1 /* $OpenBSD: cipher.c,v 1.117 2020/04/03 04:27:03 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 <sys/types.h> 39 40 #include <string.h> 41 #include <stdarg.h> 42 #include <stdio.h> 43 44 #include "cipher.h" 45 #include "misc.h" 46 #include "sshbuf.h" 47 #include "ssherr.h" 48 #include "digest.h" 49 50 #ifndef WITH_OPENSSL 51 #define EVP_CIPHER_CTX void 52 #endif 53 54 struct sshcipher_ctx { 55 int plaintext; 56 int encrypt; 57 EVP_CIPHER_CTX *evp; 58 struct chachapoly_ctx *cp_ctx; 59 struct aesctr_ctx ac_ctx; /* XXX union with evp? */ 60 const struct sshcipher *cipher; 61 }; 62 63 struct sshcipher { 64 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 const char * 139 compression_alg_list(int compression) 140 { 141 #ifdef WITH_ZLIB 142 return compression ? "zlib@openssh.com,zlib,none" : 143 "none,zlib@openssh.com,zlib"; 144 #else 145 return "none"; 146 #endif 147 } 148 149 u_int 150 cipher_blocksize(const struct sshcipher *c) 151 { 152 return (c->block_size); 153 } 154 155 u_int 156 cipher_keylen(const struct sshcipher *c) 157 { 158 return (c->key_len); 159 } 160 161 u_int 162 cipher_seclen(const struct sshcipher *c) 163 { 164 if (strcmp("3des-cbc", c->name) == 0) 165 return 14; 166 return cipher_keylen(c); 167 } 168 169 u_int 170 cipher_authlen(const struct sshcipher *c) 171 { 172 return (c->auth_len); 173 } 174 175 u_int 176 cipher_ivlen(const struct sshcipher *c) 177 { 178 /* 179 * Default is cipher block size, except for chacha20+poly1305 that 180 * needs no IV. XXX make iv_len == -1 default? 181 */ 182 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ? 183 c->iv_len : c->block_size; 184 } 185 186 u_int 187 cipher_is_cbc(const struct sshcipher *c) 188 { 189 return (c->flags & CFLAG_CBC) != 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; 215 216 if (names == NULL || strcmp(names, "") == 0) 217 return 0; 218 if ((cipher_list = cp = strdup(names)) == NULL) 219 return 0; 220 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 221 (p = strsep(&cp, CIPHER_SEP))) { 222 c = cipher_by_name(p); 223 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) { 224 free(cipher_list); 225 return 0; 226 } 227 } 228 free(cipher_list); 229 return 1; 230 } 231 232 const char * 233 cipher_warning_message(const struct sshcipher_ctx *cc) 234 { 235 if (cc == NULL || cc->cipher == NULL) 236 return NULL; 237 /* XXX repurpose for CBC warning */ 238 return NULL; 239 } 240 241 int 242 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher, 243 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 244 int do_encrypt) 245 { 246 struct sshcipher_ctx *cc = NULL; 247 int ret = SSH_ERR_INTERNAL_ERROR; 248 #ifdef WITH_OPENSSL 249 const EVP_CIPHER *type; 250 int klen; 251 #endif 252 253 *ccp = NULL; 254 if ((cc = calloc(sizeof(*cc), 1)) == NULL) 255 return SSH_ERR_ALLOC_FAIL; 256 257 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0; 258 cc->encrypt = do_encrypt; 259 260 if (keylen < cipher->key_len || 261 (iv != NULL && ivlen < cipher_ivlen(cipher))) { 262 ret = SSH_ERR_INVALID_ARGUMENT; 263 goto out; 264 } 265 266 cc->cipher = cipher; 267 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 268 cc->cp_ctx = chachapoly_new(key, keylen); 269 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT; 270 goto out; 271 } 272 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 273 ret = 0; 274 goto out; 275 } 276 #ifndef WITH_OPENSSL 277 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 278 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen); 279 aesctr_ivsetup(&cc->ac_ctx, iv); 280 ret = 0; 281 goto out; 282 } 283 ret = SSH_ERR_INVALID_ARGUMENT; 284 goto out; 285 #else /* WITH_OPENSSL */ 286 type = (*cipher->evptype)(); 287 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) { 288 ret = SSH_ERR_ALLOC_FAIL; 289 goto out; 290 } 291 if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv, 292 (do_encrypt == CIPHER_ENCRYPT)) == 0) { 293 ret = SSH_ERR_LIBCRYPTO_ERROR; 294 goto out; 295 } 296 if (cipher_authlen(cipher) && 297 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED, 298 -1, (u_char *)iv)) { 299 ret = SSH_ERR_LIBCRYPTO_ERROR; 300 goto out; 301 } 302 klen = EVP_CIPHER_CTX_key_length(cc->evp); 303 if (klen > 0 && keylen != (u_int)klen) { 304 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) { 305 ret = SSH_ERR_LIBCRYPTO_ERROR; 306 goto out; 307 } 308 } 309 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) { 310 ret = SSH_ERR_LIBCRYPTO_ERROR; 311 goto out; 312 } 313 ret = 0; 314 #endif /* WITH_OPENSSL */ 315 out: 316 if (ret == 0) { 317 /* success */ 318 *ccp = cc; 319 } else { 320 if (cc != NULL) { 321 #ifdef WITH_OPENSSL 322 EVP_CIPHER_CTX_free(cc->evp); 323 #endif /* WITH_OPENSSL */ 324 freezero(cc, sizeof(*cc)); 325 } 326 } 327 return ret; 328 } 329 330 /* 331 * cipher_crypt() operates as following: 332 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'. 333 * These bytes are treated as additional authenticated data for 334 * authenticated encryption modes. 335 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. 336 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag. 337 * This tag is written on encryption and verified on decryption. 338 * Both 'aadlen' and 'authlen' can be set to 0. 339 */ 340 int 341 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest, 342 const u_char *src, u_int len, u_int aadlen, u_int authlen) 343 { 344 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 345 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src, 346 len, aadlen, authlen, cc->encrypt); 347 } 348 if ((cc->cipher->flags & CFLAG_NONE) != 0) { 349 memcpy(dest, src, aadlen + len); 350 return 0; 351 } 352 #ifndef WITH_OPENSSL 353 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 354 if (aadlen) 355 memcpy(dest, src, aadlen); 356 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen, 357 dest + aadlen, len); 358 return 0; 359 } 360 return SSH_ERR_INVALID_ARGUMENT; 361 #else 362 if (authlen) { 363 u_char lastiv[1]; 364 365 if (authlen != cipher_authlen(cc->cipher)) 366 return SSH_ERR_INVALID_ARGUMENT; 367 /* increment IV */ 368 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 369 1, lastiv)) 370 return SSH_ERR_LIBCRYPTO_ERROR; 371 /* set tag on decyption */ 372 if (!cc->encrypt && 373 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG, 374 authlen, (u_char *)src + aadlen + len)) 375 return SSH_ERR_LIBCRYPTO_ERROR; 376 } 377 if (aadlen) { 378 if (authlen && 379 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0) 380 return SSH_ERR_LIBCRYPTO_ERROR; 381 memcpy(dest, src, aadlen); 382 } 383 if (len % cc->cipher->block_size) 384 return SSH_ERR_INVALID_ARGUMENT; 385 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen, 386 len) < 0) 387 return SSH_ERR_LIBCRYPTO_ERROR; 388 if (authlen) { 389 /* compute tag (on encrypt) or verify tag (on decrypt) */ 390 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0) 391 return cc->encrypt ? 392 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID; 393 if (cc->encrypt && 394 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG, 395 authlen, dest + aadlen + len)) 396 return SSH_ERR_LIBCRYPTO_ERROR; 397 } 398 return 0; 399 #endif 400 } 401 402 /* Extract the packet length, including any decryption necessary beforehand */ 403 int 404 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr, 405 const u_char *cp, u_int len) 406 { 407 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 408 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr, 409 cp, len); 410 if (len < 4) 411 return SSH_ERR_MESSAGE_INCOMPLETE; 412 *plenp = PEEK_U32(cp); 413 return 0; 414 } 415 416 void 417 cipher_free(struct sshcipher_ctx *cc) 418 { 419 if (cc == NULL) 420 return; 421 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 422 chachapoly_free(cc->cp_ctx); 423 cc->cp_ctx = NULL; 424 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0) 425 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx)); 426 #ifdef WITH_OPENSSL 427 EVP_CIPHER_CTX_free(cc->evp); 428 cc->evp = NULL; 429 #endif 430 freezero(cc, sizeof(*cc)); 431 } 432 433 /* 434 * Exports an IV from the sshcipher_ctx required to export the key 435 * state back from the unprivileged child to the privileged parent 436 * process. 437 */ 438 int 439 cipher_get_keyiv_len(const struct sshcipher_ctx *cc) 440 { 441 const struct sshcipher *c = cc->cipher; 442 443 if ((c->flags & CFLAG_CHACHAPOLY) != 0) 444 return 0; 445 else if ((c->flags & CFLAG_AESCTR) != 0) 446 return sizeof(cc->ac_ctx.ctr); 447 #ifdef WITH_OPENSSL 448 return EVP_CIPHER_CTX_iv_length(cc->evp); 449 #else 450 return 0; 451 #endif 452 } 453 454 int 455 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len) 456 { 457 #ifdef WITH_OPENSSL 458 const struct sshcipher *c = cc->cipher; 459 int evplen; 460 #endif 461 462 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) { 463 if (len != 0) 464 return SSH_ERR_INVALID_ARGUMENT; 465 return 0; 466 } 467 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) { 468 if (len != sizeof(cc->ac_ctx.ctr)) 469 return SSH_ERR_INVALID_ARGUMENT; 470 memcpy(iv, cc->ac_ctx.ctr, len); 471 return 0; 472 } 473 if ((cc->cipher->flags & CFLAG_NONE) != 0) 474 return 0; 475 476 #ifdef WITH_OPENSSL 477 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 478 if (evplen == 0) 479 return 0; 480 else if (evplen < 0) 481 return SSH_ERR_LIBCRYPTO_ERROR; 482 if ((size_t)evplen != len) 483 return SSH_ERR_INVALID_ARGUMENT; 484 if (cipher_authlen(c)) { 485 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN, 486 len, iv)) 487 return SSH_ERR_LIBCRYPTO_ERROR; 488 } else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len)) 489 return SSH_ERR_LIBCRYPTO_ERROR; 490 #endif 491 return 0; 492 } 493 494 int 495 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len) 496 { 497 #ifdef WITH_OPENSSL 498 const struct sshcipher *c = cc->cipher; 499 int evplen = 0; 500 #endif 501 502 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) 503 return 0; 504 if ((cc->cipher->flags & CFLAG_NONE) != 0) 505 return 0; 506 507 #ifdef WITH_OPENSSL 508 evplen = EVP_CIPHER_CTX_iv_length(cc->evp); 509 if (evplen <= 0) 510 return SSH_ERR_LIBCRYPTO_ERROR; 511 if ((size_t)evplen != len) 512 return SSH_ERR_INVALID_ARGUMENT; 513 if (cipher_authlen(c)) { 514 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */ 515 if (!EVP_CIPHER_CTX_ctrl(cc->evp, 516 EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv)) 517 return SSH_ERR_LIBCRYPTO_ERROR; 518 } else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen)) 519 return SSH_ERR_LIBCRYPTO_ERROR; 520 #endif 521 return 0; 522 } 523 524