1 /* $OpenBSD: cipher.c,v 1.107 2017/05/07 23:12:57 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 "cipher.h" 47 #include "misc.h" 48 #include "sshbuf.h" 49 #include "ssherr.h" 50 #include "digest.h" 51 52 #include "openbsd-compat/openssl-compat.h" 53 54 55 struct sshcipher_ctx { 56 int plaintext; 57 int encrypt; 58 EVP_CIPHER_CTX *evp; 59 struct chachapoly_ctx cp_ctx; /* XXX union with evp? */ 60 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 61 const struct sshcipher *cipher; 62 }; 63 64 struct sshcipher { 65 char *name; 66 u_int block_size; 67 u_int key_len; 68 u_int iv_len; /* defaults to block_size */ 69 u_int auth_len; 70 u_int flags; 71 #define CFLAG_CBC (1<<0) 72 #define CFLAG_CHACHAPOLY (1<<1) 73 #define CFLAG_AESCTR (1<<2) 74 #define CFLAG_NONE (1<<3) 75 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */ 76 #ifdef WITH_OPENSSL 77 const EVP_CIPHER *(*evptype)(void); 78 #else 79 void *ignored; 80 #endif 81 }; 82 83 static const struct sshcipher ciphers[] = { 84 #ifdef WITH_OPENSSL 85 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 86 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 87 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 88 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 89 { "rijndael-cbc@lysator.liu.se", 90 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 91 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 92 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 93 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 94 # ifdef OPENSSL_HAVE_EVPGCM 95 { "aes128-gcm@openssh.com", 96 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 97 { "aes256-gcm@openssh.com", 98 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 99 # endif /* OPENSSL_HAVE_EVPGCM */ 100 #else 101 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL }, 102 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL }, 103 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL }, 104 #endif 105 { "chacha20-poly1305@openssh.com", 106 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL }, 107 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL }, 108 109 { NULL, 0, 0, 0, 0, 0, NULL } 110 }; 111 112 /*--*/ 113 114 /* Returns a comma-separated list of supported ciphers. */ 115 char * 116 cipher_alg_list(char sep, int auth_only) 117 { 118 char *tmp, *ret = NULL; 119 size_t nlen, rlen = 0; 120 const struct sshcipher *c; 121 122 for (c = ciphers; c->name != NULL; c++) { 123 if ((c->flags & CFLAG_INTERNAL) != 0) 124 continue; 125 if (auth_only && c->auth_len == 0) 126 continue; 127 if (ret != NULL) 128 ret[rlen++] = sep; 129 nlen = strlen(c->name); 130 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 131 free(ret); 132 return NULL; 133 } 134 ret = tmp; 135 memcpy(ret + rlen, c->name, nlen + 1); 136 rlen += nlen; 137 } 138 return ret; 139 } 140 141 u_int 142 cipher_blocksize(const struct sshcipher *c) 143 { 144 return (c->block_size); 145 } 146 147 u_int 148 cipher_keylen(const struct sshcipher *c) 149 { 150 return (c->key_len); 151 } 152 153 u_int 154 cipher_seclen(const struct sshcipher *c) 155 { 156 if (strcmp("3des-cbc", c->name) == 0) 157 return 14; 158 return cipher_keylen(c); 159 } 160 161 u_int 162 cipher_authlen(const struct sshcipher *c) 163 { 164 return (c->auth_len); 165 } 166 167 u_int 168 cipher_ivlen(const struct sshcipher *c) 169 { 170 /* 171 * Default is cipher block size, except for chacha20+poly1305 that 172 * needs no IV. XXX make iv_len == -1 default? 173 */ 174 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 175 c->iv_len : c->block_size; 176 } 177 178 u_int 179 cipher_is_cbc(const struct sshcipher *c) 180 { 181 return (c->flags & CFLAG_CBC) != 0; 182 } 183 184 u_int 185 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 186 { 187 return cc->plaintext; 188 } 189 190 const struct sshcipher * 191 cipher_by_name(const char *name) 192 { 193 const struct sshcipher *c; 194 for (c = ciphers; c->name != NULL; c++) 195 if (strcmp(c->name, name) == 0) 196 return c; 197 return NULL; 198 } 199 200 #define CIPHER_SEP "," 201 int 202 ciphers_valid(const char *names) 203 { 204 const struct sshcipher *c; 205 char *cipher_list, *cp; 206 char *p; 207 208 if (names == NULL || strcmp(names, "") == 0) 209 return 0; 210 if ((cipher_list = cp = strdup(names)) == NULL) 211 return 0; 212 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 213 (p = strsep(&cp, CIPHER_SEP))) { 214 c = cipher_by_name(p); 215 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) { 216 free(cipher_list); 217 return 0; 218 } 219 } 220 free(cipher_list); 221 return 1; 222 } 223 224 const char * 225 cipher_warning_message(const struct sshcipher_ctx *cc) 226 { 227 if (cc == NULL || cc->cipher == NULL) 228 return NULL; 229 /* XXX repurpose for CBC warning */ 230 return NULL; 231 } 232 233 int 234 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 235 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 236 int do_encrypt) 237 { 238 struct sshcipher_ctx *cc = NULL; 239 int ret = SSH_ERR_INTERNAL_ERROR; 240 #ifdef WITH_OPENSSL 241 const EVP_CIPHER *type; 242 int klen; 243 #endif 244 245 *ccp = NULL; 246 if ((cc = calloc(sizeof(*cc), 1)) == NULL) 247 return SSH_ERR_ALLOC_FAIL; 248 249 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 250 cc->encrypt = do_encrypt; 251 252 if (keylen < cipher->key_len || 253 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 254 ret = SSH_ERR_INVALID_ARGUMENT; 255 goto out; 256 } 257 258 cc->cipher = cipher; 259 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 260 ret = chachapoly_init(&cc->cp_ctx, key, keylen); 261 goto out; 262 } 263 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 264 ret = 0; 265 goto out; 266 } 267 #ifndef WITH_OPENSSL 268 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 269 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 270 aesctr_ivsetup(&cc->ac_ctx, iv); 271 ret = 0; 272 goto out; 273 } 274 ret = SSH_ERR_INVALID_ARGUMENT; 275 goto out; 276 #else /* WITH_OPENSSL */ 277 type = (*cipher->evptype)(); 278 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 279 ret = SSH_ERR_ALLOC_FAIL; 280 goto out; 281 } 282 if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv, 283 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 284 ret = SSH_ERR_LIBCRYPTO_ERROR; 285 goto out; 286 } 287 if (cipher_authlen(cipher) && 288 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 289 -1, (u_char *)iv)) { 290 ret = SSH_ERR_LIBCRYPTO_ERROR; 291 goto out; 292 } 293 klen = EVP_CIPHER_CTX_key_length(cc->evp); 294 if (klen > 0 && keylen != (u_int)klen) { 295 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 296 ret = SSH_ERR_LIBCRYPTO_ERROR; 297 goto out; 298 } 299 } 300 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) { 301 ret = SSH_ERR_LIBCRYPTO_ERROR; 302 goto out; 303 } 304 ret = 0; 305 #endif /* WITH_OPENSSL */ 306 out: 307 if (ret == 0) { 308 /* success */ 309 *ccp = cc; 310 } else { 311 if (cc != NULL) { 312 #ifdef WITH_OPENSSL 313 if (cc->evp != NULL) 314 EVP_CIPHER_CTX_free(cc->evp); 315 #endif /* WITH_OPENSSL */ 316 explicit_bzero(cc, sizeof(*cc)); 317 free(cc); 318 } 319 } 320 return ret; 321 } 322 323 /* 324 * cipher_crypt() operates as following: 325 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 326 * Theses bytes are treated as additional authenticated data for 327 * authenticated encryption modes. 328 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 329 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 330 * This tag is written on encryption and verified on decryption. 331 * Both 'aadlen' and 'authlen' can be set to 0. 332 */ 333 int 334 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 335 const u_char *src, u_int len, u_int aadlen, u_int authlen) 336 { 337 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 338 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, 339 len, aadlen, authlen, cc->encrypt); 340 } 341 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 342 memcpy(dest, src, aadlen + len); 343 return 0; 344 } 345 #ifndef WITH_OPENSSL 346 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 347 if (aadlen) 348 memcpy(dest, src, aadlen); 349 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 350 dest + aadlen, len); 351 return 0; 352 } 353 return SSH_ERR_INVALID_ARGUMENT; 354 #else 355 if (authlen) { 356 u_char lastiv[1]; 357 358 if (authlen != cipher_authlen(cc->cipher)) 359 return SSH_ERR_INVALID_ARGUMENT; 360 /* increment IV */ 361 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 362 1, lastiv)) 363 return SSH_ERR_LIBCRYPTO_ERROR; 364 /* set tag on decyption */ 365 if (!cc->encrypt && 366 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 367 authlen, (u_char *)src + aadlen + len)) 368 return SSH_ERR_LIBCRYPTO_ERROR; 369 } 370 if (aadlen) { 371 if (authlen && 372 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0) 373 return SSH_ERR_LIBCRYPTO_ERROR; 374 memcpy(dest, src, aadlen); 375 } 376 if (len % cc->cipher->block_size) 377 return SSH_ERR_INVALID_ARGUMENT; 378 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen, 379 len) < 0) 380 return SSH_ERR_LIBCRYPTO_ERROR; 381 if (authlen) { 382 /* compute tag (on encrypt) or verify tag (on decrypt) */ 383 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 384 return cc->encrypt ? 385 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 386 if (cc->encrypt && 387 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 388 authlen, dest + aadlen + len)) 389 return SSH_ERR_LIBCRYPTO_ERROR; 390 } 391 return 0; 392 #endif 393 } 394 395 /* Extract the packet length, including any decryption necessary beforehand */ 396 int 397 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 398 const u_char *cp, u_int len) 399 { 400 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 401 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr, 402 cp, len); 403 if (len < 4) 404 return SSH_ERR_MESSAGE_INCOMPLETE; 405 *plenp = get_u32(cp); 406 return 0; 407 } 408 409 void 410 cipher_free(struct sshcipher_ctx *cc) 411 { 412 if (cc == NULL) 413 return; 414 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 415 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx)); 416 else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 417 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 418 #ifdef WITH_OPENSSL 419 if (cc->evp != NULL) { 420 EVP_CIPHER_CTX_free(cc->evp); 421 cc->evp = NULL; 422 } 423 #endif 424 explicit_bzero(cc, sizeof(*cc)); 425 free(cc); 426 } 427 428 /* 429 * Exports an IV from the sshcipher_ctx required to export the key 430 * state back from the unprivileged child to the privileged parent 431 * process. 432 */ 433 int 434 cipher_get_keyiv_len(const struct sshcipher_ctx *cc) 435 { 436 const struct sshcipher *c = cc->cipher; 437 438 if ((c->flags & CFLAG_CHACHAPOLY) != 0) 439 return 0; 440 else if ((c->flags & CFLAG_AESCTR) != 0) 441 return sizeof(cc->ac_ctx.ctr); 442 #ifdef WITH_OPENSSL 443 return EVP_CIPHER_CTX_iv_length(cc->evp); 444 #else 445 return 0; 446 #endif 447 } 448 449 int 450 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, u_int len) 451 { 452 const struct sshcipher *c = cc->cipher; 453 #ifdef WITH_OPENSSL 454 int evplen; 455 #endif 456 457 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 458 if (len != 0) 459 return SSH_ERR_INVALID_ARGUMENT; 460 return 0; 461 } 462 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 463 if (len != sizeof(cc->ac_ctx.ctr)) 464 return SSH_ERR_INVALID_ARGUMENT; 465 memcpy(iv, cc->ac_ctx.ctr, len); 466 return 0; 467 } 468 if ((cc->cipher->flags & CFLAG_NONE) != 0) 469 return 0; 470 471 #ifdef WITH_OPENSSL 472 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 473 if (evplen == 0) 474 return 0; 475 else if (evplen < 0) 476 return SSH_ERR_LIBCRYPTO_ERROR; 477 if ((u_int)evplen != len) 478 return SSH_ERR_INVALID_ARGUMENT; 479 #ifndef OPENSSL_HAVE_EVPCTR 480 if (c->evptype == evp_aes_128_ctr) 481 ssh_aes_ctr_iv(cc->evp, 0, iv, len); 482 else 483 #endif 484 if (cipher_authlen(c)) { 485 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 486 len, iv)) 487 return SSH_ERR_LIBCRYPTO_ERROR; 488 } else 489 memcpy(iv, cc->evp->iv, len); 490 #endif 491 return 0; 492 } 493 494 int 495 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv) 496 { 497 const struct sshcipher *c = cc->cipher; 498 #ifdef WITH_OPENSSL 499 int evplen = 0; 500 #endif 501 502 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 503 return 0; 504 if ((cc->cipher->flags & CFLAG_NONE) != 0) 505 return 0; 506 507 #ifdef WITH_OPENSSL 508 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 509 if (evplen <= 0) 510 return SSH_ERR_LIBCRYPTO_ERROR; 511 #ifndef OPENSSL_HAVE_EVPCTR 512 /* XXX iv arg is const, but ssh_aes_ctr_iv isn't */ 513 if (c->evptype == evp_aes_128_ctr) 514 ssh_aes_ctr_iv(cc->evp, 1, (u_char *)iv, evplen); 515 else 516 #endif 517 if (cipher_authlen(c)) { 518 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 519 if (!EVP_CIPHER_CTX_ctrl(cc->evp, 520 EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv)) 521 return SSH_ERR_LIBCRYPTO_ERROR; 522 } else 523 memcpy(cc->evp->iv, iv, evplen); 524 #endif 525 return 0; 526 } 527 528 #ifdef WITH_OPENSSL 529 #define EVP_X_STATE(evp) (evp)->cipher_data 530 #define EVP_X_STATE_LEN(evp) (evp)->cipher->ctx_size 531 #endif 532 533 int 534 cipher_get_keycontext(const struct sshcipher_ctx *cc, u_char *dat) 535 { 536 #if defined(WITH_OPENSSL) && !defined(OPENSSL_NO_RC4) 537 const struct sshcipher *c = cc->cipher; 538 int plen = 0; 539 540 if (c->evptype == EVP_rc4) { 541 plen = EVP_X_STATE_LEN(cc->evp); 542 if (dat == NULL) 543 return (plen); 544 memcpy(dat, EVP_X_STATE(cc->evp), plen); 545 } 546 return (plen); 547 #else 548 return 0; 549 #endif 550 } 551 552 void 553 cipher_set_keycontext(struct sshcipher_ctx *cc, const u_char *dat) 554 { 555 #if defined(WITH_OPENSSL) && !defined(OPENSSL_NO_RC4) 556 const struct sshcipher *c = cc->cipher; 557 int plen; 558 559 if (c->evptype == EVP_rc4) { 560 plen = EVP_X_STATE_LEN(cc->evp); 561 memcpy(EVP_X_STATE(cc->evp), dat, plen); 562 } 563 #endif 564 } 565