| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: pkcs1.c,v 1.4 2004/04/08 01:36:15 mdw Exp $ |
| 4 | * |
| 5 | * PKCS#1 1.5 packing |
| 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 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include <string.h> |
| 33 | |
| 34 | #include <mLib/bits.h> |
| 35 | #include <mLib/dstr.h> |
| 36 | |
| 37 | #include "grand.h" |
| 38 | #include "rsa.h" |
| 39 | |
| 40 | /*----- Main code ---------------------------------------------------------*/ |
| 41 | |
| 42 | /* --- @pkcs1_cryptencode@ --- * |
| 43 | * |
| 44 | * Arguments: @mp *d@ = where to put the answer |
| 45 | * @const void *m@ = pointer to message data |
| 46 | * @size_t msz@ = size of message data |
| 47 | * @octet *b@ = spare buffer |
| 48 | * @size_t sz@ = size of the buffer (big enough) |
| 49 | * @unsigned long nbits@ = length of bits of @n@ |
| 50 | * @void *p@ = pointer to PKCS1 parameter block |
| 51 | * |
| 52 | * Returns: The encoded result, or null. |
| 53 | * |
| 54 | * Use: Implements the operation @EME-PKCS1-V1_5-ENCODE@, as defined |
| 55 | * in PKCS#1 v. 2.0 (RFC2437). |
| 56 | */ |
| 57 | |
| 58 | mp *pkcs1_cryptencode(mp *d, const void *m, size_t msz, octet *b, size_t sz, |
| 59 | unsigned long nbits, void *p) |
| 60 | { |
| 61 | pkcs1 *pp = p; |
| 62 | grand *r = pp->r; |
| 63 | octet *q; |
| 64 | size_t i, n; |
| 65 | |
| 66 | /* --- Ensure that the buffer is sensibly sized --- */ |
| 67 | |
| 68 | if (pp->epsz + msz + 11 > sz) |
| 69 | return (0); |
| 70 | |
| 71 | /* --- Allocate the buffer and fill it in --- */ |
| 72 | |
| 73 | q = b; |
| 74 | *q++ = 0x00; |
| 75 | *q++ = 0x02; |
| 76 | n = sz - msz - pp->epsz - 3; |
| 77 | GR_FILL(r, q, n); |
| 78 | for (i = 0; i < n; i++) { |
| 79 | if (*q == 0) |
| 80 | *q = r->ops->range(r, 255) + 1; |
| 81 | q++; |
| 82 | } |
| 83 | *q++ = 0; |
| 84 | if (pp->ep) { |
| 85 | memcpy(q, pp->ep, pp->epsz); |
| 86 | q += pp->epsz; |
| 87 | } |
| 88 | memcpy(q, m, msz); |
| 89 | q += msz; |
| 90 | assert(q == b + sz); |
| 91 | |
| 92 | /* --- Collect the result --- */ |
| 93 | |
| 94 | return (mp_loadb(d, b, sz)); |
| 95 | } |
| 96 | |
| 97 | /* --- @pkcs1_cryptdecode@ --- * |
| 98 | * |
| 99 | * Arguments: @mp *m@ = the decrypted message |
| 100 | * @octet *b@ = pointer to a buffer to work in |
| 101 | * @size_t sz@ = the size of the buffer (big enough) |
| 102 | * @unsigned long nbits@ = the number of bits in @n@ |
| 103 | * @void *p@ = pointer to PKCS1 parameter block |
| 104 | * |
| 105 | * Returns: The length of the output string if successful, negative on |
| 106 | * failure. |
| 107 | * |
| 108 | * Use: Implements the operation @EME-PKCS1-V1_5-DECODE@, as defined |
| 109 | * in PKCS#1 v. 2.0 (RFC2437). |
| 110 | */ |
| 111 | |
| 112 | static int memeq(const void *xx, const void *yy, size_t sz) |
| 113 | { |
| 114 | int eq = 1; |
| 115 | const octet *x = xx, *y = yy; |
| 116 | while (sz) { /* Always check every byte */ |
| 117 | if (*x++ != *y++) eq = 0; |
| 118 | sz--; |
| 119 | } |
| 120 | return (eq); |
| 121 | } |
| 122 | |
| 123 | int pkcs1_cryptdecode(mp *m, octet *b, size_t sz, |
| 124 | unsigned long nbits, void *p) |
| 125 | { |
| 126 | pkcs1 *pp = p; |
| 127 | const octet *q, *qq; |
| 128 | size_t n, i; |
| 129 | int bad = 0; |
| 130 | |
| 131 | /* --- Check the size of the block looks sane --- */ |
| 132 | |
| 133 | if (pp->epsz + 11 > sz) /* OK: independent of ciphertext */ |
| 134 | return (-1); |
| 135 | mp_storeb(m, b, sz); |
| 136 | q = b; |
| 137 | qq = q + sz; |
| 138 | |
| 139 | /* --- Ensure that the block looks OK --- */ |
| 140 | |
| 141 | bad |= (*q++ != 0x00 || *q++ != 0x02); |
| 142 | |
| 143 | /* --- Check the nonzero padding --- */ |
| 144 | |
| 145 | i = 0; |
| 146 | while (*q != 0 && q < qq) |
| 147 | i++, q++; |
| 148 | bad |= (i < 8 || qq - q < pp->epsz + 1); |
| 149 | q++; |
| 150 | |
| 151 | /* --- Check the encoding parameters --- */ |
| 152 | |
| 153 | bad |= (pp->ep && !memeq(bad ? b : q, pp->ep, pp->epsz)); |
| 154 | q += pp->epsz; |
| 155 | |
| 156 | /* --- Done --- */ |
| 157 | |
| 158 | n = qq - q; |
| 159 | memmove(b, bad ? b + 1 : q, n); |
| 160 | return (bad ? -1 : n); |
| 161 | } |
| 162 | |
| 163 | /* --- @pkcs1_sigencode@ --- * |
| 164 | * |
| 165 | * Arguments: @mp *d@ = where to put the answer |
| 166 | * @const void *m@ = pointer to message data |
| 167 | * @size_t msz@ = size of message data |
| 168 | * @octet *b@ = spare buffer |
| 169 | * @size_t sz@ = size of the buffer (big enough) |
| 170 | * @unsigned long nbits@ = length of bits of @n@ |
| 171 | * @void *p@ = pointer to PKCS1 parameter block |
| 172 | * |
| 173 | * Returns: The encoded message representative, or null. |
| 174 | * |
| 175 | * Use: Implements the operation @EMSA-PKCS1-V1_5-ENCODE@, as defined |
| 176 | * in PKCS#1 v. 2.0 (RFC2437). |
| 177 | */ |
| 178 | |
| 179 | mp *pkcs1_sigencode(mp *d, const void *m, size_t msz, octet *b, size_t sz, |
| 180 | unsigned long nbits, void *p) |
| 181 | { |
| 182 | pkcs1 *pp = p; |
| 183 | octet *q; |
| 184 | size_t n; |
| 185 | |
| 186 | /* --- Ensure that the buffer is sensibly sized --- */ |
| 187 | |
| 188 | if (pp->epsz + msz + 11 > sz) |
| 189 | return (0); |
| 190 | |
| 191 | /* --- Fill in the buffer --- */ |
| 192 | |
| 193 | q = b; |
| 194 | *q++ = 0x00; |
| 195 | *q++ = 0x01; |
| 196 | n = sz - msz - pp->epsz - 3; |
| 197 | memset(q, 0xff, n); |
| 198 | q += n; |
| 199 | *q++ = 0; |
| 200 | if (pp->ep) { |
| 201 | memcpy(q, pp->ep, pp->epsz); |
| 202 | q += pp->epsz; |
| 203 | } |
| 204 | memcpy(q, m, msz); |
| 205 | q += msz; |
| 206 | assert(q == b + sz); |
| 207 | return (mp_loadb(d, b, sz)); |
| 208 | } |
| 209 | |
| 210 | /* --- @pkcs1_sigdecode@ --- * |
| 211 | * |
| 212 | * Arguments: @mp *s@ = the message representative |
| 213 | * @const void *m@ = the original message, or null (ignored) |
| 214 | * @size_t msz@ = the message size (ignored) |
| 215 | * @octet *b@ = a scratch buffer |
| 216 | * @size_t sz@ = size of the buffer (large enough) |
| 217 | * @unsigned long nbits@ = number of bits in @n@ |
| 218 | * @void *p@ = pointer to PKCS1 parameters |
| 219 | * |
| 220 | * Returns: The length of the output string if successful, negative on |
| 221 | * failure. |
| 222 | * |
| 223 | * Use: Implements the operation @EMSA-PKCS1-V1_5-DECODE@, as defined |
| 224 | * in PKCS#1 v. 2.0 (RFC2437). |
| 225 | */ |
| 226 | |
| 227 | int pkcs1_sigdecode(mp *s, const void *m, size_t msz, octet *b, size_t sz, |
| 228 | unsigned long nbits, void *p) |
| 229 | { |
| 230 | pkcs1 *pp = p; |
| 231 | const octet *q, *qq; |
| 232 | size_t i, n; |
| 233 | |
| 234 | /* --- Check the size of the block looks sane --- */ |
| 235 | |
| 236 | if (pp->epsz + 10 > sz) |
| 237 | return (-1); |
| 238 | mp_storeb(s, b, sz); |
| 239 | q = b; |
| 240 | qq = q + sz; |
| 241 | |
| 242 | /* --- Ensure that the block looks OK --- */ |
| 243 | |
| 244 | if (*q++ != 0x00 || *q++ != 0x01) |
| 245 | return (-1); |
| 246 | |
| 247 | /* --- Check the padding --- */ |
| 248 | |
| 249 | i = 0; |
| 250 | while (*q == 0xff && q < qq) |
| 251 | i++, q++; |
| 252 | if (i < 8 || qq - q < pp->epsz + 1 || *q++ != 0) |
| 253 | return (-1); |
| 254 | |
| 255 | /* --- Check the encoding parameters --- */ |
| 256 | |
| 257 | if (pp->ep && memcmp(q, pp->ep, pp->epsz) != 0) |
| 258 | return (-1); |
| 259 | q += pp->epsz; |
| 260 | |
| 261 | /* --- Done --- */ |
| 262 | |
| 263 | n = qq - q; |
| 264 | memmove(b, q, n); |
| 265 | return (n); |
| 266 | } |
| 267 | |
| 268 | /*----- That's all, folks -------------------------------------------------*/ |