1 /* $NetBSD: cipher.c,v 1.26 2025/12/28 09:39:35 nia Exp $ */ 2 /* $OpenBSD: cipher.c,v 1.125 2025/09/02 11:08:34 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 1.26 2025/12/28 09:39:35 nia 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 #include "digest.h" 53 54 #ifndef WITH_OPENSSL 55 #define EVP_CIPHER_CTX void 56 #endif 57 58 // XXX: from libressl 59 #ifdef WITH_OPENSSL 60 #define HAVE_EVP_CIPHER_CTX_IV 61 62 static int 63 EVP_CIPHER_CTX_get_iv(const EVP_CIPHER_CTX *ctx, unsigned char *iv, size_t len) 64 { 65 if (ctx == NULL) 66 return 0; 67 if (EVP_CIPHER_CTX_iv_length(ctx) < 0) 68 return 0; 69 if (len != (size_t)EVP_CIPHER_CTX_iv_length(ctx)) 70 return 0; 71 if (len > EVP_MAX_IV_LENGTH) 72 return 0; /* sanity check; shouldn't happen */ 73 /* 74 * Skip the memcpy entirely when the requested IV length is zero, 75 * since the iv pointer may be NULL or invalid. 76 */ 77 if (len != 0) { 78 if (iv == NULL) 79 return 0; 80 # ifdef HAVE_EVP_CIPHER_CTX_IV 81 memcpy(iv, EVP_CIPHER_CTX_iv(ctx), len); 82 # else 83 memcpy(iv, ctx->iv, len); 84 # endif /* HAVE_EVP_CIPHER_CTX_IV */ 85 } 86 return 1; 87 } 88 #endif 89 // XXX: end 90 91 struct sshcipher_ctx { 92 int plaintext; 93 int encrypt; 94 EVP_CIPHER_CTX *evp; 95 struct chachapoly_ctx *cp_ctx; 96 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 97 const struct sshcipher *cipher; 98 }; 99 100 struct sshcipher { 101 const char *name; 102 u_int block_size; 103 u_int key_len; 104 u_int iv_len; /* defaults to block_size */ 105 u_int auth_len; 106 u_int flags; 107 #define CFLAG_CBC (1<<0) 108 #define CFLAG_CHACHAPOLY (1<<1) 109 #define CFLAG_AESCTR (1<<2) 110 #define CFLAG_NONE (1<<3) 111 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */ 112 #ifdef WITH_OPENSSL 113 const EVP_CIPHER *(*evptype)(void); 114 #else 115 void *ignored; 116 #endif 117 }; 118 119 static const struct sshcipher ciphers[] = { 120 #ifdef WITH_OPENSSL 121 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 122 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 123 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 124 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc }, 125 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr }, 126 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr }, 127 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr }, 128 { "aes128-gcm (at) openssh.com", 129 16, 16, 12, 16, 0, EVP_aes_128_gcm }, 130 { "aes256-gcm (at) openssh.com", 131 16, 32, 12, 16, 0, EVP_aes_256_gcm }, 132 #else 133 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL }, 134 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL }, 135 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL }, 136 #endif 137 { "chacha20-poly1305 (at) openssh.com", 138 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL }, 139 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL }, 140 141 { NULL, 0, 0, 0, 0, 0, NULL } 142 }; 143 144 /*--*/ 145 146 /* Returns a comma-separated list of supported ciphers. */ 147 char * 148 cipher_alg_list(char sep, int auth_only) 149 { 150 char *ret = NULL; 151 const struct sshcipher *c; 152 char sep_str[2] = {sep, '\0'}; 153 154 for (c = ciphers; c->name != NULL; c++) { 155 if ((c->flags & CFLAG_INTERNAL) != 0) 156 continue; 157 if (auth_only && c->auth_len == 0) 158 continue; 159 xextendf(&ret, sep_str, "%s", c->name); 160 } 161 return ret; 162 } 163 164 const char * 165 compression_alg_list(int compression) 166 { 167 #ifdef WITH_ZLIB 168 return compression ? "zlib (at) openssh.com,none" : 169 "none,zlib (at) openssh.com"; 170 #else 171 return "none"; 172 #endif 173 } 174 175 u_int 176 cipher_blocksize(const struct sshcipher *c) 177 { 178 return (c->block_size); 179 } 180 181 u_int 182 cipher_keylen(const struct sshcipher *c) 183 { 184 return (c->key_len); 185 } 186 187 u_int 188 cipher_seclen(const struct sshcipher *c) 189 { 190 if (strcmp("3des-cbc", c->name) == 0) 191 return 14; 192 return cipher_keylen(c); 193 } 194 195 u_int 196 cipher_authlen(const struct sshcipher *c) 197 { 198 return (c->auth_len); 199 } 200 201 u_int 202 cipher_ivlen(const struct sshcipher *c) 203 { 204 /* 205 * Default is cipher block size, except for chacha20+poly1305 that 206 * needs no IV. XXX make iv_len == -1 default? 207 */ 208 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 209 c->iv_len : c->block_size; 210 } 211 212 u_int 213 cipher_is_cbc(const struct sshcipher *c) 214 { 215 return (c->flags & CFLAG_CBC) != 0; 216 } 217 218 u_int 219 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 220 { 221 return cc->plaintext; 222 } 223 224 const struct sshcipher * 225 cipher_by_name(const char *name) 226 { 227 const struct sshcipher *c; 228 for (c = ciphers; c->name != NULL; c++) 229 if (strcmp(c->name, name) == 0) 230 return c; 231 return NULL; 232 } 233 234 #define CIPHER_SEP "," 235 int 236 ciphers_valid(const char *names) 237 { 238 const struct sshcipher *c; 239 char *cipher_list, *cp; 240 char *p; 241 242 if (names == NULL || strcmp(names, "") == 0) 243 return 0; 244 if ((cipher_list = cp = strdup(names)) == NULL) 245 return 0; 246 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 247 (p = strsep(&cp, CIPHER_SEP))) { 248 c = cipher_by_name(p); 249 if (c == NULL || (c->flags & (CFLAG_INTERNAL|CFLAG_NONE)) != 0) { 250 free(cipher_list); 251 return 0; 252 } 253 } 254 free(cipher_list); 255 return 1; 256 } 257 258 const char * 259 cipher_warning_message(const struct sshcipher_ctx *cc) 260 { 261 if (cc == NULL || cc->cipher == NULL) 262 return NULL; 263 /* XXX repurpose for CBC warning */ 264 return NULL; 265 } 266 267 int 268 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 269 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 270 int do_encrypt) 271 { 272 struct sshcipher_ctx *cc = NULL; 273 int ret = SSH_ERR_INTERNAL_ERROR; 274 #ifdef WITH_OPENSSL 275 const EVP_CIPHER *type; 276 int klen; 277 #endif 278 279 *ccp = NULL; 280 if ((cc = calloc(1, sizeof(*cc))) == NULL) 281 return SSH_ERR_ALLOC_FAIL; 282 283 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 284 cc->encrypt = do_encrypt; 285 286 if (keylen < cipher->key_len || 287 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 288 ret = SSH_ERR_INVALID_ARGUMENT; 289 goto out; 290 } 291 292 cc->cipher = cipher; 293 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 294 cc->cp_ctx = chachapoly_new(key, keylen); 295 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 296 goto out; 297 } 298 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 299 ret = 0; 300 goto out; 301 } 302 #ifndef WITH_OPENSSL 303 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 304 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 305 aesctr_ivsetup(&cc->ac_ctx, iv); 306 ret = 0; 307 goto out; 308 } 309 ret = SSH_ERR_INVALID_ARGUMENT; 310 goto out; 311 #else /* WITH_OPENSSL */ 312 type = (*cipher->evptype)(); 313 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 314 ret = SSH_ERR_ALLOC_FAIL; 315 goto out; 316 } 317 if (EVP_CipherInit(cc->evp, type, NULL, (const u_char *)iv, 318 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 319 ret = SSH_ERR_LIBCRYPTO_ERROR; 320 goto out; 321 } 322 if (cipher_authlen(cipher) && 323 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 324 -1, __UNCONST(iv)) <= 0) { 325 ret = SSH_ERR_LIBCRYPTO_ERROR; 326 goto out; 327 } 328 klen = EVP_CIPHER_CTX_key_length(cc->evp); 329 if (klen > 0 && keylen != (u_int)klen) { 330 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 331 ret = SSH_ERR_LIBCRYPTO_ERROR; 332 goto out; 333 } 334 } 335 /* in OpenSSL 1.1.0, EVP_CipherInit clears all previous setups; 336 use EVP_CipherInit_ex for augmenting */ 337 if (EVP_CipherInit_ex(cc->evp, NULL, NULL, __UNCONST(key), NULL, -1) == 0) { 338 ret = SSH_ERR_LIBCRYPTO_ERROR; 339 goto out; 340 } 341 ret = 0; 342 #endif /* WITH_OPENSSL */ 343 out: 344 if (ret == 0) { 345 /* success */ 346 *ccp = cc; 347 } else { 348 if (cc != NULL) { 349 #ifdef WITH_OPENSSL 350 EVP_CIPHER_CTX_free(cc->evp); 351 #endif /* WITH_OPENSSL */ 352 freezero(cc, sizeof(*cc)); 353 } 354 } 355 return ret; 356 } 357 358 /* 359 * cipher_crypt() operates as following: 360 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 361 * These bytes are treated as additional authenticated data for 362 * authenticated encryption modes. 363 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 364 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 365 * This tag is written on encryption and verified on decryption. 366 * Both 'aadlen' and 'authlen' can be set to 0. 367 */ 368 int 369 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 370 const u_char *src, u_int len, u_int aadlen, u_int authlen) 371 { 372 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 373 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 374 len, aadlen, authlen, cc->encrypt); 375 } 376 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 377 memcpy(dest, src, aadlen + len); 378 return 0; 379 } 380 #ifndef WITH_OPENSSL 381 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 382 if (aadlen) 383 memcpy(dest, src, aadlen); 384 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 385 dest + aadlen, len); 386 return 0; 387 } 388 return SSH_ERR_INVALID_ARGUMENT; 389 #else 390 if (authlen) { 391 u_char lastiv[1]; 392 393 if (authlen != cipher_authlen(cc->cipher)) 394 return SSH_ERR_INVALID_ARGUMENT; 395 /* increment IV */ 396 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 397 1, lastiv) <= 0) 398 return SSH_ERR_LIBCRYPTO_ERROR; 399 /* set tag on decryption */ 400 if (!cc->encrypt && 401 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 402 authlen, __UNCONST(src + aadlen + len)) <= 0) 403 return SSH_ERR_LIBCRYPTO_ERROR; 404 } 405 if (aadlen) { 406 if (authlen && 407 EVP_Cipher(cc->evp, NULL, (const u_char *)src, aadlen) < 0) 408 return SSH_ERR_LIBCRYPTO_ERROR; 409 memcpy(dest, src, aadlen); 410 } 411 if (len % cc->cipher->block_size) 412 return SSH_ERR_INVALID_ARGUMENT; 413 if (EVP_Cipher(cc->evp, dest + aadlen, (const u_char *)src + aadlen, 414 len) < 0) 415 return SSH_ERR_LIBCRYPTO_ERROR; 416 if (authlen) { 417 /* compute tag (on encrypt) or verify tag (on decrypt) */ 418 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 419 return cc->encrypt ? 420 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 421 if (cc->encrypt && 422 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 423 authlen, dest + aadlen + len) <= 0) 424 return SSH_ERR_LIBCRYPTO_ERROR; 425 } 426 return 0; 427 #endif 428 } 429 430 /* Extract the packet length, including any decryption necessary beforehand */ 431 int 432 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 433 const u_char *cp, u_int len) 434 { 435 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 436 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 437 cp, len); 438 if (len < 4) 439 return SSH_ERR_MESSAGE_INCOMPLETE; 440 *plenp = PEEK_U32(cp); 441 return 0; 442 } 443 444 void 445 cipher_free(struct sshcipher_ctx *cc) 446 { 447 if (cc == NULL) 448 return; 449 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 450 chachapoly_free(cc->cp_ctx); 451 cc->cp_ctx = NULL; 452 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 453 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 454 #ifdef WITH_OPENSSL 455 EVP_CIPHER_CTX_free(cc->evp); 456 cc->evp = NULL; 457 #endif 458 freezero(cc, sizeof(*cc)); 459 } 460 461 int 462 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 463 { 464 #ifdef WITH_OPENSSL 465 const struct sshcipher *c = cc->cipher; 466 int evplen; 467 #endif 468 469 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 470 if (len != 0) 471 return SSH_ERR_INVALID_ARGUMENT; 472 return 0; 473 } 474 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 475 if (len != sizeof(cc->ac_ctx.ctr)) 476 return SSH_ERR_INVALID_ARGUMENT; 477 memcpy(iv, cc->ac_ctx.ctr, len); 478 return 0; 479 } 480 if ((cc->cipher->flags & CFLAG_NONE) != 0) 481 return 0; 482 483 #ifdef WITH_OPENSSL 484 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 485 if (evplen == 0) 486 return 0; 487 else if (evplen < 0) 488 return SSH_ERR_LIBCRYPTO_ERROR; 489 if ((size_t)evplen != len) 490 return SSH_ERR_INVALID_ARGUMENT; 491 if (cipher_authlen(c)) { 492 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, len, 493 iv) <= 0) 494 return SSH_ERR_LIBCRYPTO_ERROR; 495 } else if (EVP_CIPHER_CTX_get_iv(cc->evp, iv, len) <= 0) 496 return SSH_ERR_LIBCRYPTO_ERROR; 497 #endif 498 return 0; 499 } 500 501 int 502 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 503 { 504 #ifdef WITH_OPENSSL 505 const struct sshcipher *c = cc->cipher; 506 int evplen = 0; 507 #endif 508 509 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 510 return 0; 511 if ((cc->cipher->flags & CFLAG_NONE) != 0) 512 return 0; 513 514 #ifdef WITH_OPENSSL 515 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 516 if (evplen <= 0) 517 return SSH_ERR_LIBCRYPTO_ERROR; 518 if ((size_t)evplen != len) 519 return SSH_ERR_INVALID_ARGUMENT; 520 if (cipher_authlen(c)) { 521 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 522 if (EVP_CIPHER_CTX_ctrl(cc->evp, 523 EVP_CTRL_GCM_SET_IV_FIXED, -1, __UNCONST(iv)) <= 0) 524 return SSH_ERR_LIBCRYPTO_ERROR; 525 } else 526 memcpy(EVP_CIPHER_CTX_iv_noconst(cc->evp), iv, evplen); 527 #endif 528 return 0; 529 } 530
Indexes created Sun Mar 01 05:31:48 UTC 2026