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comparison pkcs_1_pss_encode.c @ 3:7faae8f46238 libtomcrypt-orig

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Branch renaming
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:25:41 +0000
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-1:000000000000 3:7faae8f46238
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 "mycrypt.h"
12
13 /* PKCS #1 PSS Signature Padding -- Tom St Denis */
14
15 #ifdef PKCS_1
16
17 int pkcs_1_pss_encode(const unsigned char *msghash, unsigned long msghashlen,
18 unsigned long saltlen, int hash_idx,
19 int prng_idx, prng_state *prng,
20 unsigned long modulus_bitlen,
21 unsigned char *out, unsigned long *outlen)
22 {
23 unsigned char DB[1024], mask[sizeof(DB)], salt[sizeof(DB)], hash[sizeof(DB)];
24 unsigned long x, y, hLen, modulus_len;
25 int err;
26 hash_state md;
27
28 _ARGCHK(msghash != NULL);
29 _ARGCHK(out != NULL);
30 _ARGCHK(outlen != NULL);
31
32 /* ensure hash and PRNG are valid */
33 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
34 return err;
35 }
36 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
37 return err;
38 }
39
40 hLen = hash_descriptor[hash_idx].hashsize;
41 modulus_len = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);
42
43 /* check sizes */
44 if ((saltlen > sizeof(salt)) || (modulus_len > sizeof(DB)) || (modulus_len < hLen + saltlen + 2)) {
45 return CRYPT_INVALID_ARG;
46 }
47
48 /* generate random salt */
49 if (saltlen > 0) {
50 if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) {
51 return CRYPT_ERROR_READPRNG;
52 }
53 }
54
55 /* M = (eight) 0x00 || msghash || salt, hash = H(M) */
56 hash_descriptor[hash_idx].init(&md);
57 zeromem(DB, 8);
58 if ((err = hash_descriptor[hash_idx].process(&md, DB, 8)) != CRYPT_OK) {
59 return err;
60 }
61 if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) {
62 return err;
63 }
64 if ((err = hash_descriptor[hash_idx].process(&md, salt, saltlen)) != CRYPT_OK) {
65 return err;
66 }
67 if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) {
68 return err;
69 }
70
71 /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */
72 for (x = 0; x < (modulus_len - saltlen - hLen - 2); x++) {
73 DB[x] = 0x00;
74 }
75 DB[x++] = 0x01;
76 for (y = 0; y < saltlen; y++) {
77 DB[x++] = salt[y];
78 }
79
80 /* generate mask of length modulus_len - hLen - 1 from hash */
81 if ((err = pkcs_1_mgf1(hash, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
82 return err;
83 }
84
85 /* xor against DB */
86 for (y = 0; y < (modulus_len - hLen - 1); y++) {
87 DB[y] ^= mask[y];
88 }
89
90 /* output is DB || hash || 0xBC */
91 if (*outlen < modulus_len) {
92 return CRYPT_BUFFER_OVERFLOW;
93 }
94
95 /* DB */
96 for (y = x = 0; x < modulus_len - hLen - 1; x++) {
97 out[y++] = DB[x];
98 }
99 /* hash */
100 for (x = 0; x < hLen; x++) {
101 out[y++] = hash[x];
102 }
103 /* 0xBC */
104 out[y] = 0xBC;
105
106 /* now clear the 8*modulus_len - modulus_bitlen most significant bits */
107 out[0] &= 0xFF >> ((modulus_len<<3) - modulus_bitlen);
108
109 /* store output size */
110 *outlen = modulus_len;
111
112 #ifdef CLEAN_STACK
113 zeromem(DB, sizeof(DB));
114 zeromem(mask, sizeof(mask));
115 zeromem(salt, sizeof(salt));
116 zeromem(hash, sizeof(hash));
117 #endif
118
119 return CRYPT_OK;
120 }
121
122 #endif /* PKCS_1 */