Implement writing of CID extension in ServerHello

This commit is contained in:
Hanno Becker 2019-04-26 15:46:55 +01:00
parent c008cb5f8c
commit 072d4eca2e

View file

@ -2142,6 +2142,54 @@ static void ssl_write_truncated_hmac_ext( mbedtls_ssl_context *ssl,
}
#endif /* MBEDTLS_SSL_TRUNCATED_HMAC */
#if defined(MBEDTLS_SSL_TRUNCATED_HMAC)
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;
*olen = 0;
/* Skip writing the extension if we don't want to use it or if
* the client hasn't offered it. */
if( ssl->handshake->cid_in_use == MBEDTLS_SSL_CID_DISABLED )
return;
/* 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;
}
MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, adding CID extension" ) );
/*
* Quoting
* https://tools.ietf.org/html/draft-ietf-tls-dtls-connection-id-04:
*
* struct {
* opaque cid<0..2^8-1>;
* } ConnectionId;
*/
*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_TRUNCATED_HMAC */
#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
static void ssl_write_encrypt_then_mac_ext( mbedtls_ssl_context *ssl,
unsigned char *buf,
@ -2663,6 +2711,11 @@ static int ssl_write_server_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
#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
ssl_write_encrypt_then_mac_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;