1 /* $OpenBSD: cipher.c,v 1.87 2013/01/26 06:11:05 djm Exp $ */ 2 /* $FreeBSD$ */ 3 /* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * 15 * Copyright (c) 1999 Niels Provos. All rights reserved. 16 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 41 #include <sys/types.h> 42 43 #include <openssl/md5.h> 44 45 #include <string.h> 46 #include <stdarg.h> 47 48 #include "xmalloc.h" 49 #include "log.h" 50 #include "cipher.h" 51 52 /* compatibility with old or broken OpenSSL versions */ 53 #include "openbsd-compat/openssl-compat.h" 54 55 extern const EVP_CIPHER *evp_ssh1_bf(void); 56 extern const EVP_CIPHER *evp_ssh1_3des(void); 57 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 58 59 struct Cipher { 60 char *name; 61 int number; /* for ssh1 only */ 62 u_int block_size; 63 u_int key_len; 64 u_int iv_len; /* defaults to block_size */ 65 u_int auth_len; 66 u_int discard_len; 67 u_int cbc_mode; 68 const EVP_CIPHER *(*evptype)(void); 69 } 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 #ifdef OPENSSL_HAVE_EVPGCM 92 { "aes128-gcm@openssh.com", 93 SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm }, 94 { "aes256-gcm@openssh.com", 95 SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm }, 96 #endif 97 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL } 98 }; 99 100 /*--*/ 101 102 u_int 103 cipher_blocksize(const Cipher *c) 104 { 105 return (c->block_size); 106 } 107 108 u_int 109 cipher_keylen(const Cipher *c) 110 { 111 return (c->key_len); 112 } 113 114 u_int 115 cipher_authlen(const Cipher *c) 116 { 117 return (c->auth_len); 118 } 119 120 u_int 121 cipher_ivlen(const Cipher *c) 122 { 123 return (c->iv_len ? c->iv_len : c->block_size); 124 } 125 126 u_int 127 cipher_get_number(const Cipher *c) 128 { 129 return (c->number); 130 } 131 132 u_int 133 cipher_is_cbc(const Cipher *c) 134 { 135 return (c->cbc_mode); 136 } 137 138 u_int 139 cipher_mask_ssh1(int client) 140 { 141 u_int mask = 0; 142 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 143 mask |= 1 << SSH_CIPHER_BLOWFISH; 144 if (client) { 145 mask |= 1 << SSH_CIPHER_DES; 146 } 147 return mask; 148 } 149 150 Cipher * 151 cipher_by_name(const char *name) 152 { 153 Cipher *c; 154 for (c = ciphers; c->name != NULL; c++) 155 if (strcmp(c->name, name) == 0) 156 return c; 157 return NULL; 158 } 159 160 Cipher * 161 cipher_by_number(int id) 162 { 163 Cipher *c; 164 for (c = ciphers; c->name != NULL; c++) 165 if (c->number == id) 166 return c; 167 return NULL; 168 } 169 170 #define CIPHER_SEP "," 171 int 172 ciphers_valid(const char *names) 173 { 174 Cipher *c; 175 char *cipher_list, *cp; 176 char *p; 177 178 if (names == NULL || strcmp(names, "") == 0) 179 return 0; 180 cipher_list = cp = xstrdup(names); 181 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 182 (p = strsep(&cp, CIPHER_SEP))) { 183 c = cipher_by_name(p); 184 #ifdef NONE_CIPHER_ENABLED 185 if (c == NULL || (c->number != SSH_CIPHER_SSH2 && 186 c->number != SSH_CIPHER_NONE)) { 187 #else 188 if (c == NULL || (c->number != SSH_CIPHER_SSH2)) { 189 #endif 190 debug("bad cipher %s [%s]", p, names); 191 xfree(cipher_list); 192 return 0; 193 } else { 194 debug3("cipher ok: %s [%s]", p, names); 195 } 196 } 197 debug3("ciphers ok: [%s]", names); 198 xfree(cipher_list); 199 return 1; 200 } 201 202 /* 203 * Parses the name of the cipher. Returns the number of the corresponding 204 * cipher, or -1 on error. 205 */ 206 207 int 208 cipher_number(const char *name) 209 { 210 Cipher *c; 211 if (name == NULL) 212 return -1; 213 for (c = ciphers; c->name != NULL; c++) 214 if (strcasecmp(c->name, name) == 0) 215 return c->number; 216 return -1; 217 } 218 219 char * 220 cipher_name(int id) 221 { 222 Cipher *c = cipher_by_number(id); 223 return (c==NULL) ? "<unknown>" : c->name; 224 } 225 226 void 227 cipher_init(CipherContext *cc, Cipher *cipher, 228 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 229 int do_encrypt) 230 { 231 static int dowarn = 1; 232 #ifdef SSH_OLD_EVP 233 EVP_CIPHER *type; 234 #else 235 const EVP_CIPHER *type; 236 int klen; 237 #endif 238 u_char *junk, *discard; 239 240 if (cipher->number == SSH_CIPHER_DES) { 241 if (dowarn) { 242 error("Warning: use of DES is strongly discouraged " 243 "due to cryptographic weaknesses"); 244 dowarn = 0; 245 } 246 if (keylen > 8) 247 keylen = 8; 248 } 249 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 250 cc->encrypt = do_encrypt; 251 252 if (keylen < cipher->key_len) 253 fatal("cipher_init: key length %d is insufficient for %s.", 254 keylen, cipher->name); 255 if (iv != NULL && ivlen < cipher_ivlen(cipher)) 256 fatal("cipher_init: iv length %d is insufficient for %s.", 257 ivlen, cipher->name); 258 cc->cipher = cipher; 259 260 type = (*cipher->evptype)(); 261 262 EVP_CIPHER_CTX_init(&cc->evp); 263 #ifdef SSH_OLD_EVP 264 if (type->key_len > 0 && type->key_len != keylen) { 265 debug("cipher_init: set keylen (%d -> %d)", 266 type->key_len, keylen); 267 type->key_len = keylen; 268 } 269 EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv, 270 (do_encrypt == CIPHER_ENCRYPT)); 271 #else 272 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 273 (do_encrypt == CIPHER_ENCRYPT)) == 0) 274 fatal("cipher_init: EVP_CipherInit failed for %s", 275 cipher->name); 276 if (cipher_authlen(cipher) && 277 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 278 -1, (u_char *)iv)) 279 fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s", 280 cipher->name); 281 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 282 if (klen > 0 && keylen != (u_int)klen) { 283 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 284 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 285 fatal("cipher_init: set keylen failed (%d -> %d)", 286 klen, keylen); 287 } 288 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 289 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 290 cipher->name); 291 #endif 292 293 if (cipher->discard_len > 0) { 294 junk = xmalloc(cipher->discard_len); 295 discard = xmalloc(cipher->discard_len); 296 if (EVP_Cipher(&cc->evp, discard, junk, 297 cipher->discard_len) == 0) 298 fatal("evp_crypt: EVP_Cipher failed during discard"); 299 memset(discard, 0, cipher->discard_len); 300 xfree(junk); 301 xfree(discard); 302 } 303 } 304 305 /* 306 * cipher_crypt() operates as following: 307 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 308 * Theses bytes are treated as additional authenticated data for 309 * authenticated encryption modes. 310 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 311 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 312 * This tag is written on encryption and verified on decryption. 313 * Both 'aadlen' and 'authlen' can be set to 0. 314 */ 315 void 316 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, 317 u_int len, u_int aadlen, u_int authlen) 318 { 319 if (authlen) { 320 u_char lastiv[1]; 321 322 if (authlen != cipher_authlen(cc->cipher)) 323 fatal("%s: authlen mismatch %d", __func__, authlen); 324 /* increment IV */ 325 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 326 1, lastiv)) 327 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 328 /* set tag on decyption */ 329 if (!cc->encrypt && 330 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG, 331 authlen, (u_char *)src + aadlen + len)) 332 fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__); 333 } 334 if (aadlen) { 335 if (authlen && 336 EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0) 337 fatal("%s: EVP_Cipher(aad) failed", __func__); 338 memcpy(dest, src, aadlen); 339 } 340 if (len % cc->cipher->block_size) 341 fatal("%s: bad plaintext length %d", __func__, len); 342 if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen, 343 len) < 0) 344 fatal("%s: EVP_Cipher failed", __func__); 345 if (authlen) { 346 /* compute tag (on encrypt) or verify tag (on decrypt) */ 347 if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) { 348 if (cc->encrypt) 349 fatal("%s: EVP_Cipher(final) failed", __func__); 350 else 351 fatal("Decryption integrity check failed"); 352 } 353 if (cc->encrypt && 354 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG, 355 authlen, dest + aadlen + len)) 356 fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__); 357 } 358 } 359 360 void 361 cipher_cleanup(CipherContext *cc) 362 { 363 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 364 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 365 } 366 367 /* 368 * Selects the cipher, and keys if by computing the MD5 checksum of the 369 * passphrase and using the resulting 16 bytes as the key. 370 */ 371 372 void 373 cipher_set_key_string(CipherContext *cc, Cipher *cipher, 374 const char *passphrase, int do_encrypt) 375 { 376 MD5_CTX md; 377 u_char digest[16]; 378 379 MD5_Init(&md); 380 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); 381 MD5_Final(digest, &md); 382 383 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 384 385 memset(digest, 0, sizeof(digest)); 386 memset(&md, 0, sizeof(md)); 387 } 388 389 /* 390 * Exports an IV from the CipherContext required to export the key 391 * state back from the unprivileged child to the privileged parent 392 * process. 393 */ 394 395 int 396 cipher_get_keyiv_len(const CipherContext *cc) 397 { 398 Cipher *c = cc->cipher; 399 int ivlen; 400 401 if (c->number == SSH_CIPHER_3DES) 402 ivlen = 24; 403 else 404 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 405 return (ivlen); 406 } 407 408 void 409 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 410 { 411 Cipher *c = cc->cipher; 412 int evplen; 413 414 switch (c->number) { 415 #ifdef NONE_CIPHER_ENABLED 416 case SSH_CIPHER_NONE: 417 #endif 418 case SSH_CIPHER_SSH2: 419 case SSH_CIPHER_DES: 420 case SSH_CIPHER_BLOWFISH: 421 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 422 if (evplen <= 0) 423 return; 424 if ((u_int)evplen != len) 425 fatal("%s: wrong iv length %d != %d", __func__, 426 evplen, len); 427 #ifdef USE_BUILTIN_RIJNDAEL 428 if (c->evptype == evp_rijndael) 429 ssh_rijndael_iv(&cc->evp, 0, iv, len); 430 else 431 #endif 432 #ifndef OPENSSL_HAVE_EVPCTR 433 if (c->evptype == evp_aes_128_ctr) 434 ssh_aes_ctr_iv(&cc->evp, 0, iv, len); 435 else 436 #endif 437 memcpy(iv, cc->evp.iv, len); 438 break; 439 case SSH_CIPHER_3DES: 440 ssh1_3des_iv(&cc->evp, 0, iv, 24); 441 break; 442 default: 443 fatal("%s: bad cipher %d", __func__, c->number); 444 } 445 } 446 447 void 448 cipher_set_keyiv(CipherContext *cc, u_char *iv) 449 { 450 Cipher *c = cc->cipher; 451 int evplen = 0; 452 453 switch (c->number) { 454 #ifdef NONE_CIPHER_ENABLED 455 case SSH_CIPHER_NONE: 456 #endif 457 case SSH_CIPHER_SSH2: 458 case SSH_CIPHER_DES: 459 case SSH_CIPHER_BLOWFISH: 460 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 461 if (evplen == 0) 462 return; 463 #ifdef USE_BUILTIN_RIJNDAEL 464 if (c->evptype == evp_rijndael) 465 ssh_rijndael_iv(&cc->evp, 1, iv, evplen); 466 else 467 #endif 468 #ifndef OPENSSL_HAVE_EVPCTR 469 if (c->evptype == evp_aes_128_ctr) 470 ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen); 471 else 472 #endif 473 memcpy(cc->evp.iv, iv, evplen); 474 break; 475 case SSH_CIPHER_3DES: 476 ssh1_3des_iv(&cc->evp, 1, iv, 24); 477 break; 478 default: 479 fatal("%s: bad cipher %d", __func__, c->number); 480 } 481 } 482 483 int 484 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 485 { 486 Cipher *c = cc->cipher; 487 int plen = 0; 488 489 if (c->evptype == EVP_rc4) { 490 plen = EVP_X_STATE_LEN(cc->evp); 491 if (dat == NULL) 492 return (plen); 493 memcpy(dat, EVP_X_STATE(cc->evp), plen); 494 } 495 return (plen); 496 } 497 498 void 499 cipher_set_keycontext(CipherContext *cc, u_char *dat) 500 { 501 Cipher *c = cc->cipher; 502 int plen; 503 504 if (c->evptype == EVP_rc4) { 505 plen = EVP_X_STATE_LEN(cc->evp); 506 memcpy(EVP_X_STATE(cc->evp), dat, plen); 507 } 508 } 509