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comparison src/pk/asn1/der/bit/der_decode_bit_string.c @ 209:39d5d58461d6 libtomcrypt-orig LTC_1.05

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Import of libtomcrypt 1.05
author Matt Johnston <matt@ucc.asn.au>
date Wed, 06 Jul 2005 03:53:40 +0000
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children d5faf4814ddb
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191:1c15b283127b 209:39d5d58461d6
1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, [email protected], http://libtomcrypt.org
10 */
11 #include "tomcrypt.h"
12
13 /**
14 @file der_decode_bit_string.c
15 ASN.1 DER, encode a BIT STRING, Tom St Denis
16 */
17
18
19 #ifdef LTC_DER
20
21 /**
22 Store a BIT STRING
23 @param in The DER encoded BIT STRING
24 @param inlen The size of the DER BIT STRING
25 @param out [out] The array of bits stored (one per char)
26 @param outlen [in/out] The number of bits stored
27 @return CRYPT_OK if successful
28 */
29 int der_decode_bit_string(const unsigned char *in, unsigned long inlen,
30 unsigned char *out, unsigned long *outlen)
31 {
32 unsigned long dlen, blen, x, y;
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 if (in[x] & 0x80) {
53 /* long format get number of length bytes */
54 y = in[x++] & 127;
55
56 /* invalid if 0 or > 2 */
57 if (y == 0 || y > 2) {
58 return CRYPT_INVALID_PACKET;
59 }
60
61 /* read the data len */
62 dlen = 0;
63 while (y--) {
64 dlen = (dlen << 8) | (unsigned long)in[x++];
65 }
66 } else {
67 /* short format */
68 dlen = in[x++] & 127;
69 }
70
71 /* is the data len too long or too short? */
72 if ((dlen == 0) || (dlen + x > inlen)) {
73 return CRYPT_INVALID_PACKET;
74 }
75
76 /* get padding count */
77 blen = ((dlen - 1) << 3) - (in[x++] & 7);
78
79 /* too many bits? */
80 if (blen > *outlen) {
81 return CRYPT_BUFFER_OVERFLOW;
82 }
83
84 /* decode/store the bits */
85 for (y = 0; y < blen; y++) {
86 out[y] = (in[x] & (1 << (7 - (y & 7)))) ? 1 : 0;
87 if ((y & 7) == 7) {
88 ++x;
89 }
90 }
91
92 /* we done */
93 *outlen = blen;
94 return CRYPT_OK;
95 }
96
97 #endif
98
99 /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_decode_bit_string.c,v $ */
100 /* $Revision: 1.1 $ */
101 /* $Date: 2005/05/16 15:08:11 $ */