| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: ofb.h,v 1.1 1999/09/03 08:41:12 mdw Exp $ |
| 4 | * |
| 5 | * Output feedback for block ciphers |
| 6 | * |
| 7 | * (c) 1999 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: ofb.h,v $ |
| 33 | * Revision 1.1 1999/09/03 08:41:12 mdw |
| 34 | * Initial import. |
| 35 | * |
| 36 | */ |
| 37 | |
| 38 | #ifndef OFB_H |
| 39 | #define OFB_H |
| 40 | |
| 41 | #ifdef __cplusplus |
| 42 | extern "C" { |
| 43 | #endif |
| 44 | |
| 45 | /*----- Header files ------------------------------------------------------*/ |
| 46 | |
| 47 | #include <string.h> |
| 48 | |
| 49 | #include <mLib/bits.h> |
| 50 | |
| 51 | #ifndef BLKC_H |
| 52 | # include "blkc.h" |
| 53 | #endif |
| 54 | |
| 55 | #ifndef PARANOIA_H |
| 56 | # include "paranoia.h" |
| 57 | #endif |
| 58 | |
| 59 | /*----- Macros ------------------------------------------------------------*/ |
| 60 | |
| 61 | /* --- @OFB_DECL@ --- * |
| 62 | * |
| 63 | * Arguments: @PRE@, @pre@ = prefixes for block cipher definitions |
| 64 | * |
| 65 | * Use: Makes declarations for output feedback mode. |
| 66 | */ |
| 67 | |
| 68 | #define OFB_DECL(PRE, pre) \ |
| 69 | \ |
| 70 | typedef struct pre ## _ofbctx { \ |
| 71 | pre ## _ctx ctx; /* Underlying cipher context */ \ |
| 72 | int off; /* Current offset in buffer */ \ |
| 73 | octet iv[PRE ## _BLKSZ]; /* Output buffer and IV */ \ |
| 74 | } pre ## _ofbctx; \ |
| 75 | \ |
| 76 | extern void pre ## _ofbgetiv(const pre ## _ofbctx */*ctx*/, \ |
| 77 | void */*iv*/); \ |
| 78 | \ |
| 79 | extern void pre ## _ofbsetiv(pre ## _ofbctx */*ctx*/, \ |
| 80 | const void */*iv*/); \ |
| 81 | \ |
| 82 | extern void pre ## _ofbbdry(pre ## _ofbctx */*ctx*/); \ |
| 83 | \ |
| 84 | extern void pre ## _ofbsetkey(pre ## _ofbctx */*ctx*/, \ |
| 85 | const pre ## _ctx */*k*/); \ |
| 86 | \ |
| 87 | extern void pre ## _ofbinit(pre ## _ofbctx */*ctx*/, \ |
| 88 | const void */*key*/, size_t /*sz*/, \ |
| 89 | const void */*iv*/); \ |
| 90 | \ |
| 91 | extern void pre ## _ofbencrypt(pre ## _ofbctx */*ctx*/, \ |
| 92 | const void */*src*/, void */*dest*/, \ |
| 93 | size_t /*sz*/); |
| 94 | |
| 95 | /* --- @OFB_DEF@ --- * |
| 96 | * |
| 97 | * Arguments: @PRE@, @pre@ = prefixes for the underlying block cipher |
| 98 | * |
| 99 | * Use: Creates definitions for output feedback mode. |
| 100 | */ |
| 101 | |
| 102 | #define OFB_DEF(PRE, pre) \ |
| 103 | \ |
| 104 | /* --- @pre_ofbgetiv@ --- * \ |
| 105 | * \ |
| 106 | * Arguments: @const pre_ofbctx *ctx@ = pointer to OFB context block \ |
| 107 | * @void *iv#@ = pointer to output data block \ |
| 108 | * \ |
| 109 | * Returns: --- \ |
| 110 | * \ |
| 111 | * Use: Reads the currently set IV. Reading and setting an IV \ |
| 112 | * is not transparent to the cipher. It will add a `step' \ |
| 113 | * which must be matched by a similar operation during \ |
| 114 | * decryption. \ |
| 115 | */ \ |
| 116 | \ |
| 117 | void pre ## _ofbgetiv(const pre ## _ofbctx *ctx, void *iv) \ |
| 118 | { \ |
| 119 | octet *p = iv; \ |
| 120 | int off = ctx->off; \ |
| 121 | int rest = PRE ## _BLKSZ - off; \ |
| 122 | memcpy(p, ctx->iv + off, rest); \ |
| 123 | memcpy(p + rest, ctx->iv, off); \ |
| 124 | } \ |
| 125 | \ |
| 126 | /* --- @pre_ofbsetiv@ --- * \ |
| 127 | * \ |
| 128 | * Arguments: @pre_ofbctx *ctx@ = pointer to OFB context block \ |
| 129 | * @cnost void *iv@ = pointer to IV to set \ |
| 130 | * \ |
| 131 | * Returns: --- \ |
| 132 | * \ |
| 133 | * Use: Sets the IV to use for subsequent encryption. \ |
| 134 | */ \ |
| 135 | \ |
| 136 | void pre ## _ofbsetiv(pre ## _ofbctx *ctx, const void *iv) \ |
| 137 | { \ |
| 138 | uint32 niv[PRE ## _BLKSZ / 4]; \ |
| 139 | BLKC_LOAD(PRE, niv, iv); \ |
| 140 | pre ## _eblk(&ctx->ctx, niv, niv); \ |
| 141 | BLKC_STORE(PRE, ctx->iv, niv); \ |
| 142 | ctx->off = 0; \ |
| 143 | } \ |
| 144 | \ |
| 145 | /* --- @pre_ofbbdry@ --- * \ |
| 146 | * \ |
| 147 | * Arguments: @pre_ofbctx *ctx@ = pointer to OFB context block \ |
| 148 | * \ |
| 149 | * Returns: --- \ |
| 150 | * \ |
| 151 | * Use: Inserts a boundary during encryption. Successful \ |
| 152 | * decryption must place a similar boundary. \ |
| 153 | */ \ |
| 154 | \ |
| 155 | void pre ## _ofbbdry(pre ## _ofbctx *ctx) \ |
| 156 | { \ |
| 157 | octet iv[PRE ## _BLKSZ]; \ |
| 158 | pre ## _ofbgetiv(ctx, iv); \ |
| 159 | pre ## _ofbsetiv(ctx, iv); \ |
| 160 | BURN(iv); \ |
| 161 | } \ |
| 162 | \ |
| 163 | /* --- @pre_ofbsetkey@ --- * \ |
| 164 | * \ |
| 165 | * Arguments: @pre_ofbctx *ctx@ = pointer to OFB context block \ |
| 166 | * @const pre_ctx *k@ = pointer to cipher context \ |
| 167 | * \ |
| 168 | * Returns: --- \ |
| 169 | * \ |
| 170 | * Use: Sets the OFB context to use a different cipher key. \ |
| 171 | */ \ |
| 172 | \ |
| 173 | void pre ## _ofbsetkey(pre ## _ofbctx *ctx, const pre ## _ctx *k) \ |
| 174 | { \ |
| 175 | ctx->ctx = *k; \ |
| 176 | } \ |
| 177 | \ |
| 178 | /* --- @pre_ofbinit@ --- * \ |
| 179 | * \ |
| 180 | * Arguments: @pre_ofbctx *ctx@ = pointer to cipher context \ |
| 181 | * @const void *key@ = pointer to the key buffer \ |
| 182 | * @size_t sz@ = size of the key \ |
| 183 | * @const void *iv@ = pointer to initialization vector \ |
| 184 | * \ |
| 185 | * Returns: --- \ |
| 186 | * \ |
| 187 | * Use: Initializes a OFB context ready for use. You should \ |
| 188 | * ensure that the IV chosen is unique: reusing an IV will \ |
| 189 | * compromise the security of the entire plaintext. This \ |
| 190 | * is equivalent to calls to @pre_init@, @pre_ofbsetkey@ \ |
| 191 | * and @pre_ofbsetiv@. \ |
| 192 | */ \ |
| 193 | \ |
| 194 | void pre ## _ofbinit(pre ## _ofbctx *ctx, \ |
| 195 | const void *key, size_t sz, \ |
| 196 | const void *iv) \ |
| 197 | { \ |
| 198 | static octet zero[PRE ## _BLKSZ] = { 0 }; \ |
| 199 | pre ## _init(&ctx->ctx, key, sz); \ |
| 200 | pre ## _ofbsetiv(ctx, iv ? iv : zero); \ |
| 201 | } \ |
| 202 | \ |
| 203 | /* --- @pre_ofbencrypt@ --- * \ |
| 204 | * \ |
| 205 | * Arguments: @pre_ofbctx *ctx@ = pointer to OFB context block \ |
| 206 | * @const void *src@ = pointer to source data \ |
| 207 | * @void *dest@ = pointer to destination data \ |
| 208 | * @size_t sz@ = size of block to be encrypted \ |
| 209 | * \ |
| 210 | * Returns: --- \ |
| 211 | * \ |
| 212 | * Use: Encrypts or decrypts a block with a block cipher in OFB \ |
| 213 | * mode: encryption and decryption are the same in OFB. \ |
| 214 | * The destination may be null to just churn the feedback \ |
| 215 | * round for a bit. The source may be null to use the \ |
| 216 | * cipher as a random data generator. \ |
| 217 | */ \ |
| 218 | \ |
| 219 | void pre ## _ofbencrypt(pre ## _ofbctx *ctx, \ |
| 220 | const void *src, void *dest, \ |
| 221 | size_t sz) \ |
| 222 | { \ |
| 223 | const octet *s = src; \ |
| 224 | octet *d = dest; \ |
| 225 | int off = ctx->off; \ |
| 226 | \ |
| 227 | /* --- Empty blocks are trivial --- */ \ |
| 228 | \ |
| 229 | if (!sz) \ |
| 230 | return; \ |
| 231 | \ |
| 232 | /* --- If I can deal with the block from my buffer, do that --- */ \ |
| 233 | \ |
| 234 | if (sz < PRE ## _BLKSZ - off) \ |
| 235 | goto small; \ |
| 236 | \ |
| 237 | /* --- Finish off what's left in my buffer --- */ \ |
| 238 | \ |
| 239 | if (!d) \ |
| 240 | sz -= off; \ |
| 241 | else { \ |
| 242 | while (off < PRE ## _BLKSZ) { \ |
| 243 | register octet x = s ? *s++ : 0; \ |
| 244 | *d++ = ctx->iv[off++] ^ x; \ |
| 245 | sz--; \ |
| 246 | } \ |
| 247 | } \ |
| 248 | \ |
| 249 | /* --- Main encryption loop --- */ \ |
| 250 | \ |
| 251 | { \ |
| 252 | uint32 iv[PRE ## _BLKSZ / 4]; \ |
| 253 | BLKC_LOAD(PRE, iv, ctx->iv); \ |
| 254 | \ |
| 255 | for (;;) { \ |
| 256 | pre ## _eblk(&ctx->ctx, iv, iv); \ |
| 257 | if (sz < PRE ## _BLKSZ) \ |
| 258 | break; \ |
| 259 | if (d) { \ |
| 260 | if (!s) \ |
| 261 | BLKC_STORE(PRE, d, iv); \ |
| 262 | else { \ |
| 263 | uint32 x[PRE ## _BLKSZ / 4]; \ |
| 264 | BLKC_LOAD(PRE, x, s); \ |
| 265 | BLKC_XSTORE(PRE, d, iv, x); \ |
| 266 | s += PRE ## _BLKSZ; \ |
| 267 | } \ |
| 268 | d += PRE ## _BLKSZ; \ |
| 269 | } \ |
| 270 | sz -= PRE ## _BLKSZ; \ |
| 271 | } \ |
| 272 | \ |
| 273 | BLKC_STORE(PRE, ctx->iv, iv); \ |
| 274 | off = 0; \ |
| 275 | } \ |
| 276 | \ |
| 277 | /* --- Tidying up the tail end --- */ \ |
| 278 | \ |
| 279 | if (sz) { \ |
| 280 | small: \ |
| 281 | if (!d) \ |
| 282 | off += sz; \ |
| 283 | else do { \ |
| 284 | register octet x = s ? *s++ : 0; \ |
| 285 | *d++ = ctx->iv[off++] ^ x; \ |
| 286 | sz--; \ |
| 287 | } while (sz); \ |
| 288 | } \ |
| 289 | \ |
| 290 | /* --- Done --- */ \ |
| 291 | \ |
| 292 | ctx->off = off; \ |
| 293 | return; \ |
| 294 | } \ |
| 295 | \ |
| 296 | OFB_TEST(PRE, pre) |
| 297 | |
| 298 | /*----- Test rig ----------------------------------------------------------*/ |
| 299 | |
| 300 | #ifdef TEST_RIG |
| 301 | |
| 302 | #include <stdio.h> |
| 303 | |
| 304 | #include "daftstory.h" |
| 305 | |
| 306 | /* --- @OFB_TEST@ --- * |
| 307 | * |
| 308 | * Arguments: @PRE@, @pre@ = prefixes for block cipher definitions |
| 309 | * |
| 310 | * Use: Standard test rig for OFB functions. |
| 311 | */ |
| 312 | |
| 313 | #define OFB_TEST(PRE, pre) \ |
| 314 | \ |
| 315 | /* --- Initial plaintext for the test --- */ \ |
| 316 | \ |
| 317 | static const octet text[] = TEXT; \ |
| 318 | \ |
| 319 | /* --- Key and IV to use --- */ \ |
| 320 | \ |
| 321 | static const octet key[] = KEY; \ |
| 322 | static const octet iv[] = IV; \ |
| 323 | \ |
| 324 | /* --- Buffers for encryption and decryption output --- */ \ |
| 325 | \ |
| 326 | static octet ct[sizeof(text)]; \ |
| 327 | static octet pt[sizeof(text)]; \ |
| 328 | \ |
| 329 | static void hexdump(const octet *p, size_t sz) \ |
| 330 | { \ |
| 331 | const octet *q = p + sz; \ |
| 332 | for (sz = 0; p < q; p++, sz++) { \ |
| 333 | printf("%02x", *p); \ |
| 334 | if ((sz + 1) % PRE ## _BLKSZ == 0) \ |
| 335 | putchar(':'); \ |
| 336 | } \ |
| 337 | } \ |
| 338 | \ |
| 339 | int main(void) \ |
| 340 | { \ |
| 341 | size_t sz = 0, rest; \ |
| 342 | pre ## _ofbctx ctx; \ |
| 343 | int status = 0; \ |
| 344 | int done = 0; \ |
| 345 | pre ## _ctx k; \ |
| 346 | \ |
| 347 | size_t keysz = PRE ## _KEYSZ ? \ |
| 348 | PRE ## _KEYSZ : strlen((const char *)key); \ |
| 349 | \ |
| 350 | fputs(#pre "-ofb: ", stdout); \ |
| 351 | \ |
| 352 | pre ## _init(&k, key, keysz); \ |
| 353 | pre ## _ofbsetkey(&ctx, &k); \ |
| 354 | \ |
| 355 | while (sz <= sizeof(text)) { \ |
| 356 | rest = sizeof(text) - sz; \ |
| 357 | memcpy(ct, text, sizeof(text)); \ |
| 358 | pre ## _ofbsetiv(&ctx, iv); \ |
| 359 | pre ## _ofbencrypt(&ctx, ct, ct, sz); \ |
| 360 | pre ## _ofbencrypt(&ctx, ct + sz, ct + sz, rest); \ |
| 361 | memcpy(pt, ct, sizeof(text)); \ |
| 362 | pre ## _ofbsetiv(&ctx, iv); \ |
| 363 | pre ## _ofbencrypt(&ctx, pt, pt, rest); \ |
| 364 | pre ## _ofbencrypt(&ctx, pt + rest, pt + rest, sz); \ |
| 365 | if (memcmp(pt, text, sizeof(text)) == 0) { \ |
| 366 | done++; \ |
| 367 | if (sizeof(text) < 40 || done % 8 == 0) \ |
| 368 | fputc('.', stdout); \ |
| 369 | if (done % 480 == 0) \ |
| 370 | fputs("\n\t", stdout); \ |
| 371 | fflush(stdout); \ |
| 372 | } else { \ |
| 373 | printf("\nError (sz = %lu)\n", (unsigned long)sz); \ |
| 374 | status = 1; \ |
| 375 | printf("\tplaintext = "); hexdump(text, sz); \ |
| 376 | printf(", "); hexdump(text + sz, rest); \ |
| 377 | fputc('\n', stdout); \ |
| 378 | printf("\tciphertext = "); hexdump(ct, sz); \ |
| 379 | printf(", "); hexdump(ct + sz, rest); \ |
| 380 | fputc('\n', stdout); \ |
| 381 | printf("\trecovered text = "); hexdump(pt, sz); \ |
| 382 | printf(", "); hexdump(pt + sz, rest); \ |
| 383 | fputc('\n', stdout); \ |
| 384 | fputc('\n', stdout); \ |
| 385 | } \ |
| 386 | if (sz < 63) \ |
| 387 | sz++; \ |
| 388 | else \ |
| 389 | sz += 9; \ |
| 390 | } \ |
| 391 | \ |
| 392 | fputs(status ? " failed\n" : " ok\n", stdout); \ |
| 393 | return (status); \ |
| 394 | } |
| 395 | |
| 396 | #else |
| 397 | # define OFB_TEST(PRE, pre) |
| 398 | #endif |
| 399 | |
| 400 | /*----- That's all, folks -------------------------------------------------*/ |
| 401 | |
| 402 | #ifdef __cplusplus |
| 403 | } |
| 404 | #endif |
| 405 | |
| 406 | #endif |