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Added bounds checking for TLS extensions

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IOTSSL-478 - Added checks to prevent buffer overflows.
This commit is contained in:
Simon Butcher 2015-09-28 02:14:30 +01:00
parent 89f77623b8
commit ed9976634f
1 changed files with 108 additions and 3 deletions
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111
library/ssl_cli.c
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@ -60,6 +60,7 @@ static void ssl_write_hostname_ext( mbedtls_ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
size_t hostname_len;
*olen = 0;
@ -72,6 +73,13 @@ static void ssl_write_hostname_ext( mbedtls_ssl_context *ssl,
hostname_len = strlen( ssl->hostname );
if( (size_t)(end - p) < hostname_len + 9 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small for hostname" ) );
return;
}
/*
* struct {
* NameType name_type;
@ -115,6 +123,7 @@ static void ssl_write_renegotiation_ext( mbedtls_ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
*olen = 0;
@ -123,6 +132,12 @@ static void ssl_write_renegotiation_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding renegotiation extension" ) );
if( (size_t)(end - p) < 5 + ssl->verify_data_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
/*
* Secure renegotiation
*/
@ -149,6 +164,7 @@ static void ssl_write_signature_algorithms_ext( mbedtls_ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
size_t sig_alg_len = 0;
const int *md;
#if defined(MBEDTLS_RSA_C) || defined(MBEDTLS_ECDSA_C)
@ -162,9 +178,27 @@ static void ssl_write_signature_algorithms_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding signature_algorithms extension" ) );
for( md = ssl->conf->sig_hashes; *md != MBEDTLS_MD_NONE; md++ )
{
#if defined(MBEDTLS_ECDSA_C)
sig_alg_len += 2;
#endif
#if defined(MBEDTLS_RSA_C)
sig_alg_len += 2;
#endif
}
if( (size_t)(end - p) < sig_alg_len + 6 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
/*
* Prepare signature_algorithms extension (TLS 1.2)
*/
sig_alg_len = 0;
for( md = ssl->conf->sig_hashes; *md != MBEDTLS_MD_NONE; md++ )
{
#if defined(MBEDTLS_ECDSA_C)
@ -214,6 +248,7 @@ static void ssl_write_supported_elliptic_curves_ext( mbedtls_ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
unsigned char *elliptic_curve_list = p + 6;
size_t elliptic_curve_len = 0;
const mbedtls_ecp_curve_info *info;
@ -227,6 +262,25 @@ static void ssl_write_supported_elliptic_curves_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding supported_elliptic_curves extension" ) );
#if defined(MBEDTLS_ECP_C)
for( grp_id = ssl->conf->curve_list; *grp_id != MBEDTLS_ECP_DP_NONE; grp_id++ )
{
info = mbedtls_ecp_curve_info_from_grp_id( *grp_id );
#else
for( info = mbedtls_ecp_curve_list(); info->grp_id != MBEDTLS_ECP_DP_NONE; info++ )
{
#endif
elliptic_curve_len += 2;
}
if( (size_t)(end - p) < 6 + elliptic_curve_len )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
elliptic_curve_len = 0;
#if defined(MBEDTLS_ECP_C)
for( grp_id = ssl->conf->curve_list; *grp_id != MBEDTLS_ECP_DP_NONE; grp_id++ )
{
@ -260,12 +314,18 @@ static void ssl_write_supported_point_formats_ext( mbedtls_ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
((void) ssl);
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
*olen = 0;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding supported_point_formats extension" ) );
if( (size_t)(end - p) < 6 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_SUPPORTED_POINT_FORMATS >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_SUPPORTED_POINT_FORMATS ) & 0xFF );
@ -285,6 +345,7 @@ static void ssl_write_max_fragment_length_ext( mbedtls_ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
if( ssl->conf->mfl_code == MBEDTLS_SSL_MAX_FRAG_LEN_NONE ) {
*olen = 0;
@ -293,6 +354,12 @@ static void ssl_write_max_fragment_length_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding max_fragment_length extension" ) );
if( (size_t)(end - p) < 5 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_MAX_FRAGMENT_LENGTH >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_MAX_FRAGMENT_LENGTH ) & 0xFF );
@ -310,6 +377,7 @@ static void ssl_write_truncated_hmac_ext( mbedtls_ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
if( ssl->conf->trunc_hmac == MBEDTLS_SSL_TRUNC_HMAC_DISABLED )
{
@ -319,6 +387,12 @@ static void ssl_write_truncated_hmac_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding truncated_hmac extension" ) );
if( (size_t)(end - p) < 4 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_TRUNCATED_HMAC >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_TRUNCATED_HMAC ) & 0xFF );
@ -334,6 +408,7 @@ static void ssl_write_encrypt_then_mac_ext( mbedtls_ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
if( ssl->conf->encrypt_then_mac == MBEDTLS_SSL_ETM_DISABLED ||
ssl->conf->max_minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
@ -345,6 +420,12 @@ static void ssl_write_encrypt_then_mac_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding encrypt_then_mac "
"extension" ) );
if( (size_t)(end - p) < 4 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_ENCRYPT_THEN_MAC >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_ENCRYPT_THEN_MAC ) & 0xFF );
@ -360,6 +441,7 @@ static void ssl_write_extended_ms_ext( mbedtls_ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
if( ssl->conf->extended_ms == MBEDTLS_SSL_EXTENDED_MS_DISABLED ||
ssl->conf->max_minor_ver == MBEDTLS_SSL_MINOR_VERSION_0 )
@ -371,6 +453,12 @@ static void ssl_write_extended_ms_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding extended_master_secret "
"extension" ) );
if( (size_t)(end - p) < 4 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_EXTENDED_MASTER_SECRET >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_EXTENDED_MASTER_SECRET ) & 0xFF );
@ -386,6 +474,7 @@ static void ssl_write_session_ticket_ext( mbedtls_ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
size_t tlen = ssl->session_negotiate->ticket_len;
if( ssl->conf->session_tickets == MBEDTLS_SSL_SESSION_TICKETS_DISABLED )
@ -396,6 +485,12 @@ static void ssl_write_session_ticket_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding session ticket extension" ) );
if( (size_t)(end - p) < 4 + tlen )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_SESSION_TICKET >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_SESSION_TICKET ) & 0xFF );
@ -404,8 +499,7 @@ static void ssl_write_session_ticket_ext( mbedtls_ssl_context *ssl,
*olen = 4;
if( ssl->session_negotiate->ticket == NULL ||
ssl->session_negotiate->ticket_len == 0 )
if( ssl->session_negotiate->ticket == NULL || tlen == 0 )
{
return;
}
@ -423,6 +517,8 @@ static void ssl_write_alpn_ext( mbedtls_ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_MAX_CONTENT_LEN;
size_t alpnlen = 0;
const char **cur;
if( ssl->conf->alpn_list == NULL )
@ -433,6 +529,15 @@ static void ssl_write_alpn_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding alpn extension" ) );
for( cur = ssl->conf->alpn_list; *cur != NULL; cur++ )
alpnlen += *p = (unsigned char)( strlen( *cur ) & 0xFF );
if( (size_t)(end - p) < 6 + alpnlen )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_ALPN >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_ALPN ) & 0xFF );