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comparison libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_decode.c @ 398:59c7938af2bd

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merge of '1250b8af44b62d8f4fe0f8d9fc7e7a1cc34e7e1c' and '7f8670ac3bb975f40967f3979d09d2199b7e90c8'
author Matt Johnston <matt@ucc.asn.au>
date Sat, 03 Feb 2007 08:20:30 +0000
parents 0cbe8f6dbf9e
children f849a5ca2efc
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396:e7c1a77d2921 398:59c7938af2bd
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.com
10 */
11 #include "tomcrypt.h"
12
13 /** @file pkcs_1_v1_5_decode.c
14 *
15 * PKCS #1 v1.5 Padding. (Andreas Lange)
16 */
17
18 #ifdef PKCS_1
19
20 /** @brief PKCS #1 v1.5 decode.
21 *
22 * @param msg The encoded data to decode
23 * @param msglen The length of the encoded data (octets)
24 * @param block_type Block type to use in padding (\sa ltc_pkcs_1_v1_5_blocks)
25 * @param modulus_bitlen The bit length of the RSA modulus
26 * @param out [out] Destination of decoding
27 * @param outlen [in/out] The max size and resulting size of the decoding
28 * @param is_valid [out] Boolean whether the padding was valid
29 *
30 * @return CRYPT_OK if successful (even if invalid)
31 */
32 int pkcs_1_v1_5_decode(const unsigned char *msg,
33 unsigned long msglen,
34 int block_type,
35 unsigned long modulus_bitlen,
36 unsigned char *out,
37 unsigned long *outlen,
38 int *is_valid)
39 {
40 unsigned long modulus_len, ps_len, i;
41 int result;
42
43 /* default to invalid packet */
44 *is_valid = 0;
45
46 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
47
48 /* test message size */
49
50 if ((msglen > modulus_len) || (modulus_len < 11)) {
51 return CRYPT_PK_INVALID_SIZE;
52 }
53
54 /* separate encoded message */
55
56 if ((msg[0] != 0x00) || (msg[1] != (unsigned char)block_type)) {
57 result = CRYPT_INVALID_PACKET;
58 goto bail;
59 }
60
61 if (block_type == LTC_PKCS_1_EME) {
62 for (i = 2; i < modulus_len; i++) {
63 /* separator */
64 if (msg[i] == 0x00) { break; }
65 }
66 ps_len = i++ - 2;
67
68 if ((i >= modulus_len) || (ps_len < 8)) {
69 /* There was no octet with hexadecimal value 0x00 to separate ps from m,
70 * or the length of ps is less than 8 octets.
71 */
72 result = CRYPT_INVALID_PACKET;
73 goto bail;
74 }
75 } else {
76 for (i = 2; i < modulus_len - 1; i++) {
77 if (msg[i] != 0xFF) { break; }
78 }
79
80 /* separator check */
81 if (msg[i] != 0) {
82 /* There was no octet with hexadecimal value 0x00 to separate ps from m. */
83 result = CRYPT_INVALID_PACKET;
84 goto bail;
85 }
86
87 ps_len = i - 2;
88 }
89
90 if (*outlen < (msglen - (2 + ps_len + 1))) {
91 *outlen = msglen - (2 + ps_len + 1);
92 result = CRYPT_BUFFER_OVERFLOW;
93 goto bail;
94 }
95
96 *outlen = (msglen - (2 + ps_len + 1));
97 XMEMCPY(out, &msg[2 + ps_len + 1], *outlen);
98
99 /* valid packet */
100 *is_valid = 1;
101 result = CRYPT_OK;
102 bail:
103 return result;
104 } /* pkcs_1_v1_5_decode */
105
106 #endif /* #ifdef PKCS_1 */
107
108 /* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_decode.c,v $ */
109 /* $Revision: 1.5 $ */
110 /* $Date: 2006/12/16 17:41:21 $ */