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/*
* Copyright (C) 2017-2018 Red Hat, Inc.
*
* Author: Nikos Mavrogiannopoulos
*
* This file is part of GnuTLS.
*
* The GnuTLS is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library 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
* Lesser 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 "gnutls_int.h"
#include "hello_ext.h"
#include "errors.h"
#include "extv.h"
/* Iterates through all extensions found, and calls the cb()
* function with their data */
int _gnutls_extv_parse(void *ctx,
gnutls_ext_raw_process_func cb,
const uint8_t * data, int data_size)
{
int next, ret;
int pos = 0;
uint16_t tls_id;
const uint8_t *sdata;
uint16_t size;
if (data_size == 0)
return 0;
DECR_LENGTH_RET(data_size, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
next = _gnutls_read_uint16(data);
pos += 2;
DECR_LENGTH_RET(data_size, next, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
if (next == 0 && data_size == 0) /* field is present, but has zero length? Ignore it. */
return 0;
else if (data_size > 0) /* forbid unaccounted data */
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
do {
DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
tls_id = _gnutls_read_uint16(&data[pos]);
pos += 2;
DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
size = _gnutls_read_uint16(&data[pos]);
pos += 2;
DECR_LENGTH_RET(next, size, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
sdata = &data[pos];
pos += size;
ret = cb(ctx, tls_id, sdata, size);
if (ret < 0)
return gnutls_assert_val(ret);
}
while (next > 2);
/* forbid leftovers */
if (next > 0)
return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
return 0;
}
#define HANDSHAKE_SESSION_ID_POS (34)
/**
* gnutls_ext_raw_parse:
* @ctx: a pointer to pass to callback function
* @cb: callback function to process each extension found
* @data: TLS extension data
* @flags: should be zero or %GNUTLS_EXT_RAW_FLAG_CLIENT_HELLO
*
* This function iterates through the TLS extensions as passed in
* @data, passing the individual extension data to callback. The
* @data must conform to Extension extensions<0..2^16-1> format.
*
* If flags is %GNUTLS_EXT_RAW_FLAG_CLIENT_HELLO then this function
* will parse the extension data from the position, as if the packet in
* @data is a client hello (without record or handshake headers) -
* as provided by gnutls_handshake_set_hook_function().
*
* The return value of the callback will be propagated.
*
* Returns: %GNUTLS_E_SUCCESS on success, or an error code. On unknown
* flags it returns %GNUTLS_E_INVALID_REQUEST.
*
* Since: 3.6.3
**/
int gnutls_ext_raw_parse(void *ctx, gnutls_ext_raw_process_func cb,
const gnutls_datum_t *data, unsigned int flags)
{
if (flags & GNUTLS_EXT_RAW_FLAG_CLIENT_HELLO) {
ssize_t size = data->size;
size_t len;
uint8_t *p = data->data;
DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);
if (p[0] != 0x03)
return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
p += HANDSHAKE_SESSION_ID_POS;
/* skip session id */
DECR_LEN(size, 1);
len = p[0];
p++;
DECR_LEN(size, len);
p += len;
/* CipherSuites */
DECR_LEN(size, 2);
len = _gnutls_read_uint16(p);
p += 2;
DECR_LEN(size, len);
p += len;
/* legacy_compression_methods */
DECR_LEN(size, 1);
len = p[0];
p++;
DECR_LEN(size, len);
p += len;
if (size <= 0)
return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);
return _gnutls_extv_parse(ctx, cb, p, size);
}
if (flags != 0)
return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
return _gnutls_extv_parse(ctx, cb, data->data, data->size);
}
/* Returns:
* * On success the number of bytes appended (always positive), or zero if not sent
* * On failure, a negative error code.
*/
int _gnutls_extv_append(gnutls_buffer_st *buf,
uint16_t tls_id,
void *ctx,
int (*cb)(void *ctx, gnutls_buffer_st *buf))
{
int size_pos, appended, ret;
size_t size_prev;
ret = _gnutls_buffer_append_prefix(buf, 16, tls_id);
if (ret < 0)
return gnutls_assert_val(ret);
size_pos = buf->length;
ret = _gnutls_buffer_append_prefix(buf, 16, 0);
if (ret < 0)
return gnutls_assert_val(ret);
size_prev = buf->length;
ret = cb(ctx, buf);
if (ret < 0 && ret != GNUTLS_E_INT_RET_0) {
return gnutls_assert_val(ret);
}
/* returning GNUTLS_E_INT_RET_0 means to send an empty
* extension of this type.
*/
appended = buf->length - size_prev;
if (appended > 0 || ret == GNUTLS_E_INT_RET_0) {
if (ret == GNUTLS_E_INT_RET_0)
appended = 0;
/* write the real size */
_gnutls_write_uint16(appended,
&buf->data[size_pos]);
} else if (appended == 0) {
buf->length -= 4; /* reset type and size */
return 0;
}
return appended + 4;
}
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