1 /* $OpenBSD: cipher.c,v 1.89 2013/05/17 00:13:13 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 <openssl/md5.h> 41 42 #include <string.h> 43 #include <stdarg.h> 44 45 #include "xmalloc.h" 46 #include "log.h" 47 #include "cipher.h" 48 49 extern const EVP_CIPHER *evp_ssh1_bf(void); 50 extern const EVP_CIPHER *evp_ssh1_3des(void); 51 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 52 53 struct Cipher { 54 char *name; 55 int number; /* for ssh1 only */ 56 u_int block_size; 57 u_int key_len; 58 u_int iv_len; /* defaults to block_size */ 59 u_int auth_len; 60 u_int discard_len; 61 u_int cbc_mode; 62 const EVP_CIPHER *(*evptype)(void); 63 }; 64 65 static const struct Cipher ciphers[] = { 66 { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null }, 67 { "des", SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc }, 68 { "3des", SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des }, 69 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf }, 70 71 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc }, 72 { "blowfish-cbc", 73 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc }, 74 { "cast128-cbc", 75 SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc }, 76 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 }, 77 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 }, 78 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 }, 79 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc }, 80 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc }, 81 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc }, 82 { "rijndael-cbc@lysator.liu.se", 83 SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc }, 84 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr }, 85 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr }, 86 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr }, 87 { "aes128-gcm@openssh.com", 88 SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm }, 89 { "aes256-gcm@openssh.com", 90 SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm }, 91 92 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL } 93 }; 94 95 /*--*/ 96 97 /* Returns a comma-separated list of supported ciphers. */ 98 char * 99 cipher_alg_list(void) 100 { 101 char *ret = NULL; 102 size_t nlen, rlen = 0; 103 const Cipher *c; 104 105 for (c = ciphers; c->name != NULL; c++) { 106 if (c->number != SSH_CIPHER_SSH2) 107 continue; 108 if (ret != NULL) 109 ret[rlen++] = '\n'; 110 nlen = strlen(c->name); 111 ret = xrealloc(ret, 1, rlen + nlen + 2); 112 memcpy(ret + rlen, c->name, nlen + 1); 113 rlen += nlen; 114 } 115 return ret; 116 } 117 118 u_int 119 cipher_blocksize(const Cipher *c) 120 { 121 return (c->block_size); 122 } 123 124 u_int 125 cipher_keylen(const Cipher *c) 126 { 127 return (c->key_len); 128 } 129 130 u_int 131 cipher_authlen(const Cipher *c) 132 { 133 return (c->auth_len); 134 } 135 136 u_int 137 cipher_ivlen(const Cipher *c) 138 { 139 return (c->iv_len ? c->iv_len : c->block_size); 140 } 141 142 u_int 143 cipher_get_number(const Cipher *c) 144 { 145 return (c->number); 146 } 147 148 u_int 149 cipher_is_cbc(const Cipher *c) 150 { 151 return (c->cbc_mode); 152 } 153 154 u_int 155 cipher_mask_ssh1(int client) 156 { 157 u_int mask = 0; 158 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 159 mask |= 1 << SSH_CIPHER_BLOWFISH; 160 if (client) { 161 mask |= 1 << SSH_CIPHER_DES; 162 } 163 return mask; 164 } 165 166 const Cipher * 167 cipher_by_name(const char *name) 168 { 169 const Cipher *c; 170 for (c = ciphers; c->name != NULL; c++) 171 if (strcmp(c->name, name) == 0) 172 return c; 173 return NULL; 174 } 175 176 const Cipher * 177 cipher_by_number(int id) 178 { 179 const Cipher *c; 180 for (c = ciphers; c->name != NULL; c++) 181 if (c->number == id) 182 return c; 183 return NULL; 184 } 185 186 #define CIPHER_SEP "," 187 int 188 ciphers_valid(const char *names) 189 { 190 const Cipher *c; 191 char *cipher_list, *cp; 192 char *p; 193 194 if (names == NULL || strcmp(names, "") == 0) 195 return 0; 196 cipher_list = cp = xstrdup(names); 197 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 198 (p = strsep(&cp, CIPHER_SEP))) { 199 c = cipher_by_name(p); 200 if (c == NULL || c->number != SSH_CIPHER_SSH2) { 201 debug("bad cipher %s [%s]", p, names); 202 free(cipher_list); 203 return 0; 204 } else { 205 debug3("cipher ok: %s [%s]", p, names); 206 } 207 } 208 debug3("ciphers ok: [%s]", names); 209 free(cipher_list); 210 return 1; 211 } 212 213 /* 214 * Parses the name of the cipher. Returns the number of the corresponding 215 * cipher, or -1 on error. 216 */ 217 218 int 219 cipher_number(const char *name) 220 { 221 const Cipher *c; 222 if (name == NULL) 223 return -1; 224 for (c = ciphers; c->name != NULL; c++) 225 if (strcasecmp(c->name, name) == 0) 226 return c->number; 227 return -1; 228 } 229 230 char * 231 cipher_name(int id) 232 { 233 const Cipher *c = cipher_by_number(id); 234 return (c==NULL) ? "<unknown>" : c->name; 235 } 236 237 void 238 cipher_init(CipherContext *cc, const Cipher *cipher, 239 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 240 int do_encrypt) 241 { 242 static int dowarn = 1; 243 const EVP_CIPHER *type; 244 int klen; 245 u_char *junk, *discard; 246 247 if (cipher->number == SSH_CIPHER_DES) { 248 if (dowarn) { 249 error("Warning: use of DES is strongly discouraged " 250 "due to cryptographic weaknesses"); 251 dowarn = 0; 252 } 253 if (keylen > 8) 254 keylen = 8; 255 } 256 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 257 cc->encrypt = do_encrypt; 258 259 if (keylen < cipher->key_len) 260 fatal("cipher_init: key length %d is insufficient for %s.", 261 keylen, cipher->name); 262 if (iv != NULL && ivlen < cipher_ivlen(cipher)) 263 fatal("cipher_init: iv length %d is insufficient for %s.", 264 ivlen, cipher->name); 265 cc->cipher = cipher; 266 267 type = (*cipher->evptype)(); 268 269 EVP_CIPHER_CTX_init(&cc->evp); 270 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 271 (do_encrypt == CIPHER_ENCRYPT)) == 0) 272 fatal("cipher_init: EVP_CipherInit failed for %s", 273 cipher->name); 274 if (cipher_authlen(cipher) && 275 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 276 -1, (u_char *)iv)) 277 fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s", 278 cipher->name); 279 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 280 if (klen > 0 && keylen != (u_int)klen) { 281 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 282 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 283 fatal("cipher_init: set keylen failed (%d -> %d)", 284 klen, keylen); 285 } 286 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 287 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 288 cipher->name); 289 290 if (cipher->discard_len > 0) { 291 junk = xmalloc(cipher->discard_len); 292 discard = xmalloc(cipher->discard_len); 293 if (EVP_Cipher(&cc->evp, discard, junk, 294 cipher->discard_len) == 0) 295 fatal("evp_crypt: EVP_Cipher failed during discard"); 296 memset(discard, 0, cipher->discard_len); 297 free(junk); 298 free(discard); 299 } 300 } 301 302 /* 303 * cipher_crypt() operates as following: 304 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 305 * Theses bytes are treated as additional authenticated data for 306 * authenticated encryption modes. 307 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 308 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 309 * This tag is written on encryption and verified on decryption. 310 * Both 'aadlen' and 'authlen' can be set to 0. 311 */ 312 void 313 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, 314 u_int len, u_int aadlen, u_int authlen) 315 { 316 if (authlen) { 317 u_char lastiv[1]; 318 319 if (authlen != cipher_authlen(cc->cipher)) 320 fatal("%s: authlen mismatch %d", __func__, authlen); 321 /* increment IV */ 322 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 323 1, lastiv)) 324 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 325 /* set tag on decyption */ 326 if (!cc->encrypt && 327 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG, 328 authlen, (u_char *)src + aadlen + len)) 329 fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__); 330 } 331 if (aadlen) { 332 if (authlen && 333 EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0) 334 fatal("%s: EVP_Cipher(aad) failed", __func__); 335 memcpy(dest, src, aadlen); 336 } 337 if (len % cc->cipher->block_size) 338 fatal("%s: bad plaintext length %d", __func__, len); 339 if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen, 340 len) < 0) 341 fatal("%s: EVP_Cipher failed", __func__); 342 if (authlen) { 343 /* compute tag (on encrypt) or verify tag (on decrypt) */ 344 if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) { 345 if (cc->encrypt) 346 fatal("%s: EVP_Cipher(final) failed", __func__); 347 else 348 fatal("Decryption integrity check failed"); 349 } 350 if (cc->encrypt && 351 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG, 352 authlen, dest + aadlen + len)) 353 fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__); 354 } 355 } 356 357 void 358 cipher_cleanup(CipherContext *cc) 359 { 360 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 361 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 362 } 363 364 /* 365 * Selects the cipher, and keys if by computing the MD5 checksum of the 366 * passphrase and using the resulting 16 bytes as the key. 367 */ 368 369 void 370 cipher_set_key_string(CipherContext *cc, const Cipher *cipher, 371 const char *passphrase, int do_encrypt) 372 { 373 MD5_CTX md; 374 u_char digest[16]; 375 376 MD5_Init(&md); 377 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); 378 MD5_Final(digest, &md); 379 380 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 381 382 memset(digest, 0, sizeof(digest)); 383 memset(&md, 0, sizeof(md)); 384 } 385 386 /* 387 * Exports an IV from the CipherContext required to export the key 388 * state back from the unprivileged child to the privileged parent 389 * process. 390 */ 391 392 int 393 cipher_get_keyiv_len(const CipherContext *cc) 394 { 395 const Cipher *c = cc->cipher; 396 int ivlen; 397 398 if (c->number == SSH_CIPHER_3DES) 399 ivlen = 24; 400 else 401 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 402 return (ivlen); 403 } 404 405 void 406 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 407 { 408 const Cipher *c = cc->cipher; 409 int evplen; 410 411 switch (c->number) { 412 case SSH_CIPHER_SSH2: 413 case SSH_CIPHER_DES: 414 case SSH_CIPHER_BLOWFISH: 415 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 416 if (evplen <= 0) 417 return; 418 if ((u_int)evplen != len) 419 fatal("%s: wrong iv length %d != %d", __func__, 420 evplen, len); 421 if (cipher_authlen(c)) { 422 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 423 len, iv)) 424 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 425 } else 426 memcpy(iv, cc->evp.iv, len); 427 break; 428 case SSH_CIPHER_3DES: 429 ssh1_3des_iv(&cc->evp, 0, iv, 24); 430 break; 431 default: 432 fatal("%s: bad cipher %d", __func__, c->number); 433 } 434 } 435 436 void 437 cipher_set_keyiv(CipherContext *cc, u_char *iv) 438 { 439 const Cipher *c = cc->cipher; 440 int evplen = 0; 441 442 switch (c->number) { 443 case SSH_CIPHER_SSH2: 444 case SSH_CIPHER_DES: 445 case SSH_CIPHER_BLOWFISH: 446 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 447 if (evplen == 0) 448 return; 449 if (cipher_authlen(c)) { 450 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, 451 EVP_CTRL_GCM_SET_IV_FIXED, -1, iv)) 452 fatal("%s: EVP_CTRL_GCM_SET_IV_FIXED failed", 453 __func__); 454 } else 455 memcpy(cc->evp.iv, iv, evplen); 456 break; 457 case SSH_CIPHER_3DES: 458 ssh1_3des_iv(&cc->evp, 1, iv, 24); 459 break; 460 default: 461 fatal("%s: bad cipher %d", __func__, c->number); 462 } 463 } 464 465 #define EVP_X_STATE(evp) (evp).cipher_data 466 #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size 467 468 int 469 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 470 { 471 const Cipher *c = cc->cipher; 472 int plen = 0; 473 474 if (c->evptype == EVP_rc4) { 475 plen = EVP_X_STATE_LEN(cc->evp); 476 if (dat == NULL) 477 return (plen); 478 memcpy(dat, EVP_X_STATE(cc->evp), plen); 479 } 480 return (plen); 481 } 482 483 void 484 cipher_set_keycontext(CipherContext *cc, u_char *dat) 485 { 486 const Cipher *c = cc->cipher; 487 int plen; 488 489 if (c->evptype == EVP_rc4) { 490 plen = EVP_X_STATE_LEN(cc->evp); 491 memcpy(EVP_X_STATE(cc->evp), dat, plen); 492 } 493 } 494