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99a01cb9 | 1 | /* -*-c-*- |
99a01cb9 | 2 | * |
3 | * Optimal asymmetric encryption packing | |
4 | * | |
5 | * (c) 2000 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
99a01cb9 | 9 | * |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
45c0fd36 | 16 | * |
99a01cb9 | 17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
45c0fd36 | 21 | * |
99a01cb9 | 22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
99a01cb9 | 28 | /*----- Header files ------------------------------------------------------*/ |
29 | ||
30 | #include <string.h> | |
31 | ||
32 | #include <mLib/alloc.h> | |
33 | #include <mLib/bits.h> | |
34 | #include <mLib/dstr.h> | |
35 | ||
52f339e9 | 36 | #include "ct.h" |
99a01cb9 | 37 | #include "gcipher.h" |
38 | #include "ghash.h" | |
39 | #include "grand.h" | |
b817bfc6 | 40 | #include "rsa.h" |
99a01cb9 | 41 | |
42 | /*----- Main code ---------------------------------------------------------*/ | |
43 | ||
44 | /* --- @oaep_encode@ --- * | |
45 | * | |
b817bfc6 | 46 | * Arguments: @mp *d@ = where to put the answer |
47 | * @const void *m@ = pointer to message data | |
99a01cb9 | 48 | * @size_t msz@ = size of message data |
b817bfc6 | 49 | * @octet *b@ = spare buffer |
50 | * @size_t sz@ = size of the buffer (big enough) | |
51 | * @unsigned long nbits@ = length of bits of @n@ | |
99a01cb9 | 52 | * @void *p@ = pointer to OAEP parameter block |
53 | * | |
b817bfc6 | 54 | * Returns: The encoded plaintext, or null on failure. |
99a01cb9 | 55 | * |
56 | * Use: Implements the operation @EME-OAEP-ENCODE@, as defined in | |
57 | * PKCS#1 v. 2.0 (RFC2437). | |
58 | */ | |
59 | ||
b817bfc6 | 60 | mp *oaep_encode(mp *d, const void *m, size_t msz, octet *b, size_t sz, |
61 | unsigned long nbits, void *p) | |
99a01cb9 | 62 | { |
63 | oaep *o = p; | |
64 | size_t hsz = o->ch->hashsz; | |
827a6719 | 65 | ghash *h; |
52f339e9 | 66 | octet *q, *mq; |
99a01cb9 | 67 | octet *pp; |
68 | gcipher *c; | |
69 | size_t n; | |
70 | ||
71 | /* --- Ensure that everything is sensibly sized --- */ | |
72 | ||
73 | if (2 * hsz + 2 + msz > sz) | |
b817bfc6 | 74 | return (0); |
99a01cb9 | 75 | |
76 | /* --- Make the `seed' value --- */ | |
77 | ||
b817bfc6 | 78 | q = b; |
99a01cb9 | 79 | *q++ = 0; sz--; |
80 | mq = q + hsz; | |
b817bfc6 | 81 | GR_FILL(o->r, q, hsz); |
99a01cb9 | 82 | |
83 | /* --- Fill in the rest of the buffer --- */ | |
84 | ||
b817bfc6 | 85 | h = GH_INIT(o->ch); |
86 | GH_HASH(h, o->ep, o->epsz); | |
87 | GH_DONE(h, mq); | |
88 | GH_DESTROY(h); | |
99a01cb9 | 89 | pp = mq + hsz; |
90 | n = sz - 2 * hsz - msz - 1; | |
91 | memset(pp, 0, n); | |
92 | pp += n; | |
93 | *pp++ = 1; | |
b817bfc6 | 94 | memcpy(pp, m, msz); |
99a01cb9 | 95 | |
96 | /* --- Do the packing --- */ | |
97 | ||
98 | n = sz - hsz; | |
b817bfc6 | 99 | c = GC_INIT(o->cc, q, hsz); |
100 | GC_ENCRYPT(c, mq, mq, n); | |
101 | GC_DESTROY(c); | |
99a01cb9 | 102 | |
b817bfc6 | 103 | c = GC_INIT(o->cc, mq, n); |
104 | GC_ENCRYPT(c, q, q, hsz); | |
105 | GC_DESTROY(c); | |
99a01cb9 | 106 | |
107 | /* --- Done --- */ | |
108 | ||
b817bfc6 | 109 | return (mp_loadb(d, b, sz + 1)); |
99a01cb9 | 110 | } |
111 | ||
112 | /* --- @oaep_decode@ --- * | |
113 | * | |
b817bfc6 | 114 | * Arguments: @mp *m@ = the decrypted message |
115 | * @octet *b@ = pointer to a buffer to work in | |
116 | * @size_t sz@ = the size of the buffer (big enough) | |
117 | * @unsigned long nbits@ = the number of bits in @n@ | |
99a01cb9 | 118 | * @void *p@ = pointer to OAEP parameter block |
119 | * | |
120 | * Returns: The length of the output string if successful, negative on | |
121 | * failure. | |
122 | * | |
123 | * Use: Implements the operation @EME-OAEP-DECODE@, as defined in | |
124 | * PKCS#1 v. 2.0 (RFC2437). | |
125 | */ | |
126 | ||
b817bfc6 | 127 | int oaep_decode(mp *m, octet *b, size_t sz, unsigned long nbits, void *p) |
99a01cb9 | 128 | { |
129 | oaep *o = p; | |
130 | gcipher *c; | |
131 | ghash *h; | |
132 | octet *q, *mq, *qq; | |
133 | octet *pp; | |
52f339e9 | 134 | uint32 goodp = 1; |
99a01cb9 | 135 | size_t n; |
136 | size_t hsz = o->ch->hashsz; | |
99a01cb9 | 137 | |
138 | /* --- Ensure that the block is large enough --- */ | |
139 | ||
b817bfc6 | 140 | if (sz < 2 * hsz) /* Doesn't depend on ciphertext */ |
99a01cb9 | 141 | return (-1); |
142 | ||
99a01cb9 | 143 | /* --- Decrypt the message --- */ |
144 | ||
b817bfc6 | 145 | mp_storeb(m, b, sz); |
146 | q = b; | |
52f339e9 | 147 | goodp &= ct_inteq(*q, 0); |
99a01cb9 | 148 | q++; sz--; |
149 | mq = q + hsz; | |
150 | qq = q + sz; | |
151 | n = sz - hsz; | |
b817bfc6 | 152 | c = GC_INIT(o->cc, mq, n); |
153 | GC_DECRYPT(c, q, q, hsz); | |
154 | GC_DESTROY(c); | |
99a01cb9 | 155 | |
b817bfc6 | 156 | c = GC_INIT(o->cc, q, hsz); |
157 | GC_DECRYPT(c, mq, mq, n); | |
158 | GC_DESTROY(c); | |
99a01cb9 | 159 | q--; |
160 | ||
161 | /* --- Check the hash on the encoding parameters --- */ | |
162 | ||
b817bfc6 | 163 | h = GH_INIT(o->ch); |
164 | GH_HASH(h, o->ep, o->epsz); | |
165 | GH_DONE(h, q); | |
166 | GH_DESTROY(h); | |
52f339e9 | 167 | goodp &= ct_memeq(q, mq, hsz); |
99a01cb9 | 168 | |
169 | /* --- Now find the start of the actual message --- */ | |
170 | ||
171 | pp = mq + hsz; | |
172 | while (*pp == 0 && pp < qq) | |
173 | pp++; | |
52f339e9 MW |
174 | goodp &= ~ct_intle(qq - b, pp - b); |
175 | goodp &= ct_inteq(*pp, 1); | |
78ec50fa | 176 | pp++; |
99a01cb9 | 177 | n = qq - pp; |
b817bfc6 | 178 | memmove(q, pp, n); |
52f339e9 | 179 | return (goodp ? n : -1); |
49db8dbe | 180 | } |
181 | ||
99a01cb9 | 182 | /*----- That's all, folks -------------------------------------------------*/ |