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 <sys/types.h> 39 40 #include <string.h> 41 #include <stdarg.h> 42 #include <stdio.h> 43 44 #include "xmalloc.h" 45 #include "log.h" 46 #include "misc.h" 47 #include "cipher.h" 48 #include "buffer.h" 49 #include "digest.h" 50 51 extern const EVP_CIPHER *evp_ssh1_bf(void); 52 extern const EVP_CIPHER *evp_ssh1_3des(void); 53 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 54 55 struct Cipher { 56 char *name; 57 int number; /* for ssh1 only */ 58 u_int block_size; 59 u_int key_len; 60 u_int iv_len; /* defaults to block_size */ 61 u_int auth_len; 62 u_int discard_len; 63 u_int flags; 64 #define CFLAG_CBC (1<<0) 65 #define CFLAG_CHACHAPOLY (1<<1) 66 const EVP_CIPHER *(*evptype)(void); 67 }; 68 69 static const struct Cipher ciphers[] = { 70 { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null }, 71 { "des", SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc }, 72 { "3des", SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des }, 73 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf }, 74 75 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc }, 76 { "blowfish-cbc", 77 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc }, 78 { "cast128-cbc", 79 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc }, 80 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 }, 81 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 }, 82 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 }, 83 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc }, 84 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc }, 85 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc }, 86 { "rijndael-cbc@lysator.liu.se", 87 SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc }, 88 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr }, 89 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr }, 90 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr }, 91 { "aes128-gcm@openssh.com", 92 SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm }, 93 { "aes256-gcm@openssh.com", 94 SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm }, 95 { "chacha20-poly1305@openssh.com", 96 SSH_CIPHER_SSH2, 8, 64, 0, 16, 0, CFLAG_CHACHAPOLY, NULL }, 97 98 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL } 99 }; 100 101 /*--*/ 102 103 /* Returns a list of supported ciphers separated by the specified char. */ 104 char * 105 cipher_alg_list(char sep, int auth_only) 106 { 107 char *ret = NULL; 108 size_t nlen, rlen = 0; 109 const Cipher *c; 110 111 for (c = ciphers; c->name != NULL; c++) { 112 if (c->number != SSH_CIPHER_SSH2) 113 continue; 114 if (auth_only && c->auth_len == 0) 115 continue; 116 if (ret != NULL) 117 ret[rlen++] = sep; 118 nlen = strlen(c->name); 119 ret = xrealloc(ret, 1, rlen + nlen + 2); 120 memcpy(ret + rlen, c->name, nlen + 1); 121 rlen += nlen; 122 } 123 return ret; 124 } 125 126 u_int 127 cipher_blocksize(const Cipher *c) 128 { 129 return (c->block_size); 130 } 131 132 u_int 133 cipher_keylen(const Cipher *c) 134 { 135 return (c->key_len); 136 } 137 138 u_int 139 cipher_seclen(const Cipher *c) 140 { 141 if (strcmp("3des-cbc", c->name) == 0) 142 return 14; 143 return cipher_keylen(c); 144 } 145 146 u_int 147 cipher_authlen(const Cipher *c) 148 { 149 return (c->auth_len); 150 } 151 152 u_int 153 cipher_ivlen(const Cipher *c) 154 { 155 /* 156 * Default is cipher block size, except for chacha20+poly1305 that 157 * needs no IV. XXX make iv_len == -1 default? 158 */ 159 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 160 c->iv_len : c->block_size; 161 } 162 163 u_int 164 cipher_get_number(const Cipher *c) 165 { 166 return (c->number); 167 } 168 169 u_int 170 cipher_is_cbc(const Cipher *c) 171 { 172 return (c->flags & CFLAG_CBC) != 0; 173 } 174 175 u_int 176 cipher_mask_ssh1(int client) 177 { 178 u_int mask = 0; 179 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 180 mask |= 1 << SSH_CIPHER_BLOWFISH; 181 if (client) { 182 mask |= 1 << SSH_CIPHER_DES; 183 } 184 return mask; 185 } 186 187 const Cipher * 188 cipher_by_name(const char *name) 189 { 190 const Cipher *c; 191 for (c = ciphers; c->name != NULL; c++) 192 if (strcmp(c->name, name) == 0) 193 return c; 194 return NULL; 195 } 196 197 const Cipher * 198 cipher_by_number(int id) 199 { 200 const Cipher *c; 201 for (c = ciphers; c->name != NULL; c++) 202 if (c->number == id) 203 return c; 204 return NULL; 205 } 206 207 #define CIPHER_SEP "," 208 int 209 ciphers_valid(const char *names) 210 { 211 const Cipher *c; 212 char *cipher_list, *cp; 213 char *p; 214 215 if (names == NULL || strcmp(names, "") == 0) 216 return 0; 217 cipher_list = cp = xstrdup(names); 218 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 219 (p = strsep(&cp, CIPHER_SEP))) { 220 c = cipher_by_name(p); 221 if (c == NULL || c->number != SSH_CIPHER_SSH2) { 222 debug("bad cipher %s [%s]", p, names); 223 free(cipher_list); 224 return 0; 225 } 226 } 227 debug3("ciphers ok: [%s]", names); 228 free(cipher_list); 229 return 1; 230 } 231 232 /* 233 * Parses the name of the cipher. Returns the number of the corresponding 234 * cipher, or -1 on error. 235 */ 236 237 int 238 cipher_number(const char *name) 239 { 240 const Cipher *c; 241 if (name == NULL) 242 return -1; 243 for (c = ciphers; c->name != NULL; c++) 244 if (strcasecmp(c->name, name) == 0) 245 return c->number; 246 return -1; 247 } 248 249 char * 250 cipher_name(int id) 251 { 252 const Cipher *c = cipher_by_number(id); 253 return (c==NULL) ? "<unknown>" : c->name; 254 } 255 256 void 257 cipher_init(CipherContext *cc, const Cipher *cipher, 258 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 259 int do_encrypt) 260 { 261 static int dowarn = 1; 262 const EVP_CIPHER *type; 263 int klen; 264 u_char *junk, *discard; 265 266 if (cipher->number == SSH_CIPHER_DES) { 267 if (dowarn) { 268 error("Warning: use of DES is strongly discouraged " 269 "due to cryptographic weaknesses"); 270 dowarn = 0; 271 } 272 if (keylen > 8) 273 keylen = 8; 274 } 275 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 276 cc->encrypt = do_encrypt; 277 278 if (keylen < cipher->key_len) 279 fatal("cipher_init: key length %d is insufficient for %s.", 280 keylen, cipher->name); 281 if (iv != NULL && ivlen < cipher_ivlen(cipher)) 282 fatal("cipher_init: iv length %d is insufficient for %s.", 283 ivlen, cipher->name); 284 cc->cipher = cipher; 285 286 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 287 chachapoly_init(&cc->cp_ctx, key, keylen); 288 return; 289 } 290 type = (*cipher->evptype)(); 291 EVP_CIPHER_CTX_init(&cc->evp); 292 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 293 (do_encrypt == CIPHER_ENCRYPT)) == 0) 294 fatal("cipher_init: EVP_CipherInit failed for %s", 295 cipher->name); 296 if (cipher_authlen(cipher) && 297 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 298 -1, (u_char *)iv)) 299 fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s", 300 cipher->name); 301 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 302 if (klen > 0 && keylen != (u_int)klen) { 303 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 304 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 305 fatal("cipher_init: set keylen failed (%d -> %d)", 306 klen, keylen); 307 } 308 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 309 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 310 cipher->name); 311 312 if (cipher->discard_len > 0) { 313 junk = xmalloc(cipher->discard_len); 314 discard = xmalloc(cipher->discard_len); 315 if (EVP_Cipher(&cc->evp, discard, junk, 316 cipher->discard_len) == 0) 317 fatal("evp_crypt: EVP_Cipher failed during discard"); 318 explicit_bzero(discard, cipher->discard_len); 319 free(junk); 320 free(discard); 321 } 322 } 323 324 /* 325 * cipher_crypt() operates as following: 326 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 327 * Theses bytes are treated as additional authenticated data for 328 * authenticated encryption modes. 329 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 330 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 331 * This tag is written on encryption and verified on decryption. 332 * Both 'aadlen' and 'authlen' can be set to 0. 333 * cipher_crypt() returns 0 on success and -1 if the decryption integrity 334 * check fails. 335 */ 336 int 337 cipher_crypt(CipherContext *cc, u_int seqnr, u_char *dest, const u_char *src, 338 u_int len, u_int aadlen, u_int authlen) 339 { 340 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 341 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, len, 342 aadlen, authlen, cc->encrypt); 343 if (authlen) { 344 u_char lastiv[1]; 345 346 if (authlen != cipher_authlen(cc->cipher)) 347 fatal("%s: authlen mismatch %d", __func__, authlen); 348 /* increment IV */ 349 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 350 1, lastiv)) 351 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 352 /* set tag on decyption */ 353 if (!cc->encrypt && 354 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG, 355 authlen, (u_char *)src + aadlen + len)) 356 fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__); 357 } 358 if (aadlen) { 359 if (authlen && 360 EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0) 361 fatal("%s: EVP_Cipher(aad) failed", __func__); 362 memcpy(dest, src, aadlen); 363 } 364 if (len % cc->cipher->block_size) 365 fatal("%s: bad plaintext length %d", __func__, len); 366 if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen, 367 len) < 0) 368 fatal("%s: EVP_Cipher failed", __func__); 369 if (authlen) { 370 /* compute tag (on encrypt) or verify tag (on decrypt) */ 371 if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) { 372 if (cc->encrypt) 373 fatal("%s: EVP_Cipher(final) failed", __func__); 374 else 375 return -1; 376 } 377 if (cc->encrypt && 378 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG, 379 authlen, dest + aadlen + len)) 380 fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__); 381 } 382 return 0; 383 } 384 385 /* Extract the packet length, including any decryption necessary beforehand */ 386 int 387 cipher_get_length(CipherContext *cc, u_int *plenp, u_int seqnr, 388 const u_char *cp, u_int len) 389 { 390 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 391 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr, 392 cp, len); 393 if (len < 4) 394 return -1; 395 *plenp = get_u32(cp); 396 return 0; 397 } 398 399 void 400 cipher_cleanup(CipherContext *cc) 401 { 402 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 403 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx)); 404 else if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 405 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 406 } 407 408 /* 409 * Selects the cipher, and keys if by computing the MD5 checksum of the 410 * passphrase and using the resulting 16 bytes as the key. 411 */ 412 413 void 414 cipher_set_key_string(CipherContext *cc, const Cipher *cipher, 415 const char *passphrase, int do_encrypt) 416 { 417 u_char digest[16]; 418 419 if (ssh_digest_memory(SSH_DIGEST_MD5, passphrase, strlen(passphrase), 420 digest, sizeof(digest)) < 0) 421 fatal("%s: md5 failed", __func__); 422 423 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 424 425 explicit_bzero(digest, sizeof(digest)); 426 } 427 428 /* 429 * Exports an IV from the CipherContext required to export the key 430 * state back from the unprivileged child to the privileged parent 431 * process. 432 */ 433 434 int 435 cipher_get_keyiv_len(const CipherContext *cc) 436 { 437 const Cipher *c = cc->cipher; 438 int ivlen; 439 440 if (c->number == SSH_CIPHER_3DES) 441 ivlen = 24; 442 else if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 443 ivlen = 0; 444 else 445 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 446 return (ivlen); 447 } 448 449 void 450 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 451 { 452 const Cipher *c = cc->cipher; 453 int evplen; 454 455 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 456 if (len != 0) 457 fatal("%s: wrong iv length %d != %d", __func__, len, 0); 458 return; 459 } 460 461 switch (c->number) { 462 case SSH_CIPHER_SSH2: 463 case SSH_CIPHER_DES: 464 case SSH_CIPHER_BLOWFISH: 465 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 466 if (evplen <= 0) 467 return; 468 if ((u_int)evplen != len) 469 fatal("%s: wrong iv length %d != %d", __func__, 470 evplen, len); 471 if (cipher_authlen(c)) { 472 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 473 len, iv)) 474 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 475 } else 476 memcpy(iv, cc->evp.iv, len); 477 break; 478 case SSH_CIPHER_3DES: 479 ssh1_3des_iv(&cc->evp, 0, iv, 24); 480 break; 481 default: 482 fatal("%s: bad cipher %d", __func__, c->number); 483 } 484 } 485 486 void 487 cipher_set_keyiv(CipherContext *cc, u_char *iv) 488 { 489 const Cipher *c = cc->cipher; 490 int evplen = 0; 491 492 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 493 return; 494 495 switch (c->number) { 496 case SSH_CIPHER_SSH2: 497 case SSH_CIPHER_DES: 498 case SSH_CIPHER_BLOWFISH: 499 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 500 if (evplen == 0) 501 return; 502 if (cipher_authlen(c)) { 503 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, 504 EVP_CTRL_GCM_SET_IV_FIXED, -1, iv)) 505 fatal("%s: EVP_CTRL_GCM_SET_IV_FIXED failed", 506 __func__); 507 } else 508 memcpy(cc->evp.iv, iv, evplen); 509 break; 510 case SSH_CIPHER_3DES: 511 ssh1_3des_iv(&cc->evp, 1, iv, 24); 512 break; 513 default: 514 fatal("%s: bad cipher %d", __func__, c->number); 515 } 516 } 517 518 #define EVP_X_STATE(evp) (evp).cipher_data 519 #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size 520 521 int 522 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 523 { 524 const Cipher *c = cc->cipher; 525 int plen = 0; 526 527 if (c->evptype == EVP_rc4) { 528 plen = EVP_X_STATE_LEN(cc->evp); 529 if (dat == NULL) 530 return (plen); 531 memcpy(dat, EVP_X_STATE(cc->evp), plen); 532 } 533 return (plen); 534 } 535 536 void 537 cipher_set_keycontext(CipherContext *cc, u_char *dat) 538 { 539 const Cipher *c = cc->cipher; 540 int plen; 541 542 if (c->evptype == EVP_rc4) { 543 plen = EVP_X_STATE_LEN(cc->evp); 544 memcpy(EVP_X_STATE(cc->evp), dat, plen); 545 } 546 } 547