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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 const EVP_CIPHER *evp_aes_ctr_mt(void); | |
59 | extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); | |
60 | ||
61 | struct Cipher { | |
62 | char *name; | |
63 | int number; /* for ssh1 only */ | |
64 | u_int block_size; | |
65 | u_int key_len; | |
66 | u_int discard_len; | |
67 | const EVP_CIPHER *(*evptype)(void); | |
68 | } ciphers[] = { | |
69 | { "none", SSH_CIPHER_NONE, 8, 0, 0, EVP_enc_null }, | |
70 | { "des", SSH_CIPHER_DES, 8, 8, 0, EVP_des_cbc }, | |
71 | { "3des", SSH_CIPHER_3DES, 8, 16, 0, evp_ssh1_3des }, | |
72 | { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, evp_ssh1_bf }, | |
73 | ||
74 | { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, EVP_des_ede3_cbc }, | |
75 | { "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, 0, EVP_bf_cbc }, | |
76 | { "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, 0, EVP_cast5_cbc }, | |
77 | { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, EVP_rc4 }, | |
78 | { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 1536, EVP_rc4 }, | |
79 | { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 1536, EVP_rc4 }, | |
80 | { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, EVP_aes_128_cbc }, | |
81 | { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, EVP_aes_192_cbc }, | |
82 | { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc }, | |
83 | { "rijndael-cbc@lysator.liu.se", | |
84 | SSH_CIPHER_SSH2, 16, 32, 0, EVP_aes_256_cbc }, | |
85 | { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, evp_aes_ctr_mt }, | |
86 | { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, evp_aes_ctr_mt }, | |
87 | { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, evp_aes_ctr_mt }, | |
88 | #ifdef USE_CIPHER_ACSS | |
89 | { "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, 0, EVP_acss }, | |
90 | #endif | |
91 | { NULL, SSH_CIPHER_INVALID, 0, 0, 0, NULL } | |
92 | }; | |
93 | ||
94 | /*--*/ | |
95 | ||
96 | u_int | |
97 | cipher_blocksize(const Cipher *c) | |
98 | { | |
99 | return (c->block_size); | |
100 | } | |
101 | ||
102 | u_int | |
103 | cipher_keylen(const Cipher *c) | |
104 | { | |
105 | return (c->key_len); | |
106 | } | |
107 | ||
108 | u_int | |
109 | cipher_get_number(const Cipher *c) | |
110 | { | |
111 | return (c->number); | |
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 | c->number != SSH_CIPHER_NONE)) { | |
162 | debug("bad cipher %s [%s]", p, names); | |
163 | xfree(cipher_list); | |
164 | return 0; | |
165 | } else { | |
166 | debug3("cipher ok: %s [%s]", p, names); | |
167 | } | |
168 | } | |
169 | debug3("ciphers ok: [%s]", names); | |
170 | xfree(cipher_list); | |
171 | return 1; | |
172 | } | |
173 | ||
174 | /* | |
175 | * Parses the name of the cipher. Returns the number of the corresponding | |
176 | * cipher, or -1 on error. | |
177 | */ | |
178 | ||
179 | int | |
180 | cipher_number(const char *name) | |
181 | { | |
182 | Cipher *c; | |
183 | if (name == NULL) | |
184 | return -1; | |
185 | for (c = ciphers; c->name != NULL; c++) | |
186 | if (strcasecmp(c->name, name) == 0) | |
187 | return c->number; | |
188 | return -1; | |
189 | } | |
190 | ||
191 | char * | |
192 | cipher_name(int id) | |
193 | { | |
194 | Cipher *c = cipher_by_number(id); | |
195 | return (c==NULL) ? "<unknown>" : c->name; | |
196 | } | |
197 | ||
198 | void | |
199 | cipher_init(CipherContext *cc, Cipher *cipher, | |
200 | const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, | |
201 | int do_encrypt) | |
202 | { | |
203 | static int dowarn = 1; | |
204 | #ifdef SSH_OLD_EVP | |
205 | EVP_CIPHER *type; | |
206 | #else | |
207 | const EVP_CIPHER *type; | |
208 | int klen; | |
209 | #endif | |
210 | u_char *junk, *discard; | |
211 | ||
212 | if (cipher->number == SSH_CIPHER_DES) { | |
213 | if (dowarn) { | |
214 | error("Warning: use of DES is strongly discouraged " | |
215 | "due to cryptographic weaknesses"); | |
216 | dowarn = 0; | |
217 | } | |
218 | if (keylen > 8) | |
219 | keylen = 8; | |
220 | } | |
221 | cc->plaintext = (cipher->number == SSH_CIPHER_NONE); | |
222 | ||
223 | if (keylen < cipher->key_len) | |
224 | fatal("cipher_init: key length %d is insufficient for %s.", | |
225 | keylen, cipher->name); | |
226 | if (iv != NULL && ivlen < cipher->block_size) | |
227 | fatal("cipher_init: iv length %d is insufficient for %s.", | |
228 | ivlen, cipher->name); | |
229 | cc->cipher = cipher; | |
230 | ||
231 | type = (*cipher->evptype)(); | |
232 | ||
233 | EVP_CIPHER_CTX_init(&cc->evp); | |
234 | #ifdef SSH_OLD_EVP | |
235 | if (type->key_len > 0 && type->key_len != keylen) { | |
236 | debug("cipher_init: set keylen (%d -> %d)", | |
237 | type->key_len, keylen); | |
238 | type->key_len = keylen; | |
239 | } | |
240 | EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv, | |
241 | (do_encrypt == CIPHER_ENCRYPT)); | |
242 | #else | |
243 | if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, | |
244 | (do_encrypt == CIPHER_ENCRYPT)) == 0) | |
245 | fatal("cipher_init: EVP_CipherInit failed for %s", | |
246 | cipher->name); | |
247 | klen = EVP_CIPHER_CTX_key_length(&cc->evp); | |
248 | if (klen > 0 && keylen != (u_int)klen) { | |
249 | debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); | |
250 | if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) | |
251 | fatal("cipher_init: set keylen failed (%d -> %d)", | |
252 | klen, keylen); | |
253 | } | |
254 | if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) | |
255 | fatal("cipher_init: EVP_CipherInit: set key failed for %s", | |
256 | cipher->name); | |
257 | #endif | |
258 | ||
259 | if (cipher->discard_len > 0) { | |
260 | junk = xmalloc(cipher->discard_len); | |
261 | discard = xmalloc(cipher->discard_len); | |
262 | if (EVP_Cipher(&cc->evp, discard, junk, | |
263 | cipher->discard_len) == 0) | |
264 | fatal("evp_crypt: EVP_Cipher failed during discard"); | |
265 | memset(discard, 0, cipher->discard_len); | |
266 | xfree(junk); | |
267 | xfree(discard); | |
268 | } | |
269 | } | |
270 | ||
271 | void | |
272 | cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len) | |
273 | { | |
274 | if (len % cc->cipher->block_size) | |
275 | fatal("cipher_encrypt: bad plaintext length %d", len); | |
276 | if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0) | |
277 | fatal("evp_crypt: EVP_Cipher failed"); | |
278 | } | |
279 | ||
280 | void | |
281 | cipher_cleanup(CipherContext *cc) | |
282 | { | |
283 | if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) | |
284 | error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); | |
285 | } | |
286 | ||
287 | /* | |
288 | * Selects the cipher, and keys if by computing the MD5 checksum of the | |
289 | * passphrase and using the resulting 16 bytes as the key. | |
290 | */ | |
291 | ||
292 | void | |
293 | cipher_set_key_string(CipherContext *cc, Cipher *cipher, | |
294 | const char *passphrase, int do_encrypt) | |
295 | { | |
296 | MD5_CTX md; | |
297 | u_char digest[16]; | |
298 | ||
299 | MD5_Init(&md); | |
300 | MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); | |
301 | MD5_Final(digest, &md); | |
302 | ||
303 | cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); | |
304 | ||
305 | memset(digest, 0, sizeof(digest)); | |
306 | memset(&md, 0, sizeof(md)); | |
307 | } | |
308 | ||
309 | /* | |
310 | * Exports an IV from the CipherContext required to export the key | |
311 | * state back from the unprivileged child to the privileged parent | |
312 | * process. | |
313 | */ | |
314 | ||
315 | int | |
316 | cipher_get_keyiv_len(const CipherContext *cc) | |
317 | { | |
318 | Cipher *c = cc->cipher; | |
319 | int ivlen; | |
320 | ||
321 | if (c->number == SSH_CIPHER_3DES) | |
322 | ivlen = 24; | |
323 | else | |
324 | ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); | |
325 | return (ivlen); | |
326 | } | |
327 | ||
328 | void | |
329 | cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) | |
330 | { | |
331 | Cipher *c = cc->cipher; | |
332 | int evplen; | |
333 | ||
334 | switch (c->number) { | |
335 | case SSH_CIPHER_NONE: | |
336 | case SSH_CIPHER_SSH2: | |
337 | case SSH_CIPHER_DES: | |
338 | case SSH_CIPHER_BLOWFISH: | |
339 | evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); | |
340 | if (evplen <= 0) | |
341 | return; | |
342 | if ((u_int)evplen != len) | |
343 | fatal("%s: wrong iv length %d != %d", __func__, | |
344 | evplen, len); | |
345 | #ifdef USE_BUILTIN_RIJNDAEL | |
346 | if (c->evptype == evp_rijndael) | |
347 | ssh_rijndael_iv(&cc->evp, 0, iv, len); | |
348 | else | |
349 | #endif | |
350 | if (c->evptype == evp_aes_128_ctr) | |
351 | ssh_aes_ctr_iv(&cc->evp, 0, iv, len); | |
352 | else | |
353 | memcpy(iv, cc->evp.iv, len); | |
354 | break; | |
355 | case SSH_CIPHER_3DES: | |
356 | ssh1_3des_iv(&cc->evp, 0, iv, 24); | |
357 | break; | |
358 | default: | |
359 | fatal("%s: bad cipher %d", __func__, c->number); | |
360 | } | |
361 | } | |
362 | ||
363 | void | |
364 | cipher_set_keyiv(CipherContext *cc, u_char *iv) | |
365 | { | |
366 | Cipher *c = cc->cipher; | |
367 | int evplen = 0; | |
368 | ||
369 | switch (c->number) { | |
370 | case SSH_CIPHER_NONE: | |
371 | case SSH_CIPHER_SSH2: | |
372 | case SSH_CIPHER_DES: | |
373 | case SSH_CIPHER_BLOWFISH: | |
374 | evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); | |
375 | if (evplen == 0) | |
376 | return; | |
377 | #ifdef USE_BUILTIN_RIJNDAEL | |
378 | if (c->evptype == evp_rijndael) | |
379 | ssh_rijndael_iv(&cc->evp, 1, iv, evplen); | |
380 | else | |
381 | #endif | |
382 | if (c->evptype == evp_aes_128_ctr) | |
383 | ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen); | |
384 | else | |
385 | memcpy(cc->evp.iv, iv, evplen); | |
386 | break; | |
387 | case SSH_CIPHER_3DES: | |
388 | ssh1_3des_iv(&cc->evp, 1, iv, 24); | |
389 | break; | |
390 | default: | |
391 | fatal("%s: bad cipher %d", __func__, c->number); | |
392 | } | |
393 | } | |
394 | ||
395 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
396 | #define EVP_X_STATE(evp) &(evp).c | |
397 | #define EVP_X_STATE_LEN(evp) sizeof((evp).c) | |
398 | #else | |
399 | #define EVP_X_STATE(evp) (evp).cipher_data | |
400 | #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size | |
401 | #endif | |
402 | ||
403 | int | |
404 | cipher_get_keycontext(const CipherContext *cc, u_char *dat) | |
405 | { | |
406 | Cipher *c = cc->cipher; | |
407 | int plen = 0; | |
408 | ||
409 | if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { | |
410 | plen = EVP_X_STATE_LEN(cc->evp); | |
411 | if (dat == NULL) | |
412 | return (plen); | |
413 | memcpy(dat, EVP_X_STATE(cc->evp), plen); | |
414 | } | |
415 | return (plen); | |
416 | } | |
417 | ||
418 | void | |
419 | cipher_set_keycontext(CipherContext *cc, u_char *dat) | |
420 | { | |
421 | Cipher *c = cc->cipher; | |
422 | int plen; | |
423 | ||
424 | if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { | |
425 | plen = EVP_X_STATE_LEN(cc->evp); | |
426 | memcpy(EVP_X_STATE(cc->evp), dat, plen); | |
427 | } | |
428 | } |