| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: pss.c,v 1.1 2000/07/20 20:13:38 mdw Exp $ |
| 4 | * |
| 5 | * Probabistic signature scheme |
| 6 | * |
| 7 | * (c) 2000 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of Catacomb. |
| 13 | * |
| 14 | * Catacomb is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU Library General Public License as |
| 16 | * published by the Free Software Foundation; either version 2 of the |
| 17 | * License, or (at your option) any later version. |
| 18 | * |
| 19 | * Catacomb is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU Library General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU Library General Public |
| 25 | * License along with Catacomb; if not, write to the Free |
| 26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Revision history --------------------------------------------------* |
| 31 | * |
| 32 | * $Log: pss.c,v $ |
| 33 | * Revision 1.1 2000/07/20 20:13:38 mdw |
| 34 | * Added Bellare and Rogaway's PSS encoding for RSA signatures. |
| 35 | * |
| 36 | */ |
| 37 | |
| 38 | /*----- Header files ------------------------------------------------------*/ |
| 39 | |
| 40 | #include <string.h> |
| 41 | |
| 42 | #include <mLib/alloc.h> |
| 43 | #include <mLib/bits.h> |
| 44 | #include <mLib/dstr.h> |
| 45 | |
| 46 | #include "gcipher.h" |
| 47 | #include "ghash.h" |
| 48 | #include "grand.h" |
| 49 | #include "pss.h" |
| 50 | |
| 51 | /*----- Main code ---------------------------------------------------------*/ |
| 52 | |
| 53 | /* --- @pss_presign@ --- * |
| 54 | * |
| 55 | * Arguments: @pss *pp@ = pointer to PSS parameter block |
| 56 | * |
| 57 | * Returns: An initialized generic hash context. |
| 58 | * |
| 59 | * Use: Initializes a hash function for signing with PSS. A salt is |
| 60 | * chosen and written into the parameter block. |
| 61 | */ |
| 62 | |
| 63 | ghash *pss_presign(pss *pp) |
| 64 | { |
| 65 | size_t hsz = pp->ch->hashsz; |
| 66 | octet *salt = xmalloc(hsz); |
| 67 | ghash *h; |
| 68 | |
| 69 | pp->r->ops->fill(pp->r, salt, hsz); |
| 70 | pp->salt = salt; |
| 71 | h = pp->ch->init(); |
| 72 | h->ops->hash(h, salt, hsz); |
| 73 | return (h); |
| 74 | } |
| 75 | |
| 76 | /* --- @pss_encode@ --- * |
| 77 | * |
| 78 | * Arguments: @const void *msg@ = pointer to message (hash) data |
| 79 | * @size_t msz@ = size of message data |
| 80 | * @void *buf@ = pointer to output buffer |
| 81 | * @size_t sz@ = size of the output buffer |
| 82 | * @void *p@ = pointer to PSS parameter block |
| 83 | * |
| 84 | * Returns: Zero of all went well, negative on failure. |
| 85 | * |
| 86 | * Use: Implements the operation @EMSA-PSS-ENCODE@, as defined in |
| 87 | * PKCS#1 v. 2.1 draft 1. |
| 88 | */ |
| 89 | |
| 90 | int pss_encode(const void *msg, size_t msz, void *buf, size_t sz, void *p) |
| 91 | { |
| 92 | pss *pp = p; |
| 93 | octet *q, *mq, *qq; |
| 94 | gcipher *c; |
| 95 | size_t hsz = pp->ch->hashsz; |
| 96 | size_t n; |
| 97 | |
| 98 | /* --- Ensure that everything is sensibly sized --- */ |
| 99 | |
| 100 | if (hsz + msz + 1 > sz) |
| 101 | return (-1); |
| 102 | |
| 103 | /* --- Fill in the initial buffer --- */ |
| 104 | |
| 105 | q = buf; |
| 106 | *q++ = 0; sz--; |
| 107 | mq = q + msz; |
| 108 | qq = q + sz; |
| 109 | n = sz - msz; |
| 110 | memcpy(q, msg, msz); |
| 111 | if (pp->salt) |
| 112 | memcpy(mq, pp->salt, hsz); |
| 113 | else |
| 114 | memset(mq, 0, hsz); |
| 115 | memset(mq + hsz, 0, n - hsz); |
| 116 | |
| 117 | /* --- Do the encryption --- */ |
| 118 | |
| 119 | c = pp->cc->init(msg, msz); |
| 120 | c->ops->encrypt(c, mq, mq, n); |
| 121 | c->ops->destroy(c); |
| 122 | |
| 123 | /* --- Done --- */ |
| 124 | |
| 125 | return (0); |
| 126 | } |
| 127 | |
| 128 | /* --- @pss_decode@ --- * |
| 129 | * |
| 130 | * Arguments: @const void *buf@ = pointer to encoded buffer |
| 131 | * @size_t sz@ = size of the encoded byffer |
| 132 | * @dstr *d@ = pointer to destination string |
| 133 | * @void *p@ = pointer to PSS parameter block |
| 134 | * |
| 135 | * Returns: The length of the output string (hash) if successful, |
| 136 | * negative on failure. |
| 137 | * |
| 138 | * Use: Implements most of the operation @EMSA_PSS_VERIFY@, as |
| 139 | * defined in PCSK#1 v. 2.1 draft 1. The salt value is filled |
| 140 | * in ready for hashing of the data to start. |
| 141 | */ |
| 142 | |
| 143 | int pss_decode(const void *buf, size_t sz, dstr *d, void *p) |
| 144 | { |
| 145 | pss *pp = p; |
| 146 | gcipher *c; |
| 147 | octet *q, *mq, *qq; |
| 148 | octet *ppp; |
| 149 | size_t n; |
| 150 | size_t hsz = pp->ch->hashsz; |
| 151 | int rc = -1; |
| 152 | |
| 153 | /* --- Ensure that the block is large enough --- */ |
| 154 | |
| 155 | if (sz < 2 * hsz + 1) |
| 156 | return (-1); |
| 157 | |
| 158 | q = x_alloc(d->a, sz); |
| 159 | memcpy(q, buf, sz); |
| 160 | |
| 161 | /* --- Recover the salt --- */ |
| 162 | |
| 163 | if (*q++ != 0) |
| 164 | goto fail; |
| 165 | sz--; |
| 166 | mq = q + hsz; |
| 167 | qq = q + sz; |
| 168 | n = sz - hsz; |
| 169 | c = pp->cc->init(q, hsz); |
| 170 | c->ops->decrypt(c, mq, mq, n); |
| 171 | c->ops->destroy(c); |
| 172 | |
| 173 | /* --- Now check the recovery --- */ |
| 174 | |
| 175 | ppp = mq + hsz; |
| 176 | while (ppp < qq) { |
| 177 | if (*ppp) |
| 178 | goto fail; |
| 179 | ppp++; |
| 180 | } |
| 181 | |
| 182 | /* --- Done --- */ |
| 183 | |
| 184 | if (pp->salt) { |
| 185 | if (memcmp(pp->salt, mq, hsz) != 0) |
| 186 | goto fail; |
| 187 | } else { |
| 188 | qq = xmalloc(hsz); |
| 189 | memcpy(qq, mq, hsz); |
| 190 | pp->salt = qq; |
| 191 | } |
| 192 | dstr_putm(d, q, hsz); |
| 193 | rc = hsz; |
| 194 | |
| 195 | fail: |
| 196 | x_free(d->a, q - 1); |
| 197 | return (rc); |
| 198 | } |
| 199 | |
| 200 | /* --- @pss_preverify@ --- * |
| 201 | * |
| 202 | * Arguments: @pss *pp@ = pointer to PSS parameter block |
| 203 | * |
| 204 | * Returns: An initialized generic hash context. |
| 205 | * |
| 206 | * Use: Initializes a hash function for use with PSS. A salt is |
| 207 | * read from the parameter block, where @pss_decode@ should have |
| 208 | * left it. |
| 209 | */ |
| 210 | |
| 211 | ghash *pss_preverify(pss *pp) |
| 212 | { |
| 213 | size_t hsz = pp->ch->hashsz; |
| 214 | ghash *h = pp->ch->init(); |
| 215 | h->ops->hash(h, pp->salt, hsz); |
| 216 | return (h); |
| 217 | } |
| 218 | |
| 219 | /* --- @pss_done@ --- * |
| 220 | * |
| 221 | * Arguments: @pss *pp@ = pointer to PSS parameter block |
| 222 | * |
| 223 | * Returns: --- |
| 224 | * |
| 225 | * Use: Disposes of a PSS parameter block once it's finished with. |
| 226 | */ |
| 227 | |
| 228 | void pss_done(pss *pp) |
| 229 | { |
| 230 | if (pp->salt) { |
| 231 | xfree(pp->salt); |
| 232 | pp->salt = 0; |
| 233 | } |
| 234 | } |
| 235 | |
| 236 | /*----- That's all, folks -------------------------------------------------*/ |