1 /* $OpenBSD: cipher.c,v 1.81 2006/08/03 03:34:42 deraadt 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 <openssl/md5.h> 43 44 #include <string.h> 45 #include <stdarg.h> 46 47 #include "xmalloc.h" 48 #include "log.h" 49 #include "cipher.h" 50 51 /* compatibility with old or broken OpenSSL versions */ 52 #include "openbsd-compat/openssl-compat.h" 53 54 extern const EVP_CIPHER *evp_ssh1_bf(void); 55 extern const EVP_CIPHER *evp_ssh1_3des(void); 56 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 57 extern const EVP_CIPHER *evp_aes_128_ctr(void); 58 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); 59 60 struct Cipher { 61 char *name; 62 int number; /* for ssh1 only */ 63 u_int block_size; 64 u_int key_len; 65 u_int discard_len; 66 const EVP_CIPHER *(*evptype)(void); 67 } ciphers[] = { 68 { "none", SSH_CIPHER_NONE, 8, 0, 0, EVP_enc_null }, 69 { "des", SSH_CIPHER_DES, 8, 8, 0, EVP_des_cbc }, 70 { "3des", SSH_CIPHER_3DES, 8, 16, 0, evp_ssh1_3des }, 71 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, evp_ssh1_bf }, 72 73 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, EVP_des_ede3_cbc }, 74 { "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, 0, EVP_bf_cbc }, 75 { "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, 0, EVP_cast5_cbc }, 76 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, EVP_rc4 }, 77 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 1536, EVP_rc4 }, 78 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 1536, EVP_rc4 }, 79 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, EVP_aes_128_cbc }, 80 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, EVP_aes_192_cbc }, 81 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc }, 82 { "rijndael-cbc@lysator.liu.se", 83 SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc }, 84 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, evp_aes_128_ctr }, 85 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, evp_aes_128_ctr }, 86 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, evp_aes_128_ctr }, 87 #ifdef USE_CIPHER_ACSS 88 { "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss }, 89 #endif 90 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, NULL } 91 }; 92 93 /*--*/ 94 95 u_int 96 cipher_blocksize(const Cipher *c) 97 { 98 return (c->block_size); 99 } 100 101 u_int 102 cipher_keylen(const Cipher *c) 103 { 104 return (c->key_len); 105 } 106 107 u_int 108 cipher_get_number(const Cipher *c) 109 { 110 return (c->number); 111 } 112 113 u_int 114 cipher_mask_ssh1(int client) 115 { 116 u_int mask = 0; 117 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 118 mask |= 1 << SSH_CIPHER_BLOWFISH; 119 if (client) { 120 mask |= 1 << SSH_CIPHER_DES; 121 } 122 return mask; 123 } 124 125 Cipher * 126 cipher_by_name(const char *name) 127 { 128 Cipher *c; 129 for (c = ciphers; c->name != NULL; c++) 130 if (strcmp(c->name, name) == 0) 131 return c; 132 return NULL; 133 } 134 135 Cipher * 136 cipher_by_number(int id) 137 { 138 Cipher *c; 139 for (c = ciphers; c->name != NULL; c++) 140 if (c->number == id) 141 return c; 142 return NULL; 143 } 144 145 #define CIPHER_SEP "," 146 int 147 ciphers_valid(const char *names) 148 { 149 Cipher *c; 150 char *cipher_list, *cp; 151 char *p; 152 153 if (names == NULL || strcmp(names, "") == 0) 154 return 0; 155 cipher_list = cp = xstrdup(names); 156 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 157 (p = strsep(&cp, CIPHER_SEP))) { 158 c = cipher_by_name(p); 159 if (c == NULL || c->number != SSH_CIPHER_SSH2) { 160 debug("bad cipher %s [%s]", p, names); 161 xfree(cipher_list); 162 return 0; 163 } else { 164 debug3("cipher ok: %s [%s]", p, names); 165 } 166 } 167 debug3("ciphers ok: [%s]", names); 168 xfree(cipher_list); 169 return 1; 170 } 171 172 /* 173 * Parses the name of the cipher. Returns the number of the corresponding 174 * cipher, or -1 on error. 175 */ 176 177 int 178 cipher_number(const char *name) 179 { 180 Cipher *c; 181 if (name == NULL) 182 return -1; 183 for (c = ciphers; c->name != NULL; c++) 184 if (strcasecmp(c->name, name) == 0) 185 return c->number; 186 return -1; 187 } 188 189 char * 190 cipher_name(int id) 191 { 192 Cipher *c = cipher_by_number(id); 193 return (c==NULL) ? "<unknown>" : c->name; 194 } 195 196 void 197 cipher_init(CipherContext *cc, Cipher *cipher, 198 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 199 int do_encrypt) 200 { 201 static int dowarn = 1; 202 #ifdef SSH_OLD_EVP 203 EVP_CIPHER *type; 204 #else 205 const EVP_CIPHER *type; 206 int klen; 207 #endif 208 u_char *junk, *discard; 209 210 if (cipher->number == SSH_CIPHER_DES) { 211 if (dowarn) { 212 error("Warning: use of DES is strongly discouraged " 213 "due to cryptographic weaknesses"); 214 dowarn = 0; 215 } 216 if (keylen > 8) 217 keylen = 8; 218 } 219 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 220 221 if (keylen < cipher->key_len) 222 fatal("cipher_init: key length %d is insufficient for %s.", 223 keylen, cipher->name); 224 if (iv != NULL && ivlen < cipher->block_size) 225 fatal("cipher_init: iv length %d is insufficient for %s.", 226 ivlen, cipher->name); 227 cc->cipher = cipher; 228 229 type = (*cipher->evptype)(); 230 231 EVP_CIPHER_CTX_init(&cc->evp); 232 #ifdef SSH_OLD_EVP 233 if (type->key_len > 0 && type->key_len != keylen) { 234 debug("cipher_init: set keylen (%d -> %d)", 235 type->key_len, keylen); 236 type->key_len = keylen; 237 } 238 EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv, 239 (do_encrypt == CIPHER_ENCRYPT)); 240 #else 241 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 242 (do_encrypt == CIPHER_ENCRYPT)) == 0) 243 fatal("cipher_init: EVP_CipherInit failed for %s", 244 cipher->name); 245 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 246 if (klen > 0 && keylen != (u_int)klen) { 247 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 248 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 249 fatal("cipher_init: set keylen failed (%d -> %d)", 250 klen, keylen); 251 } 252 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 253 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 254 cipher->name); 255 #endif 256 257 if (cipher->discard_len > 0) { 258 junk = xmalloc(cipher->discard_len); 259 discard = xmalloc(cipher->discard_len); 260 if (EVP_Cipher(&cc->evp, discard, junk, 261 cipher->discard_len) == 0) 262 fatal("evp_crypt: EVP_Cipher failed during discard"); 263 memset(discard, 0, cipher->discard_len); 264 xfree(junk); 265 xfree(discard); 266 } 267 } 268 269 void 270 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len) 271 { 272 if (len % cc->cipher->block_size) 273 fatal("cipher_encrypt: bad plaintext length %d", len); 274 if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0) 275 fatal("evp_crypt: EVP_Cipher failed"); 276 } 277 278 void 279 cipher_cleanup(CipherContext *cc) 280 { 281 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 282 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 283 } 284 285 /* 286 * Selects the cipher, and keys if by computing the MD5 checksum of the 287 * passphrase and using the resulting 16 bytes as the key. 288 */ 289 290 void 291 cipher_set_key_string(CipherContext *cc, Cipher *cipher, 292 const char *passphrase, int do_encrypt) 293 { 294 MD5_CTX md; 295 u_char digest[16]; 296 297 MD5_Init(&md); 298 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); 299 MD5_Final(digest, &md); 300 301 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 302 303 memset(digest, 0, sizeof(digest)); 304 memset(&md, 0, sizeof(md)); 305 } 306 307 /* 308 * Exports an IV from the CipherContext required to export the key 309 * state back from the unprivileged child to the privileged parent 310 * process. 311 */ 312 313 int 314 cipher_get_keyiv_len(const CipherContext *cc) 315 { 316 Cipher *c = cc->cipher; 317 int ivlen; 318 319 if (c->number == SSH_CIPHER_3DES) 320 ivlen = 24; 321 else 322 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 323 return (ivlen); 324 } 325 326 void 327 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 328 { 329 Cipher *c = cc->cipher; 330 int evplen; 331 332 switch (c->number) { 333 case SSH_CIPHER_SSH2: 334 case SSH_CIPHER_DES: 335 case SSH_CIPHER_BLOWFISH: 336 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 337 if (evplen <= 0) 338 return; 339 if ((u_int)evplen != len) 340 fatal("%s: wrong iv length %d != %d", __func__, 341 evplen, len); 342 #ifdef USE_BUILTIN_RIJNDAEL 343 if (c->evptype == evp_rijndael) 344 ssh_rijndael_iv(&cc->evp, 0, iv, len); 345 else 346 #endif 347 if (c->evptype == evp_aes_128_ctr) 348 ssh_aes_ctr_iv(&cc->evp, 0, iv, len); 349 else 350 memcpy(iv, cc->evp.iv, len); 351 break; 352 case SSH_CIPHER_3DES: 353 ssh1_3des_iv(&cc->evp, 0, iv, 24); 354 break; 355 default: 356 fatal("%s: bad cipher %d", __func__, c->number); 357 } 358 } 359 360 void 361 cipher_set_keyiv(CipherContext *cc, u_char *iv) 362 { 363 Cipher *c = cc->cipher; 364 int evplen = 0; 365 366 switch (c->number) { 367 case SSH_CIPHER_SSH2: 368 case SSH_CIPHER_DES: 369 case SSH_CIPHER_BLOWFISH: 370 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 371 if (evplen == 0) 372 return; 373 #ifdef USE_BUILTIN_RIJNDAEL 374 if (c->evptype == evp_rijndael) 375 ssh_rijndael_iv(&cc->evp, 1, iv, evplen); 376 else 377 #endif 378 if (c->evptype == evp_aes_128_ctr) 379 ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen); 380 else 381 memcpy(cc->evp.iv, iv, evplen); 382 break; 383 case SSH_CIPHER_3DES: 384 ssh1_3des_iv(&cc->evp, 1, iv, 24); 385 break; 386 default: 387 fatal("%s: bad cipher %d", __func__, c->number); 388 } 389 } 390 391 #if OPENSSL_VERSION_NUMBER < 0x00907000L 392 #define EVP_X_STATE(evp) &(evp).c 393 #define EVP_X_STATE_LEN(evp) sizeof((evp).c) 394 #else 395 #define EVP_X_STATE(evp) (evp).cipher_data 396 #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size 397 #endif 398 399 int 400 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 401 { 402 Cipher *c = cc->cipher; 403 int plen = 0; 404 405 if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { 406 plen = EVP_X_STATE_LEN(cc->evp); 407 if (dat == NULL) 408 return (plen); 409 memcpy(dat, EVP_X_STATE(cc->evp), plen); 410 } 411 return (plen); 412 } 413 414 void 415 cipher_set_keycontext(CipherContext *cc, u_char *dat) 416 { 417 Cipher *c = cc->cipher; 418 int plen; 419 420 if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { 421 plen = EVP_X_STATE_LEN(cc->evp); 422 memcpy(EVP_X_STATE(cc->evp), dat, plen); 423 } 424 } 425