1 /* $OpenBSD: cipher.c,v 1.125 2025/09/02 11:08:34 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 *ret = NULL; 120 const struct sshcipher *c; 121 char sep_str[2] = {sep, '\0'}; 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 xextendf(&ret, sep_str, "%s", c->name); 129 } 130 return ret; 131 } 132 133 const char * 134 compression_alg_list(int compression) 135 { 136 #ifdef WITH_ZLIB 137 return compression ? "zlib@openssh.com,none" : 138 "none,zlib@openssh.com"; 139 #else 140 return "none"; 141 #endif 142 } 143 144 u_int 145 cipher_blocksize(const struct sshcipher *c) 146 { 147 return (c->block_size); 148 } 149 150 u_int 151 cipher_keylen(const struct sshcipher *c) 152 { 153 return (c->key_len); 154 } 155 156 u_int 157 cipher_seclen(const struct sshcipher *c) 158 { 159 if (strcmp("3des-cbc", c->name) == 0) 160 return 14; 161 return cipher_keylen(c); 162 } 163 164 u_int 165 cipher_authlen(const struct sshcipher *c) 166 { 167 return (c->auth_len); 168 } 169 170 u_int 171 cipher_ivlen(const struct sshcipher *c) 172 { 173 /* 174 * Default is cipher block size, except for chacha20+poly1305 that 175 * needs no IV. XXX make iv_len == -1 default? 176 */ 177 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 178 c->iv_len : c->block_size; 179 } 180 181 u_int 182 cipher_is_cbc(const struct sshcipher *c) 183 { 184 return (c->flags & CFLAG_CBC) != 0; 185 } 186 187 u_int 188 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 189 { 190 return cc->plaintext; 191 } 192 193 const struct sshcipher * 194 cipher_by_name(const char *name) 195 { 196 const struct sshcipher *c; 197 for (c = ciphers; c->name != NULL; c++) 198 if (strcmp(c->name, name) == 0) 199 return c; 200 return NULL; 201 } 202 203 #define CIPHER_SEP "," 204 int 205 ciphers_valid(const char *names) 206 { 207 const struct sshcipher *c; 208 char *cipher_list, *cp; 209 char *p; 210 211 if (names == NULL || strcmp(names, "") == 0) 212 return 0; 213 if ((cipher_list = cp = strdup(names)) == NULL) 214 return 0; 215 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 216 (p = strsep(&cp, CIPHER_SEP))) { 217 c = cipher_by_name(p); 218 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) { 219 free(cipher_list); 220 return 0; 221 } 222 } 223 free(cipher_list); 224 return 1; 225 } 226 227 const char * 228 cipher_warning_message(const struct sshcipher_ctx *cc) 229 { 230 if (cc == NULL || cc->cipher == NULL) 231 return NULL; 232 /* XXX repurpose for CBC warning */ 233 return NULL; 234 } 235 236 int 237 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 238 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 239 int do_encrypt) 240 { 241 struct sshcipher_ctx *cc = NULL; 242 int ret = SSH_ERR_INTERNAL_ERROR; 243 #ifdef WITH_OPENSSL 244 const EVP_CIPHER *type; 245 int klen; 246 #endif 247 248 *ccp = NULL; 249 if ((cc = calloc(1, sizeof(*cc))) == NULL) 250 return SSH_ERR_ALLOC_FAIL; 251 252 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 253 cc->encrypt = do_encrypt; 254 255 if (keylen < cipher->key_len || 256 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 257 ret = SSH_ERR_INVALID_ARGUMENT; 258 goto out; 259 } 260 261 cc->cipher = cipher; 262 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 263 cc->cp_ctx = chachapoly_new(key, keylen); 264 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 265 goto out; 266 } 267 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 268 ret = 0; 269 goto out; 270 } 271 #ifndef WITH_OPENSSL 272 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 273 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 274 aesctr_ivsetup(&cc->ac_ctx, iv); 275 ret = 0; 276 goto out; 277 } 278 ret = SSH_ERR_INVALID_ARGUMENT; 279 goto out; 280 #else /* WITH_OPENSSL */ 281 type = (*cipher->evptype)(); 282 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 283 ret = SSH_ERR_ALLOC_FAIL; 284 goto out; 285 } 286 if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv, 287 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 288 ret = SSH_ERR_LIBCRYPTO_ERROR; 289 goto out; 290 } 291 if (cipher_authlen(cipher) && 292 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 293 -1, (u_char *)iv) <= 0) { 294 ret = SSH_ERR_LIBCRYPTO_ERROR; 295 goto out; 296 } 297 klen = EVP_CIPHER_CTX_key_length(cc->evp); 298 if (klen > 0 && keylen != (u_int)klen) { 299 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 300 ret = SSH_ERR_LIBCRYPTO_ERROR; 301 goto out; 302 } 303 } 304 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) { 305 ret = SSH_ERR_LIBCRYPTO_ERROR; 306 goto out; 307 } 308 ret = 0; 309 #endif /* WITH_OPENSSL */ 310 out: 311 if (ret == 0) { 312 /* success */ 313 *ccp = cc; 314 } else { 315 if (cc != NULL) { 316 #ifdef WITH_OPENSSL 317 EVP_CIPHER_CTX_free(cc->evp); 318 #endif /* WITH_OPENSSL */ 319 freezero(cc, sizeof(*cc)); 320 } 321 } 322 return ret; 323 } 324 325 /* 326 * cipher_crypt() operates as following: 327 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 328 * These bytes are treated as additional authenticated data for 329 * authenticated encryption modes. 330 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 331 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 332 * This tag is written on encryption and verified on decryption. 333 * Both 'aadlen' and 'authlen' can be set to 0. 334 */ 335 int 336 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 337 const u_char *src, u_int len, u_int aadlen, u_int authlen) 338 { 339 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 340 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 341 len, aadlen, authlen, cc->encrypt); 342 } 343 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 344 memcpy(dest, src, aadlen + len); 345 return 0; 346 } 347 #ifndef WITH_OPENSSL 348 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 349 if (aadlen) 350 memcpy(dest, src, aadlen); 351 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 352 dest + aadlen, len); 353 return 0; 354 } 355 return SSH_ERR_INVALID_ARGUMENT; 356 #else 357 if (authlen) { 358 u_char lastiv[1]; 359 360 if (authlen != cipher_authlen(cc->cipher)) 361 return SSH_ERR_INVALID_ARGUMENT; 362 /* increment IV */ 363 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 364 1, lastiv) <= 0) 365 return SSH_ERR_LIBCRYPTO_ERROR; 366 /* set tag on decryption */ 367 if (!cc->encrypt && 368 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 369 authlen, (u_char *)src + aadlen + len) <= 0) 370 return SSH_ERR_LIBCRYPTO_ERROR; 371 } 372 if (aadlen) { 373 if (authlen && 374 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0) 375 return SSH_ERR_LIBCRYPTO_ERROR; 376 memcpy(dest, src, aadlen); 377 } 378 if (len % cc->cipher->block_size) 379 return SSH_ERR_INVALID_ARGUMENT; 380 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen, 381 len) < 0) 382 return SSH_ERR_LIBCRYPTO_ERROR; 383 if (authlen) { 384 /* compute tag (on encrypt) or verify tag (on decrypt) */ 385 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 386 return cc->encrypt ? 387 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 388 if (cc->encrypt && 389 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 390 authlen, dest + aadlen + len) <= 0) 391 return SSH_ERR_LIBCRYPTO_ERROR; 392 } 393 return 0; 394 #endif 395 } 396 397 /* Extract the packet length, including any decryption necessary beforehand */ 398 int 399 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 400 const u_char *cp, u_int len) 401 { 402 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 403 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 404 cp, len); 405 if (len < 4) 406 return SSH_ERR_MESSAGE_INCOMPLETE; 407 *plenp = PEEK_U32(cp); 408 return 0; 409 } 410 411 void 412 cipher_free(struct sshcipher_ctx *cc) 413 { 414 if (cc == NULL) 415 return; 416 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 417 chachapoly_free(cc->cp_ctx); 418 cc->cp_ctx = NULL; 419 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 420 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 421 #ifdef WITH_OPENSSL 422 EVP_CIPHER_CTX_free(cc->evp); 423 cc->evp = NULL; 424 #endif 425 freezero(cc, sizeof(*cc)); 426 } 427 428 int 429 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 430 { 431 #ifdef WITH_OPENSSL 432 const struct sshcipher *c = cc->cipher; 433 int evplen; 434 #endif 435 436 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 437 if (len != 0) 438 return SSH_ERR_INVALID_ARGUMENT; 439 return 0; 440 } 441 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 442 if (len != sizeof(cc->ac_ctx.ctr)) 443 return SSH_ERR_INVALID_ARGUMENT; 444 memcpy(iv, cc->ac_ctx.ctr, len); 445 return 0; 446 } 447 if ((cc->cipher->flags & CFLAG_NONE) != 0) 448 return 0; 449 450 #ifdef WITH_OPENSSL 451 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 452 if (evplen == 0) 453 return 0; 454 else if (evplen < 0) 455 return SSH_ERR_LIBCRYPTO_ERROR; 456 if ((size_t)evplen != len) 457 return SSH_ERR_INVALID_ARGUMENT; 458 if (cipher_authlen(c)) { 459 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, len, 460 iv) <= 0) 461 return SSH_ERR_LIBCRYPTO_ERROR; 462 } else if (EVP_CIPHER_CTX_get_iv(cc->evp, iv, len) <= 0) 463 return SSH_ERR_LIBCRYPTO_ERROR; 464 #endif 465 return 0; 466 } 467 468 int 469 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 470 { 471 #ifdef WITH_OPENSSL 472 const struct sshcipher *c = cc->cipher; 473 int evplen = 0; 474 #endif 475 476 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 477 return 0; 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 SSH_ERR_LIBCRYPTO_ERROR; 485 if ((size_t)evplen != len) 486 return SSH_ERR_INVALID_ARGUMENT; 487 if (cipher_authlen(c)) { 488 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 489 if (EVP_CIPHER_CTX_ctrl(cc->evp, 490 EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv) <= 0) 491 return SSH_ERR_LIBCRYPTO_ERROR; 492 } else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen)) 493 return SSH_ERR_LIBCRYPTO_ERROR; 494 #endif 495 return 0; 496 } 497