1 /* $OpenBSD: cipher.c,v 1.82 2009/01/26 09:58:15 markus 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 <openssl/md5.h> 41 42 #include <string.h> 43 #include <stdarg.h> 44 45 #include "xmalloc.h" 46 #include "log.h" 47 #include "cipher.h" 48 49 extern const EVP_CIPHER *evp_ssh1_bf(void); 50 extern const EVP_CIPHER *evp_ssh1_3des(void); 51 extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 52 extern const EVP_CIPHER *evp_aes_128_ctr(void); 53 extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); 54 55 struct Cipher { 56 char *name; 57 int number; /* for ssh1 only */ 58 u_int block_size; 59 u_int key_len; 60 u_int discard_len; 61 u_int cbc_mode; 62 const EVP_CIPHER *(*evptype)(void); 63 } ciphers[] = { 64 { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, EVP_enc_null }, 65 { "des", SSH_CIPHER_DES, 8, 8, 0, 1, EVP_des_cbc }, 66 { "3des", SSH_CIPHER_3DES, 8, 16, 0, 1, evp_ssh1_3des }, 67 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 1, evp_ssh1_bf }, 68 69 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 1, EVP_des_ede3_cbc }, 70 { "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_bf_cbc }, 71 { "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_cast5_cbc }, 72 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, EVP_rc4 }, 73 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 1536, 0, EVP_rc4 }, 74 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 1536, 0, EVP_rc4 }, 75 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 1, EVP_aes_128_cbc }, 76 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 1, EVP_aes_192_cbc }, 77 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc }, 78 { "rijndael-cbc@lysator.liu.se", 79 SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc }, 80 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, evp_aes_128_ctr }, 81 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, evp_aes_128_ctr }, 82 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, evp_aes_128_ctr }, 83 { "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, 0, 0, EVP_acss }, 84 85 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, NULL } 86 }; 87 88 /*--*/ 89 90 u_int 91 cipher_blocksize(const Cipher *c) 92 { 93 return (c->block_size); 94 } 95 96 u_int 97 cipher_keylen(const Cipher *c) 98 { 99 return (c->key_len); 100 } 101 102 u_int 103 cipher_get_number(const Cipher *c) 104 { 105 return (c->number); 106 } 107 108 u_int 109 cipher_is_cbc(const Cipher *c) 110 { 111 return (c->cbc_mode); 112 } 113 114 u_int 115 cipher_mask_ssh1(int client) 116 { 117 u_int mask = 0; 118 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 119 mask |= 1 << SSH_CIPHER_BLOWFISH; 120 if (client) { 121 mask |= 1 << SSH_CIPHER_DES; 122 } 123 return mask; 124 } 125 126 Cipher * 127 cipher_by_name(const char *name) 128 { 129 Cipher *c; 130 for (c = ciphers; c->name != NULL; c++) 131 if (strcmp(c->name, name) == 0) 132 return c; 133 return NULL; 134 } 135 136 Cipher * 137 cipher_by_number(int id) 138 { 139 Cipher *c; 140 for (c = ciphers; c->name != NULL; c++) 141 if (c->number == id) 142 return c; 143 return NULL; 144 } 145 146 #define CIPHER_SEP "," 147 int 148 ciphers_valid(const char *names) 149 { 150 Cipher *c; 151 char *cipher_list, *cp; 152 char *p; 153 154 if (names == NULL || strcmp(names, "") == 0) 155 return 0; 156 cipher_list = cp = xstrdup(names); 157 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 158 (p = strsep(&cp, CIPHER_SEP))) { 159 c = cipher_by_name(p); 160 if (c == NULL || c->number != SSH_CIPHER_SSH2) { 161 debug("bad cipher %s [%s]", p, names); 162 xfree(cipher_list); 163 return 0; 164 } else { 165 debug3("cipher ok: %s [%s]", p, names); 166 } 167 } 168 debug3("ciphers ok: [%s]", names); 169 xfree(cipher_list); 170 return 1; 171 } 172 173 /* 174 * Parses the name of the cipher. Returns the number of the corresponding 175 * cipher, or -1 on error. 176 */ 177 178 int 179 cipher_number(const char *name) 180 { 181 Cipher *c; 182 if (name == NULL) 183 return -1; 184 for (c = ciphers; c->name != NULL; c++) 185 if (strcasecmp(c->name, name) == 0) 186 return c->number; 187 return -1; 188 } 189 190 char * 191 cipher_name(int id) 192 { 193 Cipher *c = cipher_by_number(id); 194 return (c==NULL) ? "<unknown>" : c->name; 195 } 196 197 void 198 cipher_init(CipherContext *cc, Cipher *cipher, 199 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 200 int do_encrypt) 201 { 202 static int dowarn = 1; 203 const EVP_CIPHER *type; 204 int klen; 205 u_char *junk, *discard; 206 207 if (cipher->number == SSH_CIPHER_DES) { 208 if (dowarn) { 209 error("Warning: use of DES is strongly discouraged " 210 "due to cryptographic weaknesses"); 211 dowarn = 0; 212 } 213 if (keylen > 8) 214 keylen = 8; 215 } 216 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 217 218 if (keylen < cipher->key_len) 219 fatal("cipher_init: key length %d is insufficient for %s.", 220 keylen, cipher->name); 221 if (iv != NULL && ivlen < cipher->block_size) 222 fatal("cipher_init: iv length %d is insufficient for %s.", 223 ivlen, cipher->name); 224 cc->cipher = cipher; 225 226 type = (*cipher->evptype)(); 227 228 EVP_CIPHER_CTX_init(&cc->evp); 229 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 230 (do_encrypt == CIPHER_ENCRYPT)) == 0) 231 fatal("cipher_init: EVP_CipherInit failed for %s", 232 cipher->name); 233 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 234 if (klen > 0 && keylen != (u_int)klen) { 235 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 236 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 237 fatal("cipher_init: set keylen failed (%d -> %d)", 238 klen, keylen); 239 } 240 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 241 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 242 cipher->name); 243 244 if (cipher->discard_len > 0) { 245 junk = xmalloc(cipher->discard_len); 246 discard = xmalloc(cipher->discard_len); 247 if (EVP_Cipher(&cc->evp, discard, junk, 248 cipher->discard_len) == 0) 249 fatal("evp_crypt: EVP_Cipher failed during discard"); 250 memset(discard, 0, cipher->discard_len); 251 xfree(junk); 252 xfree(discard); 253 } 254 } 255 256 void 257 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len) 258 { 259 if (len % cc->cipher->block_size) 260 fatal("cipher_encrypt: bad plaintext length %d", len); 261 if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0) 262 fatal("evp_crypt: EVP_Cipher failed"); 263 } 264 265 void 266 cipher_cleanup(CipherContext *cc) 267 { 268 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 269 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 270 } 271 272 /* 273 * Selects the cipher, and keys if by computing the MD5 checksum of the 274 * passphrase and using the resulting 16 bytes as the key. 275 */ 276 277 void 278 cipher_set_key_string(CipherContext *cc, Cipher *cipher, 279 const char *passphrase, int do_encrypt) 280 { 281 MD5_CTX md; 282 u_char digest[16]; 283 284 MD5_Init(&md); 285 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); 286 MD5_Final(digest, &md); 287 288 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 289 290 memset(digest, 0, sizeof(digest)); 291 memset(&md, 0, sizeof(md)); 292 } 293 294 /* 295 * Exports an IV from the CipherContext required to export the key 296 * state back from the unprivileged child to the privileged parent 297 * process. 298 */ 299 300 int 301 cipher_get_keyiv_len(const CipherContext *cc) 302 { 303 Cipher *c = cc->cipher; 304 int ivlen; 305 306 if (c->number == SSH_CIPHER_3DES) 307 ivlen = 24; 308 else 309 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 310 return (ivlen); 311 } 312 313 void 314 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 315 { 316 Cipher *c = cc->cipher; 317 int evplen; 318 319 switch (c->number) { 320 case SSH_CIPHER_SSH2: 321 case SSH_CIPHER_DES: 322 case SSH_CIPHER_BLOWFISH: 323 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 324 if (evplen <= 0) 325 return; 326 if ((u_int)evplen != len) 327 fatal("%s: wrong iv length %d != %d", __func__, 328 evplen, len); 329 if (c->evptype == evp_aes_128_ctr) 330 ssh_aes_ctr_iv(&cc->evp, 0, iv, len); 331 else 332 memcpy(iv, cc->evp.iv, len); 333 break; 334 case SSH_CIPHER_3DES: 335 ssh1_3des_iv(&cc->evp, 0, iv, 24); 336 break; 337 default: 338 fatal("%s: bad cipher %d", __func__, c->number); 339 } 340 } 341 342 void 343 cipher_set_keyiv(CipherContext *cc, u_char *iv) 344 { 345 Cipher *c = cc->cipher; 346 int evplen = 0; 347 348 switch (c->number) { 349 case SSH_CIPHER_SSH2: 350 case SSH_CIPHER_DES: 351 case SSH_CIPHER_BLOWFISH: 352 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 353 if (evplen == 0) 354 return; 355 if (c->evptype == evp_aes_128_ctr) 356 ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen); 357 else 358 memcpy(cc->evp.iv, iv, evplen); 359 break; 360 case SSH_CIPHER_3DES: 361 ssh1_3des_iv(&cc->evp, 1, iv, 24); 362 break; 363 default: 364 fatal("%s: bad cipher %d", __func__, c->number); 365 } 366 } 367 368 #define EVP_X_STATE(evp) (evp).cipher_data 369 #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size 370 371 int 372 cipher_get_keycontext(const CipherContext *cc, u_char *dat) 373 { 374 Cipher *c = cc->cipher; 375 int plen = 0; 376 377 if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { 378 plen = EVP_X_STATE_LEN(cc->evp); 379 if (dat == NULL) 380 return (plen); 381 memcpy(dat, EVP_X_STATE(cc->evp), plen); 382 } 383 return (plen); 384 } 385 386 void 387 cipher_set_keycontext(CipherContext *cc, u_char *dat) 388 { 389 Cipher *c = cc->cipher; 390 int plen; 391 392 if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { 393 plen = EVP_X_STATE_LEN(cc->evp); 394 memcpy(EVP_X_STATE(cc->evp), dat, plen); 395 } 396 } 397