1 /* $OpenBSD: cipher.c,v 1.97 2014/02/07 06:55:54 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * 7 * As far as I am concerned, the code I have written for this software 8 * can be used freely for any purpose. Any derived versions of this 9 * software must be clearly marked as such, and if the derived work is 10 * incompatible with the protocol description in the RFC file, it must be 11 * called by a name other than "ssh" or "Secure Shell". 12 * 13 * 14 * Copyright (c) 1999 Niels Provos. All rights reserved. 15 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include "includes.h" 39 40 #include <sys/types.h> 41 42 #include <string.h> 43 #include <stdarg.h> 44 #include <stdio.h> 45 46 #include "xmalloc.h" 47 #include "log.h" 48 #include "misc.h" 49 #include "cipher.h" 50 #include "buffer.h" 51 #include "digest.h" 52 53 /* compatibility with old or broken OpenSSL versions */ 54 #include "openbsd-compat/openssl-compat.h" 55 56 extern const EVP_CIPHER *evp_ssh1_bf(void); 57 extern const EVP_CIPHER *evp_ssh1_3des(void); 58 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 59 60 struct Cipher { 61 char *name; 62 int number; /* for ssh1 only */ 63 u_int block_size; 64 u_int key_len; 65 u_int iv_len; /* defaults to block_size */ 66 u_int auth_len; 67 u_int discard_len; 68 u_int flags; 69 #define CFLAG_CBC (1<<0) 70 #define CFLAG_CHACHAPOLY (1<<1) 71 const EVP_CIPHER *(*evptype)(void); 72 }; 73 74 static const struct Cipher ciphers[] = { 75 { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null }, 76 { "des", SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc }, 77 { "3des", SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des }, 78 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf }, 79 80 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc }, 81 { "blowfish-cbc", 82 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc }, 83 { "cast128-cbc", 84 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc }, 85 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 }, 86 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 }, 87 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 }, 88 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc }, 89 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc }, 90 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc }, 91 { "rijndael-cbc@lysator.liu.se", 92 SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc }, 93 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr }, 94 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr }, 95 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr }, 96 #ifdef OPENSSL_HAVE_EVPGCM 97 { "aes128-gcm@openssh.com", 98 SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm }, 99 { "aes256-gcm@openssh.com", 100 SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm }, 101 #endif 102 { "chacha20-poly1305@openssh.com", 103 SSH_CIPHER_SSH2, 8, 64, 0, 16, 0, CFLAG_CHACHAPOLY, NULL }, 104 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL } 105 }; 106 107 /*--*/ 108 109 /* Returns a list of supported ciphers separated by the specified char. */ 110 char * 111 cipher_alg_list(char sep, int auth_only) 112 { 113 char *ret = NULL; 114 size_t nlen, rlen = 0; 115 const Cipher *c; 116 117 for (c = ciphers; c->name != NULL; c++) { 118 if (c->number != SSH_CIPHER_SSH2) 119 continue; 120 if (auth_only && c->auth_len == 0) 121 continue; 122 if (ret != NULL) 123 ret[rlen++] = sep; 124 nlen = strlen(c->name); 125 ret = xrealloc(ret, 1, rlen + nlen + 2); 126 memcpy(ret + rlen, c->name, nlen + 1); 127 rlen += nlen; 128 } 129 return ret; 130 } 131 132 u_int 133 cipher_blocksize(const Cipher *c) 134 { 135 return (c->block_size); 136 } 137 138 u_int 139 cipher_keylen(const Cipher *c) 140 { 141 return (c->key_len); 142 } 143 144 u_int 145 cipher_seclen(const Cipher *c) 146 { 147 if (strcmp("3des-cbc", c->name) == 0) 148 return 14; 149 return cipher_keylen(c); 150 } 151 152 u_int 153 cipher_authlen(const Cipher *c) 154 { 155 return (c->auth_len); 156 } 157 158 u_int 159 cipher_ivlen(const Cipher *c) 160 { 161 /* 162 * Default is cipher block size, except for chacha20+poly1305 that 163 * needs no IV. XXX make iv_len == -1 default? 164 */ 165 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 166 c->iv_len : c->block_size; 167 } 168 169 u_int 170 cipher_get_number(const Cipher *c) 171 { 172 return (c->number); 173 } 174 175 u_int 176 cipher_is_cbc(const Cipher *c) 177 { 178 return (c->flags & CFLAG_CBC) != 0; 179 } 180 181 u_int 182 cipher_mask_ssh1(int client) 183 { 184 u_int mask = 0; 185 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 186 mask |= 1 << SSH_CIPHER_BLOWFISH; 187 if (client) { 188 mask |= 1 << SSH_CIPHER_DES; 189 } 190 return mask; 191 } 192 193 const Cipher * 194 cipher_by_name(const char *name) 195 { 196 const Cipher *c; 197 for (c = ciphers; c->name != NULL; c++) 198 if (strcmp(c->name, name) == 0) 199 return c; 200 return NULL; 201 } 202 203 const Cipher * 204 cipher_by_number(int id) 205 { 206 const Cipher *c; 207 for (c = ciphers; c->name != NULL; c++) 208 if (c->number == id) 209 return c; 210 return NULL; 211 } 212 213 #define CIPHER_SEP "," 214 int 215 ciphers_valid(const char *names) 216 { 217 const Cipher *c; 218 char *cipher_list, *cp; 219 char *p; 220 221 if (names == NULL || strcmp(names, "") == 0) 222 return 0; 223 cipher_list = cp = xstrdup(names); 224 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 225 (p = strsep(&cp, CIPHER_SEP))) { 226 c = cipher_by_name(p); 227 if (c == NULL || c->number != SSH_CIPHER_SSH2) { 228 debug("bad cipher %s [%s]", p, names); 229 free(cipher_list); 230 return 0; 231 } 232 } 233 debug3("ciphers ok: [%s]", names); 234 free(cipher_list); 235 return 1; 236 } 237 238 /* 239 * Parses the name of the cipher. Returns the number of the corresponding 240 * cipher, or -1 on error. 241 */ 242 243 int 244 cipher_number(const char *name) 245 { 246 const Cipher *c; 247 if (name == NULL) 248 return -1; 249 for (c = ciphers; c->name != NULL; c++) 250 if (strcasecmp(c->name, name) == 0) 251 return c->number; 252 return -1; 253 } 254 255 char * 256 cipher_name(int id) 257 { 258 const Cipher *c = cipher_by_number(id); 259 return (c==NULL) ? "<unknown>" : c->name; 260 } 261 262 void 263 cipher_init(CipherContext *cc, const Cipher *cipher, 264 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 265 int do_encrypt) 266 { 267 static int dowarn = 1; 268 #ifdef SSH_OLD_EVP 269 EVP_CIPHER *type; 270 #else 271 const EVP_CIPHER *type; 272 int klen; 273 #endif 274 u_char *junk, *discard; 275 276 if (cipher->number == SSH_CIPHER_DES) { 277 if (dowarn) { 278 error("Warning: use of DES is strongly discouraged " 279 "due to cryptographic weaknesses"); 280 dowarn = 0; 281 } 282 if (keylen > 8) 283 keylen = 8; 284 } 285 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 286 cc->encrypt = do_encrypt; 287 288 if (keylen < cipher->key_len) 289 fatal("cipher_init: key length %d is insufficient for %s.", 290 keylen, cipher->name); 291 if (iv != NULL && ivlen < cipher_ivlen(cipher)) 292 fatal("cipher_init: iv length %d is insufficient for %s.", 293 ivlen, cipher->name); 294 cc->cipher = cipher; 295 296 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 297 chachapoly_init(&cc->cp_ctx, key, keylen); 298 return; 299 } 300 type = (*cipher->evptype)(); 301 EVP_CIPHER_CTX_init(&cc->evp); 302 #ifdef SSH_OLD_EVP 303 if (type->key_len > 0 && type->key_len != keylen) { 304 debug("cipher_init: set keylen (%d -> %d)", 305 type->key_len, keylen); 306 type->key_len = keylen; 307 } 308 EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv, 309 (do_encrypt == CIPHER_ENCRYPT)); 310 #else 311 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 312 (do_encrypt == CIPHER_ENCRYPT)) == 0) 313 fatal("cipher_init: EVP_CipherInit failed for %s", 314 cipher->name); 315 if (cipher_authlen(cipher) && 316 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 317 -1, (u_char *)iv)) 318 fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s", 319 cipher->name); 320 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 321 if (klen > 0 && keylen != (u_int)klen) { 322 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 323 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 324 fatal("cipher_init: set keylen failed (%d -> %d)", 325 klen, keylen); 326 } 327 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 328 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 329 cipher->name); 330 #endif 331 332 if (cipher->discard_len > 0) { 333 junk = xmalloc(cipher->discard_len); 334 discard = xmalloc(cipher->discard_len); 335 if (EVP_Cipher(&cc->evp, discard, junk, 336 cipher->discard_len) == 0) 337 fatal("evp_crypt: EVP_Cipher failed during discard"); 338 explicit_bzero(discard, cipher->discard_len); 339 free(junk); 340 free(discard); 341 } 342 } 343 344 /* 345 * cipher_crypt() operates as following: 346 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 347 * Theses bytes are treated as additional authenticated data for 348 * authenticated encryption modes. 349 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 350 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 351 * This tag is written on encryption and verified on decryption. 352 * Both 'aadlen' and 'authlen' can be set to 0. 353 * cipher_crypt() returns 0 on success and -1 if the decryption integrity 354 * check fails. 355 */ 356 int 357 cipher_crypt(CipherContext *cc, u_int seqnr, u_char *dest, const u_char *src, 358 u_int len, u_int aadlen, u_int authlen) 359 { 360 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 361 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, len, 362 aadlen, authlen, cc->encrypt); 363 if (authlen) { 364 u_char lastiv[1]; 365 366 if (authlen != cipher_authlen(cc->cipher)) 367 fatal("%s: authlen mismatch %d", __func__, authlen); 368 /* increment IV */ 369 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 370 1, lastiv)) 371 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 372 /* set tag on decyption */ 373 if (!cc->encrypt && 374 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG, 375 authlen, (u_char *)src + aadlen + len)) 376 fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__); 377 } 378 if (aadlen) { 379 if (authlen && 380 EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0) 381 fatal("%s: EVP_Cipher(aad) failed", __func__); 382 memcpy(dest, src, aadlen); 383 } 384 if (len % cc->cipher->block_size) 385 fatal("%s: bad plaintext length %d", __func__, len); 386 if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen, 387 len) < 0) 388 fatal("%s: EVP_Cipher failed", __func__); 389 if (authlen) { 390 /* compute tag (on encrypt) or verify tag (on decrypt) */ 391 if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) { 392 if (cc->encrypt) 393 fatal("%s: EVP_Cipher(final) failed", __func__); 394 else 395 return -1; 396 } 397 if (cc->encrypt && 398 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG, 399 authlen, dest + aadlen + len)) 400 fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__); 401 } 402 return 0; 403 } 404 405 /* Extract the packet length, including any decryption necessary beforehand */ 406 int 407 cipher_get_length(CipherContext *cc, u_int *plenp, u_int seqnr, 408 const u_char *cp, u_int len) 409 { 410 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 411 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr, 412 cp, len); 413 if (len < 4) 414 return -1; 415 *plenp = get_u32(cp); 416 return 0; 417 } 418 419 void 420 cipher_cleanup(CipherContext *cc) 421 { 422 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 423 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx)); 424 else if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 425 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 426 } 427 428 /* 429 * Selects the cipher, and keys if by computing the MD5 checksum of the 430 * passphrase and using the resulting 16 bytes as the key. 431 */ 432 433 void 434 cipher_set_key_string(CipherContext *cc, const Cipher *cipher, 435 const char *passphrase, int do_encrypt) 436 { 437 u_char digest[16]; 438 439 if (ssh_digest_memory(SSH_DIGEST_MD5, passphrase, strlen(passphrase), 440 digest, sizeof(digest)) < 0) 441 fatal("%s: md5 failed", __func__); 442 443 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 444 445 explicit_bzero(digest, sizeof(digest)); 446 } 447 448 /* 449 * Exports an IV from the CipherContext required to export the key 450 * state back from the unprivileged child to the privileged parent 451 * process. 452 */ 453 454 int 455 cipher_get_keyiv_len(const CipherContext *cc) 456 { 457 const Cipher *c = cc->cipher; 458 int ivlen; 459 460 if (c->number == SSH_CIPHER_3DES) 461 ivlen = 24; 462 else if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 463 ivlen = 0; 464 else 465 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 466 return (ivlen); 467 } 468 469 void 470 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 471 { 472 const Cipher *c = cc->cipher; 473 int evplen; 474 475 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 476 if (len != 0) 477 fatal("%s: wrong iv length %d != %d", __func__, len, 0); 478 return; 479 } 480 481 switch (c->number) { 482 case SSH_CIPHER_SSH2: 483 case SSH_CIPHER_DES: 484 case SSH_CIPHER_BLOWFISH: 485 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 486 if (evplen <= 0) 487 return; 488 if ((u_int)evplen != len) 489 fatal("%s: wrong iv length %d != %d", __func__, 490 evplen, len); 491 #ifdef USE_BUILTIN_RIJNDAEL 492 if (c->evptype == evp_rijndael) 493 ssh_rijndael_iv(&cc->evp, 0, iv, len); 494 else 495 #endif 496 #ifndef OPENSSL_HAVE_EVPCTR 497 if (c->evptype == evp_aes_128_ctr) 498 ssh_aes_ctr_iv(&cc->evp, 0, iv, len); 499 else 500 #endif 501 memcpy(iv, cc->evp.iv, len); 502 break; 503 case SSH_CIPHER_3DES: 504 ssh1_3des_iv(&cc->evp, 0, iv, 24); 505 break; 506 default: 507 fatal("%s: bad cipher %d", __func__, c->number); 508 } 509 } 510 511 void 512 cipher_set_keyiv(CipherContext *cc, u_char *iv) 513 { 514 const Cipher *c = cc->cipher; 515 int evplen = 0; 516 517 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 518 return; 519 520 switch (c->number) { 521 case SSH_CIPHER_SSH2: 522 case SSH_CIPHER_DES: 523 case SSH_CIPHER_BLOWFISH: 524 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 525 if (evplen == 0) 526 return; 527 #ifdef USE_BUILTIN_RIJNDAEL 528 if (c->evptype == evp_rijndael) 529 ssh_rijndael_iv(&cc->evp, 1, iv, evplen); 530 else 531 #endif 532 #ifndef OPENSSL_HAVE_EVPCTR 533 if (c->evptype == evp_aes_128_ctr) 534 ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen); 535 else 536 #endif 537 memcpy(cc->evp.iv, iv, evplen); 538 break; 539 case SSH_CIPHER_3DES: 540 ssh1_3des_iv(&cc->evp, 1, iv, 24); 541 break; 542 default: 543 fatal("%s: bad cipher %d", __func__, c->number); 544 } 545 } 546 547 int 548 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 549 { 550 const Cipher *c = cc->cipher; 551 int plen = 0; 552 553 if (c->evptype == EVP_rc4) { 554 plen = EVP_X_STATE_LEN(cc->evp); 555 if (dat == NULL) 556 return (plen); 557 memcpy(dat, EVP_X_STATE(cc->evp), plen); 558 } 559 return (plen); 560 } 561 562 void 563 cipher_set_keycontext(CipherContext *cc, u_char *dat) 564 { 565 const Cipher *c = cc->cipher; 566 int plen; 567 568 if (c->evptype == EVP_rc4) { 569 plen = EVP_X_STATE_LEN(cc->evp); 570 memcpy(EVP_X_STATE(cc->evp), dat, plen); 571 } 572 } 573