| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: crypt.c,v 1.2 1997/08/04 10:24:21 mdw Exp $ |
| 4 | * |
| 5 | * Cryptographic transfer of `become' requests |
| 6 | * |
| 7 | * (c) 1997 EBI |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of `become' |
| 13 | * |
| 14 | * `Become' is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU General Public License as published by |
| 16 | * the Free Software Foundation; either version 2 of the License, or |
| 17 | * (at your option) any later version. |
| 18 | * |
| 19 | * `Become' 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 General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with `become'; if not, write to the Free Software Foundation, |
| 26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 27 | */ |
| 28 | |
| 29 | /*----- Revision history --------------------------------------------------* |
| 30 | * |
| 31 | * $Log: crypt.c,v $ |
| 32 | * Revision 1.2 1997/08/04 10:24:21 mdw |
| 33 | * Sources placed under CVS control. |
| 34 | * |
| 35 | * Revision 1.1 1997/07/21 13:47:51 mdw |
| 36 | * Initial revision |
| 37 | * |
| 38 | */ |
| 39 | |
| 40 | /*----- Header files ------------------------------------------------------*/ |
| 41 | |
| 42 | /* --- ANSI headers --- */ |
| 43 | |
| 44 | #include <ctype.h> |
| 45 | #include <errno.h> |
| 46 | #include <stdio.h> |
| 47 | #include <stdlib.h> |
| 48 | #include <string.h> |
| 49 | #include <time.h> |
| 50 | |
| 51 | /* --- Unix headers --- */ |
| 52 | |
| 53 | #include <sys/types.h> |
| 54 | #include <sys/time.h> |
| 55 | #include <unistd.h> |
| 56 | #include <syslog.h> |
| 57 | #include <fcntl.h> |
| 58 | |
| 59 | /* --- Local headers --- */ |
| 60 | |
| 61 | #include "become.h" |
| 62 | #include "config.h" |
| 63 | #include "crypt.h" |
| 64 | #include "icrypt.h" |
| 65 | #include "idea.h" |
| 66 | #include "md5.h" |
| 67 | #include "noise.h" |
| 68 | #include "rand.h" |
| 69 | #include "tx.h" |
| 70 | #include "utils.h" |
| 71 | |
| 72 | /*----- Magic numbers -----------------------------------------------------*/ |
| 73 | |
| 74 | #define crypt__timeError 60 /* Seconds error to permit */ |
| 75 | |
| 76 | /*----- Main code ---------------------------------------------------------*/ |
| 77 | |
| 78 | /* --- @crypt__sessionKey@ --- * |
| 79 | * |
| 80 | * Arguments: @const char *seedfile@ = pointer to name of seed file |
| 81 | * @unsigned char *k@ = our secret key |
| 82 | * @unsigned *sk@ = where to store the session key |
| 83 | * @unsigned char *iv@ = where to store the IV |
| 84 | * |
| 85 | * Returns: --- |
| 86 | * |
| 87 | * Use: Decides on a random session key and initialisation vector. |
| 88 | */ |
| 89 | |
| 90 | static void crypt__sessionKey(const char *seedfile, unsigned char *k, |
| 91 | unsigned char *sk, unsigned char *iv) |
| 92 | { |
| 93 | FILE *fp; /* File handle for reading */ |
| 94 | struct flock l; |
| 95 | int ok = 1; |
| 96 | |
| 97 | /* --- Open the random seed file --- * |
| 98 | * |
| 99 | * If I can't manage that, create a new one. |
| 100 | */ |
| 101 | |
| 102 | if ((fp = fopen(seedfile, "r+")) == 0) { |
| 103 | ok = 0; |
| 104 | if ((fp = fopen(seedfile, "w+")) == 0) |
| 105 | die("can't create random number file: %s", strerror(errno)); |
| 106 | rand_clear(); |
| 107 | } |
| 108 | |
| 109 | /* --- Lock the seed file against concurrency problems --- */ |
| 110 | |
| 111 | l.l_type = F_WRLCK; |
| 112 | l.l_whence = SEEK_SET; |
| 113 | l.l_start = 0; |
| 114 | l.l_len = 0; |
| 115 | if (fcntl(fileno(fp), F_SETLKW, &l) < 0) |
| 116 | die("can't lock random number file: %s", strerror(errno)); |
| 117 | |
| 118 | /* --- Now read the file, and launder the seed --- */ |
| 119 | |
| 120 | if (ok) |
| 121 | rand_read(fp); |
| 122 | |
| 123 | /* --- Encrypt the pool using the secret key --- */ |
| 124 | |
| 125 | { |
| 126 | icrypt_job j; |
| 127 | icrypt_init(&j, k, 0); |
| 128 | rand_encrypt(&j); |
| 129 | burn(j); |
| 130 | } |
| 131 | |
| 132 | /* --- Generate the session key and IV --- */ |
| 133 | |
| 134 | noise_acquire(); |
| 135 | rand_extract(sk, IDEA_KEYSIZE); |
| 136 | rand_extract(iv, IDEA_BLKSIZE); |
| 137 | |
| 138 | IF_TRACING(TRACE_CRYPTO, |
| 139 | traceblk(TRACE_CRYPTO, "crypto: session key:", sk, IDEA_KEYSIZE); |
| 140 | traceblk(TRACE_CRYPTO, "crypto: initialisation vector:", |
| 141 | iv, IDEA_BLKSIZE); |
| 142 | ); |
| 143 | |
| 144 | /* --- Write the seed back --- */ |
| 145 | |
| 146 | rewind(fp); |
| 147 | rand_write(fp); |
| 148 | fclose(fp); |
| 149 | |
| 150 | } |
| 151 | |
| 152 | /* --- @crypt_packRequest@ --- * |
| 153 | * |
| 154 | * Arguments: @request *rq@ = pointer to request block |
| 155 | * @unsigned char *buff@ = pointer to a buffer |
| 156 | * @time_t t@ = the current time |
| 157 | * @pid_t pid@ = my process ID |
| 158 | * @unsigned char *k@ = pointer to 128-bit key |
| 159 | * @unsigned char *sk@ = where to put the session key |
| 160 | * |
| 161 | * Returns: --- |
| 162 | * |
| 163 | * Use: Packs a request block into a buffer. The buffer should have |
| 164 | * space for at least @crq_size@ bytes. The buffer comes back |
| 165 | * encrypted and ready to send. |
| 166 | */ |
| 167 | |
| 168 | void crypt_packRequest(request *rq, unsigned char *buff, |
| 169 | time_t t, pid_t pid, |
| 170 | unsigned char *k, unsigned char *sk) |
| 171 | { |
| 172 | /* --- First, build the easy stuff in the block --- */ |
| 173 | |
| 174 | buff[crq_cryptType] = cryptType_idea; |
| 175 | store32(buff + crq_time, t); |
| 176 | store32(buff + crq_pid, pid); |
| 177 | store32(buff + crq_from, rq->from); |
| 178 | store32(buff + crq_to, rq->to); |
| 179 | |
| 180 | /* --- Now generate session keys and things --- */ |
| 181 | |
| 182 | crypt__sessionKey(file_RANDSEED, k, sk, buff + crq_iv); |
| 183 | memcpy(buff + crq_session, sk, IDEA_KEYSIZE); |
| 184 | |
| 185 | /* --- The string causes a few problems --- * |
| 186 | * |
| 187 | * There's a good chance that the string will be a good deal shorter than |
| 188 | * the space allowed for it. This will probably mean lots of zeroes, and a |
| 189 | * very easy known-plaintext job for a potential attacker. (An early |
| 190 | * version of this code used @strncpy@ which is even worse!) |
| 191 | * |
| 192 | * I'll fill the block with random (from @rand@(3) -- nothing too |
| 193 | * elaborate) and then encrypt it using IDEA in CFB mode, using the first |
| 194 | * few bytes as the key. This should provide a sufficiently unpredictable |
| 195 | * background for the block. |
| 196 | */ |
| 197 | |
| 198 | { |
| 199 | icrypt_job j; |
| 200 | unsigned char *p; |
| 201 | unsigned u; |
| 202 | md5 md; |
| 203 | unsigned char qk[IDEA_KEYSIZE]; |
| 204 | |
| 205 | /* --- Initialise the buffer with junk --- */ |
| 206 | |
| 207 | srand((unsigned int)(t ^ pid)); /* Seed the (bad) RNG */ |
| 208 | for (p = buff + crq_cmd; p < buff + crq_cmd + CMDLEN_MAX; p++) { |
| 209 | u = rand(); *p = u ^ (u >> 8); |
| 210 | } |
| 211 | |
| 212 | /* --- Now make the junk a whole lot harder to predict --- */ |
| 213 | |
| 214 | p = buff + crq_cmd; |
| 215 | md5_init(&md); md5_buffer(&md, p, CMDLEN_MAX); md5_final(&md, qk); |
| 216 | icrypt_init(&j, qk, 0); icrypt_encrypt(&j, p, p, CMDLEN_MAX); |
| 217 | burn(j); burn(qk); burn(md); |
| 218 | |
| 219 | /* --- Copy the string into here --- */ |
| 220 | |
| 221 | strcpy((char *)buff + crq_cmd, rq->cmd); |
| 222 | } |
| 223 | |
| 224 | /* --- Checksum the finished data --- */ |
| 225 | |
| 226 | { |
| 227 | md5 md; |
| 228 | unsigned char mdbuf[MD5_HASHSIZE]; |
| 229 | |
| 230 | md5_init(&md); |
| 231 | md5_buffer(&md, buff + crq_cipher, crq_check - crq_cipher); |
| 232 | md5_final(&md, mdbuf); |
| 233 | memcpy(buff + crq_check, mdbuf, 4); |
| 234 | burn(md); burn(mdbuf); |
| 235 | } |
| 236 | |
| 237 | /* --- Encrypt the block --- * |
| 238 | * |
| 239 | * First, encrypt the session key using the master key. Since the session |
| 240 | * key is effectively random, this makes cracking the master key much |
| 241 | * harder. The rest of the block is then encrypted with the session key, |
| 242 | * using the IV left over from encrypting the session key. |
| 243 | */ |
| 244 | |
| 245 | { |
| 246 | icrypt_job j; |
| 247 | |
| 248 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext request:", |
| 249 | buff, crq_size); ) |
| 250 | |
| 251 | icrypt_init(&j, k, buff + crq_iv); |
| 252 | icrypt_encrypt(&j, buff + crq_session, buff + crq_session, IDEA_KEYSIZE); |
| 253 | icrypt_reset(&j, sk, 0); |
| 254 | icrypt_encrypt(&j, buff + crq_cipher, |
| 255 | buff + crq_cipher, crq_size - crq_cipher); |
| 256 | burn(j); |
| 257 | |
| 258 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext request:", |
| 259 | buff, crq_size); ) |
| 260 | } |
| 261 | } |
| 262 | |
| 263 | /* --- @crypt_unpackRequest@ --- * |
| 264 | * |
| 265 | * Arguments: @reqest *rq@ = pointer to destination request block |
| 266 | * @unsigned char *buff@ = pointer to source buffer |
| 267 | * @unsigned char *k@ = pointer to encryption key |
| 268 | * @unsigned char *sk@ = pointer to where to store session key |
| 269 | * @unsigned char *rpl@ = where to start building reply |
| 270 | * |
| 271 | * Returns: Nonzero if it was decrypted OK |
| 272 | * |
| 273 | * Use: Decrypts and unpacks a request buffer. |
| 274 | */ |
| 275 | |
| 276 | int crypt_unpackRequest(request *rq, unsigned char *buff, |
| 277 | unsigned char *k, unsigned char *sk, |
| 278 | unsigned char *rpl) |
| 279 | { |
| 280 | { |
| 281 | /* --- Check the encryption format --- */ |
| 282 | |
| 283 | if (buff[crq_cryptType] != cryptType_idea) |
| 284 | return (0); |
| 285 | } |
| 286 | |
| 287 | { |
| 288 | /* --- First things first: decrypt the block --- */ |
| 289 | |
| 290 | icrypt_job j; |
| 291 | |
| 292 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext request:", |
| 293 | buff, crq_size); ) |
| 294 | |
| 295 | icrypt_init(&j, k, buff + crq_iv); |
| 296 | icrypt_decrypt(&j, buff + crq_session, buff + crq_session, IDEA_KEYSIZE); |
| 297 | memcpy(sk, buff + crq_session, IDEA_KEYSIZE); |
| 298 | icrypt_reset(&j, sk, 0); |
| 299 | icrypt_decrypt(&j, buff + crq_cipher, |
| 300 | buff + crq_cipher, crq_size - crq_cipher); |
| 301 | icrypt_saveIV(&j, rpl + crp_iv); |
| 302 | |
| 303 | memset(buff + crq_session, 0, IDEA_KEYSIZE); /* Burn, baby, burn */ |
| 304 | burn(j); |
| 305 | |
| 306 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext request:", |
| 307 | buff, crq_size); ) |
| 308 | } |
| 309 | |
| 310 | { |
| 311 | /* --- Check the validity of the data therein --- */ |
| 312 | |
| 313 | md5 md; |
| 314 | unsigned char mdbuf[MD5_HASHSIZE]; |
| 315 | |
| 316 | md5_init(&md); |
| 317 | md5_buffer(&md, buff + crq_cipher, crq_check - crq_cipher); |
| 318 | md5_final(&md, mdbuf); |
| 319 | if (memcmp(mdbuf, buff + crq_check, 4) != 0) { |
| 320 | syslog(LOG_INFO, "packet rejected: bad checksum"); |
| 321 | T( trace(TRACE_CRYPTO, "crypto: bad checksum on incoming request"); ) |
| 322 | return (0); |
| 323 | } |
| 324 | burn(md); burn(mdbuf); |
| 325 | } |
| 326 | |
| 327 | { |
| 328 | /* --- Extract fields from the block --- */ |
| 329 | |
| 330 | rq->from = load32(buff + crq_from); |
| 331 | rq->to = load32(buff + crq_to); |
| 332 | memcpy(rq->cmd, buff + crq_cmd, CMDLEN_MAX); |
| 333 | } |
| 334 | |
| 335 | { |
| 336 | /* --- Fill in bits of the reply block --- */ |
| 337 | |
| 338 | long t = (long)time(0); |
| 339 | long u = (long)load32(buff + crq_time); |
| 340 | |
| 341 | if (t - u > crypt__timeError || u - t > crypt__timeError) { |
| 342 | syslog(LOG_INFO, "packet rejected: bad time"); |
| 343 | T( trace(TRACE_CRYPTO, "crypto: bad time on incoming request"); ) |
| 344 | return (0); |
| 345 | } |
| 346 | memcpy(rpl + crp_time, buff + crq_time, 8); |
| 347 | } |
| 348 | |
| 349 | /* --- Done --- */ |
| 350 | |
| 351 | T( trace(TRACE_CRYPTO, "crypto: valid request received"); ) |
| 352 | return (1); |
| 353 | } |
| 354 | |
| 355 | /* --- @crypt_packReply@ --- * |
| 356 | * |
| 357 | * Arguments: @char *buff@ = pointer to reply block |
| 358 | * @unsigned char *sk@ = pointer to session key |
| 359 | * @int answer@ = yes or no |
| 360 | * |
| 361 | * Returns: --- |
| 362 | * |
| 363 | * Use: Packs and encrypts a reply block. |
| 364 | */ |
| 365 | |
| 366 | void crypt_packReply(unsigned char *buff, unsigned char *sk, int answer) |
| 367 | { |
| 368 | { |
| 369 | /* --- Store the answer --- */ |
| 370 | |
| 371 | buff[crp_answer] = (answer != 0); |
| 372 | } |
| 373 | |
| 374 | { |
| 375 | /* --- Build the checksum --- */ |
| 376 | |
| 377 | md5 md; |
| 378 | unsigned char mdbuf[MD5_HASHSIZE]; |
| 379 | |
| 380 | md5_init(&md); |
| 381 | md5_buffer(&md, buff + crp_cipher, crp_check - crp_cipher); |
| 382 | md5_final(&md, mdbuf); |
| 383 | memcpy(buff + crp_check, mdbuf, 4); |
| 384 | burn(md); burn(mdbuf); |
| 385 | } |
| 386 | |
| 387 | { |
| 388 | /* --- Encrypt the buffer --- */ |
| 389 | |
| 390 | icrypt_job j; |
| 391 | |
| 392 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext reply:", buff, crp_size); ) |
| 393 | |
| 394 | icrypt_init(&j, sk, buff + crp_iv); |
| 395 | icrypt_encrypt(&j, buff + crp_cipher, |
| 396 | buff + crp_cipher, crp_size - crp_cipher); |
| 397 | burn(j); |
| 398 | |
| 399 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext reply:", buff, crp_size); ) |
| 400 | } |
| 401 | } |
| 402 | |
| 403 | /* --- @crypt_unpackReply@ --- * |
| 404 | * |
| 405 | * Arguments: @unsigned char *buff@ = pointer to reply buffer |
| 406 | * @unsigned char *sk@ = pointer to session key |
| 407 | * @time_t t@ = time at which request was sent |
| 408 | * @pid_t pid@ = my process ID |
| 409 | * |
| 410 | * Returns: >0 if request granted, zero if denied, <0 if reply rejected |
| 411 | * |
| 412 | * Use: Unpacks a reply block, and informs the caller of the outcome. |
| 413 | */ |
| 414 | |
| 415 | int crypt_unpackReply(unsigned char *buff, unsigned char *sk, |
| 416 | time_t t, pid_t pid) |
| 417 | { |
| 418 | { |
| 419 | /* --- Decrypt my reply block --- */ |
| 420 | |
| 421 | icrypt_job j; |
| 422 | |
| 423 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext reply:", buff, crp_size); ) |
| 424 | |
| 425 | icrypt_init(&j, sk, buff + crp_iv); |
| 426 | icrypt_decrypt(&j, buff + crp_cipher, |
| 427 | buff + crp_cipher, crp_size - crp_cipher); |
| 428 | burn(j); |
| 429 | |
| 430 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext reply:", buff, crp_size); ) |
| 431 | } |
| 432 | |
| 433 | { |
| 434 | /* --- Check validity --- */ |
| 435 | |
| 436 | md5 md; |
| 437 | unsigned char mdbuf[MD5_HASHSIZE]; |
| 438 | char b[8]; |
| 439 | |
| 440 | /* --- Check the checksum --- */ |
| 441 | |
| 442 | md5_init(&md); |
| 443 | md5_buffer(&md, buff + crp_cipher, crp_check - crp_cipher); |
| 444 | md5_final(&md, mdbuf); |
| 445 | if (memcmp(buff + crp_check, mdbuf, 4) != 0) { |
| 446 | syslog(LOG_INFO, "reply rejected: bad checksum"); |
| 447 | T( trace(TRACE_CRYPTO, "crypto: bad checksum on reply"); ) |
| 448 | return (-1); |
| 449 | } |
| 450 | |
| 451 | /* --- Check the identifier --- */ |
| 452 | |
| 453 | store32(b + 0, t); store32(b + 4, pid); |
| 454 | if (memcmp(b, buff + crp_time, sizeof(b)) != 0) { |
| 455 | syslog(LOG_INFO, "reply rejected: bad identification marker"); |
| 456 | T( trace(TRACE_CRYPTO, "crypto: bad id on reply"); ) |
| 457 | return (-1); |
| 458 | } |
| 459 | } |
| 460 | |
| 461 | /* --- Return the value --- */ |
| 462 | |
| 463 | T( trace(TRACE_CRYPTO, "crypto: valid reply received"); ) |
| 464 | return (buff[crp_answer]); |
| 465 | } |
| 466 | |
| 467 | /*----- Test rig ----------------------------------------------------------*/ |
| 468 | |
| 469 | #ifdef TEST_RIG |
| 470 | |
| 471 | int main(int argc, char *argv[]) |
| 472 | { |
| 473 | unsigned char buff[8]; |
| 474 | unsigned char sk[IDEA_KEYSIZE], k[IDEA_KEYSIZE]; |
| 475 | FILE *fp; |
| 476 | |
| 477 | ego(argv[0]); |
| 478 | traceon(stdout, TRACE_CRYPTO); |
| 479 | if (argc < 3) |
| 480 | die("bad args"); |
| 481 | fp = fopen(argv[1], "r"); |
| 482 | if (!fp) |
| 483 | die("fopen: %s", strerror(errno)); |
| 484 | tx_getBits(k, 128, fp); |
| 485 | fclose(fp); |
| 486 | crypt__sessionKey(argv[2], k, sk, buff); |
| 487 | return (0); |
| 488 | } |
| 489 | |
| 490 | #endif |
| 491 | |
| 492 | /*----- That's all, folks -------------------------------------------------*/ |