1 /* $OpenBSD: cipher.c,v 1.119 2021/04/03 06:18:40 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 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 95 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 96 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 97 { "aes128-gcm@openssh.com", 98 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 99 { "aes256-gcm@openssh.com", 100 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 101 #else 102 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL }, 103 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL }, 104 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL }, 105 #endif 106 { "chacha20-poly1305@openssh.com", 107 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL }, 108 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL }, 109 110 { NULL, 0, 0, 0, 0, 0, NULL } 111 }; 112 113 /*--*/ 114 115 /* Returns a comma-separated list of supported ciphers. */ 116 char * 117 cipher_alg_list(char sep, int auth_only) 118 { 119 char *tmp, *ret = NULL; 120 size_t nlen, rlen = 0; 121 const struct sshcipher *c; 122 123 for (c = ciphers; c->name != NULL; c++) { 124 if ((c->flags & CFLAG_INTERNAL) != 0) 125 continue; 126 if (auth_only && c->auth_len == 0) 127 continue; 128 if (ret != NULL) 129 ret[rlen++] = sep; 130 nlen = strlen(c->name); 131 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 132 free(ret); 133 return NULL; 134 } 135 ret = tmp; 136 memcpy(ret + rlen, c->name, nlen + 1); 137 rlen += nlen; 138 } 139 return ret; 140 } 141 142 const char * 143 compression_alg_list(int compression) 144 { 145 #ifdef WITH_ZLIB 146 return compression ? "zlib@openssh.com,zlib,none" : 147 "none,zlib@openssh.com,zlib"; 148 #else 149 return "none"; 150 #endif 151 } 152 153 u_int 154 cipher_blocksize(const struct sshcipher *c) 155 { 156 return (c->block_size); 157 } 158 159 u_int 160 cipher_keylen(const struct sshcipher *c) 161 { 162 return (c->key_len); 163 } 164 165 u_int 166 cipher_seclen(const struct sshcipher *c) 167 { 168 if (strcmp("3des-cbc", c->name) == 0) 169 return 14; 170 return cipher_keylen(c); 171 } 172 173 u_int 174 cipher_authlen(const struct sshcipher *c) 175 { 176 return (c->auth_len); 177 } 178 179 u_int 180 cipher_ivlen(const struct sshcipher *c) 181 { 182 /* 183 * Default is cipher block size, except for chacha20+poly1305 that 184 * needs no IV. XXX make iv_len == -1 default? 185 */ 186 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 187 c->iv_len : c->block_size; 188 } 189 190 u_int 191 cipher_is_cbc(const struct sshcipher *c) 192 { 193 return (c->flags & CFLAG_CBC) != 0; 194 } 195 196 u_int 197 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 198 { 199 return cc->plaintext; 200 } 201 202 const struct sshcipher * 203 cipher_by_name(const char *name) 204 { 205 const struct sshcipher *c; 206 for (c = ciphers; c->name != NULL; c++) 207 if (strcmp(c->name, name) == 0) 208 return c; 209 return NULL; 210 } 211 212 #define CIPHER_SEP "," 213 int 214 ciphers_valid(const char *names) 215 { 216 const struct sshcipher *c; 217 char *cipher_list, *cp; 218 char *p; 219 220 if (names == NULL || strcmp(names, "") == 0) 221 return 0; 222 if ((cipher_list = cp = strdup(names)) == NULL) 223 return 0; 224 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 225 (p = strsep(&cp, CIPHER_SEP))) { 226 c = cipher_by_name(p); 227 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) { 228 free(cipher_list); 229 return 0; 230 } 231 } 232 free(cipher_list); 233 return 1; 234 } 235 236 const char * 237 cipher_warning_message(const struct sshcipher_ctx *cc) 238 { 239 if (cc == NULL || cc->cipher == NULL) 240 return NULL; 241 /* XXX repurpose for CBC warning */ 242 return NULL; 243 } 244 245 int 246 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 247 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 248 int do_encrypt) 249 { 250 struct sshcipher_ctx *cc = NULL; 251 int ret = SSH_ERR_INTERNAL_ERROR; 252 #ifdef WITH_OPENSSL 253 const EVP_CIPHER *type; 254 int klen; 255 #endif 256 257 *ccp = NULL; 258 if ((cc = calloc(sizeof(*cc), 1)) == NULL) 259 return SSH_ERR_ALLOC_FAIL; 260 261 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 262 cc->encrypt = do_encrypt; 263 264 if (keylen < cipher->key_len || 265 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 266 ret = SSH_ERR_INVALID_ARGUMENT; 267 goto out; 268 } 269 270 cc->cipher = cipher; 271 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 272 cc->cp_ctx = chachapoly_new(key, keylen); 273 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 274 goto out; 275 } 276 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 277 ret = 0; 278 goto out; 279 } 280 #ifndef WITH_OPENSSL 281 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 282 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 283 aesctr_ivsetup(&cc->ac_ctx, iv); 284 ret = 0; 285 goto out; 286 } 287 ret = SSH_ERR_INVALID_ARGUMENT; 288 goto out; 289 #else /* WITH_OPENSSL */ 290 type = (*cipher->evptype)(); 291 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 292 ret = SSH_ERR_ALLOC_FAIL; 293 goto out; 294 } 295 if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv, 296 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 297 ret = SSH_ERR_LIBCRYPTO_ERROR; 298 goto out; 299 } 300 if (cipher_authlen(cipher) && 301 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 302 -1, (u_char *)iv)) { 303 ret = SSH_ERR_LIBCRYPTO_ERROR; 304 goto out; 305 } 306 klen = EVP_CIPHER_CTX_key_length(cc->evp); 307 if (klen > 0 && keylen != (u_int)klen) { 308 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 309 ret = SSH_ERR_LIBCRYPTO_ERROR; 310 goto out; 311 } 312 } 313 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) { 314 ret = SSH_ERR_LIBCRYPTO_ERROR; 315 goto out; 316 } 317 ret = 0; 318 #endif /* WITH_OPENSSL */ 319 out: 320 if (ret == 0) { 321 /* success */ 322 *ccp = cc; 323 } else { 324 if (cc != NULL) { 325 #ifdef WITH_OPENSSL 326 EVP_CIPHER_CTX_free(cc->evp); 327 #endif /* WITH_OPENSSL */ 328 freezero(cc, sizeof(*cc)); 329 } 330 } 331 return ret; 332 } 333 334 /* 335 * cipher_crypt() operates as following: 336 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 337 * These bytes are treated as additional authenticated data for 338 * authenticated encryption modes. 339 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 340 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 341 * This tag is written on encryption and verified on decryption. 342 * Both 'aadlen' and 'authlen' can be set to 0. 343 */ 344 int 345 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 346 const u_char *src, u_int len, u_int aadlen, u_int authlen) 347 { 348 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 349 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 350 len, aadlen, authlen, cc->encrypt); 351 } 352 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 353 memcpy(dest, src, aadlen + len); 354 return 0; 355 } 356 #ifndef WITH_OPENSSL 357 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 358 if (aadlen) 359 memcpy(dest, src, aadlen); 360 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 361 dest + aadlen, len); 362 return 0; 363 } 364 return SSH_ERR_INVALID_ARGUMENT; 365 #else 366 if (authlen) { 367 u_char lastiv[1]; 368 369 if (authlen != cipher_authlen(cc->cipher)) 370 return SSH_ERR_INVALID_ARGUMENT; 371 /* increment IV */ 372 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 373 1, lastiv)) 374 return SSH_ERR_LIBCRYPTO_ERROR; 375 /* set tag on decyption */ 376 if (!cc->encrypt && 377 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 378 authlen, (u_char *)src + aadlen + len)) 379 return SSH_ERR_LIBCRYPTO_ERROR; 380 } 381 if (aadlen) { 382 if (authlen && 383 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0) 384 return SSH_ERR_LIBCRYPTO_ERROR; 385 memcpy(dest, src, aadlen); 386 } 387 if (len % cc->cipher->block_size) 388 return SSH_ERR_INVALID_ARGUMENT; 389 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen, 390 len) < 0) 391 return SSH_ERR_LIBCRYPTO_ERROR; 392 if (authlen) { 393 /* compute tag (on encrypt) or verify tag (on decrypt) */ 394 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 395 return cc->encrypt ? 396 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 397 if (cc->encrypt && 398 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 399 authlen, dest + aadlen + len)) 400 return SSH_ERR_LIBCRYPTO_ERROR; 401 } 402 return 0; 403 #endif 404 } 405 406 /* Extract the packet length, including any decryption necessary beforehand */ 407 int 408 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 409 const u_char *cp, u_int len) 410 { 411 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 412 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 413 cp, len); 414 if (len < 4) 415 return SSH_ERR_MESSAGE_INCOMPLETE; 416 *plenp = PEEK_U32(cp); 417 return 0; 418 } 419 420 void 421 cipher_free(struct sshcipher_ctx *cc) 422 { 423 if (cc == NULL) 424 return; 425 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 426 chachapoly_free(cc->cp_ctx); 427 cc->cp_ctx = NULL; 428 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 429 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 430 #ifdef WITH_OPENSSL 431 EVP_CIPHER_CTX_free(cc->evp); 432 cc->evp = NULL; 433 #endif 434 freezero(cc, sizeof(*cc)); 435 } 436 437 /* 438 * Exports an IV from the sshcipher_ctx required to export the key 439 * state back from the unprivileged child to the privileged parent 440 * process. 441 */ 442 int 443 cipher_get_keyiv_len(const struct sshcipher_ctx *cc) 444 { 445 const struct sshcipher *c = cc->cipher; 446 447 if ((c->flags & CFLAG_CHACHAPOLY) != 0) 448 return 0; 449 else if ((c->flags & CFLAG_AESCTR) != 0) 450 return sizeof(cc->ac_ctx.ctr); 451 #ifdef WITH_OPENSSL 452 return EVP_CIPHER_CTX_iv_length(cc->evp); 453 #else 454 return 0; 455 #endif 456 } 457 458 int 459 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 460 { 461 #ifdef WITH_OPENSSL 462 const struct sshcipher *c = cc->cipher; 463 int evplen; 464 #endif 465 466 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 467 if (len != 0) 468 return SSH_ERR_INVALID_ARGUMENT; 469 return 0; 470 } 471 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 472 if (len != sizeof(cc->ac_ctx.ctr)) 473 return SSH_ERR_INVALID_ARGUMENT; 474 memcpy(iv, cc->ac_ctx.ctr, len); 475 return 0; 476 } 477 if ((cc->cipher->flags & CFLAG_NONE) != 0) 478 return 0; 479 480 #ifdef WITH_OPENSSL 481 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 482 if (evplen == 0) 483 return 0; 484 else if (evplen < 0) 485 return SSH_ERR_LIBCRYPTO_ERROR; 486 if ((size_t)evplen != len) 487 return SSH_ERR_INVALID_ARGUMENT; 488 if (cipher_authlen(c)) { 489 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 490 len, iv)) 491 return SSH_ERR_LIBCRYPTO_ERROR; 492 } else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len)) 493 return SSH_ERR_LIBCRYPTO_ERROR; 494 #endif 495 return 0; 496 } 497 498 int 499 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 500 { 501 #ifdef WITH_OPENSSL 502 const struct sshcipher *c = cc->cipher; 503 int evplen = 0; 504 #endif 505 506 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 507 return 0; 508 if ((cc->cipher->flags & CFLAG_NONE) != 0) 509 return 0; 510 511 #ifdef WITH_OPENSSL 512 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 513 if (evplen <= 0) 514 return SSH_ERR_LIBCRYPTO_ERROR; 515 if ((size_t)evplen != len) 516 return SSH_ERR_INVALID_ARGUMENT; 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 if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen)) 523 return SSH_ERR_LIBCRYPTO_ERROR; 524 #endif 525 return 0; 526 } 527