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comparison libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_encode.c @ 285:1b9e69c058d2

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 20dccfc09627970a312d77fb41dc2970b62689c3) to branch 'au.asn.ucc.matt.dropbear' (head fdf4a7a3b97ae5046139915de7e40399cceb2c01)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:58 +0000
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281:997e6f7dc01e 285:1b9e69c058d2
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 pkcs_1_oaep_encode.c
15 OAEP Padding for PKCS #1, Tom St Denis
16 */
17
18 #ifdef PKCS_1
19
20 /**
21 PKCS #1 v2.00 OAEP encode
22 @param msg The data to encode
23 @param msglen The length of the data to encode (octets)
24 @param lparam A session or system parameter (can be NULL)
25 @param lparamlen The length of the lparam data
26 @param modulus_bitlen The bit length of the RSA modulus
27 @param prng An active PRNG state
28 @param prng_idx The index of the PRNG desired
29 @param hash_idx The index of the hash desired
30 @param out [out] The destination for the encoded data
31 @param outlen [in/out] The max size and resulting size of the encoded data
32 @return CRYPT_OK if successful
33 */
34 int pkcs_1_oaep_encode(const unsigned char *msg, unsigned long msglen,
35 const unsigned char *lparam, unsigned long lparamlen,
36 unsigned long modulus_bitlen, prng_state *prng,
37 int prng_idx, int hash_idx,
38 unsigned char *out, unsigned long *outlen)
39 {
40 unsigned char *DB, *seed, *mask;
41 unsigned long hLen, x, y, modulus_len;
42 int err;
43
44 LTC_ARGCHK(msg != NULL);
45 LTC_ARGCHK(out != NULL);
46 LTC_ARGCHK(outlen != NULL);
47
48 /* test valid hash */
49 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
50 return err;
51 }
52
53 /* valid prng */
54 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
55 return err;
56 }
57
58 hLen = hash_descriptor[hash_idx].hashsize;
59 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
60
61 /* test message size */
62 if ((2*hLen >= (modulus_len - 2)) || (msglen > (modulus_len - 2*hLen - 2))) {
63 return CRYPT_PK_INVALID_SIZE;
64 }
65
66 /* allocate ram for DB/mask/salt of size modulus_len */
67 DB = XMALLOC(modulus_len);
68 mask = XMALLOC(modulus_len);
69 seed = XMALLOC(hLen);
70 if (DB == NULL || mask == NULL || seed == NULL) {
71 if (DB != NULL) {
72 XFREE(DB);
73 }
74 if (mask != NULL) {
75 XFREE(mask);
76 }
77 if (seed != NULL) {
78 XFREE(seed);
79 }
80 return CRYPT_MEM;
81 }
82
83 /* get lhash */
84 /* DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */
85 x = modulus_len;
86 if (lparam != NULL) {
87 if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) {
88 goto LBL_ERR;
89 }
90 } else {
91 /* can't pass hash_memory a NULL so use DB with zero length */
92 if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) {
93 goto LBL_ERR;
94 }
95 }
96
97 /* append PS then 0x01 (to lhash) */
98 x = hLen;
99 y = modulus_len - msglen - 2*hLen - 2;
100 XMEMSET(DB+x, 0, y);
101 x += y;
102
103 /* 0x01 byte */
104 DB[x++] = 0x01;
105
106 /* message (length = msglen) */
107 XMEMCPY(DB+x, msg, msglen);
108 x += msglen;
109
110 /* now choose a random seed */
111 if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) {
112 err = CRYPT_ERROR_READPRNG;
113 goto LBL_ERR;
114 }
115
116 /* compute MGF1 of seed (k - hlen - 1) */
117 if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
118 goto LBL_ERR;
119 }
120
121 /* xor against DB */
122 for (y = 0; y < (modulus_len - hLen - 1); y++) {
123 DB[y] ^= mask[y];
124 }
125
126 /* compute MGF1 of maskedDB (hLen) */
127 if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) {
128 goto LBL_ERR;
129 }
130
131 /* XOR against seed */
132 for (y = 0; y < hLen; y++) {
133 seed[y] ^= mask[y];
134 }
135
136 /* create string of length modulus_len */
137 if (*outlen < modulus_len) {
138 err = CRYPT_BUFFER_OVERFLOW;
139 goto LBL_ERR;
140 }
141
142 /* start output which is 0x00 || maskedSeed || maskedDB */
143 x = 0;
144 out[x++] = 0x00;
145 XMEMCPY(out+x, seed, hLen);
146 x += hLen;
147 XMEMCPY(out+x, DB, modulus_len - hLen - 1);
148 x += modulus_len - hLen - 1;
149
150 *outlen = x;
151
152 err = CRYPT_OK;
153 LBL_ERR:
154 #ifdef LTC_CLEAN_STACK
155 zeromem(DB, modulus_len);
156 zeromem(seed, hLen);
157 zeromem(mask, modulus_len);
158 #endif
159
160 XFREE(seed);
161 XFREE(mask);
162 XFREE(DB);
163
164 return err;
165 }
166
167 #endif /* PKCS_1 */
168
169
170 /* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_encode.c,v $ */
171 /* $Revision: 1.4 $ */
172 /* $Date: 2005/05/05 14:35:59 $ */