1 /* $NetBSD: cipher.c,v 1.28 2026/09/21 21:30:59 christos Exp $ */ 2 /* $OpenBSD: cipher.c,v 1.129 2026/06/19 05:26:04 djm Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo (at) cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 * 15 * 16 * Copyright (c) 1999 Niels Provos. All rights reserved. 17 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. 18 * 19 * Redistribution and use in source and binary forms, with or without 20 * modification, are permitted provided that the following conditions 21 * are met: 22 * 1. Redistributions of source code must retain the above copyright 23 * notice, this list of conditions and the following disclaimer. 24 * 2. Redistributions in binary form must reproduce the above copyright 25 * notice, this list of conditions and the following disclaimer in the 26 * documentation and/or other materials provided with the distribution. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 #include "includes.h" 41 __RCSID("$NetBSD: cipher.c,v 1.28 2026/09/21 21:30:59 christos Exp $"); 42 #include <sys/types.h> 43 44 #include <string.h> 45 #include <stdarg.h> 46 #include <stdio.h> 47 48 #include "cipher.h" 49 #include "misc.h" 50 #include "sshbuf.h" 51 #include "ssherr.h" 52 53 #ifndef WITH_OPENSSL 54 #define EVP_CIPHER_CTX void 55 #endif 56 57 // XXX: from libressl 58 #ifdef WITH_OPENSSL 59 #define HAVE_EVP_CIPHER_CTX_IV 60 61 static int 62 EVP_CIPHER_CTX_get_iv(const EVP_CIPHER_CTX *ctx, unsigned char *iv, size_t len) 63 { 64 if (ctx == NULL) 65 return 0; 66 if (EVP_CIPHER_CTX_iv_length(ctx) < 0) 67 return 0; 68 if (len != (size_t)EVP_CIPHER_CTX_iv_length(ctx)) 69 return 0; 70 if (len > EVP_MAX_IV_LENGTH) 71 return 0; /* sanity check; shouldn't happen */ 72 /* 73 * Skip the memcpy entirely when the requested IV length is zero, 74 * since the iv pointer may be NULL or invalid. 75 */ 76 if (len != 0) { 77 if (iv == NULL) 78 return 0; 79 # ifdef HAVE_EVP_CIPHER_CTX_IV 80 memcpy(iv, EVP_CIPHER_CTX_iv(ctx), len); 81 # else 82 memcpy(iv, ctx->iv, len); 83 # endif /* HAVE_EVP_CIPHER_CTX_IV */ 84 } 85 return 1; 86 } 87 #endif 88 // XXX: end 89 90 struct sshcipher_ctx { 91 int plaintext; 92 int encrypt; 93 EVP_CIPHER_CTX *evp; 94 struct chachapoly_ctx *cp_ctx; 95 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 96 const struct sshcipher *cipher; 97 }; 98 99 struct sshcipher { 100 const char *name; 101 u_int block_size; 102 u_int key_len; 103 u_int iv_len; /* defaults to block_size */ 104 u_int auth_len; 105 u_int flags; 106 #define CFLAG_CBC (1<<0) 107 #define CFLAG_CHACHAPOLY (1<<1) 108 #define CFLAG_AESCTR (1<<2) 109 #define CFLAG_NONE (1<<3) 110 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */ 111 #ifdef WITH_OPENSSL 112 const EVP_CIPHER *(*evptype)(void); 113 #else 114 void *ignored; 115 #endif 116 }; 117 118 static const struct sshcipher ciphers[] = { 119 #ifdef WITH_OPENSSL 120 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 121 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 122 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 123 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 124 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 125 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 126 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 127 { "aes128-gcm (at) openssh.com", 128 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 129 { "aes256-gcm (at) openssh.com", 130 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 131 #else 132 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL }, 133 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL }, 134 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL }, 135 #endif 136 { "chacha20-poly1305 (at) openssh.com", 137 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL }, 138 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL }, 139 140 { NULL, 0, 0, 0, 0, 0, NULL } 141 }; 142 143 /*--*/ 144 145 /* Returns a comma-separated list of supported ciphers. */ 146 char * 147 cipher_alg_list(char sep, int auth_only) 148 { 149 char *ret = NULL; 150 const struct sshcipher *c; 151 char sep_str[2] = {sep, '\0'}; 152 153 for (c = ciphers; c->name != NULL; c++) { 154 if ((c->flags & CFLAG_INTERNAL) != 0) 155 continue; 156 if (auth_only && c->auth_len == 0) 157 continue; 158 xextendf(&ret, sep_str, "%s", c->name); 159 } 160 return ret; 161 } 162 163 const char * 164 compression_alg_list(int compression) 165 { 166 #ifdef WITH_ZLIB 167 return compression ? "zlib (at) openssh.com,none" : 168 "none,zlib (at) openssh.com"; 169 #else 170 return "none"; 171 #endif 172 } 173 174 u_int 175 cipher_blocksize(const struct sshcipher *c) 176 { 177 return (c->block_size); 178 } 179 180 u_int 181 cipher_keylen(const struct sshcipher *c) 182 { 183 return (c->key_len); 184 } 185 186 u_int 187 cipher_seclen(const struct sshcipher *c) 188 { 189 if (strcmp("3des-cbc", c->name) == 0) 190 return 14; 191 return cipher_keylen(c); 192 } 193 194 u_int 195 cipher_authlen(const struct sshcipher *c) 196 { 197 return (c->auth_len); 198 } 199 200 u_int 201 cipher_ivlen(const struct sshcipher *c) 202 { 203 /* 204 * Default is cipher block size, except for chacha20+poly1305 that 205 * needs no IV. XXX make iv_len == -1 default? 206 */ 207 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 208 c->iv_len : c->block_size; 209 } 210 211 u_int 212 cipher_is_cbc(const struct sshcipher *c) 213 { 214 return (c->flags & CFLAG_CBC) != 0; 215 } 216 217 u_int 218 cipher_is_internal(const struct sshcipher *c) 219 { 220 return (c->flags & CFLAG_INTERNAL) != 0; 221 } 222 223 u_int 224 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 225 { 226 return cc->plaintext; 227 } 228 229 const struct sshcipher * 230 cipher_by_name(const char *name) 231 { 232 const struct sshcipher *c; 233 for (c = ciphers; c->name != NULL; c++) 234 if (strcmp(c->name, name) == 0) 235 return c; 236 return NULL; 237 } 238 239 #define CIPHER_SEP "," 240 int 241 ciphers_valid(const char *names) 242 { 243 const struct sshcipher *c; 244 char *cipher_list, *cp; 245 char *p; 246 int found = 0; 247 248 if (names == NULL || strcmp(names, "") == 0) 249 return 0; 250 if ((cipher_list = cp = strdup(names)) == NULL) 251 return 0; 252 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 253 (p = strsep(&cp, CIPHER_SEP))) { 254 c = cipher_by_name(p); 255 if (c == NULL || (c->flags & (CFLAG_INTERNAL|CFLAG_NONE)) != 0) { 256 free(cipher_list); 257 return 0; 258 } else 259 found = 1; 260 } 261 free(cipher_list); 262 return found; 263 } 264 265 const char * 266 cipher_warning_message(const struct sshcipher_ctx *cc) 267 { 268 if (cc == NULL || cc->cipher == NULL) 269 return NULL; 270 /* XXX repurpose for CBC warning */ 271 return NULL; 272 } 273 274 int 275 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 276 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 277 int do_encrypt) 278 { 279 struct sshcipher_ctx *cc = NULL; 280 int ret = SSH_ERR_INTERNAL_ERROR; 281 #ifdef WITH_OPENSSL 282 const EVP_CIPHER *type; 283 int klen; 284 #endif 285 286 *ccp = NULL; 287 if ((cc = calloc(1, sizeof(*cc))) == NULL) 288 return SSH_ERR_ALLOC_FAIL; 289 290 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 291 cc->encrypt = do_encrypt; 292 293 if (keylen < cipher->key_len || 294 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 295 ret = SSH_ERR_INVALID_ARGUMENT; 296 goto out; 297 } 298 299 cc->cipher = cipher; 300 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 301 cc->cp_ctx = chachapoly_new(key, keylen); 302 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 303 goto out; 304 } 305 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 306 ret = 0; 307 goto out; 308 } 309 #ifndef WITH_OPENSSL 310 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 311 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 312 aesctr_ivsetup(&cc->ac_ctx, iv); 313 ret = 0; 314 goto out; 315 } 316 ret = SSH_ERR_INVALID_ARGUMENT; 317 goto out; 318 #else /* WITH_OPENSSL */ 319 type = (*cipher->evptype)(); 320 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 321 ret = SSH_ERR_ALLOC_FAIL; 322 goto out; 323 } 324 if (EVP_CipherInit(cc->evp, type, NULL, (const u_char *)iv, 325 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 326 ret = SSH_ERR_LIBCRYPTO_ERROR; 327 goto out; 328 } 329 if (cipher_authlen(cipher) && 330 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 331 -1, __UNCONST(iv)) <= 0) { 332 ret = SSH_ERR_LIBCRYPTO_ERROR; 333 goto out; 334 } 335 klen = EVP_CIPHER_CTX_key_length(cc->evp); 336 if (klen > 0 && keylen != (u_int)klen) { 337 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 338 ret = SSH_ERR_LIBCRYPTO_ERROR; 339 goto out; 340 } 341 } 342 /* in OpenSSL 1.1.0, EVP_CipherInit clears all previous setups; 343 use EVP_CipherInit_ex for augmenting */ 344 if (EVP_CipherInit_ex(cc->evp, NULL, NULL, __UNCONST(key), NULL, -1) == 0) { 345 ret = SSH_ERR_LIBCRYPTO_ERROR; 346 goto out; 347 } 348 ret = 0; 349 #endif /* WITH_OPENSSL */ 350 out: 351 if (ret == 0) { 352 /* success */ 353 *ccp = cc; 354 } else { 355 if (cc != NULL) { 356 #ifdef WITH_OPENSSL 357 EVP_CIPHER_CTX_free(cc->evp); 358 #endif /* WITH_OPENSSL */ 359 freezero(cc, sizeof(*cc)); 360 } 361 } 362 return ret; 363 } 364 365 /* 366 * cipher_crypt() operates as following: 367 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 368 * These bytes are treated as additional authenticated data for 369 * authenticated encryption modes. 370 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 371 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 372 * This tag is written on encryption and verified on decryption. 373 * Both 'aadlen' and 'authlen' can be set to 0. 374 */ 375 int 376 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 377 const u_char *src, u_int len, u_int aadlen, u_int authlen) 378 { 379 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 380 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 381 len, aadlen, authlen, cc->encrypt); 382 } 383 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 384 memcpy(dest, src, aadlen + len); 385 return 0; 386 } 387 #ifndef WITH_OPENSSL 388 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 389 if (aadlen) 390 memcpy(dest, src, aadlen); 391 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 392 dest + aadlen, len); 393 return 0; 394 } 395 return SSH_ERR_INVALID_ARGUMENT; 396 #else 397 if (authlen) { 398 u_char lastiv[1]; 399 400 if (authlen != cipher_authlen(cc->cipher)) 401 return SSH_ERR_INVALID_ARGUMENT; 402 /* increment IV */ 403 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 404 1, lastiv) <= 0) 405 return SSH_ERR_LIBCRYPTO_ERROR; 406 /* set tag on decryption */ 407 if (!cc->encrypt && 408 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 409 authlen, __UNCONST(src + aadlen + len)) <= 0) 410 return SSH_ERR_LIBCRYPTO_ERROR; 411 } 412 if (aadlen) { 413 if (authlen && 414 EVP_Cipher(cc->evp, NULL, (const u_char *)src, aadlen) < 0) 415 return SSH_ERR_LIBCRYPTO_ERROR; 416 memcpy(dest, src, aadlen); 417 } 418 if (len % cc->cipher->block_size) 419 return SSH_ERR_INVALID_ARGUMENT; 420 if (EVP_Cipher(cc->evp, dest + aadlen, (const u_char *)src + aadlen, 421 len) < 0) 422 return SSH_ERR_LIBCRYPTO_ERROR; 423 if (authlen) { 424 /* compute tag (on encrypt) or verify tag (on decrypt) */ 425 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 426 return cc->encrypt ? 427 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 428 if (cc->encrypt && 429 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 430 authlen, dest + aadlen + len) <= 0) 431 return SSH_ERR_LIBCRYPTO_ERROR; 432 } 433 return 0; 434 #endif 435 } 436 437 /* Extract the packet length, including any decryption necessary beforehand */ 438 int 439 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 440 const u_char *cp, u_int len) 441 { 442 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 443 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 444 cp, len); 445 if (len < 4) 446 return SSH_ERR_MESSAGE_INCOMPLETE; 447 *plenp = PEEK_U32(cp); 448 return 0; 449 } 450 451 void 452 cipher_free(struct sshcipher_ctx *cc) 453 { 454 if (cc == NULL) 455 return; 456 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 457 chachapoly_free(cc->cp_ctx); 458 cc->cp_ctx = NULL; 459 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 460 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 461 #ifdef WITH_OPENSSL 462 EVP_CIPHER_CTX_free(cc->evp); 463 cc->evp = NULL; 464 #endif 465 freezero(cc, sizeof(*cc)); 466 } 467 468 int 469 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 470 { 471 #ifdef WITH_OPENSSL 472 const struct sshcipher *c = cc->cipher; 473 int evplen; 474 #endif 475 476 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 477 if (len != 0) 478 return SSH_ERR_INVALID_ARGUMENT; 479 return 0; 480 } 481 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 482 if (len != sizeof(cc->ac_ctx.ctr)) 483 return SSH_ERR_INVALID_ARGUMENT; 484 memcpy(iv, cc->ac_ctx.ctr, len); 485 return 0; 486 } 487 if ((cc->cipher->flags & CFLAG_NONE) != 0) 488 return 0; 489 490 #ifdef WITH_OPENSSL 491 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 492 if (evplen == 0) 493 return 0; 494 else if (evplen < 0) 495 return SSH_ERR_LIBCRYPTO_ERROR; 496 if ((size_t)evplen != len) 497 return SSH_ERR_INVALID_ARGUMENT; 498 if (cipher_authlen(c)) { 499 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, len, 500 iv) <= 0) 501 return SSH_ERR_LIBCRYPTO_ERROR; 502 } else if (EVP_CIPHER_CTX_get_iv(cc->evp, iv, len) <= 0) 503 return SSH_ERR_LIBCRYPTO_ERROR; 504 #endif 505 return 0; 506 } 507
Indexes created Fri Oct 09 00:27:48 UTC 2026