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Merge pull request #873 from hanno-arm/ssl_write_client_hello

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Bounds checks in ssl_write_client_hello
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Manuel Pégourié-Gonnard 2020-06-15 10:57:51 +02:00 committed by GitHub
commit a92e3def48
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GPG Key ID: 4AEE18F83AFDEB23
9 changed files with 681 additions and 389 deletions
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9
ChangeLog.d/uniformize_bounds_checks.txt Normal file
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@ -0,0 +1,9 @@
Bugfix
* Add additional bounds checks in ssl_write_client_hello() preventing
output buffer overflow if the configuration declared a buffer that was
too small.
Changes
* Abort the ClientHello writing function as soon as some extension doesn't
fit into the record buffer. Previously, such extensions were silently
dropped. As a consequence, the TLS handshake now fails when the output
buffer is not large enough to hold the ClientHello.

2
include/mbedtls/error.h
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@ -101,7 +101,7 @@
* ECP 4 10 (Started from top)
* MD 5 5
* HKDF 5 1 (Started from top)
* SSL 5 1 (Started from 0x5F00)
* SSL 5 2 (Started from 0x5F00)
* CIPHER 6 8 (Started from 0x6080)
* SSL 6 24 (Started from top, plus 0x6000)
* SSL 7 32

4
include/mbedtls/ssl.h
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@ -129,6 +129,7 @@
#define MBEDTLS_ERR_SSL_UNEXPECTED_CID -0x6000 /**< An encrypted DTLS-frame with an unexpected CID was received. */
#define MBEDTLS_ERR_SSL_VERSION_MISMATCH -0x5F00 /**< An operation failed due to an unexpected version or configuration. */
#define MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS -0x7000 /**< A cryptographic operation is in progress. Try again later. */
#define MBEDTLS_ERR_SSL_BAD_CONFIG -0x5E80 /**< Invalid value in SSL config */
/*
* Various constants
@ -144,6 +145,9 @@
#define MBEDTLS_SSL_TRANSPORT_DATAGRAM 1 /*!< DTLS */
#define MBEDTLS_SSL_MAX_HOST_NAME_LEN 255 /*!< Maximum host name defined in RFC 1035 */
#define MBEDTLS_SSL_MAX_ALPN_NAME_LEN 255 /*!< Maximum size in bytes of a protocol name in alpn ext., RFC 7301 */
#define MBEDTLS_SSL_MAX_ALPN_LIST_LEN 65535 /*!< Maximum size in bytes of list in alpn ext., RFC 7301 */
/* RFC 6066 section 4, see also mfl_code_to_length in ssl_tls.c
* NONE must be zero so that memset()ing structure to zero works */

41
include/mbedtls/ssl_internal.h
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@ -207,6 +207,12 @@
: ( MBEDTLS_SSL_IN_CONTENT_LEN ) \
)
/* Maximum size in bytes of list in sig-hash algorithm ext., RFC 5246 */
#define MBEDTLS_SSL_MAX_SIG_HASH_ALG_LIST_LEN 65534
/* Maximum size in bytes of list in supported elliptic curve ext., RFC 4492 */
#define MBEDTLS_SSL_MAX_CURVE_LIST_LEN 65535
/*
* Check that we obey the standard's message size bounds
*/
@ -299,6 +305,41 @@ static inline uint32_t mbedtls_ssl_get_input_buflen( const mbedtls_ssl_context *
#define MBEDTLS_TLS_EXT_SUPPORTED_POINT_FORMATS_PRESENT (1 << 0)
#define MBEDTLS_TLS_EXT_ECJPAKE_KKPP_OK (1 << 1)
/**
* \brief This function checks if the remaining size in a buffer is
* greater or equal than a needed space.
*
* \param cur Pointer to the current position in the buffer.
* \param end Pointer to one past the end of the buffer.
* \param need Needed space in bytes.
*
* \return Zero if the needed space is available in the buffer, non-zero
* otherwise.
*/
static inline int mbedtls_ssl_chk_buf_ptr( const uint8_t *cur,
const uint8_t *end, size_t need )
{
return( ( cur > end ) || ( need > (size_t)( end - cur ) ) );
}
/**
* \brief This macro checks if the remaining size in a buffer is
* greater or equal than a needed space. If it is not the case,
* it returns an SSL_BUFFER_TOO_SMALL error.
*
* \param cur Pointer to the current position in the buffer.
* \param end Pointer to one past the end of the buffer.
* \param need Needed space in bytes.
*
*/
#define MBEDTLS_SSL_CHK_BUF_PTR( cur, end, need ) \
do { \
if( mbedtls_ssl_chk_buf_ptr( ( cur ), ( end ), ( need ) ) != 0 ) \
{ \
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); \
} \
} while( 0 )
#ifdef __cplusplus
extern "C" {
#endif

2
library/error.c
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@ -526,6 +526,8 @@ const char * mbedtls_high_level_strerr( int error_code )
return( "SSL - An operation failed due to an unexpected version or configuration" );
case -(MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS):
return( "SSL - A cryptographic operation is in progress. Try again later" );
case -(MBEDTLS_ERR_SSL_BAD_CONFIG):
return( "SSL - Invalid value in SSL config" );
#endif /* MBEDTLS_SSL_TLS_C */
#if defined(MBEDTLS_X509_USE_C) || defined(MBEDTLS_X509_CREATE_C)

998
library/ssl_cli.c
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File diff suppressed because it is too large Load Diff

6
library/ssl_cookie.c
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@ -134,8 +134,7 @@ static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
{
unsigned char hmac_out[COOKIE_MD_OUTLEN];
if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
@ -165,8 +164,7 @@ int mbedtls_ssl_cookie_write( void *p_ctx,
if( ctx == NULL || cli_id == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( (size_t)( end - *p ) < COOKIE_LEN )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
#if defined(MBEDTLS_HAVE_TIME)
t = (unsigned long) mbedtls_time( NULL );

4
library/ssl_ticket.c
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@ -35,6 +35,7 @@
#define mbedtls_free free
#endif
#include "mbedtls/ssl_internal.h"
#include "mbedtls/ssl_ticket.h"
#include "mbedtls/error.h"
#include "mbedtls/platform_util.h"
@ -224,8 +225,7 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
/* 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 < TICKET_MIN_LEN )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
MBEDTLS_SSL_CHK_BUF_PTR( start, end, TICKET_MIN_LEN );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )

4
library/ssl_tls.c
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@ -4665,7 +4665,9 @@ int mbedtls_ssl_conf_alpn_protocols( mbedtls_ssl_config *conf, const char **prot
cur_len = strlen( *p );
tot_len += cur_len;
if( cur_len == 0 || cur_len > 255 || tot_len > 65535 )
if( ( cur_len == 0 ) ||
( cur_len > MBEDTLS_SSL_MAX_ALPN_NAME_LEN ) ||
( tot_len > MBEDTLS_SSL_MAX_ALPN_LIST_LEN ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}