1 /* $NetBSD: cipher.c,v 1.4 2013/03/29 16:19:45 christos Exp $ */ 2 /* $OpenBSD: cipher.c,v 1.87 2013/01/26 06:11:05 djm Exp $ */ 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 __RCSID("$NetBSD: cipher.c,v 1.4 2013/03/29 16:19:45 christos Exp $"); 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 extern const EVP_CIPHER *evp_ssh1_bf(void); 53 extern const EVP_CIPHER *evp_ssh1_3des(void); 54 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 55 extern const EVP_CIPHER *evp_aes_128_ctr(void); 56 extern const EVP_CIPHER *evp_aes_ctr_mt(void); 57 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); 58 59 struct Cipher { 60 const 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 #ifdef AES_CTR_MT 89 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, evp_aes_ctr_mt }, 90 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, evp_aes_ctr_mt }, 91 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, evp_aes_ctr_mt }, 92 #else 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 #endif 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 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL } 102 }; 103 104 /*--*/ 105 106 u_int 107 cipher_blocksize(const Cipher *c) 108 { 109 return (c->block_size); 110 } 111 112 u_int 113 cipher_keylen(const Cipher *c) 114 { 115 return (c->key_len); 116 } 117 118 u_int 119 cipher_authlen(const Cipher *c) 120 { 121 return (c->auth_len); 122 } 123 124 u_int 125 cipher_ivlen(const Cipher *c) 126 { 127 return (c->iv_len ? c->iv_len : c->block_size); 128 } 129 130 u_int 131 cipher_get_number(const Cipher *c) 132 { 133 return (c->number); 134 } 135 136 u_int 137 cipher_is_cbc(const Cipher *c) 138 { 139 return (c->cbc_mode); 140 } 141 142 u_int 143 cipher_mask_ssh1(int client) 144 { 145 u_int mask = 0; 146 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 147 mask |= 1 << SSH_CIPHER_BLOWFISH; 148 if (client) { 149 mask |= 1 << SSH_CIPHER_DES; 150 } 151 return mask; 152 } 153 154 Cipher * 155 cipher_by_name(const char *name) 156 { 157 Cipher *c; 158 for (c = ciphers; c->name != NULL; c++) 159 if (strcmp(c->name, name) == 0) 160 return c; 161 return NULL; 162 } 163 164 Cipher * 165 cipher_by_number(int id) 166 { 167 Cipher *c; 168 for (c = ciphers; c->name != NULL; c++) 169 if (c->number == id) 170 return c; 171 return NULL; 172 } 173 174 #define CIPHER_SEP "," 175 int 176 ciphers_valid(const char *names) 177 { 178 Cipher *c; 179 char *cipher_list, *cp; 180 char *p; 181 182 if (names == NULL || strcmp(names, "") == 0) 183 return 0; 184 cipher_list = cp = xstrdup(names); 185 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 186 (p = strsep(&cp, CIPHER_SEP))) { 187 c = cipher_by_name(p); 188 if (c == NULL || (c->number != SSH_CIPHER_SSH2 && 189 c->number != SSH_CIPHER_NONE)) { 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 const 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 const EVP_CIPHER *type; 233 int klen; 234 u_char *junk, *discard; 235 236 if (cipher->number == SSH_CIPHER_DES) { 237 if (dowarn) { 238 error("Warning: use of DES is strongly discouraged " 239 "due to cryptographic weaknesses"); 240 dowarn = 0; 241 } 242 if (keylen > 8) 243 keylen = 8; 244 } 245 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 246 cc->encrypt = do_encrypt; 247 248 if (keylen < cipher->key_len) 249 fatal("cipher_init: key length %d is insufficient for %s.", 250 keylen, cipher->name); 251 if (iv != NULL && ivlen < cipher_ivlen(cipher)) 252 fatal("cipher_init: iv length %d is insufficient for %s.", 253 ivlen, cipher->name); 254 cc->cipher = cipher; 255 256 type = (*cipher->evptype)(); 257 258 EVP_CIPHER_CTX_init(&cc->evp); 259 if (EVP_CipherInit(&cc->evp, type, NULL, __UNCONST(iv), 260 (do_encrypt == CIPHER_ENCRYPT)) == 0) 261 fatal("cipher_init: EVP_CipherInit failed for %s", 262 cipher->name); 263 if (cipher_authlen(cipher) && 264 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 265 -1, __UNCONST(iv))) 266 fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s", 267 cipher->name); 268 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 269 if (klen > 0 && keylen != (u_int)klen) { 270 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 271 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 272 fatal("cipher_init: set keylen failed (%d -> %d)", 273 klen, keylen); 274 } 275 if (EVP_CipherInit(&cc->evp, NULL, __UNCONST(key), NULL, -1) == 0) 276 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 277 cipher->name); 278 279 if (cipher->discard_len > 0) { 280 junk = xmalloc(cipher->discard_len); 281 discard = xmalloc(cipher->discard_len); 282 if (EVP_Cipher(&cc->evp, discard, junk, 283 cipher->discard_len) == 0) 284 fatal("evp_crypt: EVP_Cipher failed during discard"); 285 memset(discard, 0, cipher->discard_len); 286 xfree(junk); 287 xfree(discard); 288 } 289 } 290 291 /* 292 * cipher_crypt() operates as following: 293 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 294 * Theses bytes are treated as additional authenticated data for 295 * authenticated encryption modes. 296 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 297 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 298 * This tag is written on encryption and verified on decryption. 299 * Both 'aadlen' and 'authlen' can be set to 0. 300 */ 301 void 302 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, 303 u_int len, u_int aadlen, u_int authlen) 304 { 305 if (authlen) { 306 u_char lastiv[1]; 307 308 if (authlen != cipher_authlen(cc->cipher)) 309 fatal("%s: authlen mismatch %d", __func__, authlen); 310 /* increment IV */ 311 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 312 1, lastiv)) 313 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 314 /* set tag on decyption */ 315 if (!cc->encrypt && 316 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG, 317 authlen, __UNCONST(src + aadlen + len))) 318 fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__); 319 } 320 if (aadlen) { 321 if (authlen && 322 EVP_Cipher(&cc->evp, NULL, (const u_char *)src, aadlen) < 0) 323 fatal("%s: EVP_Cipher(aad) failed", __func__); 324 memcpy(dest, src, aadlen); 325 } 326 if (len % cc->cipher->block_size) 327 fatal("%s: bad plaintext length %d", __func__, len); 328 if (EVP_Cipher(&cc->evp, dest + aadlen, (const u_char *)src + aadlen, 329 len) < 0) 330 fatal("%s: EVP_Cipher failed", __func__); 331 if (authlen) { 332 /* compute tag (on encrypt) or verify tag (on decrypt) */ 333 if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) { 334 if (cc->encrypt) 335 fatal("%s: EVP_Cipher(final) failed", __func__); 336 else 337 fatal("Decryption integrity check failed"); 338 } 339 if (cc->encrypt && 340 !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG, 341 authlen, dest + aadlen + len)) 342 fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__); 343 } 344 } 345 346 void 347 cipher_cleanup(CipherContext *cc) 348 { 349 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 350 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 351 } 352 353 /* 354 * Selects the cipher, and keys if by computing the MD5 checksum of the 355 * passphrase and using the resulting 16 bytes as the key. 356 */ 357 358 void 359 cipher_set_key_string(CipherContext *cc, Cipher *cipher, 360 const char *passphrase, int do_encrypt) 361 { 362 MD5_CTX md; 363 u_char digest[16]; 364 365 MD5_Init(&md); 366 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); 367 MD5_Final(digest, &md); 368 369 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 370 371 memset(digest, 0, sizeof(digest)); 372 memset(&md, 0, sizeof(md)); 373 } 374 375 /* 376 * Exports an IV from the CipherContext required to export the key 377 * state back from the unprivileged child to the privileged parent 378 * process. 379 */ 380 381 int 382 cipher_get_keyiv_len(const CipherContext *cc) 383 { 384 Cipher *c = cc->cipher; 385 int ivlen; 386 387 if (c->number == SSH_CIPHER_3DES) 388 ivlen = 24; 389 else 390 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 391 return (ivlen); 392 } 393 394 void 395 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 396 { 397 Cipher *c = cc->cipher; 398 int evplen; 399 400 switch (c->number) { 401 case SSH_CIPHER_NONE: 402 case SSH_CIPHER_SSH2: 403 case SSH_CIPHER_DES: 404 case SSH_CIPHER_BLOWFISH: 405 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 406 if (evplen <= 0) 407 return; 408 if ((u_int)evplen != len) 409 fatal("%s: wrong iv length %d != %d", __func__, 410 evplen, len); 411 if (cipher_authlen(c)) { 412 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN, 413 len, iv)) 414 fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__); 415 } else 416 memcpy(iv, cc->evp.iv, len); 417 break; 418 case SSH_CIPHER_3DES: 419 ssh1_3des_iv(&cc->evp, 0, iv, 24); 420 break; 421 default: 422 fatal("%s: bad cipher %d", __func__, c->number); 423 } 424 } 425 426 void 427 cipher_set_keyiv(CipherContext *cc, u_char *iv) 428 { 429 Cipher *c = cc->cipher; 430 int evplen = 0; 431 432 switch (c->number) { 433 case SSH_CIPHER_NONE: 434 case SSH_CIPHER_SSH2: 435 case SSH_CIPHER_DES: 436 case SSH_CIPHER_BLOWFISH: 437 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 438 if (evplen == 0) 439 return; 440 if (cipher_authlen(c)) { 441 if (!EVP_CIPHER_CTX_ctrl(&cc->evp, 442 EVP_CTRL_GCM_SET_IV_FIXED, -1, iv)) 443 fatal("%s: EVP_CTRL_GCM_SET_IV_FIXED failed", 444 __func__); 445 } else 446 memcpy(cc->evp.iv, iv, evplen); 447 break; 448 case SSH_CIPHER_3DES: 449 ssh1_3des_iv(&cc->evp, 1, iv, 24); 450 break; 451 default: 452 fatal("%s: bad cipher %d", __func__, c->number); 453 } 454 } 455 456 #define EVP_X_STATE(evp) (evp).cipher_data 457 #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size 458 459 int 460 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 461 { 462 Cipher *c = cc->cipher; 463 int plen = 0; 464 465 if (c->evptype == EVP_rc4) { 466 plen = EVP_X_STATE_LEN(cc->evp); 467 if (dat == NULL) 468 return (plen); 469 memcpy(dat, EVP_X_STATE(cc->evp), plen); 470 } 471 return (plen); 472 } 473 474 void 475 cipher_set_keycontext(CipherContext *cc, u_char *dat) 476 { 477 Cipher *c = cc->cipher; 478 int plen; 479 480 if (c->evptype == EVP_rc4) { 481 plen = EVP_X_STATE_LEN(cc->evp); 482 memcpy(EVP_X_STATE(cc->evp), dat, plen); 483 } 484 } 485