2 * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
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:
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
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
29 br_rsa_pkcs1_sig_pad(const unsigned char *hash_oid
,
30 const unsigned char *hash
, size_t hash_len
,
31 uint32_t n_bitlen
, unsigned char *x
)
36 * Padded hash value has format:
37 * 00 01 FF .. FF 00 30 x1 30 x2 06 x3 OID 05 00 04 x4 HASH
39 * with the following rules:
41 * -- Total length is equal to the modulus length (unsigned
44 * -- There must be at least eight bytes of value 0xFF.
46 * -- x4 is equal to the hash length (hash_len).
48 * -- x3 is equal to the encoded OID value length (hash_oid[0]).
52 * -- x1 = x2 + x4 + 4 = x3 + x4 + 8.
54 * Note: the "05 00" is optional (signatures with and without
55 * that sequence exist in practice), but notes in PKCS#1 seem to
56 * indicate that the presence of that sequence (specifically,
57 * an ASN.1 NULL value for the hash parameters) may be slightly
58 * more "standard" than the opposite.
60 xlen
= (n_bitlen
+ 7) >> 3;
62 if (hash_oid
== NULL
) {
63 if (xlen
< hash_len
+ 11) {
69 memset(x
+ 2, 0xFF, u
- 3);
75 * Check that there is enough room for all the elements,
76 * including at least eight bytes of value 0xFF.
78 if (xlen
< (x3
+ hash_len
+ 21)) {
83 u
= xlen
- x3
- hash_len
- 11;
84 memset(x
+ 2, 0xFF, u
- 2);
87 x
[u
+ 2] = x3
+ hash_len
+ 8;
91 memcpy(x
+ u
+ 6, hash_oid
, x3
+ 1);
98 memcpy(x
+ u
, hash
, hash_len
);