1 /* $OpenBSD: cipher.c,v 1.117 2020/04/03 04:27:03 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 #ifndef WITH_OPENSSL 55 #define EVP_CIPHER_CTX void 56 #endif 57 58 struct sshcipher_ctx { 59 int plaintext; 60 int encrypt; 61 EVP_CIPHER_CTX *evp; 62 struct chachapoly_ctx *cp_ctx; 63 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 64 const struct sshcipher *cipher; 65 }; 66 67 struct sshcipher { 68 char *name; 69 u_int block_size; 70 u_int key_len; 71 u_int iv_len; /* defaults to block_size */ 72 u_int auth_len; 73 u_int flags; 74 #define CFLAG_CBC (1<<0) 75 #define CFLAG_CHACHAPOLY (1<<1) 76 #define CFLAG_AESCTR (1<<2) 77 #define CFLAG_NONE (1<<3) 78 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */ 79 #ifdef WITH_OPENSSL 80 const EVP_CIPHER *(*evptype)(void); 81 #else 82 void *ignored; 83 #endif 84 }; 85 86 static const struct sshcipher ciphers[] = { 87 #ifdef WITH_OPENSSL 88 #ifndef OPENSSL_NO_DES 89 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 90 #endif 91 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 92 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 93 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 94 { "rijndael-cbc@lysator.liu.se", 95 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 96 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 97 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 98 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 99 # ifdef OPENSSL_HAVE_EVPGCM 100 { "aes128-gcm@openssh.com", 101 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 102 { "aes256-gcm@openssh.com", 103 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 104 # endif /* OPENSSL_HAVE_EVPGCM */ 105 #else 106 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL }, 107 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL }, 108 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL }, 109 #endif 110 { "chacha20-poly1305@openssh.com", 111 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL }, 112 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL }, 113 114 { NULL, 0, 0, 0, 0, 0, NULL } 115 }; 116 117 /*--*/ 118 119 /* Returns a comma-separated list of supported ciphers. */ 120 char * 121 cipher_alg_list(char sep, int auth_only) 122 { 123 char *tmp, *ret = NULL; 124 size_t nlen, rlen = 0; 125 const struct sshcipher *c; 126 127 for (c = ciphers; c->name != NULL; c++) { 128 if ((c->flags & CFLAG_INTERNAL) != 0) 129 continue; 130 if (auth_only && c->auth_len == 0) 131 continue; 132 if (ret != NULL) 133 ret[rlen++] = sep; 134 nlen = strlen(c->name); 135 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 136 free(ret); 137 return NULL; 138 } 139 ret = tmp; 140 memcpy(ret + rlen, c->name, nlen + 1); 141 rlen += nlen; 142 } 143 return ret; 144 } 145 146 const char * 147 compression_alg_list(int compression) 148 { 149 #ifdef WITH_ZLIB 150 return compression ? "zlib@openssh.com,zlib,none" : 151 "none,zlib@openssh.com,zlib"; 152 #else 153 return "none"; 154 #endif 155 } 156 157 u_int 158 cipher_blocksize(const struct sshcipher *c) 159 { 160 return (c->block_size); 161 } 162 163 u_int 164 cipher_keylen(const struct sshcipher *c) 165 { 166 return (c->key_len); 167 } 168 169 u_int 170 cipher_seclen(const struct sshcipher *c) 171 { 172 if (strcmp("3des-cbc", c->name) == 0) 173 return 14; 174 return cipher_keylen(c); 175 } 176 177 u_int 178 cipher_authlen(const struct sshcipher *c) 179 { 180 return (c->auth_len); 181 } 182 183 u_int 184 cipher_ivlen(const struct sshcipher *c) 185 { 186 /* 187 * Default is cipher block size, except for chacha20+poly1305 that 188 * needs no IV. XXX make iv_len == -1 default? 189 */ 190 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 191 c->iv_len : c->block_size; 192 } 193 194 u_int 195 cipher_is_cbc(const struct sshcipher *c) 196 { 197 return (c->flags & CFLAG_CBC) != 0; 198 } 199 200 u_int 201 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 202 { 203 return cc->plaintext; 204 } 205 206 const struct sshcipher * 207 cipher_by_name(const char *name) 208 { 209 const struct sshcipher *c; 210 for (c = ciphers; c->name != NULL; c++) 211 if (strcmp(c->name, name) == 0) 212 return c; 213 return NULL; 214 } 215 216 #define CIPHER_SEP "," 217 int 218 ciphers_valid(const char *names) 219 { 220 const struct sshcipher *c; 221 char *cipher_list, *cp; 222 char *p; 223 224 if (names == NULL || strcmp(names, "") == 0) 225 return 0; 226 if ((cipher_list = cp = strdup(names)) == NULL) 227 return 0; 228 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 229 (p = strsep(&cp, CIPHER_SEP))) { 230 c = cipher_by_name(p); 231 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) { 232 free(cipher_list); 233 return 0; 234 } 235 } 236 free(cipher_list); 237 return 1; 238 } 239 240 const char * 241 cipher_warning_message(const struct sshcipher_ctx *cc) 242 { 243 if (cc == NULL || cc->cipher == NULL) 244 return NULL; 245 /* XXX repurpose for CBC warning */ 246 return NULL; 247 } 248 249 int 250 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 251 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 252 int do_encrypt) 253 { 254 struct sshcipher_ctx *cc = NULL; 255 int ret = SSH_ERR_INTERNAL_ERROR; 256 #ifdef WITH_OPENSSL 257 const EVP_CIPHER *type; 258 int klen; 259 #endif 260 261 *ccp = NULL; 262 if ((cc = calloc(sizeof(*cc), 1)) == NULL) 263 return SSH_ERR_ALLOC_FAIL; 264 265 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 266 cc->encrypt = do_encrypt; 267 268 if (keylen < cipher->key_len || 269 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 270 ret = SSH_ERR_INVALID_ARGUMENT; 271 goto out; 272 } 273 274 cc->cipher = cipher; 275 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 276 cc->cp_ctx = chachapoly_new(key, keylen); 277 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 278 goto out; 279 } 280 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 281 ret = 0; 282 goto out; 283 } 284 #ifndef WITH_OPENSSL 285 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 286 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 287 aesctr_ivsetup(&cc->ac_ctx, iv); 288 ret = 0; 289 goto out; 290 } 291 ret = SSH_ERR_INVALID_ARGUMENT; 292 goto out; 293 #else /* WITH_OPENSSL */ 294 type = (*cipher->evptype)(); 295 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 296 ret = SSH_ERR_ALLOC_FAIL; 297 goto out; 298 } 299 if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv, 300 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 301 ret = SSH_ERR_LIBCRYPTO_ERROR; 302 goto out; 303 } 304 if (cipher_authlen(cipher) && 305 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 306 -1, (u_char *)iv)) { 307 ret = SSH_ERR_LIBCRYPTO_ERROR; 308 goto out; 309 } 310 klen = EVP_CIPHER_CTX_key_length(cc->evp); 311 if (klen > 0 && keylen != (u_int)klen) { 312 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 313 ret = SSH_ERR_LIBCRYPTO_ERROR; 314 goto out; 315 } 316 } 317 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) { 318 ret = SSH_ERR_LIBCRYPTO_ERROR; 319 goto out; 320 } 321 ret = 0; 322 #endif /* WITH_OPENSSL */ 323 out: 324 if (ret == 0) { 325 /* success */ 326 *ccp = cc; 327 } else { 328 if (cc != NULL) { 329 #ifdef WITH_OPENSSL 330 EVP_CIPHER_CTX_free(cc->evp); 331 #endif /* WITH_OPENSSL */ 332 freezero(cc, sizeof(*cc)); 333 } 334 } 335 return ret; 336 } 337 338 /* 339 * cipher_crypt() operates as following: 340 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 341 * These bytes are treated as additional authenticated data for 342 * authenticated encryption modes. 343 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 344 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 345 * This tag is written on encryption and verified on decryption. 346 * Both 'aadlen' and 'authlen' can be set to 0. 347 */ 348 int 349 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 350 const u_char *src, u_int len, u_int aadlen, u_int authlen) 351 { 352 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 353 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 354 len, aadlen, authlen, cc->encrypt); 355 } 356 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 357 memcpy(dest, src, aadlen + len); 358 return 0; 359 } 360 #ifndef WITH_OPENSSL 361 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 362 if (aadlen) 363 memcpy(dest, src, aadlen); 364 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 365 dest + aadlen, len); 366 return 0; 367 } 368 return SSH_ERR_INVALID_ARGUMENT; 369 #else 370 if (authlen) { 371 u_char lastiv[1]; 372 373 if (authlen != cipher_authlen(cc->cipher)) 374 return SSH_ERR_INVALID_ARGUMENT; 375 /* increment IV */ 376 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 377 1, lastiv)) 378 return SSH_ERR_LIBCRYPTO_ERROR; 379 /* set tag on decyption */ 380 if (!cc->encrypt && 381 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 382 authlen, (u_char *)src + aadlen + len)) 383 return SSH_ERR_LIBCRYPTO_ERROR; 384 } 385 if (aadlen) { 386 if (authlen && 387 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0) 388 return SSH_ERR_LIBCRYPTO_ERROR; 389 memcpy(dest, src, aadlen); 390 } 391 if (len % cc->cipher->block_size) 392 return SSH_ERR_INVALID_ARGUMENT; 393 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen, 394 len) < 0) 395 return SSH_ERR_LIBCRYPTO_ERROR; 396 if (authlen) { 397 /* compute tag (on encrypt) or verify tag (on decrypt) */ 398 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 399 return cc->encrypt ? 400 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 401 if (cc->encrypt && 402 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 403 authlen, dest + aadlen + len)) 404 return SSH_ERR_LIBCRYPTO_ERROR; 405 } 406 return 0; 407 #endif 408 } 409 410 /* Extract the packet length, including any decryption necessary beforehand */ 411 int 412 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 413 const u_char *cp, u_int len) 414 { 415 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 416 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 417 cp, len); 418 if (len < 4) 419 return SSH_ERR_MESSAGE_INCOMPLETE; 420 *plenp = PEEK_U32(cp); 421 return 0; 422 } 423 424 void 425 cipher_free(struct sshcipher_ctx *cc) 426 { 427 if (cc == NULL) 428 return; 429 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 430 chachapoly_free(cc->cp_ctx); 431 cc->cp_ctx = NULL; 432 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 433 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 434 #ifdef WITH_OPENSSL 435 EVP_CIPHER_CTX_free(cc->evp); 436 cc->evp = NULL; 437 #endif 438 freezero(cc, sizeof(*cc)); 439 } 440 441 /* 442 * Exports an IV from the sshcipher_ctx required to export the key 443 * state back from the unprivileged child to the privileged parent 444 * process. 445 */ 446 int 447 cipher_get_keyiv_len(const struct sshcipher_ctx *cc) 448 { 449 const struct sshcipher *c = cc->cipher; 450 451 if ((c->flags & CFLAG_CHACHAPOLY) != 0) 452 return 0; 453 else if ((c->flags & CFLAG_AESCTR) != 0) 454 return sizeof(cc->ac_ctx.ctr); 455 #ifdef WITH_OPENSSL 456 return EVP_CIPHER_CTX_iv_length(cc->evp); 457 #else 458 return 0; 459 #endif 460 } 461 462 int 463 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 464 { 465 #ifdef WITH_OPENSSL 466 const struct sshcipher *c = cc->cipher; 467 int evplen; 468 #endif 469 470 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 471 if (len != 0) 472 return SSH_ERR_INVALID_ARGUMENT; 473 return 0; 474 } 475 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 476 if (len != sizeof(cc->ac_ctx.ctr)) 477 return SSH_ERR_INVALID_ARGUMENT; 478 memcpy(iv, cc->ac_ctx.ctr, len); 479 return 0; 480 } 481 if ((cc->cipher->flags & CFLAG_NONE) != 0) 482 return 0; 483 484 #ifdef WITH_OPENSSL 485 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 486 if (evplen == 0) 487 return 0; 488 else if (evplen < 0) 489 return SSH_ERR_LIBCRYPTO_ERROR; 490 if ((size_t)evplen != len) 491 return SSH_ERR_INVALID_ARGUMENT; 492 #ifndef OPENSSL_HAVE_EVPCTR 493 if (c->evptype == evp_aes_128_ctr) 494 ssh_aes_ctr_iv(cc->evp, 0, iv, len); 495 else 496 #endif 497 if (cipher_authlen(c)) { 498 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 499 len, iv)) 500 return SSH_ERR_LIBCRYPTO_ERROR; 501 } else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len)) 502 return SSH_ERR_LIBCRYPTO_ERROR; 503 #endif 504 return 0; 505 } 506 507 int 508 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 509 { 510 #ifdef WITH_OPENSSL 511 const struct sshcipher *c = cc->cipher; 512 int evplen = 0; 513 #endif 514 515 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 516 return 0; 517 if ((cc->cipher->flags & CFLAG_NONE) != 0) 518 return 0; 519 520 #ifdef WITH_OPENSSL 521 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 522 if (evplen <= 0) 523 return SSH_ERR_LIBCRYPTO_ERROR; 524 if ((size_t)evplen != len) 525 return SSH_ERR_INVALID_ARGUMENT; 526 #ifndef OPENSSL_HAVE_EVPCTR 527 /* XXX iv arg is const, but ssh_aes_ctr_iv isn't */ 528 if (c->evptype == evp_aes_128_ctr) 529 ssh_aes_ctr_iv(cc->evp, 1, (u_char *)iv, evplen); 530 else 531 #endif 532 if (cipher_authlen(c)) { 533 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 534 if (!EVP_CIPHER_CTX_ctrl(cc->evp, 535 EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv)) 536 return SSH_ERR_LIBCRYPTO_ERROR; 537 } else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen)) 538 return SSH_ERR_LIBCRYPTO_ERROR; 539 #endif 540 return 0; 541 } 542