1/* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * 6 * As far as I am concerned, the code I have written for this software 7 * can be used freely for any purpose. Any derived versions of this 8 * software must be clearly marked as such, and if the derived work is 9 * incompatible with the protocol description in the RFC file, it must be 10 * called by a name other than "ssh" or "Secure Shell". 11 * 12 * 13 * Copyright (c) 1999 Niels Provos. All rights reserved. 14 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35 */ 36 37#include "includes.h" 38RCSID("$OpenBSD: cipher.c,v 1.77 2005/07/16 01:35:24 djm Exp $"); 39 40#include "xmalloc.h" 41#include "log.h" 42#include "cipher.h" 43 44#include <openssl/md5.h> 45 46/* compatibility with old or broken OpenSSL versions */ 47#include "openbsd-compat/openssl-compat.h" 48 49extern const EVP_CIPHER *evp_ssh1_bf(void); 50extern const EVP_CIPHER *evp_ssh1_3des(void); 51extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); 52extern const EVP_CIPHER *evp_aes_128_ctr(void); 53extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); 54 55struct 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#ifdef USE_CIPHER_ACSS 83 { "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss }, 84#endif 85 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, NULL } 86}; 87 88/*--*/ 89 90u_int 91cipher_blocksize(const Cipher *c) 92{ 93 return (c->block_size); 94} 95 96u_int 97cipher_keylen(const Cipher *c) 98{ 99 return (c->key_len); 100} 101 102u_int 103cipher_get_number(const Cipher *c) 104{ 105 return (c->number); 106} 107 108u_int 109cipher_mask_ssh1(int client) 110{ 111 u_int mask = 0; 112 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ 113 mask |= 1 << SSH_CIPHER_BLOWFISH; 114 if (client) { 115 mask |= 1 << SSH_CIPHER_DES; 116 } 117 return mask; 118} 119 120Cipher * 121cipher_by_name(const char *name) 122{ 123 Cipher *c; 124 for (c = ciphers; c->name != NULL; c++) 125 if (strcmp(c->name, name) == 0) 126 return c; 127 return NULL; 128} 129 130Cipher * 131cipher_by_number(int id) 132{ 133 Cipher *c; 134 for (c = ciphers; c->name != NULL; c++) 135 if (c->number == id) 136 return c; 137 return NULL; 138} 139 140#define CIPHER_SEP "," 141int 142ciphers_valid(const char *names) 143{ 144 Cipher *c; 145 char *cipher_list, *cp; 146 char *p; 147 148 if (names == NULL || strcmp(names, "") == 0) 149 return 0; 150 cipher_list = cp = xstrdup(names); 151 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 152 (p = strsep(&cp, CIPHER_SEP))) { 153 c = cipher_by_name(p); 154 if (c == NULL || c->number != SSH_CIPHER_SSH2) { 155 debug("bad cipher %s [%s]", p, names); 156 xfree(cipher_list); 157 return 0; 158 } else { 159 debug3("cipher ok: %s [%s]", p, names); 160 } 161 } 162 debug3("ciphers ok: [%s]", names); 163 xfree(cipher_list); 164 return 1; 165} 166 167/* 168 * Parses the name of the cipher. Returns the number of the corresponding 169 * cipher, or -1 on error. 170 */ 171 172int 173cipher_number(const char *name) 174{ 175 Cipher *c; 176 if (name == NULL) 177 return -1; 178 for (c = ciphers; c->name != NULL; c++) 179 if (strcasecmp(c->name, name) == 0) 180 return c->number; 181 return -1; 182} 183 184char * 185cipher_name(int id) 186{ 187 Cipher *c = cipher_by_number(id); 188 return (c==NULL) ? "<unknown>" : c->name; 189} 190 191void 192cipher_init(CipherContext *cc, Cipher *cipher, 193 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, 194 int do_encrypt) 195{ 196 static int dowarn = 1; 197#ifdef SSH_OLD_EVP 198 EVP_CIPHER *type; 199#else 200 const EVP_CIPHER *type; 201 int klen; 202#endif 203 u_char *junk, *discard; 204 205 if (cipher->number == SSH_CIPHER_DES) { 206 if (dowarn) { 207 error("Warning: use of DES is strongly discouraged " 208 "due to cryptographic weaknesses"); 209 dowarn = 0; 210 } 211 if (keylen > 8) 212 keylen = 8; 213 } 214 cc->plaintext = (cipher->number == SSH_CIPHER_NONE); 215 216 if (keylen < cipher->key_len) 217 fatal("cipher_init: key length %d is insufficient for %s.", 218 keylen, cipher->name); 219 if (iv != NULL && ivlen < cipher->block_size) 220 fatal("cipher_init: iv length %d is insufficient for %s.", 221 ivlen, cipher->name); 222 cc->cipher = cipher; 223 224 type = (*cipher->evptype)(); 225 226 EVP_CIPHER_CTX_init(&cc->evp); 227#ifdef SSH_OLD_EVP 228 if (type->key_len > 0 && type->key_len != keylen) { 229 debug("cipher_init: set keylen (%d -> %d)", 230 type->key_len, keylen); 231 type->key_len = keylen; 232 } 233 EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv, 234 (do_encrypt == CIPHER_ENCRYPT)); 235#else 236 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, 237 (do_encrypt == CIPHER_ENCRYPT)) == 0) 238 fatal("cipher_init: EVP_CipherInit failed for %s", 239 cipher->name); 240 klen = EVP_CIPHER_CTX_key_length(&cc->evp); 241 if (klen > 0 && keylen != (u_int)klen) { 242 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); 243 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) 244 fatal("cipher_init: set keylen failed (%d -> %d)", 245 klen, keylen); 246 } 247 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) 248 fatal("cipher_init: EVP_CipherInit: set key failed for %s", 249 cipher->name); 250#endif 251 252 if (cipher->discard_len > 0) { 253 junk = xmalloc(cipher->discard_len); 254 discard = xmalloc(cipher->discard_len); 255 if (EVP_Cipher(&cc->evp, discard, junk, 256 cipher->discard_len) == 0) 257 fatal("evp_crypt: EVP_Cipher failed during discard"); 258 memset(discard, 0, cipher->discard_len); 259 xfree(junk); 260 xfree(discard); 261 } 262} 263 264void 265cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len) 266{ 267 if (len % cc->cipher->block_size) 268 fatal("cipher_encrypt: bad plaintext length %d", len); 269 if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0) 270 fatal("evp_crypt: EVP_Cipher failed"); 271} 272 273void 274cipher_cleanup(CipherContext *cc) 275{ 276 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) 277 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); 278} 279 280/* 281 * Selects the cipher, and keys if by computing the MD5 checksum of the 282 * passphrase and using the resulting 16 bytes as the key. 283 */ 284 285void 286cipher_set_key_string(CipherContext *cc, Cipher *cipher, 287 const char *passphrase, int do_encrypt) 288{ 289 MD5_CTX md; 290 u_char digest[16]; 291 292 MD5_Init(&md); 293 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); 294 MD5_Final(digest, &md); 295 296 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); 297 298 memset(digest, 0, sizeof(digest)); 299 memset(&md, 0, sizeof(md)); 300} 301 302/* 303 * Exports an IV from the CipherContext required to export the key 304 * state back from the unprivileged child to the privileged parent 305 * process. 306 */ 307 308int 309cipher_get_keyiv_len(const CipherContext *cc) 310{ 311 Cipher *c = cc->cipher; 312 int ivlen; 313 314 if (c->number == SSH_CIPHER_3DES) 315 ivlen = 24; 316 else 317 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); 318 return (ivlen); 319} 320 321void 322cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) 323{ 324 Cipher *c = cc->cipher; 325 int evplen; 326 327 switch (c->number) { 328 case SSH_CIPHER_SSH2: 329 case SSH_CIPHER_DES: 330 case SSH_CIPHER_BLOWFISH: 331 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); 332 if (evplen <= 0) 333 return; 334 if ((u_int)evplen != len) 335 fatal("%s: wrong iv length %d != %d", __func__, 336 evplen, len);
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