Improve client Hello use_srtp parsing
Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 0c7e6fd..270700f 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -783,7 +783,7 @@
{
mbedtls_ssl_srtp_profile client_protection = MBEDTLS_SRTP_UNSET_PROFILE;
size_t i,j;
- size_t profile_length;
+ size_t profile_length,mki_length;
const mbedtls_ssl_srtp_profile_info *profile_info;
/*! 2 bytes for profile length and 1 byte for mki len */
const size_t size_of_lengths = 3;
@@ -809,8 +809,9 @@
/*
* Min length is 5: at least one protection profile(2 bytes)
* 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_ALERT_MSG_HANDSHAKE_FAILURE );
@@ -821,8 +822,11 @@
/* first 2 bytes are protection profile length(in bytes) */
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_ALERT_MSG_HANDSHAKE_FAILURE );
@@ -834,8 +838,7 @@
*/
for( j=0; j < profile_length; j += 2 )
{
- /* + 2 to skip the length field */
- uint16_t protection_profile_value = buf[j + 2] << 8 | buf[j+3];
+ uint16_t protection_profile_value = buf[j] << 8 | buf[j+1];
client_protection = mbedtls_ssl_get_srtp_profile_value( protection_profile_value );
profile_info = mbedtls_ssl_dtls_srtp_profile_info_from_id( client_protection );
@@ -860,29 +863,34 @@
if( ssl->dtls_srtp_info.chosen_dtls_srtp_profile != MBEDTLS_SRTP_UNSET_PROFILE )
break;
}
- if( ( ssl->conf->dtls_srtp_mki_support == MBEDTLS_SSL_DTLS_SRTP_MKI_SUPPORTED ) &&
- ( len > ( profile_length + 2 ) ) )
- {
- 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 );
- }
+ buf += profile_length; /* buf points to the mki length */
+ mki_length = *buf;
+ buf++;
- 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,
ssl->dtls_srtp_info.mki_len );
}
- return( 0 );
+ return( 0 );
}
#endif /* MBEDTLS_SSL_DTLS_SRTP */
