Implement writing of CID extension in ClientHello

This commit is contained in:
Hanno Becker 2019-04-25 16:55:15 +01:00
parent 189a01309f
commit 49770ffd93

View file

@ -475,6 +475,54 @@ static void ssl_write_ecjpake_kkpp_ext( mbedtls_ssl_context *ssl,
}
#endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
#if defined(MBEDTLS_SSL_CID)
static void ssl_write_cid_ext( mbedtls_ssl_context *ssl,
unsigned char *buf,
size_t *olen )
{
unsigned char *p = buf;
size_t ext_len;
const unsigned char *end = ssl->out_msg + MBEDTLS_SSL_OUT_CONTENT_LEN;
/*
* Quoting
* https://tools.ietf.org/html/draft-ietf-tls-dtls-connection-id-04:
*
* struct {
* opaque cid<0..2^8-1>;
* } ConnectionId;
*/
*olen = 0;
if( ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM ||
ssl->negotiate_cid == MBEDTLS_SSL_CID_DISABLED )
{
return;
}
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding CID extension" ) );
/* ssl->own_cid_len is at most MBEDTLS_SSL_CID_IN_LEN_MAX
* which is at most 255, so the increment cannot overflow. */
if( end < p || (size_t)( end - p ) < (unsigned)( ssl->own_cid_len + 5 ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "buffer too small" ) );
return;
}
/* Add extension ID + size */
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_CID >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_CID ) & 0xFF );
ext_len = (size_t) ssl->own_cid_len + 1;
*p++ = (unsigned char)( ( ext_len >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( ext_len ) & 0xFF );
*p++ = (uint8_t) ssl->own_cid_len;
memcpy( p, ssl->own_cid, ssl->own_cid_len );
*olen = ssl->own_cid_len + 5;
}
#endif /* MBEDTLS_SSL_CID */
#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
static void ssl_write_max_fragment_length_ext( mbedtls_ssl_context *ssl,
unsigned char *buf,
@ -1085,6 +1133,11 @@ static int ssl_write_client_hello( mbedtls_ssl_context *ssl )
ext_len += olen;
#endif
#if defined(MBEDTLS_SSL_CID)
ssl_write_cid_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;
#endif /* MBEDTLS_SSL_CID */
#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
ssl_write_max_fragment_length_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;