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 "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 u_int cbc_mode;
67 const EVP_CIPHER *(*evptype)(void);
68 } ciphers[] = {
69 { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, EVP_enc_null },
70 { "des", SSH_CIPHER_DES, 8, 8, 0, 1, EVP_des_cbc },
71 { "3des", SSH_CIPHER_3DES, 8, 16, 0, 1, evp_ssh1_3des },
72 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 1, evp_ssh1_bf },
73
74 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 1, EVP_des_ede3_cbc },
75 { "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_bf_cbc },
76 #ifndef ANDROID
77 { "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, 0, 1, EVP_cast5_cbc },
78 #endif
79 { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, EVP_rc4 },
80 { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 1536, 0, EVP_rc4 },
81 { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 1536, 0, EVP_rc4 },
82 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 1, EVP_aes_128_cbc },
83 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 1, EVP_aes_192_cbc },
84 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
85 { "rijndael-cbc@lysator.liu.se",
86 SSH_CIPHER_SSH2, 16, 32, 0, 1, EVP_aes_256_cbc },
87 { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, evp_aes_128_ctr },
88 { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, evp_aes_128_ctr },
89 { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, evp_aes_128_ctr },
90 #ifdef USE_CIPHER_ACSS
91 { "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, 0, 0, EVP_acss },
92 #endif
93 { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, NULL }
94 };
95
96 /*--*/
97
98 u_int
cipher_blocksize(const Cipher * c)99 cipher_blocksize(const Cipher *c)
100 {
101 return (c->block_size);
102 }
103
104 u_int
cipher_keylen(const Cipher * c)105 cipher_keylen(const Cipher *c)
106 {
107 return (c->key_len);
108 }
109
110 u_int
cipher_get_number(const Cipher * c)111 cipher_get_number(const Cipher *c)
112 {
113 return (c->number);
114 }
115
116 u_int
cipher_is_cbc(const Cipher * c)117 cipher_is_cbc(const Cipher *c)
118 {
119 return (c->cbc_mode);
120 }
121
122 u_int
cipher_mask_ssh1(int client)123 cipher_mask_ssh1(int client)
124 {
125 u_int mask = 0;
126 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
127 mask |= 1 << SSH_CIPHER_BLOWFISH;
128 if (client) {
129 mask |= 1 << SSH_CIPHER_DES;
130 }
131 return mask;
132 }
133
134 Cipher *
cipher_by_name(const char * name)135 cipher_by_name(const char *name)
136 {
137 Cipher *c;
138 for (c = ciphers; c->name != NULL; c++)
139 if (strcmp(c->name, name) == 0)
140 return c;
141 return NULL;
142 }
143
144 Cipher *
cipher_by_number(int id)145 cipher_by_number(int id)
146 {
147 Cipher *c;
148 for (c = ciphers; c->name != NULL; c++)
149 if (c->number == id)
150 return c;
151 return NULL;
152 }
153
154 #define CIPHER_SEP ","
155 int
ciphers_valid(const char * names)156 ciphers_valid(const char *names)
157 {
158 Cipher *c;
159 char *cipher_list, *cp;
160 char *p;
161
162 if (names == NULL || strcmp(names, "") == 0)
163 return 0;
164 cipher_list = cp = xstrdup(names);
165 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
166 (p = strsep(&cp, CIPHER_SEP))) {
167 c = cipher_by_name(p);
168 if (c == NULL || c->number != SSH_CIPHER_SSH2) {
169 debug("bad cipher %s [%s]", p, names);
170 xfree(cipher_list);
171 return 0;
172 } else {
173 debug3("cipher ok: %s [%s]", p, names);
174 }
175 }
176 debug3("ciphers ok: [%s]", names);
177 xfree(cipher_list);
178 return 1;
179 }
180
181 /*
182 * Parses the name of the cipher. Returns the number of the corresponding
183 * cipher, or -1 on error.
184 */
185
186 int
cipher_number(const char * name)187 cipher_number(const char *name)
188 {
189 Cipher *c;
190 if (name == NULL)
191 return -1;
192 for (c = ciphers; c->name != NULL; c++)
193 if (strcasecmp(c->name, name) == 0)
194 return c->number;
195 return -1;
196 }
197
198 char *
cipher_name(int id)199 cipher_name(int id)
200 {
201 Cipher *c = cipher_by_number(id);
202 return (c==NULL) ? "<unknown>" : c->name;
203 }
204
205 void
cipher_init(CipherContext * cc,Cipher * cipher,const u_char * key,u_int keylen,const u_char * iv,u_int ivlen,int do_encrypt)206 cipher_init(CipherContext *cc, Cipher *cipher,
207 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
208 int do_encrypt)
209 {
210 static int dowarn = 1;
211 #ifdef SSH_OLD_EVP
212 EVP_CIPHER *type;
213 #else
214 const EVP_CIPHER *type;
215 int klen;
216 #endif
217 u_char *junk, *discard;
218
219 if (cipher->number == SSH_CIPHER_DES) {
220 if (dowarn) {
221 error("Warning: use of DES is strongly discouraged "
222 "due to cryptographic weaknesses");
223 dowarn = 0;
224 }
225 if (keylen > 8)
226 keylen = 8;
227 }
228 cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
229
230 if (keylen < cipher->key_len)
231 fatal("cipher_init: key length %d is insufficient for %s.",
232 keylen, cipher->name);
233 if (iv != NULL && ivlen < cipher->block_size)
234 fatal("cipher_init: iv length %d is insufficient for %s.",
235 ivlen, cipher->name);
236 cc->cipher = cipher;
237
238 type = (*cipher->evptype)();
239
240 EVP_CIPHER_CTX_init(&cc->evp);
241 #ifdef SSH_OLD_EVP
242 if (type->key_len > 0 && type->key_len != keylen) {
243 debug("cipher_init: set keylen (%d -> %d)",
244 type->key_len, keylen);
245 type->key_len = keylen;
246 }
247 EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv,
248 (do_encrypt == CIPHER_ENCRYPT));
249 #else
250 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
251 (do_encrypt == CIPHER_ENCRYPT)) == 0)
252 fatal("cipher_init: EVP_CipherInit failed for %s",
253 cipher->name);
254 klen = EVP_CIPHER_CTX_key_length(&cc->evp);
255 if (klen > 0 && keylen != (u_int)klen) {
256 debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
257 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
258 fatal("cipher_init: set keylen failed (%d -> %d)",
259 klen, keylen);
260 }
261 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
262 fatal("cipher_init: EVP_CipherInit: set key failed for %s",
263 cipher->name);
264 #endif
265
266 if (cipher->discard_len > 0) {
267 junk = xmalloc(cipher->discard_len);
268 discard = xmalloc(cipher->discard_len);
269 if (EVP_Cipher(&cc->evp, discard, junk,
270 cipher->discard_len) == 0)
271 fatal("evp_crypt: EVP_Cipher failed during discard");
272 memset(discard, 0, cipher->discard_len);
273 xfree(junk);
274 xfree(discard);
275 }
276 }
277
278 void
cipher_crypt(CipherContext * cc,u_char * dest,const u_char * src,u_int len)279 cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
280 {
281 if (len % cc->cipher->block_size)
282 fatal("cipher_encrypt: bad plaintext length %d", len);
283 if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
284 fatal("evp_crypt: EVP_Cipher failed");
285 }
286
287 void
cipher_cleanup(CipherContext * cc)288 cipher_cleanup(CipherContext *cc)
289 {
290 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
291 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
292 }
293
294 /*
295 * Selects the cipher, and keys if by computing the MD5 checksum of the
296 * passphrase and using the resulting 16 bytes as the key.
297 */
298
299 void
cipher_set_key_string(CipherContext * cc,Cipher * cipher,const char * passphrase,int do_encrypt)300 cipher_set_key_string(CipherContext *cc, Cipher *cipher,
301 const char *passphrase, int do_encrypt)
302 {
303 MD5_CTX md;
304 u_char digest[16];
305
306 MD5_Init(&md);
307 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
308 MD5_Final(digest, &md);
309
310 cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
311
312 memset(digest, 0, sizeof(digest));
313 memset(&md, 0, sizeof(md));
314 }
315
316 /*
317 * Exports an IV from the CipherContext required to export the key
318 * state back from the unprivileged child to the privileged parent
319 * process.
320 */
321
322 int
cipher_get_keyiv_len(const CipherContext * cc)323 cipher_get_keyiv_len(const CipherContext *cc)
324 {
325 Cipher *c = cc->cipher;
326 int ivlen;
327
328 if (c->number == SSH_CIPHER_3DES)
329 ivlen = 24;
330 else
331 ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
332 return (ivlen);
333 }
334
335 void
cipher_get_keyiv(CipherContext * cc,u_char * iv,u_int len)336 cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
337 {
338 Cipher *c = cc->cipher;
339 int evplen;
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 ((u_int)evplen != len)
349 fatal("%s: wrong iv length %d != %d", __func__,
350 evplen, len);
351 #ifdef USE_BUILTIN_RIJNDAEL
352 if (c->evptype == evp_rijndael)
353 ssh_rijndael_iv(&cc->evp, 0, iv, len);
354 else
355 #endif
356 if (c->evptype == evp_aes_128_ctr)
357 ssh_aes_ctr_iv(&cc->evp, 0, iv, len);
358 else
359 memcpy(iv, cc->evp.iv, len);
360 break;
361 case SSH_CIPHER_3DES:
362 ssh1_3des_iv(&cc->evp, 0, iv, 24);
363 break;
364 default:
365 fatal("%s: bad cipher %d", __func__, c->number);
366 }
367 }
368
369 void
cipher_set_keyiv(CipherContext * cc,u_char * iv)370 cipher_set_keyiv(CipherContext *cc, u_char *iv)
371 {
372 Cipher *c = cc->cipher;
373 int evplen = 0;
374
375 switch (c->number) {
376 case SSH_CIPHER_SSH2:
377 case SSH_CIPHER_DES:
378 case SSH_CIPHER_BLOWFISH:
379 evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
380 if (evplen == 0)
381 return;
382 #ifdef USE_BUILTIN_RIJNDAEL
383 if (c->evptype == evp_rijndael)
384 ssh_rijndael_iv(&cc->evp, 1, iv, evplen);
385 else
386 #endif
387 if (c->evptype == evp_aes_128_ctr)
388 ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen);
389 else
390 memcpy(cc->evp.iv, iv, evplen);
391 break;
392 case SSH_CIPHER_3DES:
393 ssh1_3des_iv(&cc->evp, 1, iv, 24);
394 break;
395 default:
396 fatal("%s: bad cipher %d", __func__, c->number);
397 }
398 }
399
400 #if OPENSSL_VERSION_NUMBER < 0x00907000L
401 #define EVP_X_STATE(evp) &(evp).c
402 #define EVP_X_STATE_LEN(evp) sizeof((evp).c)
403 #else
404 #define EVP_X_STATE(evp) (evp).cipher_data
405 #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size
406 #endif
407
408 int
cipher_get_keycontext(const CipherContext * cc,u_char * dat)409 cipher_get_keycontext(const CipherContext *cc, u_char *dat)
410 {
411 Cipher *c = cc->cipher;
412 int plen = 0;
413
414 if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
415 plen = EVP_X_STATE_LEN(cc->evp);
416 if (dat == NULL)
417 return (plen);
418 memcpy(dat, EVP_X_STATE(cc->evp), plen);
419 }
420 return (plen);
421 }
422
423 void
cipher_set_keycontext(CipherContext * cc,u_char * dat)424 cipher_set_keycontext(CipherContext *cc, u_char *dat)
425 {
426 Cipher *c = cc->cipher;
427 int plen;
428
429 if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) {
430 plen = EVP_X_STATE_LEN(cc->evp);
431 memcpy(EVP_X_STATE(cc->evp), dat, plen);
432 }
433 }
434