|
3
|
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 /* OAEP Padding for PKCS #1 -- Tom St Denis */ |
|
|
14 |
|
|
15 #ifdef PKCS_1 |
|
|
16 |
|
|
17 int pkcs_1_oaep_encode(const unsigned char *msg, unsigned long msglen, |
|
15
|
18 const unsigned char *lparam, unsigned long lparamlen, |
|
|
19 unsigned long modulus_bitlen, prng_state *prng, |
|
|
20 int prng_idx, int hash_idx, |
|
|
21 unsigned char *out, unsigned long *outlen) |
|
3
|
22 { |
|
143
|
23 unsigned char *DB, *seed, *mask; |
|
3
|
24 unsigned long hLen, x, y, modulus_len; |
|
|
25 int err; |
|
|
26 |
|
|
27 _ARGCHK(msg != NULL); |
|
|
28 _ARGCHK(out != NULL); |
|
|
29 _ARGCHK(outlen != NULL); |
|
|
30 |
|
|
31 /* test valid hash */ |
|
|
32 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { |
|
|
33 return err; |
|
|
34 } |
|
|
35 |
|
|
36 /* valid prng */ |
|
|
37 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) { |
|
|
38 return err; |
|
|
39 } |
|
|
40 |
|
|
41 hLen = hash_descriptor[hash_idx].hashsize; |
|
|
42 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0); |
|
|
43 |
|
143
|
44 /* allocate ram for DB/mask/salt of size modulus_len */ |
|
|
45 DB = XMALLOC(modulus_len); |
|
|
46 mask = XMALLOC(modulus_len); |
|
|
47 seed = XMALLOC(modulus_len); |
|
|
48 if (DB == NULL || mask == NULL || seed == NULL) { |
|
|
49 if (DB != NULL) { |
|
|
50 XFREE(DB); |
|
|
51 } |
|
|
52 if (mask != NULL) { |
|
|
53 XFREE(mask); |
|
|
54 } |
|
|
55 if (seed != NULL) { |
|
|
56 XFREE(seed); |
|
|
57 } |
|
|
58 return CRYPT_MEM; |
|
|
59 } |
|
|
60 |
|
3
|
61 /* test message size */ |
|
143
|
62 if (msglen > (modulus_len - 2*hLen - 2)) { |
|
|
63 err = CRYPT_PK_INVALID_SIZE; |
|
|
64 goto __ERR; |
|
3
|
65 } |
|
|
66 |
|
|
67 /* get lhash */ |
|
143
|
68 /* DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */ |
|
|
69 x = modulus_len; |
|
3
|
70 if (lparam != NULL) { |
|
|
71 if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) { |
|
143
|
72 goto __ERR; |
|
3
|
73 } |
|
|
74 } else { |
|
|
75 /* can't pass hash_memory a NULL so use DB with zero length */ |
|
|
76 if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) { |
|
143
|
77 goto __ERR; |
|
3
|
78 } |
|
|
79 } |
|
|
80 |
|
|
81 /* append PS then 0x01 (to lhash) */ |
|
|
82 x = hLen; |
|
|
83 y = modulus_len - msglen - 2*hLen - 2; |
|
|
84 while (y--) { |
|
|
85 DB[x++] = 0x00; |
|
|
86 } |
|
|
87 DB[x++] = 0x01; |
|
|
88 |
|
|
89 /* message */ |
|
|
90 y = msglen; |
|
|
91 while (y--) { |
|
|
92 DB[x++] = *msg++; |
|
|
93 } |
|
|
94 |
|
|
95 /* now choose a random seed */ |
|
|
96 if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) { |
|
143
|
97 err = CRYPT_ERROR_READPRNG; |
|
|
98 goto __ERR; |
|
3
|
99 } |
|
|
100 |
|
|
101 /* compute MGF1 of seed (k - hlen - 1) */ |
|
|
102 if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) { |
|
143
|
103 goto __ERR; |
|
3
|
104 } |
|
|
105 |
|
|
106 /* xor against DB */ |
|
|
107 for (y = 0; y < (modulus_len - hLen - 1); y++) { |
|
|
108 DB[y] ^= mask[y]; |
|
|
109 } |
|
|
110 |
|
|
111 /* compute MGF1 of maskedDB (hLen) */ |
|
|
112 if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) { |
|
143
|
113 goto __ERR; |
|
3
|
114 } |
|
|
115 |
|
|
116 /* XOR against seed */ |
|
|
117 for (y = 0; y < hLen; y++) { |
|
|
118 seed[y] ^= mask[y]; |
|
|
119 } |
|
|
120 |
|
|
121 /* create string of length modulus_len */ |
|
|
122 if (*outlen < modulus_len) { |
|
143
|
123 err = CRYPT_BUFFER_OVERFLOW; |
|
|
124 goto __ERR; |
|
3
|
125 } |
|
|
126 |
|
|
127 /* start output which is 0x00 || maskedSeed || maskedDB */ |
|
|
128 x = 0; |
|
|
129 out[x++] = 0x00; |
|
|
130 for (y = 0; y < hLen; y++) { |
|
|
131 out[x++] = seed[y]; |
|
|
132 } |
|
|
133 for (y = 0; y < modulus_len - hLen - 1; y++) { |
|
|
134 out[x++] = DB[y]; |
|
|
135 } |
|
|
136 *outlen = x; |
|
143
|
137 |
|
|
138 err = CRYPT_OK; |
|
|
139 __ERR: |
|
3
|
140 #ifdef CLEAN_STACK |
|
143
|
141 zeromem(DB, modulus_len); |
|
|
142 zeromem(seed, modulus_len); |
|
|
143 zeromem(mask, modulus_len); |
|
3
|
144 #endif |
|
|
145 |
|
143
|
146 XFREE(seed); |
|
|
147 XFREE(mask); |
|
|
148 XFREE(DB); |
|
|
149 |
|
|
150 return err; |
|
3
|
151 } |
|
|
152 |
|
|
153 #endif /* PKCS_1 */ |
|
|
154 |
