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