1 /* $NetBSD: cipher.c,v 1.15 2019/04/20 17:16:40 christos Exp $ */ 2 /* $OpenBSD: cipher.c,v 1.112 2018/09/13 02:08:33 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 1.15 2019/04/20 17:16:40 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 54 struct sshcipher_ctx { 55 int plaintext; 56 int encrypt; 57 EVP_CIPHER_CTX *evp; 58 struct chachapoly_ctx cp_ctx; /* XXX union with evp? */ 59 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 60 const struct sshcipher *cipher; 61 }; 62 63 struct sshcipher { 64 const char *name; 65 u_int block_size; 66 u_int key_len; 67 u_int iv_len; /* defaults to block_size */ 68 u_int auth_len; 69 u_int flags; 70 #define CFLAG_CBC (1<<0) 71 #define CFLAG_CHACHAPOLY (1<<1) 72 #define CFLAG_AESCTR (1<<2) 73 #define CFLAG_NONE (1<<3) 74 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */ 75 #ifdef WITH_OPENSSL 76 const EVP_CIPHER *(*evptype)(void); 77 #else 78 void *ignored; 79 #endif 80 }; 81 82 static const struct sshcipher ciphers[] = { 83 #ifdef WITH_OPENSSL 84 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 85 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 86 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 87 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 88 { "rijndael-cbc@lysator.liu.se", 89 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 90 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 91 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 92 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 93 { "aes128-gcm@openssh.com", 94 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 95 { "aes256-gcm@openssh.com", 96 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 97 #else 98 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL }, 99 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL }, 100 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL }, 101 #endif 102 { "chacha20-poly1305@openssh.com", 103 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL }, 104 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL }, 105 106 { NULL, 0, 0, 0, 0, 0, NULL } 107 }; 108 109 /*--*/ 110 111 /* Returns a comma-separated list of supported ciphers. */ 112 char * 113 cipher_alg_list(char sep, int auth_only) 114 { 115 char *tmp, *ret = NULL; 116 size_t nlen, rlen = 0; 117 const struct sshcipher *c; 118 119 for (c = ciphers; c->name != NULL; c++) { 120 if ((c->flags & CFLAG_INTERNAL) != 0) 121 continue; 122 if (auth_only && c->auth_len == 0) 123 continue; 124 if (ret != NULL) 125 ret[rlen++] = sep; 126 nlen = strlen(c->name); 127 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 128 free(ret); 129 return NULL; 130 } 131 ret = tmp; 132 memcpy(ret + rlen, c->name, nlen + 1); 133 rlen += nlen; 134 } 135 return ret; 136 } 137 138 u_int 139 cipher_blocksize(const struct sshcipher *c) 140 { 141 return (c->block_size); 142 } 143 144 u_int 145 cipher_keylen(const struct sshcipher *c) 146 { 147 return (c->key_len); 148 } 149 150 u_int 151 cipher_seclen(const struct sshcipher *c) 152 { 153 if (strcmp("3des-cbc", c->name) == 0) 154 return 14; 155 return cipher_keylen(c); 156 } 157 158 u_int 159 cipher_authlen(const struct sshcipher *c) 160 { 161 return (c->auth_len); 162 } 163 164 u_int 165 cipher_ivlen(const struct sshcipher *c) 166 { 167 /* 168 * Default is cipher block size, except for chacha20+poly1305 that 169 * needs no IV. XXX make iv_len == -1 default? 170 */ 171 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 172 c->iv_len : c->block_size; 173 } 174 175 u_int 176 cipher_is_cbc(const struct sshcipher *c) 177 { 178 return (c->flags & CFLAG_CBC) != 0; 179 } 180 181 u_int 182 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 183 { 184 return cc->plaintext; 185 } 186 187 const struct sshcipher * 188 cipher_by_name(const char *name) 189 { 190 const struct sshcipher *c; 191 for (c = ciphers; c->name != NULL; c++) 192 if (strcmp(c->name, name) == 0) 193 return c; 194 return NULL; 195 } 196 197 #define CIPHER_SEP "," 198 int 199 ciphers_valid(const char *names) 200 { 201 const struct sshcipher *c; 202 char *cipher_list, *cp; 203 char *p; 204 205 if (names == NULL || strcmp(names, "") == 0) 206 return 0; 207 if ((cipher_list = cp = strdup(names)) == NULL) 208 return 0; 209 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 210 (p = strsep(&cp, CIPHER_SEP))) { 211 c = cipher_by_name(p); 212 if (c == NULL || (c->flags & (CFLAG_INTERNAL|CFLAG_NONE)) != 0) { 213 free(cipher_list); 214 return 0; 215 } 216 } 217 free(cipher_list); 218 return 1; 219 } 220 221 const char * 222 cipher_warning_message(const struct sshcipher_ctx *cc) 223 { 224 if (cc == NULL || cc->cipher == NULL) 225 return NULL; 226 /* XXX repurpose for CBC warning */ 227 return NULL; 228 } 229 230 int 231 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 232 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 233 int do_encrypt) 234 { 235 struct sshcipher_ctx *cc = NULL; 236 int ret = SSH_ERR_INTERNAL_ERROR; 237 #ifdef WITH_OPENSSL 238 const EVP_CIPHER *type; 239 int klen; 240 #endif 241 242 *ccp = NULL; 243 if ((cc = calloc(sizeof(*cc), 1)) == NULL) 244 return SSH_ERR_ALLOC_FAIL; 245 246 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 247 cc->encrypt = do_encrypt; 248 249 if (keylen < cipher->key_len || 250 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 251 ret = SSH_ERR_INVALID_ARGUMENT; 252 goto out; 253 } 254 255 cc->cipher = cipher; 256 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 257 ret = chachapoly_init(&cc->cp_ctx, key, keylen); 258 goto out; 259 } 260 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 261 ret = 0; 262 goto out; 263 } 264 #ifndef WITH_OPENSSL 265 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 266 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 267 aesctr_ivsetup(&cc->ac_ctx, iv); 268 ret = 0; 269 goto out; 270 } 271 ret = SSH_ERR_INVALID_ARGUMENT; 272 goto out; 273 #else /* WITH_OPENSSL */ 274 type = (*cipher->evptype)(); 275 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 276 ret = SSH_ERR_ALLOC_FAIL; 277 goto out; 278 } 279 if (EVP_CipherInit(cc->evp, type, NULL, (const u_char *)iv, 280 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 281 ret = SSH_ERR_LIBCRYPTO_ERROR; 282 goto out; 283 } 284 if (cipher_authlen(cipher) && 285 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 286 -1, __UNCONST(iv))) { 287 ret = SSH_ERR_LIBCRYPTO_ERROR; 288 goto out; 289 } 290 klen = EVP_CIPHER_CTX_key_length(cc->evp); 291 if (klen > 0 && keylen != (u_int)klen) { 292 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 293 ret = SSH_ERR_LIBCRYPTO_ERROR; 294 goto out; 295 } 296 } 297 /* in OpenSSL 1.1.0, EVP_CipherInit clears all previous setups; 298 use EVP_CipherInit_ex for augmenting */ 299 if (EVP_CipherInit_ex(cc->evp, NULL, NULL, __UNCONST(key), NULL, -1) == 0) { 300 ret = SSH_ERR_LIBCRYPTO_ERROR; 301 goto out; 302 } 303 ret = 0; 304 #endif /* WITH_OPENSSL */ 305 out: 306 if (ret == 0) { 307 /* success */ 308 *ccp = cc; 309 } else { 310 if (cc != NULL) { 311 #ifdef WITH_OPENSSL 312 EVP_CIPHER_CTX_free(cc->evp); 313 #endif /* WITH_OPENSSL */ 314 explicit_bzero(cc, sizeof(*cc)); 315 free(cc); 316 } 317 } 318 return ret; 319 } 320 321 /* 322 * cipher_crypt() operates as following: 323 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 324 * Theses bytes are treated as additional authenticated data for 325 * authenticated encryption modes. 326 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 327 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 328 * This tag is written on encryption and verified on decryption. 329 * Both 'aadlen' and 'authlen' can be set to 0. 330 */ 331 int 332 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 333 const u_char *src, u_int len, u_int aadlen, u_int authlen) 334 { 335 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 336 return chachapoly_crypt(&cc->cp_ctx, seqnr, dest, src, 337 len, aadlen, authlen, cc->encrypt); 338 } 339 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 340 memcpy(dest, src, aadlen + len); 341 return 0; 342 } 343 #ifndef WITH_OPENSSL 344 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 345 if (aadlen) 346 memcpy(dest, src, aadlen); 347 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 348 dest + aadlen, len); 349 return 0; 350 } 351 return SSH_ERR_INVALID_ARGUMENT; 352 #else 353 if (authlen) { 354 u_char lastiv[1]; 355 356 if (authlen != cipher_authlen(cc->cipher)) 357 return SSH_ERR_INVALID_ARGUMENT; 358 /* increment IV */ 359 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 360 1, lastiv)) 361 return SSH_ERR_LIBCRYPTO_ERROR; 362 /* set tag on decyption */ 363 if (!cc->encrypt && 364 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 365 authlen, __UNCONST(src + aadlen + len))) 366 return SSH_ERR_LIBCRYPTO_ERROR; 367 } 368 if (aadlen) { 369 if (authlen && 370 EVP_Cipher(cc->evp, NULL, (const u_char *)src, aadlen) < 0) 371 return SSH_ERR_LIBCRYPTO_ERROR; 372 memcpy(dest, src, aadlen); 373 } 374 if (len % cc->cipher->block_size) 375 return SSH_ERR_INVALID_ARGUMENT; 376 if (EVP_Cipher(cc->evp, dest + aadlen, (const u_char *)src + aadlen, 377 len) < 0) 378 return SSH_ERR_LIBCRYPTO_ERROR; 379 if (authlen) { 380 /* compute tag (on encrypt) or verify tag (on decrypt) */ 381 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 382 return cc->encrypt ? 383 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 384 if (cc->encrypt && 385 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 386 authlen, dest + aadlen + len)) 387 return SSH_ERR_LIBCRYPTO_ERROR; 388 } 389 return 0; 390 #endif 391 } 392 393 /* Extract the packet length, including any decryption necessary beforehand */ 394 int 395 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 396 const u_char *cp, u_int len) 397 { 398 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 399 return chachapoly_get_length(&cc->cp_ctx, plenp, seqnr, 400 cp, len); 401 if (len < 4) 402 return SSH_ERR_MESSAGE_INCOMPLETE; 403 *plenp = PEEK_U32(cp); 404 return 0; 405 } 406 407 void 408 cipher_free(struct sshcipher_ctx *cc) 409 { 410 if (cc == NULL) 411 return; 412 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 413 explicit_bzero(&cc->cp_ctx, sizeof(cc->cp_ctx)); 414 else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 415 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 416 #ifdef WITH_OPENSSL 417 EVP_CIPHER_CTX_free(cc->evp); 418 cc->evp = NULL; 419 #endif 420 explicit_bzero(cc, sizeof(*cc)); 421 free(cc); 422 } 423 424 /* 425 * Exports an IV from the sshcipher_ctx required to export the key 426 * state back from the unprivileged child to the privileged parent 427 * process. 428 */ 429 int 430 cipher_get_keyiv_len(const struct sshcipher_ctx *cc) 431 { 432 const struct sshcipher *c = cc->cipher; 433 434 if ((c->flags & CFLAG_CHACHAPOLY) != 0) 435 return 0; 436 else if ((c->flags & CFLAG_AESCTR) != 0) 437 return sizeof(cc->ac_ctx.ctr); 438 #ifdef WITH_OPENSSL 439 return EVP_CIPHER_CTX_iv_length(cc->evp); 440 #else 441 return 0; 442 #endif 443 } 444 445 int 446 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 447 { 448 #ifdef WITH_OPENSSL 449 const struct sshcipher *c = cc->cipher; 450 int evplen; 451 #endif 452 453 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 454 if (len != 0) 455 return SSH_ERR_INVALID_ARGUMENT; 456 return 0; 457 } 458 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 459 if (len != sizeof(cc->ac_ctx.ctr)) 460 return SSH_ERR_INVALID_ARGUMENT; 461 memcpy(iv, cc->ac_ctx.ctr, len); 462 return 0; 463 } 464 if ((cc->cipher->flags & CFLAG_NONE) != 0) 465 return 0; 466 467 #ifdef WITH_OPENSSL 468 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 469 if (evplen == 0) 470 return 0; 471 else if (evplen < 0) 472 return SSH_ERR_LIBCRYPTO_ERROR; 473 if ((size_t)evplen != len) 474 return SSH_ERR_INVALID_ARGUMENT; 475 if (cipher_authlen(c)) { 476 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 477 len, iv)) 478 return SSH_ERR_LIBCRYPTO_ERROR; 479 } else 480 memcpy(iv, EVP_CIPHER_CTX_iv(cc->evp), len); 481 #endif 482 return 0; 483 } 484 485 int 486 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 487 { 488 #ifdef WITH_OPENSSL 489 const struct sshcipher *c = cc->cipher; 490 int evplen = 0; 491 #endif 492 493 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 494 return 0; 495 if ((cc->cipher->flags & CFLAG_NONE) != 0) 496 return 0; 497 498 #ifdef WITH_OPENSSL 499 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 500 if (evplen <= 0) 501 return SSH_ERR_LIBCRYPTO_ERROR; 502 if ((size_t)evplen != len) 503 return SSH_ERR_INVALID_ARGUMENT; 504 if (cipher_authlen(c)) { 505 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 506 if (!EVP_CIPHER_CTX_ctrl(cc->evp, 507 EVP_CTRL_GCM_SET_IV_FIXED, -1, __UNCONST(iv))) 508 return SSH_ERR_LIBCRYPTO_ERROR; 509 } else 510 memcpy(EVP_CIPHER_CTX_iv_noconst(cc->evp), iv, evplen); 511 #endif 512 return 0; 513 } 514 515