1 /* $OpenBSD: cipher.c,v 1.129 2026/06/19 05:26:04 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 51 #include "openbsd-compat/openssl-compat.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; 62 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 63 const struct sshcipher *cipher; 64 }; 65 66 struct sshcipher { 67 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 #ifndef OPENSSL_NO_DES 88 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc }, 89 #endif 90 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc }, 91 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc }, 92 { "aes256-cbc", 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 *ret = NULL; 119 const struct sshcipher *c; 120 char sep_str[2] = {sep, '\0'}; 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 xextendf(&ret, sep_str, "%s", c->name); 128 } 129 return ret; 130 } 131 132 const char * 133 compression_alg_list(int compression) 134 { 135 #ifdef WITH_ZLIB 136 return compression ? "zlib@openssh.com,none" : 137 "none,zlib@openssh.com"; 138 #else 139 return "none"; 140 #endif 141 } 142 143 u_int 144 cipher_blocksize(const struct sshcipher *c) 145 { 146 return (c->block_size); 147 } 148 149 u_int 150 cipher_keylen(const struct sshcipher *c) 151 { 152 return (c->key_len); 153 } 154 155 u_int 156 cipher_seclen(const struct sshcipher *c) 157 { 158 if (strcmp("3des-cbc", c->name) == 0) 159 return 14; 160 return cipher_keylen(c); 161 } 162 163 u_int 164 cipher_authlen(const struct sshcipher *c) 165 { 166 return (c->auth_len); 167 } 168 169 u_int 170 cipher_ivlen(const struct sshcipher *c) 171 { 172 /* 173 * Default is cipher block size, except for chacha20+poly1305 that 174 * needs no IV. XXX make iv_len == -1 default? 175 */ 176 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 177 c->iv_len : c->block_size; 178 } 179 180 u_int 181 cipher_is_cbc(const struct sshcipher *c) 182 { 183 return (c->flags & CFLAG_CBC) != 0; 184 } 185 186 u_int 187 cipher_is_internal(const struct sshcipher *c) 188 { 189 return (c->flags & CFLAG_INTERNAL) != 0; 190 } 191 192 u_int 193 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc) 194 { 195 return cc->plaintext; 196 } 197 198 const struct sshcipher * 199 cipher_by_name(const char *name) 200 { 201 const struct sshcipher *c; 202 for (c = ciphers; c->name != NULL; c++) 203 if (strcmp(c->name, name) == 0) 204 return c; 205 return NULL; 206 } 207 208 #define CIPHER_SEP "," 209 int 210 ciphers_valid(const char *names) 211 { 212 const struct sshcipher *c; 213 char *cipher_list, *cp; 214 char *p; 215 int found = 0; 216 217 if (names == NULL || strcmp(names, "") == 0) 218 return 0; 219 if ((cipher_list = cp = strdup(names)) == NULL) 220 return 0; 221 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 222 (p = strsep(&cp, CIPHER_SEP))) { 223 c = cipher_by_name(p); 224 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) { 225 free(cipher_list); 226 return 0; 227 } else 228 found = 1; 229 } 230 free(cipher_list); 231 return found; 232 } 233 234 const char * 235 cipher_warning_message(const struct sshcipher_ctx *cc) 236 { 237 if (cc == NULL || cc->cipher == NULL) 238 return NULL; 239 /* XXX repurpose for CBC warning */ 240 return NULL; 241 } 242 243 int 244 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 245 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 246 int do_encrypt) 247 { 248 struct sshcipher_ctx *cc = NULL; 249 int ret = SSH_ERR_INTERNAL_ERROR; 250 #ifdef WITH_OPENSSL 251 const EVP_CIPHER *type; 252 int klen; 253 #endif 254 255 *ccp = NULL; 256 if ((cc = calloc(1, sizeof(*cc))) == NULL) 257 return SSH_ERR_ALLOC_FAIL; 258 259 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 260 cc->encrypt = do_encrypt; 261 262 if (keylen < cipher->key_len || 263 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 264 ret = SSH_ERR_INVALID_ARGUMENT; 265 goto out; 266 } 267 268 cc->cipher = cipher; 269 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 270 cc->cp_ctx = chachapoly_new(key, keylen); 271 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 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, (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, (u_char *)iv) <= 0) { 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 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) { 312 ret = SSH_ERR_LIBCRYPTO_ERROR; 313 goto out; 314 } 315 ret = 0; 316 #endif /* WITH_OPENSSL */ 317 out: 318 if (ret == 0) { 319 /* success */ 320 *ccp = cc; 321 } else { 322 if (cc != NULL) { 323 #ifdef WITH_OPENSSL 324 EVP_CIPHER_CTX_free(cc->evp); 325 #endif /* WITH_OPENSSL */ 326 freezero(cc, sizeof(*cc)); 327 } 328 } 329 return ret; 330 } 331 332 /* 333 * cipher_crypt() operates as following: 334 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 335 * These bytes are treated as additional authenticated data for 336 * authenticated encryption modes. 337 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 338 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 339 * This tag is written on encryption and verified on decryption. 340 * Both 'aadlen' and 'authlen' can be set to 0. 341 */ 342 int 343 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 344 const u_char *src, u_int len, u_int aadlen, u_int authlen) 345 { 346 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 347 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 348 len, aadlen, authlen, cc->encrypt); 349 } 350 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 351 memcpy(dest, src, aadlen + len); 352 return 0; 353 } 354 #ifndef WITH_OPENSSL 355 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 356 if (aadlen) 357 memcpy(dest, src, aadlen); 358 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 359 dest + aadlen, len); 360 return 0; 361 } 362 return SSH_ERR_INVALID_ARGUMENT; 363 #else 364 if (authlen) { 365 u_char lastiv[1]; 366 367 if (authlen != cipher_authlen(cc->cipher)) 368 return SSH_ERR_INVALID_ARGUMENT; 369 /* increment IV */ 370 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 371 1, lastiv) <= 0) 372 return SSH_ERR_LIBCRYPTO_ERROR; 373 /* set tag on decryption */ 374 if (!cc->encrypt && 375 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 376 authlen, (u_char *)src + aadlen + len) <= 0) 377 return SSH_ERR_LIBCRYPTO_ERROR; 378 } 379 if (aadlen) { 380 if (authlen && 381 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0) 382 return SSH_ERR_LIBCRYPTO_ERROR; 383 memcpy(dest, src, aadlen); 384 } 385 if (len % cc->cipher->block_size) 386 return SSH_ERR_INVALID_ARGUMENT; 387 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen, 388 len) < 0) 389 return SSH_ERR_LIBCRYPTO_ERROR; 390 if (authlen) { 391 /* compute tag (on encrypt) or verify tag (on decrypt) */ 392 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 393 return cc->encrypt ? 394 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 395 if (cc->encrypt && 396 EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 397 authlen, dest + aadlen + len) <= 0) 398 return SSH_ERR_LIBCRYPTO_ERROR; 399 } 400 return 0; 401 #endif 402 } 403 404 /* Extract the packet length, including any decryption necessary beforehand */ 405 int 406 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 407 const u_char *cp, u_int len) 408 { 409 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 410 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 411 cp, len); 412 if (len < 4) 413 return SSH_ERR_MESSAGE_INCOMPLETE; 414 *plenp = PEEK_U32(cp); 415 return 0; 416 } 417 418 void 419 cipher_free(struct sshcipher_ctx *cc) 420 { 421 if (cc == NULL) 422 return; 423 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 424 chachapoly_free(cc->cp_ctx); 425 cc->cp_ctx = NULL; 426 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 427 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 428 #ifdef WITH_OPENSSL 429 EVP_CIPHER_CTX_free(cc->evp); 430 cc->evp = NULL; 431 #endif 432 freezero(cc, sizeof(*cc)); 433 } 434 435 int 436 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 437 { 438 #ifdef WITH_OPENSSL 439 const struct sshcipher *c = cc->cipher; 440 int evplen; 441 #endif 442 443 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 444 if (len != 0) 445 return SSH_ERR_INVALID_ARGUMENT; 446 return 0; 447 } 448 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 449 if (len != sizeof(cc->ac_ctx.ctr)) 450 return SSH_ERR_INVALID_ARGUMENT; 451 memcpy(iv, cc->ac_ctx.ctr, len); 452 return 0; 453 } 454 if ((cc->cipher->flags & CFLAG_NONE) != 0) 455 return 0; 456 457 #ifdef WITH_OPENSSL 458 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 459 if (evplen == 0) 460 return 0; 461 else if (evplen < 0) 462 return SSH_ERR_LIBCRYPTO_ERROR; 463 if ((size_t)evplen != len) 464 return SSH_ERR_INVALID_ARGUMENT; 465 if (cipher_authlen(c)) { 466 if (EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, len, 467 iv) <= 0) 468 return SSH_ERR_LIBCRYPTO_ERROR; 469 } else if (EVP_CIPHER_CTX_get_iv(cc->evp, iv, len) <= 0) 470 return SSH_ERR_LIBCRYPTO_ERROR; 471 #endif 472 return 0; 473 } 474