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Improve client Hello use_srtp parsing

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Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
This commit is contained in:
Johan Pascal 2020-08-25 12:14:02 +02:00
parent a89ca8679f
commit 042d456832
1 changed files with 28 additions and 20 deletions
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48
library/ssl_srv.c
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@ -783,7 +783,7 @@ static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
{ {
mbedtls_ssl_srtp_profile client_protection = MBEDTLS_SRTP_UNSET_PROFILE; mbedtls_ssl_srtp_profile client_protection = MBEDTLS_SRTP_UNSET_PROFILE;
size_t i,j; size_t i,j;
size_t profile_length; size_t profile_length,mki_length;
const mbedtls_ssl_srtp_profile_info *profile_info; const mbedtls_ssl_srtp_profile_info *profile_info;
/*! 2 bytes for profile length and 1 byte for mki len */ /*! 2 bytes for profile length and 1 byte for mki len */
const size_t size_of_lengths = 3; const size_t size_of_lengths = 3;
@ -809,8 +809,9 @@ static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
/* /*
* Min length is 5: at least one protection profile(2 bytes) * Min length is 5: at least one protection profile(2 bytes)
* and length(2 bytes) + srtp_mki length(1 byte) * and length(2 bytes) + srtp_mki length(1 byte)
* Check here that we have at least 2 bytes of protection profiles length
*/ */
if( len < size_of_lengths + 2 ) if( len < 2 )
{ {
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE ); MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE );
@ -821,8 +822,11 @@ static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
/* first 2 bytes are protection profile length(in bytes) */ /* first 2 bytes are protection profile length(in bytes) */
profile_length = ( buf[0] << 8 ) | buf[1]; profile_length = ( buf[0] << 8 ) | buf[1];
buf += 2;
if( profile_length > len - size_of_lengths ) /* check the buffer size: at least profiles + profile and mki length */
if( profile_length + size_of_lengths > len ||
profile_length % 2 != 0 ) /* profiles are 2 bytes long, so the length must be even */
{ {
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL, mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE ); MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE );
@ -834,8 +838,7 @@ static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
*/ */
for( j=0; j < profile_length; j += 2 ) for( j=0; j < profile_length; j += 2 )
{ {
/* + 2 to skip the length field */ uint16_t protection_profile_value = buf[j] << 8 | buf[j+1];
uint16_t protection_profile_value = buf[j + 2] << 8 | buf[j+3];
client_protection = mbedtls_ssl_get_srtp_profile_value( protection_profile_value ); client_protection = mbedtls_ssl_get_srtp_profile_value( protection_profile_value );
profile_info = mbedtls_ssl_dtls_srtp_profile_info_from_id( client_protection ); profile_info = mbedtls_ssl_dtls_srtp_profile_info_from_id( client_protection );
@ -860,29 +863,34 @@ static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
if( ssl->dtls_srtp_info.chosen_dtls_srtp_profile != MBEDTLS_SRTP_UNSET_PROFILE ) if( ssl->dtls_srtp_info.chosen_dtls_srtp_profile != MBEDTLS_SRTP_UNSET_PROFILE )
break; break;
} }
if( ( ssl->conf->dtls_srtp_mki_support == MBEDTLS_SSL_DTLS_SRTP_MKI_SUPPORTED ) && buf += profile_length; /* buf points to the mki length */
( len > ( profile_length + 2 ) ) ) mki_length = *buf;
{ buf++;
ssl->dtls_srtp_info.mki_len = buf[profile_length + 2];
if( ssl->dtls_srtp_info.mki_len > MBEDTLS_TLS_SRTP_MAX_MKI_LENGTH ||
ssl->dtls_srtp_info.mki_len + profile_length + size_of_lengths != len )
{
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE );
ssl->dtls_srtp_info.mki_len = 0;
return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
}
for( i=0; i < ssl->dtls_srtp_info.mki_len; i++ ) if( mki_length > MBEDTLS_TLS_SRTP_MAX_MKI_LENGTH ||
mki_length + profile_length + size_of_lengths != len )
{
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE );
return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
/* Parse the mki only if present and mki is supported locally */
if( ssl->conf->dtls_srtp_mki_support == MBEDTLS_SSL_DTLS_SRTP_MKI_SUPPORTED &&
mki_length > 0 )
{
ssl->dtls_srtp_info.mki_len = mki_length;
for( i=0; i < mki_length; i++ )
{ {
ssl->dtls_srtp_info.mki_value[i] = buf[profile_length + 2 + 1 + i]; ssl->dtls_srtp_info.mki_value[i] = buf[i];
} }
MBEDTLS_SSL_DEBUG_BUF( 3, "using mki", ssl->dtls_srtp_info.mki_value, MBEDTLS_SSL_DEBUG_BUF( 3, "using mki", ssl->dtls_srtp_info.mki_value,
ssl->dtls_srtp_info.mki_len ); ssl->dtls_srtp_info.mki_len );
} }
return( 0 ); return( 0 );
} }
#endif /* MBEDTLS_SSL_DTLS_SRTP */ #endif /* MBEDTLS_SSL_DTLS_SRTP */