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mbedtls/library/ssl_ticket.c
Simon Butcher b5b6af2663 Puts platform time abstraction into its own header 
Separates platform time abstraction into it's own header from the
general platform abstraction as both depend on different build options.
(MBEDTLS_PLATFORM_C vs MBEDTLS_HAVE_TIME)
2016-07-13 14:46:18 +01:00

490 lines
13 KiB
C
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/*
* TLS server tickets callbacks implementation
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* 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.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_SSL_TICKET_C)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
#include "mbedtls/ssl_ticket.h"
#include <string.h>
/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
/*
* Initialze context
*/
void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
{
memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
}
#define MAX_KEY_BYTES 32 /* 256 bits */
/*
* Generate/update a key
*/
static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
unsigned char index )
{
int ret;
unsigned char buf[MAX_KEY_BYTES];
mbedtls_ssl_ticket_key *key = ctx->keys + index;
#if defined(MBEDTLS_HAVE_TIME)
key->generation_time = (uint32_t) mbedtls_time( NULL );
#endif
if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 )
return( ret );
if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 )
return( ret );
/* With GCM and CCM, same context can encrypt & decrypt */
ret = mbedtls_cipher_setkey( &key->ctx, buf,
mbedtls_cipher_get_key_bitlen( &key->ctx ),
MBEDTLS_ENCRYPT );
mbedtls_zeroize( buf, sizeof( buf ) );
return( ret );
}
/*
* Rotate/generate keys if necessary
*/
static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
{
#if !defined(MBEDTLS_HAVE_TIME)
((void) ctx);
#else
if( ctx->ticket_lifetime != 0 )
{
uint32_t current_time = (uint32_t) mbedtls_time( NULL );
uint32_t key_time = ctx->keys[ctx->active].generation_time;
if( current_time > key_time &&
current_time - key_time < ctx->ticket_lifetime )
{
return( 0 );
}
ctx->active = 1 - ctx->active;
return( ssl_ticket_gen_key( ctx, ctx->active ) );
}
else
#endif /* MBEDTLS_HAVE_TIME */
return( 0 );
}
/*
* Setup context for actual use
*/
int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
mbedtls_cipher_type_t cipher,
uint32_t lifetime )
{
int ret;
const mbedtls_cipher_info_t *cipher_info;
ctx->f_rng = f_rng;
ctx->p_rng = p_rng;
ctx->ticket_lifetime = lifetime;
cipher_info = mbedtls_cipher_info_from_type( cipher);
if( cipher_info == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( cipher_info->mode != MBEDTLS_MODE_GCM &&
cipher_info->mode != MBEDTLS_MODE_CCM )
{
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
if( cipher_info->key_bitlen > 8 * MAX_KEY_BYTES )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 ||
( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 )
{
return( ret );
}
if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 ||
( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 )
{
return( ret );
}
return( 0 );
}
/*
* Serialize a session in the following format:
* 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session)
* n . n+2 peer_cert length = m (0 if no certificate)
* n+3 . n+2+m peer cert ASN.1
*/
static int ssl_save_session( const mbedtls_ssl_session *session,
unsigned char *buf, size_t buf_len,
size_t *olen )
{
unsigned char *p = buf;
size_t left = buf_len;
#if defined(MBEDTLS_X509_CRT_PARSE_C)
size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( left < sizeof( mbedtls_ssl_session ) )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
memcpy( p, session, sizeof( mbedtls_ssl_session ) );
p += sizeof( mbedtls_ssl_session );
left -= sizeof( mbedtls_ssl_session );
#if defined(MBEDTLS_X509_CRT_PARSE_C)
if( session->peer_cert == NULL )
cert_len = 0;
else
cert_len = session->peer_cert->raw.len;
if( left < 3 + cert_len )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
*p++ = (unsigned char)( cert_len >> 16 & 0xFF );
*p++ = (unsigned char)( cert_len >> 8 & 0xFF );
*p++ = (unsigned char)( cert_len & 0xFF );
if( session->peer_cert != NULL )
memcpy( p, session->peer_cert->raw.p, cert_len );
p += cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */
*olen = p - buf;
return( 0 );
}
/*
* Unserialise session, see ssl_save_session()
*/
static int ssl_load_session( mbedtls_ssl_session *session,
const unsigned char *buf, size_t len )
{
const unsigned char *p = buf;
const unsigned char * const end = buf + len;
#if defined(MBEDTLS_X509_CRT_PARSE_C)
size_t cert_len;
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( p + sizeof( mbedtls_ssl_session ) > end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
memcpy( session, p, sizeof( mbedtls_ssl_session ) );
p += sizeof( mbedtls_ssl_session );
#if defined(MBEDTLS_X509_CRT_PARSE_C)
if( p + 3 > end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
p += 3;
if( cert_len == 0 )
{
session->peer_cert = NULL;
}
else
{
int ret;
if( p + cert_len > end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
if( session->peer_cert == NULL )
return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
mbedtls_x509_crt_init( session->peer_cert );
if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
p, cert_len ) ) != 0 )
{
mbedtls_x509_crt_free( session->peer_cert );
mbedtls_free( session->peer_cert );
session->peer_cert = NULL;
return( ret );
}
p += cert_len;
}
#endif /* MBEDTLS_X509_CRT_PARSE_C */
if( p != end )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
return( 0 );
}
/*
* Create session ticket, with the following structure:
*
* struct {
* opaque key_name[4];
* opaque iv[12];
* opaque encrypted_state<0..2^16-1>;
* opaque tag[16];
* } ticket;
*
* The key_name, iv, and length of encrypted_state are the additional
* authenticated data.
*/
int mbedtls_ssl_ticket_write( void *p_ticket,
const mbedtls_ssl_session *session,
unsigned char *start,
const unsigned char *end,
size_t *tlen,
uint32_t *ticket_lifetime )
{
int ret;
mbedtls_ssl_ticket_context *ctx = p_ticket;
mbedtls_ssl_ticket_key *key;
unsigned char *key_name = start;
unsigned char *iv = start + 4;
unsigned char *state_len_bytes = iv + 12;
unsigned char *state = state_len_bytes + 2;
unsigned char *tag;
size_t clear_len, ciph_len;
*tlen = 0;
if( ctx == NULL || ctx->f_rng == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
/* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
* in addition to session itself, that will be checked when writing it. */
if( end - start < 4 + 12 + 2 + 16 )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
goto cleanup;
key = &ctx->keys[ctx->active];
*ticket_lifetime = ctx->ticket_lifetime;
memcpy( key_name, key->name, 4 );
if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
goto cleanup;
/* Dump session state */
if( ( ret = ssl_save_session( session,
state, end - state, &clear_len ) ) != 0 ||
(unsigned long) clear_len > 65535 )
{
goto cleanup;
}
state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
state_len_bytes[1] = ( clear_len ) & 0xff;
/* Encrypt and authenticate */
tag = state + clear_len;
if( ( ret = mbedtls_cipher_auth_encrypt( &key->ctx,
iv, 12, key_name, 4 + 12 + 2,
state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 )
{
goto cleanup;
}
if( ciph_len != clear_len )
{
ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
goto cleanup;
}
*tlen = 4 + 12 + 2 + 16 + ciph_len;
cleanup:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Select key based on name
*/
static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
mbedtls_ssl_ticket_context *ctx,
const unsigned char name[4] )
{
unsigned char i;
for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
return( &ctx->keys[i] );
return( NULL );
}
/*
* Load session ticket (see mbedtls_ssl_ticket_write for structure)
*/
int mbedtls_ssl_ticket_parse( void *p_ticket,
mbedtls_ssl_session *session,
unsigned char *buf,
size_t len )
{
int ret;
mbedtls_ssl_ticket_context *ctx = p_ticket;
mbedtls_ssl_ticket_key *key;
unsigned char *key_name = buf;
unsigned char *iv = buf + 4;
unsigned char *enc_len_p = iv + 12;
unsigned char *ticket = enc_len_p + 2;
unsigned char *tag;
size_t enc_len, clear_len;
if( ctx == NULL || ctx->f_rng == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
/* See mbedtls_ssl_ticket_write() */
if( len < 4 + 12 + 2 + 16 )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
goto cleanup;
enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
tag = ticket + enc_len;
if( len != 4 + 12 + 2 + enc_len + 16 )
{
ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
goto cleanup;
}
/* Select key */
if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
{
/* We can't know for sure but this is a likely option unless we're
* under attack - this is only informative anyway */
ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
goto cleanup;
}
/* Decrypt and authenticate */
if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx, iv, 12,
key_name, 4 + 12 + 2, ticket, enc_len,
ticket, &clear_len, tag, 16 ) ) != 0 )
{
if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
ret = MBEDTLS_ERR_SSL_INVALID_MAC;
goto cleanup;
}
if( clear_len != enc_len )
{
ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
goto cleanup;
}
/* Actually load session */
if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
goto cleanup;
#if defined(MBEDTLS_HAVE_TIME)
{
/* Check for expiration */
mbedtls_time_t current_time = mbedtls_time( NULL );
if( current_time < session->start ||
(uint32_t)( current_time - session->start ) > ctx->ticket_lifetime )
{
ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
goto cleanup;
}
}
#endif
cleanup:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Free context
*/
void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
{
mbedtls_cipher_free( &ctx->keys[0].ctx );
mbedtls_cipher_free( &ctx->keys[1].ctx );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex );
#endif
mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
}
#endif /* MBEDTLS_SSL_TICKET_C */
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