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/*
* Copyright (C) 2017 Red Hat, Inc.
*
* Author: Nikos Mavrogiannopoulos
*
* This file is part of GnuTLS.
*
* GnuTLS is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* GnuTLS is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
*/
#include "utils.h"
#define TLS_EXT_SUPPORTED_VERSIONS 43
#define TLS_EXT_POST_HANDSHAKE 49
#define SKIP16(pos, _total) { \
uint16_t _s; \
if ((size_t)pos+2 > (size_t)_total) fail("error0: at %d total: %d\n", pos+2, _total); \
_s = (msg->data[pos] << 8) | msg->data[pos+1]; \
if ((size_t)(pos+2+_s) > (size_t)_total) fail("error1: at %d field: %d, total: %d\n", pos+2, (int)_s, _total); \
pos += 2+_s; \
}
#define SKIP8(pos, _total) { \
uint8_t _s; \
if ((size_t)pos+1 > (size_t)_total) fail("error\n"); \
_s = msg->data[pos]; \
if ((size_t)(pos+1+_s) > (size_t)_total) fail("error\n"); \
pos += 1+_s; \
}
typedef void (*ext_parse_func)(void *priv, gnutls_datum_t *extdata);
#define HANDSHAKE_SESSION_ID_POS 34
/* Returns 0 if the extension was not found, 1 otherwise.
*/
static unsigned find_client_extension(const gnutls_datum_t *msg, unsigned extnr, void *priv, ext_parse_func cb)
{
unsigned pos;
if (msg->size < HANDSHAKE_SESSION_ID_POS)
fail("invalid client hello\n");
/* we expect the legacy version to be present */
/* ProtocolVersion legacy_version = 0x0303 */
if (msg->data[0] != 0x03) {
fail("ProtocolVersion contains %d.%d\n", (int)msg->data[0], (int)msg->data[1]);
}
pos = HANDSHAKE_SESSION_ID_POS;
/* legacy_session_id */
SKIP8(pos, msg->size);
/* CipherSuites */
SKIP16(pos, msg->size);
/* legacy_compression_methods */
SKIP8(pos, msg->size);
pos += 2;
while (pos < msg->size) {
uint16_t type;
if (pos+4 > msg->size)
fail("invalid client hello\n");
type = (msg->data[pos] << 8) | msg->data[pos+1];
pos+=2;
if (debug)
success("Found client extension %d\n", (int)type);
if (type != extnr) {
SKIP16(pos, msg->size);
} else { /* found */
ssize_t size = (msg->data[pos] << 8) | msg->data[pos+1];
gnutls_datum_t data;
pos+=2;
if (pos + size > msg->size) {
fail("error in extension length (pos: %d, ext: %d, total: %d)\n", pos, (int)size, msg->size);
}
data.data = &msg->data[pos];
data.size = size;
if (cb)
cb(priv, &data);
return 1;
}
}
return 0;
}
#define TLS_RANDOM_SIZE 32
static unsigned find_server_extension(const gnutls_datum_t *msg, unsigned extnr, void *priv, ext_parse_func cb)
{
unsigned pos = 0;
success("server hello of %d bytes\n", msg->size);
/* we expect the legacy version to be present */
/* ProtocolVersion legacy_version = 0x0303 */
if (msg->data[0] != 0x03 || msg->data[1] != 0x03) {
fail("ProtocolVersion contains %d.%d\n", (int)msg->data[0], (int)msg->data[1]);
}
if (msg->data[1] >= 0x04) {
success("assuming TLS 1.3 or better hello format (seen %d.%d)\n", (int)msg->data[0], (int)msg->data[1]);
}
pos += 2+TLS_RANDOM_SIZE;
/* legacy_session_id */
SKIP8(pos, msg->size);
/* CipherSuite */
pos += 2;
/* legacy_compression_methods */
SKIP8(pos, msg->size);
pos += 2;
while (pos < msg->size) {
uint16_t type;
if (pos+4 > msg->size)
fail("invalid server hello\n");
type = (msg->data[pos] << 8) | msg->data[pos+1];
pos+=2;
success("Found server extension %d\n", (int)type);
if (type != extnr) {
SKIP16(pos, msg->size);
} else { /* found */
ssize_t size = (msg->data[pos] << 8) | msg->data[pos+1];
gnutls_datum_t data;
pos+=2;
if (pos + size < msg->size) {
fail("error in server extension length (pos: %d, total: %d)\n", pos, msg->size);
}
data.data = &msg->data[pos];
data.size = size;
if (cb)
cb(priv, &data);
return 1;
}
}
return 0;
}
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