1/*
2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25#include "inner.h"
26
27/* see bearssl_rsa.h */
28uint32_t
29br_rsa_ssl_decrypt(br_rsa_private core, const br_rsa_private_key *sk,
30	unsigned char *data, size_t len)
31{
32	uint32_t x;
33	size_t u;
34
35	/*
36	 * A first check on length. Since this test works only on the
37	 * buffer length, it needs not (and cannot) be constant-time.
38	 */
39	if (len < 59 || len != (sk->n_bitlen + 7) >> 3) {
40		return 0;
41	}
42	x = core(data, sk);
43
44	x &= EQ(data[0], 0x00);
45	x &= EQ(data[1], 0x02);
46	for (u = 2; u < (len - 49); u ++) {
47		x &= NEQ(data[u], 0);
48	}
49	x &= EQ(data[len - 49], 0x00);
50	memmove(data, data + len - 48, 48);
51	return x;
52}
53