake message len * (4 is the size of handshake headers for TLS) * - ssl->out_msg[0]: the handshake type (ClientHello, ServerHello, etc) * - ssl->out_msg + 4: the handshake message body * * Outputs, ie state before passing to flight_append() or write_record(): * - ssl->out_msglen: the length of the record contents * (including handshake headers but excluding record headers) * - ssl->out_msg: the record contents (handshake headers + content) */ int mbedtls_ssl_write_handshake_msg( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const size_t hs_len = ssl->out_msglen - 4; const unsigned char hs_type = ssl->out_msg[0]; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write handshake message" ) ); /* * Sanity checks */ if( ssl->out_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE && ssl->out_msgtype != MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* Whenever we send anything different from a * HelloRequest we should be in a handshake - double check. */ if( ! ( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE && hs_type == MBEDTLS_SSL_HS_HELLO_REQUEST ) && ssl->handshake == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl->handshake != NULL && ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } #endif /* Double-check that we did not exceed the bounds * of the outgoing record buffer. * This should never fail as the various message * writing functions must obey the bounds of the * outgoing record buffer, but better be safe. * * Note: We deliberately do not check for the MTU or MFL here. */ if( ssl->out_msglen > MBEDTLS_SSL_OUT_CONTENT_LEN ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Record too large: " "size %" MBEDTLS_PRINTF_SIZET ", maximum %" MBEDTLS_PRINTF_SIZET, ssl->out_msglen, (size_t) MBEDTLS_SSL_OUT_CONTENT_LEN ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* * Fill handshake headers */ if( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) { ssl->out_msg[1] = (unsigned char)( hs_len >> 16 ); ssl->out_msg[2] = (unsigned char)( hs_len >> 8 ); ssl->out_msg[3] = (unsigned char)( hs_len ); /* * DTLS has additional fields in the Handshake layer, * between the length field and the actual payload: * uint16 message_seq; * uint24 fragment_offset; * uint24 fragment_length; */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { /* Make room for the additional DTLS fields */ if( MBEDTLS_SSL_OUT_CONTENT_LEN - ssl->out_msglen < 8 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "DTLS handshake message too large: " "size %" MBEDTLS_PRINTF_SIZET ", maximum %" MBEDTLS_PRINTF_SIZET, hs_len, (size_t) ( MBEDTLS_SSL_OUT_CONTENT_LEN - 12 ) ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } memmove( ssl->out_msg + 12, ssl->out_msg + 4, hs_len ); ssl->out_msglen += 8; /* Write message_seq and update it, except for HelloRequest */ if( hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST ) { ssl->out_msg[4] = ( ssl->handshake->out_msg_seq >> 8 ) & 0xFF; ssl->out_msg[5] = ( ssl->handshake->out_msg_seq ) & 0xFF; ++( ssl->handshake->out_msg_seq ); } else { ssl->out_msg[4] = 0; ssl->out_msg[5] = 0; } /* Handshake hashes are computed without fragmentation, * so set frag_offset = 0 and frag_len = hs_len for now */ memset( ssl->out_msg + 6, 0x00, 3 ); memcpy( ssl->out_msg + 9, ssl->out_msg + 1, 3 ); } #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* Update running hashes of handshake messages seen */ if( hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST ) ssl->handshake->update_checksum( ssl, ssl->out_msg, ssl->out_msglen ); } /* Either send now, or just save to be sent (and resent) later */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ! ( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE && hs_type == MBEDTLS_SSL_HS_HELLO_REQUEST ) ) { if( ( ret = ssl_flight_append( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_flight_append", ret ); return( ret ); } } else #endif { if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_write_record", ret ); return( ret ); } } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write handshake message" ) ); return( 0 ); } /* * Record layer functions */ /* * Write current record. * * Uses: * - ssl->out_msgtype: type of the message (AppData, Handshake, Alert, CCS) * - ssl->out_msglen: length of the record content (excl headers) * - ssl->out_msg: record content */ int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl, uint8_t force_flush ) { int ret, done = 0; size_t len = ssl->out_msglen; uint8_t flush = force_flush; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write record" ) ); if( !done ) { unsigned i; size_t protected_record_size; #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH) size_t out_buf_len = ssl->out_buf_len; #else size_t out_buf_len = MBEDTLS_SSL_OUT_BUFFER_LEN; #endif /* Skip writing the record content type to after the encryption, * as it may change when using the CID extension. */ mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver, ssl->conf->transport, ssl->out_hdr + 1 ); memcpy( ssl->out_ctr, ssl->cur_out_ctr, 8 ); ssl->out_len[0] = (unsigned char)( len >> 8 ); ssl->out_len[1] = (unsigned char)( len ); if( ssl->transform_out != NULL ) { mbedtls_record rec; rec.buf = ssl->out_iv; rec.buf_len = out_buf_len - ( ssl->out_iv - ssl->out_buf ); rec.data_len = ssl->out_msglen; rec.data_offset = ssl->out_msg - rec.buf; memcpy( &rec.ctr[0], ssl->out_ctr, 8 ); mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver, ssl->conf->transport, rec.ver ); rec.type = ssl->out_msgtype; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) /* The CID is set by mbedtls_ssl_encrypt_buf(). */ rec.cid_len = 0; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ if( ( ret = mbedtls_ssl_encrypt_buf( ssl, ssl->transform_out, &rec, ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_encrypt_buf", ret ); return( ret ); } if( rec.data_offset != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* Update the record content type and CID. */ ssl->out_msgtype = rec.type; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID ) memcpy( ssl->out_cid, rec.cid, rec.cid_len ); #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->out_msglen = len = rec.data_len; ssl->out_len[0] = (unsigned char)( rec.data_len >> 8 ); ssl->out_len[1] = (unsigned char)( rec.data_len ); } protected_record_size = len + mbedtls_ssl_out_hdr_len( ssl ); #if defined(MBEDTLS_SSL_PROTO_DTLS) /* In case of DTLS, double-check that we don't exceed * the remaining space in the datagram. */ if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { ret = ssl_get_remaining_space_in_datagram( ssl ); if( ret < 0 ) return( ret ); if( protected_record_size > (size_t) ret ) { /* Should never happen */ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } } #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* Now write the potentially updated record content type. */ ssl->out_hdr[0] = (unsigned char) ssl->out_msgtype; MBEDTLS_SSL_DEBUG_MSG( 3, ( "output record: msgtype = %u, " "version = [%u:%u], msglen = %" MBEDTLS_PRINTF_SIZET, ssl->out_hdr[0], ssl->out_hdr[1], ssl->out_hdr[2], len ) ); MBEDTLS_SSL_DEBUG_BUF( 4, "output record sent to network", ssl->out_hdr, protected_record_size ); ssl->out_left += protected_record_size; ssl->out_hdr += protected_record_size; mbedtls_ssl_update_out_pointers( ssl, ssl->transform_out ); for( i = 8; i > mbedtls_ssl_ep_len( ssl ); i-- ) if( ++ssl->cur_out_ctr[i - 1] != 0 ) break; /* The loop goes to its end iff the counter is wrapping */ if( i == mbedtls_ssl_ep_len( ssl ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "outgoing message counter would wrap" ) ); return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING ); } } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && flush == SSL_DONT_FORCE_FLUSH ) { size_t remaining; ret = ssl_get_remaining_payload_in_datagram( ssl ); if( ret < 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_get_remaining_payload_in_datagram", ret ); return( ret ); } remaining = (size_t) ret; if( remaining == 0 ) { flush = SSL_FORCE_FLUSH; } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Still %u bytes available in current datagram", (unsigned) remaining ) ); } } #endif /* MBEDTLS_SSL_PROTO_DTLS */ if( ( flush == SSL_FORCE_FLUSH ) && ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flush_output", ret ); return( ret ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write record" ) ); return( 0 ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) static int ssl_hs_is_proper_fragment( mbedtls_ssl_context *ssl ) { if( ssl->in_msglen < ssl->in_hslen || memcmp( ssl->in_msg + 6, "\0\0\0", 3 ) != 0 || memcmp( ssl->in_msg + 9, ssl->in_msg + 1, 3 ) != 0 ) { return( 1 ); } return( 0 ); } static uint32_t ssl_get_hs_frag_len( mbedtls_ssl_context const *ssl ) { return( ( ssl->in_msg[9] << 16 ) | ( ssl->in_msg[10] << 8 ) | ssl->in_msg[11] ); } static uint32_t ssl_get_hs_frag_off( mbedtls_ssl_context const *ssl ) { return( ( ssl->in_msg[6] << 16 ) | ( ssl->in_msg[7] << 8 ) | ssl->in_msg[8] ); } static int ssl_check_hs_header( mbedtls_ssl_context const *ssl ) { uint32_t msg_len, frag_off, frag_len; msg_len = ssl_get_hs_total_len( ssl ); frag_off = ssl_get_hs_frag_off( ssl ); frag_len = ssl_get_hs_frag_len( ssl ); if( frag_off > msg_len ) return( -1 ); if( frag_len > msg_len - frag_off ) return( -1 ); if( frag_len + 12 > ssl->in_msglen ) return( -1 ); return( 0 ); } /* * Mark bits in bitmask (used for DTLS HS reassembly) */ static void ssl_bitmask_set( unsigned char *mask, size_t offset, size_t len ) { unsigned int start_bits, end_bits; start_bits = 8 - ( offset % 8 ); if( start_bits != 8 ) { size_t first_byte_idx = offset / 8; /* Special case */ if( len <= start_bits ) { for( ; len != 0; len-- ) mask[first_byte_idx] |= 1 << ( start_bits - len ); /* Avoid potential issues with offset or len becoming invalid */ return; } offset += start_bits; /* Now offset % 8 == 0 */ len -= start_bits; for( ; start_bits != 0; start_bits-- ) mask[first_byte_idx] |= 1 << ( start_bits - 1 ); } end_bits = len % 8; if( end_bits != 0 ) { size_t last_byte_idx = ( offset + len ) / 8; len -= end_bits; /* Now len % 8 == 0 */ for( ; end_bits != 0; end_bits-- ) mask[last_byte_idx] |= 1 << ( 8 - end_bits ); } memset( mask + offset / 8, 0xFF, len / 8 ); } /* * Check that bitmask is full */ static int ssl_bitmask_check( unsigned char *mask, size_t len ) { size_t i; for( i = 0; i < len / 8; i++ ) if( mask[i] != 0xFF ) return( -1 ); for( i = 0; i < len % 8; i++ ) if( ( mask[len / 8] & ( 1 << ( 7 - i ) ) ) == 0 ) return( -1 ); return( 0 ); } /* msg_len does not include the handshake header */ static size_t ssl_get_reassembly_buffer_size( size_t msg_len, unsigned add_bitmap ) { size_t alloc_len; alloc_len = 12; /* Handshake header */ alloc_len += msg_len; /* Content buffer */ if( add_bitmap ) alloc_len += msg_len / 8 + ( msg_len % 8 != 0 ); /* Bitmap */ return( alloc_len ); } #endif /* MBEDTLS_SSL_PROTO_DTLS */ static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl ) { return( ( ssl->in_msg[1] << 16 ) | ( ssl->in_msg[2] << 8 ) | ssl->in_msg[3] ); } int mbedtls_ssl_prepare_handshake_record( mbedtls_ssl_context *ssl ) { if( ssl->in_msglen < mbedtls_ssl_hs_hdr_len( ssl ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake message too short: %" MBEDTLS_PRINTF_SIZET, ssl->in_msglen ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } ssl->in_hslen = mbedtls_ssl_hs_hdr_len( ssl ) + ssl_get_hs_total_len( ssl ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "handshake message: msglen =" " %" MBEDTLS_PRINTF_SIZET ", type = %u, hslen = %" MBEDTLS_PRINTF_SIZET, ssl->in_msglen, ssl->in_msg[0], ssl->in_hslen ) ); #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned int recv_msg_seq = ( ssl->in_msg[4] << 8 ) | ssl->in_msg[5]; if( ssl_check_hs_header( ssl ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid handshake header" ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } if( ssl->handshake != NULL && ( ( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER && recv_msg_seq != ssl->handshake->in_msg_seq ) || ( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER && ssl->in_msg[0] != MBEDTLS_SSL_HS_CLIENT_HELLO ) ) ) { if( recv_msg_seq > ssl->handshake->in_msg_seq ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "received future handshake message of sequence number %u (next %u)", recv_msg_seq, ssl->handshake->in_msg_seq ) ); return( MBEDTLS_ERR_SSL_EARLY_MESSAGE ); } /* Retransmit only on last message from previous flight, to avoid * too many retransmissions. * Besides, No sane server ever retransmits HelloVerifyRequest */ if( recv_msg_seq == ssl->handshake->in_flight_start_seq - 1 && ssl->in_msg[0] != MBEDTLS_SSL_HS_HELLO_VERIFY_REQUEST ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "received message from last flight, " "message_seq = %u, start_of_flight = %u", recv_msg_seq, ssl->handshake->in_flight_start_seq ) ); if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_resend", ret ); return( ret ); } } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "dropping out-of-sequence message: " "message_seq = %u, expected = %u", recv_msg_seq, ssl->handshake->in_msg_seq ) ); } return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING ); } /* Wait until message completion to increment in_msg_seq */ /* Message reassembly is handled alongside buffering of future * messages; the commonality is that both handshake fragments and * future messages cannot be forwarded immediately to the * handshake logic layer. */ if( ssl_hs_is_proper_fragment( ssl ) == 1 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "found fragmented DTLS handshake message" ) ); return( MBEDTLS_ERR_SSL_EARLY_MESSAGE ); } } else #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* With TLS we don't handle fragmentation (for now) */ if( ssl->in_msglen < ssl->in_hslen ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "TLS handshake fragmentation not supported" ) ); return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE ); } return( 0 ); } void mbedtls_ssl_update_handshake_status( mbedtls_ssl_context *ssl ) { mbedtls_ssl_handshake_params * const hs = ssl->handshake; if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER && hs != NULL ) { ssl->handshake->update_checksum( ssl, ssl->in_msg, ssl->in_hslen ); } /* Handshake message is complete, increment counter */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl->handshake != NULL ) { unsigned offset; mbedtls_ssl_hs_buffer *hs_buf; /* Increment handshake sequence number */ hs->in_msg_seq++; /* * Clear up handshake buffering and reassembly structure. */ /* Free first entry */ ssl_buffering_free_slot( ssl, 0 ); /* Shift all other entries */ for( offset = 0, hs_buf = &hs->buffering.hs[0]; offset + 1 < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++, hs_buf++ ) { *hs_buf = *(hs_buf + 1); } /* Create a fresh last entry */ memset( hs_buf, 0, sizeof( mbedtls_ssl_hs_buffer ) ); } #endif } /* * DTLS anti-replay: RFC 6347 4.1.2.6 * * in_window is a field of bits numbered from 0 (lsb) to 63 (msb). * Bit n is set iff record number in_window_top - n has been seen. * * Usually, in_window_top is the last record number seen and the lsb of * in_window is set. The only exception is the initial state (record number 0 * not seen yet). */ #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY) void mbedtls_ssl_dtls_replay_reset( mbedtls_ssl_context *ssl ) { ssl->in_window_top = 0; ssl->in_window = 0; } static inline uint64_t ssl_load_six_bytes( unsigned char *buf ) { return( ( (uint64_t) buf[0] << 40 ) | ( (uint64_t) buf[1] << 32 ) | ( (uint64_t) buf[2] << 24 ) | ( (uint64_t) buf[3] << 16 ) | ( (uint64_t) buf[4] << 8 ) | ( (uint64_t) buf[5] ) ); } static int mbedtls_ssl_dtls_record_replay_check( mbedtls_ssl_context *ssl, uint8_t *record_in_ctr ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *original_in_ctr; // save original in_ctr original_in_ctr = ssl->in_ctr; // use counter from record ssl->in_ctr = record_in_ctr; ret = mbedtls_ssl_dtls_replay_check( (mbedtls_ssl_context const *) ssl ); // restore the counter ssl->in_ctr = original_in_ctr; return ret; } /* * Return 0 if sequence number is acceptable, -1 otherwise */ int mbedtls_ssl_dtls_replay_check( mbedtls_ssl_context const *ssl ) { uint64_t rec_seqnum = ssl_load_six_bytes( ssl->in_ctr + 2 ); uint64_t bit; if( ssl->conf->anti_replay == MBEDTLS_SSL_ANTI_REPLAY_DISABLED ) return( 0 ); if( rec_seqnum > ssl->in_window_top ) return( 0 ); bit = ssl->in_window_top - rec_seqnum; if( bit >= 64 ) return( -1 ); if( ( ssl->in_window & ( (uint64_t) 1 << bit ) ) != 0 ) return( -1 ); return( 0 ); } /* * Update replay window on new validated record */ void mbedtls_ssl_dtls_replay_update( mbedtls_ssl_context *ssl ) { uint64_t rec_seqnum = ssl_load_six_bytes( ssl->in_ctr + 2 ); if( ssl->conf->anti_replay == MBEDTLS_SSL_ANTI_REPLAY_DISABLED ) return; if( rec_seqnum > ssl->in_window_top ) { /* Update window_top and the contents of the window */ uint64_t shift = rec_seqnum - ssl->in_window_top; if( shift >= 64 ) ssl->in_window = 1; else { ssl->in_window <<= shift; ssl->in_window |= 1; } ssl->in_window_top = rec_seqnum; } else { /* Mark that number as seen in the current window */ uint64_t bit = ssl->in_window_top - rec_seqnum; if( bit < 64 ) /* Always true, but be extra sure */ ssl->in_window |= (uint64_t) 1 << bit; } } #endif /* MBEDTLS_SSL_DTLS_ANTI_REPLAY */ #if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) && defined(MBEDTLS_SSL_SRV_C) /* * Without any SSL context, check if a datagram looks like a ClientHello with * a valid cookie, and if it doesn't, generate a HelloVerifyRequest message. * Both input and output include full DTLS headers. * * - if cookie is valid, return 0 * - if ClientHello looks superficially valid but cookie is not, * fill obuf and set olen, then * return MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED * - otherwise return a specific error code */ static int ssl_check_dtls_clihlo_cookie( mbedtls_ssl_cookie_write_t *f_cookie_write, mbedtls_ssl_cookie_check_t *f_cookie_check, void *p_cookie, const unsigned char *cli_id, size_t cli_id_len, const unsigned char *in, size_t in_len, unsigned char *obuf, size_t buf_len, size_t *olen ) { size_t sid_len, cookie_len; unsigned char *p; /* * Structure of ClientHello with record and handshake headers, * and expected values. We don't need to check a lot, more checks will be * done when actually parsing the ClientHello - skipping those checks * avoids code duplication and does not make cookie forging any easier. * * 0-0 ContentType type; copied, must be handshake * 1-2 ProtocolVersion version; copied * 3-4 uint16 epoch; copied, must be 0 * 5-10 uint48 sequence_number; copied * 11-12 uint16 length; (ignored) * * 13-13 HandshakeType msg_type; (ignored) * 14-16 uint24 length; (ignored) * 17-18 uint16 message_seq; copied * 19-21 uint24 fragment_offset; copied, must be 0 * 22-24 uint24 fragment_length; (ignored) * * 25-26 ProtocolVersion client_version; (ignored) * 27-58 Random random; (ignored) * 59-xx SessionID session_id; 1 byte len + sid_len content * 60+ opaque cookie<0..2^8-1>; 1 byte len + content * ... * * Minimum length is 61 bytes. */ if( in_len < 61 || in[0] != MBEDTLS_SSL_MSG_HANDSHAKE || in[3] != 0 || in[4] != 0 || in[19] != 0 || in[20] != 0 || in[21] != 0 ) { return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO ); } sid_len = in[59]; if( sid_len > in_len - 61 ) return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO ); cookie_len = in[60 + sid_len]; if( cookie_len > in_len - 60 ) return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO ); if( f_cookie_check( p_cookie, in + sid_len + 61, cookie_len, cli_id, cli_id_len ) == 0 ) { /* Valid cookie */ return( 0 ); } /* * If we get here, we've got an invalid cookie, let's prepare HVR. * * 0-0 ContentType type; copied * 1-2 ProtocolVersion version; copied * 3-4 uint16 epoch; copied * 5-10 uint48 sequence_number; copied * 11-12 uint16 length; olen - 13 * * 13-13 HandshakeType msg_type; hello_verify_request * 14-16 uint24 length; olen - 25 * 17-18 uint16 message_seq; copied * 19-21 uint24 fragment_offset; copied * 22-24 uint24 fragment_length; olen - 25 * * 25-26 ProtocolVersion server_version; 0xfe 0xff * 27-27 opaque cookie<0..2^8-1>; cookie_len = olen - 27, cookie * * Minimum length is 28. */ if( buf_len < 28 ) return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); /* Copy most fields and adapt others */ memcpy( obuf, in, 25 ); obuf[13] = MBEDTLS_SSL_HS_HELLO_VERIFY_REQUEST; obuf[25] = 0xfe; obuf[26] = 0xff; /* Generate and write actual cookie */ p = obuf + 28; if( f_cookie_write( p_cookie, &p, obuf + buf_len, cli_id, cli_id_len ) != 0 ) { return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } *olen = p - obuf; /* Go back and fill length fields */ obuf[27] = (unsigned char)( *olen - 28 ); obuf[14] = obuf[22] = (unsigned char)( ( *olen - 25 ) >> 16 ); obuf[15] = obuf[23] = (unsigned char)( ( *olen - 25 ) >> 8 ); obuf[16] = obuf[24] = (unsigned char)( ( *olen - 25 ) ); obuf[11] = (unsigned char)( ( *olen - 13 ) >> 8 ); obuf[12] = (unsigned char)( ( *olen - 13 ) ); return( MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED ); } /* * Handle possible client reconnect with the same UDP quadruplet * (RFC 6347 Section 4.2.8). * * Called by ssl_parse_record_header() in case we receive an epoch 0 record * that looks like a ClientHello. * * - if the input looks like a ClientHello without cookies, * send back HelloVerifyRequest, then return 0 * - if the input looks like a ClientHello with a valid cookie, * reset the session of the current context, and * return MBEDTLS_ERR_SSL_CLIENT_RECONNECT * - if anything goes wrong, return a specific error code * * This function is called (through ssl_check_client_reconnect()) when an * unexpected record is found in ssl_get_next_record(), which will discard the * record if we return 0, and bubble up the return value otherwise (this * includes the case of MBEDTLS_ERR_SSL_CLIENT_RECONNECT and of unexpected * errors, and is the right thing to do in both cases). */ static int ssl_handle_possible_reconnect( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t len; if( ssl->conf->f_cookie_write == NULL || ssl->conf->f_cookie_check == NULL ) { /* If we can't use cookies to verify reachability of the peer, * drop the record. */ MBEDTLS_SSL_DEBUG_MSG( 1, ( "no cookie callbacks, " "can't check reconnect validity" ) ); return( 0 ); } ret = ssl_check_dtls_clihlo_cookie( ssl->conf->f_cookie_write, ssl->conf->f_cookie_check, ssl->conf->p_cookie, ssl->cli_id, ssl->cli_id_len, ssl->in_buf, ssl->in_left, ssl->out_buf, MBEDTLS_SSL_OUT_CONTENT_LEN, &len ); MBEDTLS_SSL_DEBUG_RET( 2, "ssl_check_dtls_clihlo_cookie", ret ); if( ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED ) { int send_ret; MBEDTLS_SSL_DEBUG_MSG( 1, ( "sending HelloVerifyRequest" ) ); MBEDTLS_SSL_DEBUG_BUF( 4, "output record sent to network", ssl->out_buf, len ); /* Don't check write errors as we can't do anything here. * If the error is permanent we'll catch it later, * if it's not, then hopefully it'll work next time. */ send_ret = ssl->f_send( ssl->p_bio, ssl->out_buf, len ); MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_send", send_ret ); (void) send_ret; return( 0 ); } if( ret == 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "cookie is valid, resetting context" ) ); if( ( ret = mbedtls_ssl_session_reset_int( ssl, 1 ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "reset", ret ); return( ret ); } return( MBEDTLS_ERR_SSL_CLIENT_RECONNECT ); } return( ret ); } #endif /* MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE && MBEDTLS_SSL_SRV_C */ static int ssl_check_record_type( uint8_t record_type ) { if( record_type != MBEDTLS_SSL_MSG_HANDSHAKE && record_type != MBEDTLS_SSL_MSG_ALERT && record_type != MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC && record_type != MBEDTLS_SSL_MSG_APPLICATION_DATA ) { return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } return( 0 ); } /* * ContentType type; * ProtocolVersion version; * uint16 epoch; // DTLS only * uint48 sequence_number; // DTLS only * uint16 length; * * Return 0 if header looks sane (and, for DTLS, the record is expected) * MBEDTLS_ERR_SSL_INVALID_RECORD if the header looks bad, * MBEDTLS_ERR_SSL_UNEXPECTED_RECORD (DTLS only) if sane but unexpected. * * With DTLS, mbedtls_ssl_read_record() will: * 1. proceed with the record if this function returns 0 * 2. drop only the current record if this function returns UNEXPECTED_RECORD * 3. return CLIENT_RECONNECT if this function return that value * 4. drop the whole datagram if this function returns anything else. * Point 2 is needed when the peer is resending, and we have already received * the first record from a datagram but are still waiting for the others. */ static int ssl_parse_record_header( mbedtls_ssl_context const *ssl, unsigned char *buf, size_t len, mbedtls_record *rec ) { int major_ver, minor_ver; size_t const rec_hdr_type_offset = 0; size_t const rec_hdr_type_len = 1; size_t const rec_hdr_version_offset = rec_hdr_type_offset + rec_hdr_type_len; size_t const rec_hdr_version_len = 2; size_t const rec_hdr_ctr_len = 8; #if defined(MBEDTLS_SSL_PROTO_DTLS) uint32_t rec_epoch; size_t const rec_hdr_ctr_offset = rec_hdr_version_offset + rec_hdr_version_len; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) size_t const rec_hdr_cid_offset = rec_hdr_ctr_offset + rec_hdr_ctr_len; size_t rec_hdr_cid_len = 0; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ #endif /* MBEDTLS_SSL_PROTO_DTLS */ size_t rec_hdr_len_offset; /* To be determined */ size_t const rec_hdr_len_len = 2; /* * Check minimum lengths for record header. */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { rec_hdr_len_offset = rec_hdr_ctr_offset + rec_hdr_ctr_len; } else #endif /* MBEDTLS_SSL_PROTO_DTLS */ { rec_hdr_len_offset = rec_hdr_version_offset + rec_hdr_version_len; } if( len < rec_hdr_len_offset + rec_hdr_len_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "datagram of length %u too small to hold DTLS record header of length %u", (unsigned) len, (unsigned)( rec_hdr_len_len + rec_hdr_len_len ) ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } /* * Parse and validate record content type */ rec->type = buf[ rec_hdr_type_offset ]; /* Check record content type */ #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) rec->cid_len = 0; if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl->conf->cid_len != 0 && rec->type == MBEDTLS_SSL_MSG_CID ) { /* Shift pointers to account for record header including CID * struct { * ContentType special_type = tls12_cid; * ProtocolVersion version; * uint16 epoch; * uint48 sequence_number; * opaque cid[cid_length]; // Additional field compared to * // default DTLS record format * uint16 length; * opaque enc_content[DTLSCiphertext.length]; * } DTLSCiphertext; */ /* So far, we only support static CID lengths * fixed in the configuration. */ rec_hdr_cid_len = ssl->conf->cid_len; rec_hdr_len_offset += rec_hdr_cid_len; if( len < rec_hdr_len_offset + rec_hdr_len_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "datagram of length %u too small to hold DTLS record header including CID, length %u", (unsigned) len, (unsigned)( rec_hdr_len_offset + rec_hdr_len_len ) ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } /* configured CID len is guaranteed at most 255, see * MBEDTLS_SSL_CID_OUT_LEN_MAX in check_config.h */ rec->cid_len = (uint8_t) rec_hdr_cid_len; memcpy( rec->cid, buf + rec_hdr_cid_offset, rec_hdr_cid_len ); } else #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ { if( ssl_check_record_type( rec->type ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "unknown record type %u", (unsigned) rec->type ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } } /* * Parse and validate record version */ rec->ver[0] = buf[ rec_hdr_version_offset + 0 ]; rec->ver[1] = buf[ rec_hdr_version_offset + 1 ]; mbedtls_ssl_read_version( &major_ver, &minor_ver, ssl->conf->transport, &rec->ver[0] ); if( major_ver != ssl->major_ver ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "major version mismatch" ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } if( minor_ver > ssl->conf->max_minor_ver ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "minor version mismatch" ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } /* * Parse/Copy record sequence number. */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { /* Copy explicit record sequence number from input buffer. */ memcpy( &rec->ctr[0], buf + rec_hdr_ctr_offset, rec_hdr_ctr_len ); } else #endif /* MBEDTLS_SSL_PROTO_DTLS */ { /* Copy implicit record sequence number from SSL context structure. */ memcpy( &rec->ctr[0], ssl->in_ctr, rec_hdr_ctr_len ); } /* * Parse record length. */ rec->data_offset = rec_hdr_len_offset + rec_hdr_len_len; rec->data_len = ( (size_t) buf[ rec_hdr_len_offset + 0 ] << 8 ) | ( (size_t) buf[ rec_hdr_len_offset + 1 ] << 0 ); MBEDTLS_SSL_DEBUG_BUF( 4, "input record header", buf, rec->data_offset ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "input record: msgtype = %u, " "version = [%d:%d], msglen = %" MBEDTLS_PRINTF_SIZET, rec->type, major_ver, minor_ver, rec->data_len ) ); rec->buf = buf; rec->buf_len = rec->data_offset + rec->data_len; if( rec->data_len == 0 ) return( MBEDTLS_ERR_SSL_INVALID_RECORD ); /* * DTLS-related tests. * Check epoch before checking length constraint because * the latter varies with the epoch. E.g., if a ChangeCipherSpec * message gets duplicated before the corresponding Finished message, * the second ChangeCipherSpec should be discarded because it belongs * to an old epoch, but not because its length is shorter than * the minimum record length for packets using the new record transform. * Note that these two kinds of failures are handled differently, * as an unexpected record is silently skipped but an invalid * record leads to the entire datagram being dropped. */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { rec_epoch = ( rec->ctr[0] << 8 ) | rec->ctr[1]; /* Check that the datagram is large enough to contain a record * of the advertised length. */ if( len < rec->data_offset + rec->data_len ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Datagram of length %u too small to contain record of advertised length %u.", (unsigned) len, (unsigned)( rec->data_offset + rec->data_len ) ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } /* Records from other, non-matching epochs are silently discarded. * (The case of same-port Client reconnects must be considered in * the caller). */ if( rec_epoch != ssl->in_epoch ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "record from another epoch: " "expected %u, received %lu", ssl->in_epoch, (unsigned long) rec_epoch ) ); /* Records from the next epoch are considered for buffering * (concretely: early Finished messages). */ if( rec_epoch == (unsigned) ssl->in_epoch + 1 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Consider record for buffering" ) ); return( MBEDTLS_ERR_SSL_EARLY_MESSAGE ); } return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD ); } #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY) /* For records from the correct epoch, check whether their * sequence number has been seen before. */ else if( mbedtls_ssl_dtls_record_replay_check( (mbedtls_ssl_context *) ssl, &rec->ctr[0] ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "replayed record" ) ); return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD ); } #endif } #endif /* MBEDTLS_SSL_PROTO_DTLS */ return( 0 ); } #if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) && defined(MBEDTLS_SSL_SRV_C) static int ssl_check_client_reconnect( mbedtls_ssl_context *ssl ) { unsigned int rec_epoch = ( ssl->in_ctr[0] << 8 ) | ssl->in_ctr[1]; /* * Check for an epoch 0 ClientHello. We can't use in_msg here to * access the first byte of record content (handshake type), as we * have an active transform (possibly iv_len != 0), so use the * fact that the record header len is 13 instead. */ if( rec_epoch == 0 && ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER && ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER && ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE && ssl->in_left > 13 && ssl->in_buf[13] == MBEDTLS_SSL_HS_CLIENT_HELLO ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "possible client reconnect " "from the same port" ) ); return( ssl_handle_possible_reconnect( ssl ) ); } return( 0 ); } #endif /* MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE && MBEDTLS_SSL_SRV_C */ /* * If applicable, decrypt record content */ static int ssl_prepare_record_content( mbedtls_ssl_context *ssl, mbedtls_record *rec ) { int ret, done = 0; MBEDTLS_SSL_DEBUG_BUF( 4, "input record from network", rec->buf, rec->buf_len ); if( !done && ssl->transform_in != NULL ) { unsigned char const old_msg_type = rec->type; if( ( ret = mbedtls_ssl_decrypt_buf( ssl, ssl->transform_in, rec ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_decrypt_buf", ret ); #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) if( ret == MBEDTLS_ERR_SSL_UNEXPECTED_CID && ssl->conf->ignore_unexpected_cid == MBEDTLS_SSL_UNEXPECTED_CID_IGNORE ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "ignoring unexpected CID" ) ); ret = MBEDTLS_ERR_SSL_CONTINUE_PROCESSING; } #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ return( ret ); } if( old_msg_type != rec->type ) { MBEDTLS_SSL_DEBUG_MSG( 4, ( "record type after decrypt (before %d): %d", old_msg_type, rec->type ) ); } MBEDTLS_SSL_DEBUG_BUF( 4, "input payload after decrypt", rec->buf + rec->data_offset, rec->data_len ); #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) /* We have already checked the record content type * in ssl_parse_record_header(), failing or silently * dropping the record in the case of an unknown type. * * Since with the use of CIDs, the record content type * might change during decryption, re-check the record * content type, but treat a failure as fatal this time. */ if( ssl_check_record_type( rec->type ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "unknown record type" ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ if( rec->data_len == 0 ) { #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if( ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 && rec->type != MBEDTLS_SSL_MSG_APPLICATION_DATA ) { /* TLS v1.2 explicitly disallows zero-length messages which are not application data */ MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid zero-length message type: %d", ssl->in_msgtype ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ ssl->nb_zero++; /* * Three or more empty messages may be a DoS attack * (excessive CPU consumption). */ if( ssl->nb_zero > 3 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "received four consecutive empty " "messages, possible DoS attack" ) ); /* Treat the records as if they were not properly authenticated, * thereby failing the connection if we see more than allowed * by the configured bad MAC threshold. */ return( MBEDTLS_ERR_SSL_INVALID_MAC ); } } else ssl->nb_zero = 0; #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { ; /* in_ctr read from peer, not maintained internally */ } else #endif { unsigned i; for( i = 8; i > mbedtls_ssl_ep_len( ssl ); i-- ) if( ++ssl->in_ctr[i - 1] != 0 ) break; /* The loop goes to its end iff the counter is wrapping */ if( i == mbedtls_ssl_ep_len( ssl ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "incoming message counter would wrap" ) ); return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING ); } } } #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { mbedtls_ssl_dtls_replay_update( ssl ); } #endif /* Check actual (decrypted) record content length against * configured maximum. */ if( ssl->in_msglen > MBEDTLS_SSL_IN_CONTENT_LEN ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad message length" ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } return( 0 ); } /* * Read a record. * * Silently ignore non-fatal alert (and for DTLS, invalid records as well, * RFC 6347 4.1.2.7) and continue reading until a valid record is found. * */ /* Helper functions for mbedtls_ssl_read_record(). */ static int ssl_consume_current_message( mbedtls_ssl_context *ssl ); static int ssl_get_next_record( mbedtls_ssl_context *ssl ); static int ssl_record_is_in_progress( mbedtls_ssl_context *ssl ); int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl, unsigned update_hs_digest ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> read record" ) ); if( ssl->keep_current_message == 0 ) { do { ret = ssl_consume_current_message( ssl ); if( ret != 0 ) return( ret ); if( ssl_record_is_in_progress( ssl ) == 0 ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) int have_buffered = 0; /* We only check for buffered messages if the * current datagram is fully consumed. */ if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl_next_record_is_in_datagram( ssl ) == 0 ) { if( ssl_load_buffered_message( ssl ) == 0 ) have_buffered = 1; } if( have_buffered == 0 ) #endif /* MBEDTLS_SSL_PROTO_DTLS */ { ret = ssl_get_next_record( ssl ); if( ret == MBEDTLS_ERR_SSL_CONTINUE_PROCESSING ) continue; if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, ( "ssl_get_next_record" ), ret ); return( ret ); } } } ret = mbedtls_ssl_handle_message_type( ssl ); #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE ) { /* Buffer future message */ ret = ssl_buffer_message( ssl ); if( ret != 0 ) return( ret ); ret = MBEDTLS_ERR_SSL_CONTINUE_PROCESSING; } #endif /* MBEDTLS_SSL_PROTO_DTLS */ } while( MBEDTLS_ERR_SSL_NON_FATAL == ret || MBEDTLS_ERR_SSL_CONTINUE_PROCESSING == ret ); if( 0 != ret ) { MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_handle_message_type" ), ret ); return( ret ); } if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE && update_hs_digest == 1 ) { mbedtls_ssl_update_handshake_status( ssl ); } } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "reuse previously read message" ) ); ssl->keep_current_message = 0; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= read record" ) ); return( 0 ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) static int ssl_next_record_is_in_datagram( mbedtls_ssl_context *ssl ) { if( ssl->in_left > ssl->next_record_offset ) return( 1 ); return( 0 ); } static int ssl_load_buffered_message( mbedtls_ssl_context *ssl ) { mbedtls_ssl_handshake_params * const hs = ssl->handshake; mbedtls_ssl_hs_buffer * hs_buf; int ret = 0; if( hs == NULL ) return( -1 ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_load_buffered_messsage" ) ); if( ssl->state == MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC || ssl->state == MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC ) { /* Check if we have seen a ChangeCipherSpec before. * If yes, synthesize a CCS record. */ if( !hs->buffering.seen_ccs ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "CCS not seen in the current flight" ) ); ret = -1; goto exit; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "Injecting buffered CCS message" ) ); ssl->in_msgtype = MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC; ssl->in_msglen = 1; ssl->in_msg[0] = 1; /* As long as they are equal, the exact value doesn't matter. */ ssl->in_left = 0; ssl->next_record_offset = 0; hs->buffering.seen_ccs = 0; goto exit; } #if defined(MBEDTLS_DEBUG_C) /* Debug only */ { unsigned offset; for( offset = 1; offset < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++ ) { hs_buf = &hs->buffering.hs[offset]; if( hs_buf->is_valid == 1 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Future message with sequence number %u %s buffered.", hs->in_msg_seq + offset, hs_buf->is_complete ? "fully" : "partially" ) ); } } } #endif /* MBEDTLS_DEBUG_C */ /* Check if we have buffered and/or fully reassembled the * next handshake message. */ hs_buf = &hs->buffering.hs[0]; if( ( hs_buf->is_valid == 1 ) && ( hs_buf->is_complete == 1 ) ) { /* Synthesize a record containing the buffered HS message. */ size_t msg_len = ( hs_buf->data[1] << 16 ) | ( hs_buf->data[2] << 8 ) | hs_buf->data[3]; /* Double-check that we haven't accidentally buffered * a message that doesn't fit into the input buffer. */ if( msg_len + 12 > MBEDTLS_SSL_IN_CONTENT_LEN ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "Next handshake message has been buffered - load" ) ); MBEDTLS_SSL_DEBUG_BUF( 3, "Buffered handshake message (incl. header)", hs_buf->data, msg_len + 12 ); ssl->in_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE; ssl->in_hslen = msg_len + 12; ssl->in_msglen = msg_len + 12; memcpy( ssl->in_msg, hs_buf->data, ssl->in_hslen ); ret = 0; goto exit; } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Next handshake message %u not or only partially bufffered", hs->in_msg_seq ) ); } ret = -1; exit: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_load_buffered_message" ) ); return( ret ); } static int ssl_buffer_make_space( mbedtls_ssl_context *ssl, size_t desired ) { int offset; mbedtls_ssl_handshake_params * const hs = ssl->handshake; MBEDTLS_SSL_DEBUG_MSG( 2, ( "Attempt to free buffered messages to have %u bytes available", (unsigned) desired ) ); /* Get rid of future records epoch first, if such exist. */ ssl_free_buffered_record( ssl ); /* Check if we have enough space available now. */ if( desired <= ( MBEDTLS_SSL_DTLS_MAX_BUFFERING - hs->buffering.total_bytes_buffered ) ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Enough space available after freeing future epoch record" ) ); return( 0 ); } /* We don't have enough space to buffer the next expected handshake * message. Remove buffers used for future messages to gain space, * starting with the most distant one. */ for( offset = MBEDTLS_SSL_MAX_BUFFERED_HS - 1; offset >= 0; offset-- ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Free buffering slot %d to make space for reassembly of next handshake message", offset ) ); ssl_buffering_free_slot( ssl, (uint8_t) offset ); /* Check if we have enough space available now. */ if( desired <= ( MBEDTLS_SSL_DTLS_MAX_BUFFERING - hs->buffering.total_bytes_buffered ) ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Enough space available after freeing buffered HS messages" ) ); return( 0 ); } } return( -1 ); } static int ssl_buffer_message( mbedtls_ssl_context *ssl ) { int ret = 0; mbedtls_ssl_handshake_params * const hs = ssl->handshake; if( hs == NULL ) return( 0 ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_buffer_message" ) ); switch( ssl->in_msgtype ) { case MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC: MBEDTLS_SSL_DEBUG_MSG( 2, ( "Remember CCS message" ) ); hs->buffering.seen_ccs = 1; break; case MBEDTLS_SSL_MSG_HANDSHAKE: { unsigned recv_msg_seq_offset; unsigned recv_msg_seq = ( ssl->in_msg[4] << 8 ) | ssl->in_msg[5]; mbedtls_ssl_hs_buffer *hs_buf; size_t msg_len = ssl->in_hslen - 12; /* We should never receive an old handshake * message - double-check nonetheless. */ if( recv_msg_seq < ssl->handshake->in_msg_seq ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } recv_msg_seq_offset = recv_msg_seq - ssl->handshake->in_msg_seq; if( recv_msg_seq_offset >= MBEDTLS_SSL_MAX_BUFFERED_HS ) { /* Silently ignore -- message too far in the future */ MBEDTLS_SSL_DEBUG_MSG( 2, ( "Ignore future HS message with sequence number %u, " "buffering window %u - %u", recv_msg_seq, ssl->handshake->in_msg_seq, ssl->handshake->in_msg_seq + MBEDTLS_SSL_MAX_BUFFERED_HS - 1 ) ); goto exit; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering HS message with sequence number %u, offset %u ", recv_msg_seq, recv_msg_seq_offset ) ); hs_buf = &hs->buffering.hs[ recv_msg_seq_offset ]; /* Check if the buffering for this seq nr has already commenced. */ if( !hs_buf->is_valid ) { size_t reassembly_buf_sz; hs_buf->is_fragmented = ( ssl_hs_is_proper_fragment( ssl ) == 1 ); /* We copy the message back into the input buffer * after reassembly, so check that it's not too large. * This is an implementation-specific limitation * and not one from the standard, hence it is not * checked in ssl_check_hs_header(). */ if( msg_len + 12 > MBEDTLS_SSL_IN_CONTENT_LEN ) { /* Ignore message */ goto exit; } /* Check if we have enough space to buffer the message. */ if( hs->buffering.total_bytes_buffered > MBEDTLS_SSL_DTLS_MAX_BUFFERING ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } reassembly_buf_sz = ssl_get_reassembly_buffer_size( msg_len, hs_buf->is_fragmented ); if( reassembly_buf_sz > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING - hs->buffering.total_bytes_buffered ) ) { if( recv_msg_seq_offset > 0 ) { /* If we can't buffer a future message because * of space limitations -- ignore. */ MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future message of size %" MBEDTLS_PRINTF_SIZET " would exceed the compile-time limit %" MBEDTLS_PRINTF_SIZET " (already %" MBEDTLS_PRINTF_SIZET " bytes buffered) -- ignore\n", msg_len, (size_t) MBEDTLS_SSL_DTLS_MAX_BUFFERING, hs->buffering.total_bytes_buffered ) ); goto exit; } else { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future message of size %" MBEDTLS_PRINTF_SIZET " would exceed the compile-time limit %" MBEDTLS_PRINTF_SIZET " (already %" MBEDTLS_PRINTF_SIZET " bytes buffered) -- attempt to make space by freeing buffered future messages\n", msg_len, (size_t) MBEDTLS_SSL_DTLS_MAX_BUFFERING, hs->buffering.total_bytes_buffered ) ); } if( ssl_buffer_make_space( ssl, reassembly_buf_sz ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Reassembly of next message of size %" MBEDTLS_PRINTF_SIZET " (%" MBEDTLS_PRINTF_SIZET " with bitmap) would exceed" " the compile-time limit %" MBEDTLS_PRINTF_SIZET " (already %" MBEDTLS_PRINTF_SIZET " bytes buffered) -- fail\n", msg_len, reassembly_buf_sz, (size_t) MBEDTLS_SSL_DTLS_MAX_BUFFERING, hs->buffering.total_bytes_buffered ) ); ret = MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL; goto exit; } } MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %" MBEDTLS_PRINTF_SIZET, msg_len ) ); hs_buf->data = mbedtls_calloc( 1, reassembly_buf_sz ); if( hs_buf->data == NULL ) { ret = MBEDTLS_ERR_SSL_ALLOC_FAILED; goto exit; } hs_buf->data_len = reassembly_buf_sz; /* Prepare final header: copy msg_type, length and message_seq, * then add standardised fragment_offset and fragment_length */ memcpy( hs_buf->data, ssl->in_msg, 6 ); memset( hs_buf->data + 6, 0, 3 ); memcpy( hs_buf->data + 9, hs_buf->data + 1, 3 ); hs_buf->is_valid = 1; hs->buffering.total_bytes_buffered += reassembly_buf_sz; } else { /* Make sure msg_type and length are consistent */ if( memcmp( hs_buf->data, ssl->in_msg, 4 ) != 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "Fragment header mismatch - ignore" ) ); /* Ignore */ goto exit; } } if( !hs_buf->is_complete ) { size_t frag_len, frag_off; unsigned char * const msg = hs_buf->data + 12; /* * Check and copy current fragment */ /* Validation of header fields already done in * mbedtls_ssl_prepare_handshake_record(). */ frag_off = ssl_get_hs_frag_off( ssl ); frag_len = ssl_get_hs_frag_len( ssl ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "adding fragment, offset = %" MBEDTLS_PRINTF_SIZET ", length = %" MBEDTLS_PRINTF_SIZET, frag_off, frag_len ) ); memcpy( msg + frag_off, ssl->in_msg + 12, frag_len ); if( hs_buf->is_fragmented ) { unsigned char * const bitmask = msg + msg_len; ssl_bitmask_set( bitmask, frag_off, frag_len ); hs_buf->is_complete = ( ssl_bitmask_check( bitmask, msg_len ) == 0 ); } else { hs_buf->is_complete = 1; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "message %scomplete", hs_buf->is_complete ? "" : "not yet " ) ); } break; } default: /* We don't buffer other types of messages. */ break; } exit: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_buffer_message" ) ); return( ret ); } #endif /* MBEDTLS_SSL_PROTO_DTLS */ static int ssl_consume_current_message( mbedtls_ssl_context *ssl ) { /* * Consume last content-layer message and potentially * update in_msglen which keeps track of the contents' * consumption state. * * (1) Handshake messages: * Remove last handshake message, move content * and adapt in_msglen. * * (2) Alert messages: * Consume whole record content, in_msglen = 0. * * (3) Change cipher spec: * Consume whole record content, in_msglen = 0. * * (4) Application data: * Don't do anything - the record layer provides * the application data as a stream transport * and consumes through mbedtls_ssl_read only. * */ /* Case (1): Handshake messages */ if( ssl->in_hslen != 0 ) { /* Hard assertion to be sure that no application data * is in flight, as corrupting ssl->in_msglen during * ssl->in_offt != NULL is fatal. */ if( ssl->in_offt != NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } /* * Get next Handshake message in the current record */ /* Notes: * (1) in_hslen is not necessarily the size of the * current handshake content: If DTLS handshake * fragmentation is used, that's the fragment * size instead. Using the total handshake message * size here is faulty and should be changed at * some point. * (2) While it doesn't seem to cause problems, one * has to be very careful not to assume that in_hslen * is always <= in_msglen in a sensible communication. * Again, it's wrong for DTLS handshake fragmentation. * The following check is therefore mandatory, and * should not be treated as a silently corrected assertion. * Additionally, ssl->in_hslen might be arbitrarily out of * bounds after handling a DTLS message with an unexpected * sequence number, see mbedtls_ssl_prepare_handshake_record. */ if( ssl->in_hslen < ssl->in_msglen ) { ssl->in_msglen -= ssl->in_hslen; memmove( ssl->in_msg, ssl->in_msg + ssl->in_hslen, ssl->in_msglen ); MBEDTLS_SSL_DEBUG_BUF( 4, "remaining content in record", ssl->in_msg, ssl->in_msglen ); } else { ssl->in_msglen = 0; } ssl->in_hslen = 0; } /* Case (4): Application data */ else if( ssl->in_offt != NULL ) { return( 0 ); } /* Everything else (CCS & Alerts) */ else { ssl->in_msglen = 0; } return( 0 ); } static int ssl_record_is_in_progress( mbedtls_ssl_context *ssl ) { if( ssl->in_msglen > 0 ) return( 1 ); return( 0 ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) static void ssl_free_buffered_record( mbedtls_ssl_context *ssl ) { mbedtls_ssl_handshake_params * const hs = ssl->handshake; if( hs == NULL ) return; if( hs->buffering.future_record.data != NULL ) { hs->buffering.total_bytes_buffered -= hs->buffering.future_record.len; mbedtls_free( hs->buffering.future_record.data ); hs->buffering.future_record.data = NULL; } } static int ssl_load_buffered_record( mbedtls_ssl_context *ssl ) { mbedtls_ssl_handshake_params * const hs = ssl->handshake; unsigned char * rec; size_t rec_len; unsigned rec_epoch; #if defined(MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH) size_t in_buf_len = ssl->in_buf_len; #else size_t in_buf_len = MBEDTLS_SSL_IN_BUFFER_LEN; #endif if( ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM ) return( 0 ); if( hs == NULL ) return( 0 ); rec = hs->buffering.future_record.data; rec_len = hs->buffering.future_record.len; rec_epoch = hs->buffering.future_record.epoch; if( rec == NULL ) return( 0 ); /* Only consider loading future records if the * input buffer is empty. */ if( ssl_next_record_is_in_datagram( ssl ) == 1 ) return( 0 ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_load_buffered_record" ) ); if( rec_epoch != ssl->in_epoch ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffered record not from current epoch." ) ); goto exit; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "Found buffered record from current epoch - load" ) ); /* Double-check that the record is not too large */ if( rec_len > in_buf_len - (size_t)( ssl->in_hdr - ssl->in_buf ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } memcpy( ssl->in_hdr, rec, rec_len ); ssl->in_left = rec_len; ssl->next_record_offset = 0; ssl_free_buffered_record( ssl ); exit: MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_load_buffered_record" ) ); return( 0 ); } static int ssl_buffer_future_record( mbedtls_ssl_context *ssl, mbedtls_record const *rec ) { mbedtls_ssl_handshake_params * const hs = ssl->handshake; /* Don't buffer future records outside handshakes. */ if( hs == NULL ) return( 0 ); /* Only buffer handshake records (we are only interested * in Finished messages). */ if( rec->type != MBEDTLS_SSL_MSG_HANDSHAKE ) return( 0 ); /* Don't buffer more than one future epoch record. */ if( hs->buffering.future_record.data != NULL ) return( 0 ); /* Don't buffer record if there's not enough buffering space remaining. */ if( rec->buf_len > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING - hs->buffering.total_bytes_buffered ) ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future epoch record of size %" MBEDTLS_PRINTF_SIZET " would exceed the compile-time limit %" MBEDTLS_PRINTF_SIZET " (already %" MBEDTLS_PRINTF_SIZET " bytes buffered) -- ignore\n", rec->buf_len, (size_t) MBEDTLS_SSL_DTLS_MAX_BUFFERING, hs->buffering.total_bytes_buffered ) ); return( 0 ); } /* Buffer record */ MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffer record from epoch %u", ssl->in_epoch + 1U ) ); MBEDTLS_SSL_DEBUG_BUF( 3, "Buffered record", rec->buf, rec->buf_len ); /* ssl_parse_record_header() only considers records * of the next epoch as candidates for buffering. */ hs->buffering.future_record.epoch = ssl->in_epoch + 1; hs->buffering.future_record.len = rec->buf_len; hs->buffering.future_record.data = mbedtls_calloc( 1, hs->buffering.future_record.len ); if( hs->buffering.future_record.data == NULL ) { /* If we run out of RAM trying to buffer a * record from the next epoch, just ignore. */ return( 0 ); } memcpy( hs->buffering.future_record.data, rec->buf, rec->buf_len ); hs->buffering.total_bytes_buffered += rec->buf_len; return( 0 ); } #endif /* MBEDTLS_SSL_PROTO_DTLS */ static int ssl_get_next_record( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_record rec; #if defined(MBEDTLS_SSL_PROTO_DTLS) /* We might have buffered a future record; if so, * and if the epoch matches now, load it. * On success, this call will set ssl->in_left to * the length of the buffered record, so that * the calls to ssl_fetch_input() below will * essentially be no-ops. */ ret = ssl_load_buffered_record( ssl ); if( ret != 0 ) return( ret ); #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* Ensure that we have enough space available for the default form * of TLS / DTLS record headers (5 Bytes for TLS, 13 Bytes for DTLS, * with no space for CIDs counted in). */ ret = mbedtls_ssl_fetch_input( ssl, mbedtls_ssl_in_hdr_len( ssl ) ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_fetch_input", ret ); return( ret ); } ret = ssl_parse_record_header( ssl, ssl->in_hdr, ssl->in_left, &rec ); if( ret != 0 ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { if( ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE ) { ret = ssl_buffer_future_record( ssl, &rec ); if( ret != 0 ) return( ret ); /* Fall through to handling of unexpected records */ ret = MBEDTLS_ERR_SSL_UNEXPECTED_RECORD; } if( ret == MBEDTLS_ERR_SSL_UNEXPECTED_RECORD ) { #if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) && defined(MBEDTLS_SSL_SRV_C) /* Reset in pointers to default state for TLS/DTLS records, * assuming no CID and no offset between record content and * record plaintext. */ mbedtls_ssl_update_in_pointers( ssl ); /* Setup internal message pointers from record structure. */ ssl->in_msgtype = rec.type; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) ssl->in_len = ssl->in_cid + rec.cid_len; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->in_iv = ssl->in_msg = ssl->in_len + 2; ssl->in_msglen = rec.data_len; ret = ssl_check_client_reconnect( ssl ); MBEDTLS_SSL_DEBUG_RET( 2, "ssl_check_client_reconnect", ret ); if( ret != 0 ) return( ret ); #endif /* Skip unexpected record (but not whole datagram) */ ssl->next_record_offset = rec.buf_len; MBEDTLS_SSL_DEBUG_MSG( 1, ( "discarding unexpected record " "(header)" ) ); } else { /* Skip invalid record and the rest of the datagram */ ssl->next_record_offset = 0; ssl->in_left = 0; MBEDTLS_SSL_DEBUG_MSG( 1, ( "discarding invalid record " "(header)" ) ); } /* Get next record */ return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING ); } else #endif { return( ret ); } } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { /* Remember offset of next record within datagram. */ ssl->next_record_offset = rec.buf_len; if( ssl->next_record_offset < ssl->in_left ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "more than one record within datagram" ) ); } } else #endif { /* * Fetch record contents from underlying transport. */ ret = mbedtls_ssl_fetch_input( ssl, rec.buf_len ); if( ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_fetch_input", ret ); return( ret ); } ssl->in_left = 0; } /* * Decrypt record contents. */ if( ( ret = ssl_prepare_record_content( ssl, &rec ) ) != 0 ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { /* Silently discard invalid records */ if( ret == MBEDTLS_ERR_SSL_INVALID_MAC ) { /* Except when waiting for Finished as a bad mac here * probably means something went wrong in the handshake * (eg wrong psk used, mitm downgrade attempt, etc.) */ if( ssl->state == MBEDTLS_SSL_CLIENT_FINISHED || ssl->state == MBEDTLS_SSL_SERVER_FINISHED ) { #if defined(MBEDTLS_SSL_ALL_ALERT_MESSAGES) if( ret == MBEDTLS_ERR_SSL_INVALID_MAC ) { mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, MBEDTLS_SSL_ALERT_MSG_BAD_RECORD_MAC ); } #endif return( ret ); } if( ssl->conf->badmac_limit != 0 && ++ssl->badmac_seen >= ssl->conf->badmac_limit ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "too many records with bad MAC" ) ); return( MBEDTLS_ERR_SSL_INVALID_MAC ); } /* As above, invalid records cause * dismissal of the whole datagram. */ ssl->next_record_offset = 0; ssl->in_left = 0; MBEDTLS_SSL_DEBUG_MSG( 1, ( "discarding invalid record (mac)" ) ); return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING ); } return( ret ); } else #endif { /* Error out (and send alert) on invalid records */ #if defined(MBEDTLS_SSL_ALL_ALERT_MESSAGES) if( ret == MBEDTLS_ERR_SSL_INVALID_MAC ) { mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, MBEDTLS_SSL_ALERT_MSG_BAD_RECORD_MAC ); } #endif return( ret ); } } /* Reset in pointers to default state for TLS/DTLS records, * assuming no CID and no offset between record content and * record plaintext. */ mbedtls_ssl_update_in_pointers( ssl ); #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) ssl->in_len = ssl->in_cid + rec.cid_len; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->in_iv = ssl->in_len + 2; /* The record content type may change during decryption, * so re-read it. */ ssl->in_msgtype = rec.type; /* Also update the input buffer, because unfortunately * the server-side ssl_parse_client_hello() reparses the * record header when receiving a ClientHello initiating * a renegotiation. */ ssl->in_hdr[0] = rec.type; ssl->in_msg = rec.buf + rec.data_offset; ssl->in_msglen = rec.data_len; ssl->in_len[0] = (unsigned char)( rec.data_len >> 8 ); ssl->in_len[1] = (unsigned char)( rec.data_len ); return( 0 ); } int mbedtls_ssl_handle_message_type( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; /* * Handle particular types of records */ if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) { if( ( ret = mbedtls_ssl_prepare_handshake_record( ssl ) ) != 0 ) { return( ret ); } } if( ssl->in_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC ) { if( ssl->in_msglen != 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid CCS message, len: %" MBEDTLS_PRINTF_SIZET, ssl->in_msglen ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } if( ssl->in_msg[0] != 1 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid CCS message, content: %02x", ssl->in_msg[0] ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl->state != MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC && ssl->state != MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC ) { if( ssl->handshake == NULL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping ChangeCipherSpec outside handshake" ) ); return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD ); } MBEDTLS_SSL_DEBUG_MSG( 1, ( "received out-of-order ChangeCipherSpec - remember" ) ); return( MBEDTLS_ERR_SSL_EARLY_MESSAGE ); } #endif } if( ssl->in_msgtype == MBEDTLS_SSL_MSG_ALERT ) { if( ssl->in_msglen != 2 ) { /* Note: Standard allows for more than one 2 byte alert to be packed in a single message, but Mbed TLS doesn't currently support this. */ MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid alert message, len: %" MBEDTLS_PRINTF_SIZET, ssl->in_msglen ) ); return( MBEDTLS_ERR_SSL_INVALID_RECORD ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "got an alert message, type: [%u:%u]", ssl->in_msg[0], ssl->in_msg[1] ) ); /* * Ignore non-fatal alerts, except close_notify and no_renegotiation */ if( ssl->in_msg[0] == MBEDTLS_SSL_ALERT_LEVEL_FATAL ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "is a fatal alert message (msg %d)", ssl->in_msg[1] ) ); return( MBEDTLS_ERR_SSL_FATAL_ALERT_MESSAGE ); } if( ssl->in_msg[0] == MBEDTLS_SSL_ALERT_LEVEL_WARNING && ssl->in_msg[1] == MBEDTLS_SSL_ALERT_MSG_CLOSE_NOTIFY ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "is a close notify message" ) ); return( MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY ); } #if defined(MBEDTLS_SSL_RENEGOTIATION_ENABLED) if( ssl->in_msg[0] == MBEDTLS_SSL_ALERT_LEVEL_WARNING && ssl->in_msg[1] == MBEDTLS_SSL_ALERT_MSG_NO_RENEGOTIATION ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "is a no renegotiation alert" ) ); /* Will be handled when trying to parse ServerHello */ return( 0 ); } #endif /* Silently ignore: fetch new message */ return MBEDTLS_ERR_SSL_NON_FATAL; } #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { /* Drop unexpected ApplicationData records, * except at the beginning of renegotiations */ if( ssl->in_msgtype == MBEDTLS_SSL_MSG_APPLICATION_DATA && ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER #if defined(MBEDTLS_SSL_RENEGOTIATION) && ! ( ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_IN_PROGRESS && ssl->state == MBEDTLS_SSL_SERVER_HELLO ) #endif ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping unexpected ApplicationData" ) ); return( MBEDTLS_ERR_SSL_NON_FATAL ); } if( ssl->handshake != NULL && ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER ) { mbedtls_ssl_handshake_wrapup_free_hs_transform( ssl ); } } #endif /* MBEDTLS_SSL_PROTO_DTLS */ return( 0 ); } int mbedtls_ssl_send_fatal_handshake_failure( mbedtls_ssl_context *ssl ) { return( mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE ) ); } int mbedtls_ssl_send_alert_message( mbedtls_ssl_context *ssl, unsigned char level, unsigned char message ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; if( ssl == NULL || ssl->conf == NULL ) return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> send alert message" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "send alert level=%u message=%u", level, message )); ssl->out_msgtype = MBEDTLS_SSL_MSG_ALERT; ssl->out_msglen = 2; ssl->out_msg[0] = level; ssl->out_msg[1] = message; if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret ); return( ret ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= send alert message" ) ); return( 0 ); } int mbedtls_ssl_write_change_cipher_spec( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write change cipher spec" ) ); ssl->out_msgtype = MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC; ssl->out_msglen = 1; ssl->out_msg[0] = 1; ssl->state++; if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret ); return( ret ); } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write change cipher spec" ) ); return( 0 ); } int mbedtls_ssl_parse_change_cipher_spec( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse change cipher spec" ) ); if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret ); return( ret ); } if( ssl->in_msgtype != MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad change cipher spec message" ) ); mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE ); return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); } /* CCS records are only accepted if they have length 1 and content '1', * so we don't need to check this here. */ /* * Switch to our negotiated transform and session parameters for inbound * data. */ MBEDTLS_SSL_DEBUG_MSG( 3, ( "switching to new transform spec for inbound data" ) ); ssl->transform_in = ssl->transform_negotiate; ssl->session_in = ssl->session_negotiate; #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY) mbedtls_ssl_dtls_replay_reset( ssl ); #endif /* Increment epoch */ if( ++ssl->in_epoch == 0 ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "DTLS epoch would wrap" ) ); /* This is highly unlikely to happen for legitimate reasons, so treat it as an attack and don't send an alert. */ return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING ); } } else #endif /* MBEDTLS_SSL_PROTO_DTLS */ memset( ssl->in_ctr, 0, 8 ); mbedtls_ssl_update_in_pointers( ssl ); ssl->state++; MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse change cipher spec" ) ); return( 0 ); } /* Once ssl->out_hdr as the address of the beginning of the * next outgoing record is set, deduce the other pointers. * * Note: For TLS, we save the implicit record sequence number * (entering MAC computation) in the 8 bytes before ssl->out_hdr, * and the caller has to make sure there's space for this. */ static size_t ssl_transform_get_explicit_iv_len( mbedtls_ssl_transform const *transform ) { if( transform->minor_ver < MBEDTLS_SSL_MINOR_VERSION_3 ) return( 0 ); return( transform->ivlen - transform->fixed_ivlen ); } void mbedtls_ssl_update_out_pointers( mbedtls_ssl_context *ssl, mbedtls_ssl_transform *transform ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { ssl->out_ctr = ssl->out_hdr + 3; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) ssl->out_cid = ssl->out_ctr + 8; ssl->out_len = ssl->out_cid; if( transform != NULL ) ssl->out_len += transform->out_cid_len; #else /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->out_len = ssl->out_ctr + 8; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->out_iv = ssl->out_len + 2; } else #endif { ssl->out_len = ssl->out_hdr + 3; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) ssl->out_cid = ssl->out_len; #endif ssl->out_iv = ssl->out_hdr + 5; } ssl->out_msg = ssl->out_iv; /* Adjust out_msg to make space for explicit IV, if used. */ if( transform != NULL ) ssl->out_msg += ssl_transform_get_explicit_iv_len( transform ); } /* Once ssl->in_hdr as the address of the beginning of the * next incoming record is set, deduce the other pointers. * * Note: For TLS, we save the implicit record sequence number * (entering MAC computation) in the 8 bytes before ssl->in_hdr, * and the caller has to make sure there's space for this. */ void mbedtls_ssl_update_in_pointers( mbedtls_ssl_context *ssl ) { /* This function sets the pointers to match the case * of unprotected TLS/DTLS records, with both ssl->in_iv * and ssl->in_msg pointing to the beginning of the record * content. * * When decrypting a protected record, ssl->in_msg * will be shifted to point to the beginning of the * record plaintext. */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { /* This sets the header pointers to match records * without CID. When we receive a record containing * a CID, the fields are shifted accordingly in * ssl_parse_record_header(). */ ssl->in_ctr = ssl->in_hdr + 3; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) ssl->in_cid = ssl->in_ctr + 8; ssl->in_len = ssl->in_cid; /* Default: no CID */ #else /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->in_len = ssl->in_ctr + 8; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ ssl->in_iv = ssl->in_len + 2; } else #endif { ssl->in_ctr = ssl->in_hdr - 8; ssl->in_len = ssl->in_hdr + 3; #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) ssl->in_cid = ssl->in_len; #endif ssl->in_iv = ssl->in_hdr + 5; } /* This will be adjusted at record decryption time. */ ssl->in_msg = ssl->in_iv; } /* * Setup an SSL context */ void mbedtls_ssl_reset_in_out_pointers( mbedtls_ssl_context *ssl ) { /* Set the incoming and outgoing record pointers. */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { ssl->out_hdr = ssl->out_buf; ssl->in_hdr = ssl->in_buf; } else #endif /* MBEDTLS_SSL_PROTO_DTLS */ { ssl->out_ctr = ssl->out_buf; ssl->out_hdr = ssl->out_buf + 8; ssl->in_hdr = ssl->in_buf + 8; } /* Derive other internal pointers. */ mbedtls_ssl_update_out_pointers( ssl, NULL /* no transform enabled */ ); mbedtls_ssl_update_in_pointers ( ssl ); } /* * SSL get accessors */ size_t mbedtls_ssl_get_bytes_avail( const mbedtls_ssl_context *ssl ) { return( ssl->in_offt == NULL ? 0 : ssl->in_msglen ); } int mbedtls_ssl_check_pending( const mbedtls_ssl_context *ssl ) { /* * Case A: We're currently holding back * a message for further processing. */ if( ssl->keep_current_message == 1 ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: record held back for processing" ) ); return( 1 ); } /* * Case B: Further records are pending in the current datagram. */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl->in_left > ssl->next_record_offset ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: more records within current datagram" ) ); return( 1 ); } #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* * Case C: A handshake message is being processed. */ if( ssl->in_hslen > 0 && ssl->in_hslen < ssl->in_msglen ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: more handshake messages within current record" ) ); return( 1 ); } /* * Case D: An application data message is being processed */ if( ssl->in_offt != NULL ) { MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: application data record is being processed" ) ); return( 1 ); } /* * In all other cases, the rest of the message can be dropped. * As in ssl_get_next_record, this needs to be adapted if * we implement support for multiple alerts in single records. */ MBEDTLS_SSL_DEBUG_MSG( 3, ( "ssl_check_pending: nothing pending" ) ); return( 0 ); } int mbedtls_ssl_get_record_expansion( const mbedtls_ssl_context *ssl ) { size_t transform_expansion = 0; const mbedtls_ssl_transform *transform = ssl->transform_out; unsigned block_size; size_t out_hdr_len = mbedtls_ssl_out_hdr_len( ssl ); if( transform == NULL ) return( (int) out_hdr_len ); switch( mbedtls_cipher_get_cipher_mode( &transform->cipher_ctx_enc ) ) { case MBEDTLS_MODE_GCM: case MBEDTLS_MODE_CCM: case MBEDTLS_MODE_CHACHAPOLY: case MBEDTLS_MODE_STREAM: transform_expansion = transform->minlen; break; case MBEDTLS_MODE_CBC: block_size = mbedtls_cipher_get_block_size( &transform->cipher_ctx_enc ); /* Expansion due to the addition of the MAC. */ transform_expansion += transform->maclen; /* Expansion due to the addition of CBC padding; * Theoretically up to 256 bytes, but we never use * more than the block size of the underlying cipher. */ transform_expansion += block_size; /* For TLS 1.2 or higher, an explicit IV is added * after the record header. */ #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_3 ) transform_expansion += block_size; #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ break; default: MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID) if( transform->out_cid_len != 0 ) transform_expansion += MBEDTLS_SSL_MAX_CID_EXPANSION; #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */ return( (int)( out_hdr_len + transform_expansion ) ); } #if defined(MBEDTLS_SSL_RENEGOTIATION) /* * Check record counters and renegotiate if they're above the limit. */ static int ssl_check_ctr_renegotiate( mbedtls_ssl_context *ssl ) { size_t ep_len = mbedtls_ssl_ep_len( ssl ); int in_ctr_cmp; int out_ctr_cmp; if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER || ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING || ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED ) { return( 0 ); } in_ctr_cmp = memcmp( ssl->in_ctr + ep_len, ssl->conf->renego_period + ep_len, 8 - ep_len ); out_ctr_cmp = memcmp( ssl->cur_out_ctr + ep_len, ssl->conf->renego_period + ep_len, 8 - ep_len ); if( in_ctr_cmp <= 0 && out_ctr_cmp <= 0 ) { return( 0 ); } MBEDTLS_SSL_DEBUG_MSG( 1, ( "record counter limit reached: renegotiate" ) ); return( mbedtls_ssl_renegotiate( ssl ) ); } #endif /* MBEDTLS_SSL_RENEGOTIATION */ /* This function is called from mbedtls_ssl_read() when a handshake message is * received after the initial handshake. In this context, handshake messages * may only be sent for the purpose of initiating renegotiations. * * This function is introduced as a separate helper since the handling * of post-handshake handshake messages changes significantly in TLS 1.3, * and having a helper function allows to distinguish between TLS <= 1.2 and * TLS 1.3 in the future without bloating the logic of mbedtls_ssl_read(). */ static int ssl_handle_hs_message_post_handshake( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; /* * - For client-side, expect SERVER_HELLO_REQUEST. * - For server-side, expect CLIENT_HELLO. * - Fail (TLS) or silently drop record (DTLS) in other cases. */ #if defined(MBEDTLS_SSL_CLI_C) if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT && ( ssl->in_msg[0] != MBEDTLS_SSL_HS_HELLO_REQUEST || ssl->in_hslen != mbedtls_ssl_hs_hdr_len( ssl ) ) ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake received (not HelloRequest)" ) ); /* With DTLS, drop the packet (probably from last handshake) */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { return( 0 ); } #endif return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); } #endif /* MBEDTLS_SSL_CLI_C */ #if defined(MBEDTLS_SSL_SRV_C) if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER && ssl->in_msg[0] != MBEDTLS_SSL_HS_CLIENT_HELLO ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake received (not ClientHello)" ) ); /* With DTLS, drop the packet (probably from last handshake) */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { return( 0 ); } #endif return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); } #endif /* MBEDTLS_SSL_SRV_C */ #if defined(MBEDTLS_SSL_RENEGOTIATION) /* Determine whether renegotiation attempt should be accepted */ if( ! ( ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED || ( ssl->secure_renegotiation == MBEDTLS_SSL_LEGACY_RENEGOTIATION && ssl->conf->allow_legacy_renegotiation == MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION ) ) ) { /* * Accept renegotiation request */ /* DTLS clients need to know renego is server-initiated */ #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM && ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT ) { ssl->renego_status = MBEDTLS_SSL_RENEGOTIATION_PENDING; } #endif ret = mbedtls_ssl_start_renegotiation( ssl ); if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO && ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_start_renegotiation", ret ); return( ret ); } } else #endif /* MBEDTLS_SSL_RENEGOTIATION */ { /* * Refuse renegotiation */ MBEDTLS_SSL_DEBUG_MSG( 3, ( "refusing renegotiation, sending alert" ) ); #if defined(MBEDTLS_SSL_PROTO_TLS1_2) if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 ) { if( ( ret = mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_WARNING, MBEDTLS_SSL_ALERT_MSG_NO_RENEGOTIATION ) ) != 0 ) { return( ret ); } } else #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */ { MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) ); return( MBEDTLS_ERR_SSL_INTERNAL_ERROR ); } } return( 0 ); } /* * Receive application data decrypted from the SSL layer */ int mbedtls_ssl_read( mbedtls_ssl_context *ssl, unsigned char *buf, size_t len ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t n; if( ssl == NULL || ssl->conf == NULL ) return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> read" ) ); #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) return( ret ); if( ssl->handshake != NULL && ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING ) { if( ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 ) return( ret ); } } #endif /* * Check if renegotiation is necessary and/or handshake is * in process. If yes, perform/continue, and fall through * if an unexpected packet is received while the client * is waiting for the ServerHello. * * (There is no equivalent to the last condition on * the server-side as it is not treated as within * a handshake while waiting for the ClientHello * after a renegotiation request.) */ #if defined(MBEDTLS_SSL_RENEGOTIATION) ret = ssl_check_ctr_renegotiate( ssl ); if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO && ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_check_ctr_renegotiate", ret ); return( ret ); } #endif if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER ) { ret = mbedtls_ssl_handshake( ssl ); if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO && ret != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_handshake", ret ); return( ret ); } } /* Loop as long as no application data record is available */ while( ssl->in_offt == NULL ) { /* Start timer if not already running */ if( ssl->f_get_timer != NULL && ssl->f_get_timer( ssl->p_timer ) == -1 ) { mbedtls_ssl_set_timer( ssl, ssl->conf->read_timeout ); } if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 ) { if( ret == MBEDTLS_ERR_SSL_CONN_EOF ) return( 0 ); MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret ); return( ret ); } if( ssl->in_msglen == 0 && ssl->in_msgtype == MBEDTLS_SSL_MSG_APPLICATION_DATA ) { /* * OpenSSL sends empty messages to randomize the IV */ if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 ) { if( ret == MBEDTLS_ERR_SSL_CONN_EOF ) return( 0 ); MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret ); return( ret ); } } if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) { ret = ssl_handle_hs_message_post_handshake( ssl ); if( ret != 0) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_handle_hs_message_post_handshake", ret ); return( ret ); } /* At this point, we don't know whether the renegotiation triggered * by the post-handshake message has been completed or not. The cases * to consider are the following: * 1) The renegotiation is complete. In this case, no new record * has been read yet. * 2) The renegotiation is incomplete because the client received * an application data record while awaiting the ServerHello. * 3) The renegotiation is incomplete because the client received * a non-handshake, non-application data message while awaiting * the ServerHello. * * In each of these cases, looping will be the proper action: * - For 1), the next iteration will read a new record and check * if it's application data. * - For 2), the loop condition isn't satisfied as application data * is present, hence continue is the same as break * - For 3), the loop condition is satisfied and read_record * will re-deliver the message that was held back by the client * when expecting the ServerHello. */ continue; } #if defined(MBEDTLS_SSL_RENEGOTIATION) else if( ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING ) { if( ssl->conf->renego_max_records >= 0 ) { if( ++ssl->renego_records_seen > ssl->conf->renego_max_records ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "renegotiation requested, " "but not honored by client" ) ); return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); } } } #endif /* MBEDTLS_SSL_RENEGOTIATION */ /* Fatal and closure alerts handled by mbedtls_ssl_read_record() */ if( ssl->in_msgtype == MBEDTLS_SSL_MSG_ALERT ) { MBEDTLS_SSL_DEBUG_MSG( 2, ( "ignoring non-fatal non-closure alert" ) ); return( MBEDTLS_ERR_SSL_WANT_READ ); } if( ssl->in_msgtype != MBEDTLS_SSL_MSG_APPLICATION_DATA ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad application data message" ) ); return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE ); } ssl->in_offt = ssl->in_msg; /* We're going to return something now, cancel timer, * except if handshake (renegotiation) is in progress */ if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER ) mbedtls_ssl_set_timer( ssl, 0 ); #if defined(MBEDTLS_SSL_PROTO_DTLS) /* If we requested renego but received AppData, resend HelloRequest. * Do it now, after setting in_offt, to avoid taking this branch * again if ssl_write_hello_request() returns WANT_WRITE */ #if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_RENEGOTIATION) if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER && ssl->renego_status == MBEDTLS_SSL_RENEGOTIATION_PENDING ) { if( ( ret = mbedtls_ssl_resend_hello_request( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_resend_hello_request", ret ); return( ret ); } } #endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_RENEGOTIATION */ #endif /* MBEDTLS_SSL_PROTO_DTLS */ } n = ( len < ssl->in_msglen ) ? len : ssl->in_msglen; memcpy( buf, ssl->in_offt, n ); ssl->in_msglen -= n; /* Zeroising the plaintext buffer to erase unused application data from the memory. */ mbedtls_platform_zeroize( ssl->in_offt, n ); if( ssl->in_msglen == 0 ) { /* all bytes consumed */ ssl->in_offt = NULL; ssl->keep_current_message = 0; } else { /* more data available */ ssl->in_offt += n; } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= read" ) ); return( (int) n ); } /* * Send application data to be encrypted by the SSL layer, taking care of max * fragment length and buffer size. * * According to RFC 5246 Section 6.2.1: * * Zero-length fragments of Application data MAY be sent as they are * potentially useful as a traffic analysis countermeasure. * * Therefore, it is possible that the input message length is 0 and the * corresponding return code is 0 on success. */ static int ssl_write_real( mbedtls_ssl_context *ssl, const unsigned char *buf, size_t len ) { int ret = mbedtls_ssl_get_max_out_record_payload( ssl ); const size_t max_len = (size_t) ret; if( ret < 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_get_max_out_record_payload", ret ); return( ret ); } if( len > max_len ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { MBEDTLS_SSL_DEBUG_MSG( 1, ( "fragment larger than the (negotiated) " "maximum fragment length: %" MBEDTLS_PRINTF_SIZET " > %" MBEDTLS_PRINTF_SIZET, len, max_len ) ); return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); } else #endif len = max_len; } if( ssl->out_left != 0 ) { /* * The user has previously tried to send the data and * MBEDTLS_ERR_SSL_WANT_WRITE or the message was only partially * written. In this case, we expect the high-level write function * (e.g. mbedtls_ssl_write()) to be called with the same parameters */ if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flush_output", ret ); return( ret ); } } else { /* * The user is trying to send a message the first time, so we need to * copy the data into the internal buffers and setup the data structure * to keep track of partial writes */ ssl->out_msglen = len; ssl->out_msgtype = MBEDTLS_SSL_MSG_APPLICATION_DATA; memcpy( ssl->out_msg, buf, len ); if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret ); return( ret ); } } return( (int) len ); } /* * Write application data (public-facing wrapper) */ int mbedtls_ssl_write( mbedtls_ssl_context *ssl, const unsigned char *buf, size_t len ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write" ) ); if( ssl == NULL || ssl->conf == NULL ) return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); #if defined(MBEDTLS_SSL_RENEGOTIATION) if( ( ret = ssl_check_ctr_renegotiate( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_check_ctr_renegotiate", ret ); return( ret ); } #endif if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER ) { if( ( ret = mbedtls_ssl_handshake( ssl ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_handshake", ret ); return( ret ); } } ret = ssl_write_real( ssl, buf, len ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write" ) ); return( ret ); } /* * Notify the peer that the connection is being closed */ int mbedtls_ssl_close_notify( mbedtls_ssl_context *ssl ) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; if( ssl == NULL || ssl->conf == NULL ) return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write close notify" ) ); if( ssl->out_left != 0 ) return( mbedtls_ssl_flush_output( ssl ) ); if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER ) { if( ( ret = mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_WARNING, MBEDTLS_SSL_ALERT_MSG_CLOSE_NOTIFY ) ) != 0 ) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_send_alert_message", ret ); return( ret ); } } MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write close notify" ) ); return( 0 ); } void mbedtls_ssl_transform_free( mbedtls_ssl_transform *transform ) { if( transform == NULL ) return; mbedtls_cipher_free( &transform->cipher_ctx_enc ); mbedtls_cipher_free( &transform->cipher_ctx_dec ); #if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) mbedtls_md_free( &transform->md_ctx_enc ); mbedtls_md_free( &transform->md_ctx_dec ); #endif mbedtls_platform_zeroize( transform, sizeof( mbedtls_ssl_transform ) ); } #if defined(MBEDTLS_SSL_PROTO_DTLS) void mbedtls_ssl_buffering_free( mbedtls_ssl_context *ssl ) { unsigned offset; mbedtls_ssl_handshake_params * const hs = ssl->handshake; if( hs == NULL ) return; ssl_free_buffered_record( ssl ); for( offset = 0; offset < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++ ) ssl_buffering_free_slot( ssl, offset ); } static void ssl_buffering_free_slot( mbedtls_ssl_context *ssl, uint8_t slot ) { mbedtls_ssl_handshake_params * const hs = ssl->handshake; mbedtls_ssl_hs_buffer * const hs_buf = &hs->buffering.hs[slot]; if( slot >= MBEDTLS_SSL_MAX_BUFFERED_HS ) return; if( hs_buf->is_valid == 1 ) { hs->buffering.total_bytes_buffered -= hs_buf->data_len; mbedtls_platform_zeroize( hs_buf->data, hs_buf->data_len ); mbedtls_free( hs_buf->data ); memset( hs_buf, 0, sizeof( mbedtls_ssl_hs_buffer ) ); } } #endif /* MBEDTLS_SSL_PROTO_DTLS */ /* * Convert version numbers to/from wire format * and, for DTLS, to/from TLS equivalent. * * For TLS this is the identity. * For DTLS, use 1's complement (v -> 255 - v, and then map as follows: * 1.0 <-> 3.2 (DTLS 1.0 is based on TLS 1.1) * 1.x <-> 3.x+1 for x != 0 (DTLS 1.2 based on TLS 1.2) */ void mbedtls_ssl_write_version( int major, int minor, int transport, unsigned char ver[2] ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) if( transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { if( minor == MBEDTLS_SSL_MINOR_VERSION_2 ) --minor; /* DTLS 1.0 stored as TLS 1.1 internally */ ver[0] = (unsigned char)( 255 - ( major - 2 ) ); ver[1] = (unsigned char)( 255 - ( minor - 1 ) ); } else #else ((void) transport); #endif { ver[0] = (unsigned char) major; ver[1] = (unsigned char) minor; } } void mbedtls_ssl_read_version( int *major, int *minor, int transport, const unsigned char ver[2] ) { #if defined(MBEDTLS_SSL_PROTO_DTLS) if( transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM ) { *major = 255 - ver[0] + 2; *minor = 255 - ver[1] + 1; if( *minor == MBEDTLS_SSL_MINOR_VERSION_1 ) ++*minor; /* DTLS 1.0 stored as TLS 1.1 internally */ } else #else ((void) transport); #endif { *major = ver[0]; *minor = ver[1]; } } #endif /* MBEDTLS_SSL_TLS_C */