1 /* $NetBSD: cipher.c,v 1.17 2020/02/27 00:24:40 christos Exp $ */ 2 /* $OpenBSD: cipher.c,v 1.114 2020/01/23 10:24:29 dtucker 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 1.17 2020/02/27 00:24:40 christos Exp $"); 41 #include <sys/types.h> 42 43 #include <string.h> 44 #include <stdarg.h> 45 #include <stdio.h> 46 47 #include "cipher.h" 48 #include "misc.h" 49 #include "sshbuf.h" 50 #include "ssherr.h" 51 #include "digest.h" 52 53 #ifndef WITH_OPENSSL 54 #define EVP_CIPHER_CTX void 55 #endif 56 57 struct sshcipher_ctx { 58 int plaintext; 59 int encrypt; 60 EVP_CIPHER_CTX *evp; 61 struct chachapoly_ctx cp_ctx; /* XXX union with evp? */ 62 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 63 const struct sshcipher *cipher; 64 }; 65 66 struct sshcipher { 67 const char *name; 68 u_int block_size; 69 u_int key_len; 70 u_int iv_len; /* defaults to block_size */ 71 u_int auth_len; 72 u_int flags; 73 #define CFLAG_CBC (1<<0) 74 #define CFLAG_CHACHAPOLY (1<<1) 75 #define CFLAG_AESCTR (1<<2) 76 #define CFLAG_NONE (1<<3) 77 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */ 78 #ifdef WITH_OPENSSL 79 const EVP_CIPHER *(*evptype)(void); 80 #else 81 void *ignored; 82 #endif 83 }; 84 85 static const struct sshcipher ciphers[] = { 86 #ifdef WITH_OPENSSL 87 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 88 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 89 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 90 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 91 { "rijndael-cbc@lysator.liu.se", 92 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 93 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 94 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 95 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 96 { "aes128-gcm@openssh.com", 97 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 98 { "aes256-gcm@openssh.com", 99 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 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 const char * 142 compression_alg_list(int compression) 143 { 144 #ifdef WITH_ZLIB 145 return compression ? "zlib@openssh.com,zlib,none" : 146 "none,zlib@openssh.com,zlib"; 147 #else 148 return "none"; 149 #endif 150 } 151 152 u_int 153 cipher_blocksize(const struct sshcipher *c) 154 { 155 return (c->block_size); 156 } 157 158 u_int 159 cipher_keylen(const struct sshcipher *c) 160 { 161 return (c->key_len); 162 } 163 164 u_int 165 cipher_seclen(const struct sshcipher *c) 166 { 167 if (strcmp("3des-cbc", c->name) == 0) 168 return 14; 169 return cipher_keylen(c); 170 } 171 172 u_int 173 cipher_authlen(const struct sshcipher *c) 174 { 175 return (c->auth_len); 176 } 177 178 u_int 179 cipher_ivlen(const struct sshcipher *c) 180 { 181 /* 182 * Default is cipher block size, except for chacha20+poly1305 that 183 * needs no IV. XXX make iv_len == -1 default? 184 */ 185 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 186 c->iv_len : c->block_size; 187 } 188 189 u_int 190 cipher_is_cbc(const struct sshcipher *c) 191 { 192 return (c->flags & CFLAG_CBC) != 0; 193 } 194 195 u_int 196 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 197 { 198 return cc->plaintext; 199 } 200 201 const struct sshcipher * 202 cipher_by_name(const char *name) 203 { 204 const struct sshcipher *c; 205 for (c = ciphers; c->name != NULL; c++) 206 if (strcmp(c->name, name) == 0) 207 return c; 208 return NULL; 209 } 210 211 #define CIPHER_SEP "," 212 int 213 ciphers_valid(const char *names) 214 { 215 const struct sshcipher *c; 216 char *cipher_list, *cp; 217 char *p; 218 219 if (names == NULL || strcmp(names, "") == 0) 220 return 0; 221 if ((cipher_list = cp = strdup(names)) == NULL) 222 return 0; 223 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 224 (p = strsep(&cp, CIPHER_SEP))) { 225 c = cipher_by_name(p); 226 if (c == NULL || (c->flags & (CFLAG_INTERNAL|CFLAG_NONE)) != 0) { 227 free(cipher_list); 228 return 0; 229 } 230 } 231 free(cipher_list); 232 return 1; 233 } 234 235 const char * 236 cipher_warning_message(const struct sshcipher_ctx *cc) 237 { 238 if (cc == NULL || cc->cipher == NULL) 239 return NULL; 240 /* XXX repurpose for CBC warning */ 241 return NULL; 242 } 243 244 int 245 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 246 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 247 int do_encrypt) 248 { 249 struct sshcipher_ctx *cc = NULL; 250 int ret = SSH_ERR_INTERNAL_ERROR; 251 #ifdef WITH_OPENSSL 252 const EVP_CIPHER *type; 253 int klen; 254 #endif 255 256 *ccp = NULL; 257 if ((cc = calloc(sizeof(*cc), 1)) == NULL) 258 return SSH_ERR_ALLOC_FAIL; 259 260 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 261 cc->encrypt = do_encrypt; 262 263 if (keylen < cipher->key_len || 264 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 265 ret = SSH_ERR_INVALID_ARGUMENT; 266 goto out; 267 } 268 269 cc->cipher = cipher; 270 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 271 ret = chachapoly_init(&cc->cp_ctx, key, keylen); 272 goto out; 273 } 274 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 275 ret = 0; 276 goto out; 277 } 278 #ifndef WITH_OPENSSL 279 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 280 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 281 aesctr_ivsetup(&cc->ac_ctx, iv); 282 ret = 0; 283 goto out; 284 } 285 ret = SSH_ERR_INVALID_ARGUMENT; 286 goto out; 287 #else /* WITH_OPENSSL */ 288 type = (*cipher->evptype)(); 289 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 290 ret = SSH_ERR_ALLOC_FAIL; 291 goto out; 292 } 293 if (EVP_CipherInit(cc->evp, type, NULL, (const u_char *)iv, 294 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 295 ret = SSH_ERR_LIBCRYPTO_ERROR; 296 goto out; 297 } 298 if (cipher_authlen(cipher) && 299 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 300 -1, __UNCONST(iv))) { 301 ret = SSH_ERR_LIBCRYPTO_ERROR; 302 goto out; 303 } 304 klen = EVP_CIPHER_CTX_key_length(cc->evp); 305 if (klen > 0 && keylen != (u_int)klen) { 306 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 307 ret = SSH_ERR_LIBCRYPTO_ERROR; 308 goto out; 309 } 310 } 311 /* in OpenSSL 1.1.0, EVP_CipherInit clears all previous setups; 312 use EVP_CipherInit_ex for augmenting */ 313 if (EVP_CipherInit_ex(cc->evp, NULL, NULL, __UNCONST(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 explicit_bzero(cc, sizeof(*cc)); 329 free(cc); 330 } 331 } 332 return ret; 333 } 334 335 /* 336 * cipher_crypt() operates as following: 337 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 338 * Theses bytes are treated as additional authenticated data for 339 * authenticated encryption modes. 340 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 341 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 342 * This tag is written on encryption and verified on decryption. 343 * Both 'aadlen' and 'authlen' can be set to 0. 344 */ 345 int 346 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 347 const u_char *src, u_int len, u_int aadlen, u_int authlen) 348 { 349 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 350 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, 351 len, aadlen, authlen, cc->encrypt); 352 } 353 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 354 memcpy(dest, src, aadlen + len); 355 return 0; 356 } 357 #ifndef WITH_OPENSSL 358 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 359 if (aadlen) 360 memcpy(dest, src, aadlen); 361 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 362 dest + aadlen, len); 363 return 0; 364 } 365 return SSH_ERR_INVALID_ARGUMENT; 366 #else 367 if (authlen) { 368 u_char lastiv[1]; 369 370 if (authlen != cipher_authlen(cc->cipher)) 371 return SSH_ERR_INVALID_ARGUMENT; 372 /* increment IV */ 373 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 374 1, lastiv)) 375 return SSH_ERR_LIBCRYPTO_ERROR; 376 /* set tag on decyption */ 377 if (!cc->encrypt && 378 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 379 authlen, __UNCONST(src + aadlen + len))) 380 return SSH_ERR_LIBCRYPTO_ERROR; 381 } 382 if (aadlen) { 383 if (authlen && 384 EVP_Cipher(cc->evp, NULL, (const u_char *)src, aadlen) < 0) 385 return SSH_ERR_LIBCRYPTO_ERROR; 386 memcpy(dest, src, aadlen); 387 } 388 if (len % cc->cipher->block_size) 389 return SSH_ERR_INVALID_ARGUMENT; 390 if (EVP_Cipher(cc->evp, dest + aadlen, (const u_char *)src + aadlen, 391 len) < 0) 392 return SSH_ERR_LIBCRYPTO_ERROR; 393 if (authlen) { 394 /* compute tag (on encrypt) or verify tag (on decrypt) */ 395 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 396 return cc->encrypt ? 397 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 398 if (cc->encrypt && 399 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 400 authlen, dest + aadlen + len)) 401 return SSH_ERR_LIBCRYPTO_ERROR; 402 } 403 return 0; 404 #endif 405 } 406 407 /* Extract the packet length, including any decryption necessary beforehand */ 408 int 409 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 410 const u_char *cp, u_int len) 411 { 412 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 413 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr, 414 cp, len); 415 if (len < 4) 416 return SSH_ERR_MESSAGE_INCOMPLETE; 417 *plenp = PEEK_U32(cp); 418 return 0; 419 } 420 421 void 422 cipher_free(struct sshcipher_ctx *cc) 423 { 424 if (cc == NULL) 425 return; 426 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 427 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx)); 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 explicit_bzero(cc, sizeof(*cc)); 435 free(cc); 436 } 437 438 /* 439 * Exports an IV from the sshcipher_ctx required to export the key 440 * state back from the unprivileged child to the privileged parent 441 * process. 442 */ 443 int 444 cipher_get_keyiv_len(const struct sshcipher_ctx *cc) 445 { 446 const struct sshcipher *c = cc->cipher; 447 448 if ((c->flags & CFLAG_CHACHAPOLY) != 0) 449 return 0; 450 else if ((c->flags & CFLAG_AESCTR) != 0) 451 return sizeof(cc->ac_ctx.ctr); 452 #ifdef WITH_OPENSSL 453 return EVP_CIPHER_CTX_iv_length(cc->evp); 454 #else 455 return 0; 456 #endif 457 } 458 459 int 460 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 461 { 462 #ifdef WITH_OPENSSL 463 const struct sshcipher *c = cc->cipher; 464 int evplen; 465 #endif 466 467 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 468 if (len != 0) 469 return SSH_ERR_INVALID_ARGUMENT; 470 return 0; 471 } 472 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 473 if (len != sizeof(cc->ac_ctx.ctr)) 474 return SSH_ERR_INVALID_ARGUMENT; 475 memcpy(iv, cc->ac_ctx.ctr, len); 476 return 0; 477 } 478 if ((cc->cipher->flags & CFLAG_NONE) != 0) 479 return 0; 480 481 #ifdef WITH_OPENSSL 482 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 483 if (evplen == 0) 484 return 0; 485 else if (evplen < 0) 486 return SSH_ERR_LIBCRYPTO_ERROR; 487 if ((size_t)evplen != len) 488 return SSH_ERR_INVALID_ARGUMENT; 489 if (cipher_authlen(c)) { 490 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 491 len, iv)) 492 return SSH_ERR_LIBCRYPTO_ERROR; 493 } else 494 memcpy(iv, EVP_CIPHER_CTX_iv(cc->evp), len); 495 #endif 496 return 0; 497 } 498 499 int 500 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 501 { 502 #ifdef WITH_OPENSSL 503 const struct sshcipher *c = cc->cipher; 504 int evplen = 0; 505 #endif 506 507 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 508 return 0; 509 if ((cc->cipher->flags & CFLAG_NONE) != 0) 510 return 0; 511 512 #ifdef WITH_OPENSSL 513 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 514 if (evplen <= 0) 515 return SSH_ERR_LIBCRYPTO_ERROR; 516 if ((size_t)evplen != len) 517 return SSH_ERR_INVALID_ARGUMENT; 518 if (cipher_authlen(c)) { 519 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 520 if (!EVP_CIPHER_CTX_ctrl(cc->evp, 521 EVP_CTRL_GCM_SET_IV_FIXED, -1, __UNCONST(iv))) 522 return SSH_ERR_LIBCRYPTO_ERROR; 523 } else 524 memcpy(EVP_CIPHER_CTX_iv_noconst(cc->evp), iv, evplen); 525 #endif 526 return 0; 527 } 528 529