1 // SPDX-License-Identifier: BSD-2-Clause
2 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 *
4 * LibTomCrypt is a library that provides various cryptographic
5 * algorithms in a highly modular and flexible manner.
6 *
7 * The library is free for all purposes without any express
8 * guarantee it works.
9 */
10 #include "tomcrypt_private.h"
11
12 /**
13 @file der_decode_bit_string.c
14 ASN.1 DER, encode a BIT STRING, Tom St Denis
15 */
16
17
18 #ifdef LTC_DER
19
20 /**
21 Store a BIT STRING
22 @param in The DER encoded BIT STRING
23 @param inlen The size of the DER BIT STRING
24 @param out [out] The array of bits stored (one per char)
25 @param outlen [in/out] The number of bits stored
26 @return CRYPT_OK if successful
27 */
der_decode_bit_string(const unsigned char * in,unsigned long inlen,unsigned char * out,unsigned long * outlen)28 int der_decode_bit_string(const unsigned char *in, unsigned long inlen,
29 unsigned char *out, unsigned long *outlen)
30 {
31 unsigned long dlen, blen, x, y;
32 int err;
33
34 LTC_ARGCHK(in != NULL);
35 LTC_ARGCHK(out != NULL);
36 LTC_ARGCHK(outlen != NULL);
37
38 /* packet must be at least 4 bytes */
39 if (inlen < 4) {
40 return CRYPT_INVALID_ARG;
41 }
42
43 /* check for 0x03 */
44 if ((in[0]&0x1F) != 0x03) {
45 return CRYPT_INVALID_PACKET;
46 }
47
48 /* offset in the data */
49 x = 1;
50
51 /* get the length of the data */
52 y = inlen - 1;
53 if ((err = der_decode_asn1_length(in + x, &y, &dlen)) != CRYPT_OK) {
54 return err;
55 }
56 x += y;
57 /* is the data len too long or too short? */
58 if ((dlen == 0) || (dlen > (inlen - x))) {
59 return CRYPT_INVALID_PACKET;
60 }
61
62 /* get padding count */
63 blen = ((dlen - 1) << 3) - (in[x++] & 7);
64
65 /* too many bits? */
66 if (blen > *outlen) {
67 *outlen = blen;
68 return CRYPT_BUFFER_OVERFLOW;
69 }
70
71 /* decode/store the bits */
72 for (y = 0; y < blen; y++) {
73 out[y] = (in[x] & (1 << (7 - (y & 7)))) ? 1 : 0;
74 if ((y & 7) == 7) {
75 ++x;
76 }
77 }
78
79 /* we done */
80 *outlen = blen;
81 return CRYPT_OK;
82 }
83
84 #endif
85
86 /* ref: $Format:%D$ */
87 /* git commit: $Format:%H$ */
88 /* commit time: $Format:%ai$ */
89