More API documentation in Doxygen format (block ciphers, PEM).
[BearSSL] / src / ec / ecdsa_atr.c
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_ec.h */
28 size_t
29 br_ecdsa_asn1_to_raw(void *sig, size_t sig_len)
30 {
31 /*
32 * Note: this code is a bit lenient in that it accepts a few
33 * deviations to DER with regards to minimality of encoding of
34 * lengths and integer values. These deviations are still
35 * unambiguous.
36 */
37
38 unsigned char *buf, *r, *s;
39 size_t zlen, rlen, slen, off;
40 unsigned char tmp[254];
41
42 buf = sig;
43 if (sig_len < 8) {
44 return 0;
45 }
46 if (buf[0] != 0x30) {
47 return 0;
48 }
49 zlen = buf[1];
50 if (zlen > 0x80) {
51 if (zlen != 0x81) {
52 return 0;
53 }
54 zlen = buf[2];
55 if (zlen != sig_len - 3) {
56 return 0;
57 }
58 off = 3;
59 } else {
60 if (zlen != sig_len - 2) {
61 return 0;
62 }
63 off = 2;
64 }
65 if (buf[off ++] != 0x02) {
66 return 0;
67 }
68 rlen = buf[off ++];
69 if (rlen >= 0x80) {
70 return 0;
71 }
72 r = buf + off;
73 off += rlen;
74 if (off + 2 > sig_len) {
75 return 0;
76 }
77 if (buf[off ++] != 0x02) {
78 return 0;
79 }
80 slen = buf[off ++];
81 if (slen >= 0x80 || slen != sig_len - off) {
82 return 0;
83 }
84 s = buf + off;
85
86 while (rlen > 0 && *r == 0) {
87 rlen --;
88 r ++;
89 }
90 while (slen > 0 && *s == 0) {
91 slen --;
92 s ++;
93 }
94
95 zlen = rlen > slen ? rlen : slen;
96 sig_len = zlen << 1;
97 memset(tmp, 0, sig_len);
98 memcpy(tmp + zlen - rlen, r, rlen);
99 memcpy(tmp + sig_len - slen, s, slen);
100 memcpy(sig, tmp, sig_len);
101 return sig_len;
102 }