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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" | |
38 | RCSID("$OpenBSD: cipher.c,v 1.69 2004/06/21 17:36:31 avsm Exp $"); | |
39 | ||
40 | #include "xmalloc.h" | |
41 | #include "log.h" | |
42 | #include "cipher.h" | |
43 | ||
44 | #include <openssl/md5.h> | |
45 | ||
46 | #if OPENSSL_VERSION_NUMBER < 0x00906000L | |
47 | #define SSH_OLD_EVP | |
48 | #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data) | |
49 | #endif | |
50 | ||
51 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
52 | extern const EVP_CIPHER *evp_rijndael(void); | |
53 | extern void ssh_rijndael_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); | |
54 | #endif | |
55 | ||
56 | #if !defined(EVP_CTRL_SET_ACSS_MODE) | |
57 | # if (OPENSSL_VERSION_NUMBER >= 0x00907000L) | |
58 | extern const EVP_CIPHER *evp_acss(void); | |
59 | # define EVP_acss evp_acss | |
60 | # define EVP_CTRL_SET_ACSS_MODE xxx /* used below */ | |
61 | # else | |
62 | # define EVP_acss NULL /* Don't try to support ACSS on older OpenSSL */ | |
63 | # endif /* (OPENSSL_VERSION_NUMBER >= 0x00906000L) */ | |
64 | #endif /* !defined(EVP_CTRL_SET_ACSS_MODE) */ | |
65 | ||
66 | extern const EVP_CIPHER *evp_ssh1_bf(void); | |
67 | extern const EVP_CIPHER *evp_ssh1_3des(void); | |
68 | extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int); | |
69 | extern const EVP_CIPHER *evp_aes_128_ctr(void); | |
70 | extern void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); | |
71 | ||
72 | struct Cipher { | |
73 | char *name; | |
74 | int number; /* for ssh1 only */ | |
75 | u_int block_size; | |
76 | u_int key_len; | |
77 | const EVP_CIPHER *(*evptype)(void); | |
78 | } ciphers[] = { | |
79 | { "none", SSH_CIPHER_NONE, 8, 0, EVP_enc_null }, | |
80 | { "des", SSH_CIPHER_DES, 8, 8, EVP_des_cbc }, | |
81 | { "3des", SSH_CIPHER_3DES, 8, 16, evp_ssh1_3des }, | |
82 | { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, evp_ssh1_bf }, | |
83 | ||
84 | { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, EVP_des_ede3_cbc }, | |
85 | { "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, EVP_bf_cbc }, | |
86 | { "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, EVP_cast5_cbc }, | |
87 | { "arcfour", SSH_CIPHER_SSH2, 8, 16, EVP_rc4 }, | |
88 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
89 | { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, evp_rijndael }, | |
90 | { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, evp_rijndael }, | |
91 | { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, evp_rijndael }, | |
92 | { "rijndael-cbc@lysator.liu.se", | |
93 | SSH_CIPHER_SSH2, 16, 32, evp_rijndael }, | |
94 | #else | |
95 | { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, EVP_aes_128_cbc }, | |
96 | { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, EVP_aes_192_cbc }, | |
97 | { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc }, | |
98 | { "rijndael-cbc@lysator.liu.se", | |
99 | SSH_CIPHER_SSH2, 16, 32, EVP_aes_256_cbc }, | |
100 | #endif | |
101 | #if OPENSSL_VERSION_NUMBER >= 0x00905000L | |
102 | { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, evp_aes_128_ctr }, | |
103 | { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, evp_aes_128_ctr }, | |
104 | { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, evp_aes_128_ctr }, | |
105 | #endif | |
106 | #if defined(EVP_CTRL_SET_ACSS_MODE) | |
107 | { "acss@openssh.org", SSH_CIPHER_SSH2, 16, 5, EVP_acss }, | |
108 | #endif | |
109 | { NULL, SSH_CIPHER_ILLEGAL, 0, 0, NULL } | |
110 | }; | |
111 | ||
112 | /*--*/ | |
113 | ||
114 | u_int | |
115 | cipher_blocksize(const Cipher *c) | |
116 | { | |
117 | return (c->block_size); | |
118 | } | |
119 | ||
120 | u_int | |
121 | cipher_keylen(const Cipher *c) | |
122 | { | |
123 | return (c->key_len); | |
124 | } | |
125 | ||
126 | u_int | |
127 | cipher_get_number(const Cipher *c) | |
128 | { | |
129 | return (c->number); | |
130 | } | |
131 | ||
132 | u_int | |
133 | cipher_mask_ssh1(int client) | |
134 | { | |
135 | u_int mask = 0; | |
136 | mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ | |
137 | mask |= 1 << SSH_CIPHER_BLOWFISH; | |
138 | if (client) { | |
139 | mask |= 1 << SSH_CIPHER_DES; | |
140 | } | |
141 | return mask; | |
142 | } | |
143 | ||
144 | Cipher * | |
145 | cipher_by_name(const char *name) | |
146 | { | |
147 | Cipher *c; | |
148 | for (c = ciphers; c->name != NULL; c++) | |
149 | if (strcasecmp(c->name, name) == 0) | |
150 | return c; | |
151 | return NULL; | |
152 | } | |
153 | ||
154 | Cipher * | |
155 | cipher_by_number(int id) | |
156 | { | |
157 | Cipher *c; | |
158 | for (c = ciphers; c->name != NULL; c++) | |
159 | if (c->number == id) | |
160 | return c; | |
161 | return NULL; | |
162 | } | |
163 | ||
164 | #define CIPHER_SEP "," | |
165 | int | |
166 | ciphers_valid(const char *names) | |
167 | { | |
168 | Cipher *c; | |
169 | char *cipher_list, *cp; | |
170 | char *p; | |
171 | ||
172 | if (names == NULL || strcmp(names, "") == 0) | |
173 | return 0; | |
174 | cipher_list = cp = xstrdup(names); | |
175 | for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; | |
176 | (p = strsep(&cp, CIPHER_SEP))) { | |
177 | c = cipher_by_name(p); | |
178 | if (c == NULL || c->number != SSH_CIPHER_SSH2) { | |
179 | debug("bad cipher %s [%s]", p, names); | |
180 | xfree(cipher_list); | |
181 | return 0; | |
182 | } else { | |
183 | debug3("cipher ok: %s [%s]", p, names); | |
184 | } | |
185 | } | |
186 | debug3("ciphers ok: [%s]", names); | |
187 | xfree(cipher_list); | |
188 | return 1; | |
189 | } | |
190 | ||
191 | /* | |
192 | * Parses the name of the cipher. Returns the number of the corresponding | |
193 | * cipher, or -1 on error. | |
194 | */ | |
195 | ||
196 | int | |
197 | cipher_number(const char *name) | |
198 | { | |
199 | Cipher *c; | |
200 | if (name == NULL) | |
201 | return -1; | |
202 | c = cipher_by_name(name); | |
203 | return (c==NULL) ? -1 : c->number; | |
204 | } | |
205 | ||
206 | char * | |
207 | cipher_name(int id) | |
208 | { | |
209 | Cipher *c = cipher_by_number(id); | |
210 | return (c==NULL) ? "<unknown>" : c->name; | |
211 | } | |
212 | ||
213 | void | |
214 | cipher_init(CipherContext *cc, Cipher *cipher, | |
215 | const u_char *key, u_int keylen, const u_char *iv, u_int ivlen, | |
216 | int do_encrypt) | |
217 | { | |
218 | static int dowarn = 1; | |
219 | #ifdef SSH_OLD_EVP | |
220 | EVP_CIPHER *type; | |
221 | #else | |
222 | const EVP_CIPHER *type; | |
223 | #endif | |
224 | int klen; | |
225 | ||
226 | if (cipher->number == SSH_CIPHER_DES) { | |
227 | if (dowarn) { | |
228 | error("Warning: use of DES is strongly discouraged " | |
229 | "due to cryptographic weaknesses"); | |
230 | dowarn = 0; | |
231 | } | |
232 | if (keylen > 8) | |
233 | keylen = 8; | |
234 | } | |
235 | cc->plaintext = (cipher->number == SSH_CIPHER_NONE); | |
236 | ||
237 | if (keylen < cipher->key_len) | |
238 | fatal("cipher_init: key length %d is insufficient for %s.", | |
239 | keylen, cipher->name); | |
240 | if (iv != NULL && ivlen < cipher->block_size) | |
241 | fatal("cipher_init: iv length %d is insufficient for %s.", | |
242 | ivlen, cipher->name); | |
243 | cc->cipher = cipher; | |
244 | ||
245 | type = (*cipher->evptype)(); | |
246 | ||
247 | EVP_CIPHER_CTX_init(&cc->evp); | |
248 | #ifdef SSH_OLD_EVP | |
249 | if (type->key_len > 0 && type->key_len != keylen) { | |
250 | debug("cipher_init: set keylen (%d -> %d)", | |
251 | type->key_len, keylen); | |
252 | type->key_len = keylen; | |
253 | } | |
254 | EVP_CipherInit(&cc->evp, type, (u_char *)key, (u_char *)iv, | |
255 | (encrypt == CIPHER_ENCRYPT)); | |
256 | #else | |
257 | if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv, | |
258 | (do_encrypt == CIPHER_ENCRYPT)) == 0) | |
259 | fatal("cipher_init: EVP_CipherInit failed for %s", | |
260 | cipher->name); | |
261 | klen = EVP_CIPHER_CTX_key_length(&cc->evp); | |
262 | if (klen > 0 && keylen != klen) { | |
263 | debug2("cipher_init: set keylen (%d -> %d)", klen, keylen); | |
264 | if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0) | |
265 | fatal("cipher_init: set keylen failed (%d -> %d)", | |
266 | klen, keylen); | |
267 | } | |
268 | if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0) | |
269 | fatal("cipher_init: EVP_CipherInit: set key failed for %s", | |
270 | cipher->name); | |
271 | #endif | |
272 | } | |
273 | ||
274 | void | |
275 | cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len) | |
276 | { | |
277 | if (len % cc->cipher->block_size) | |
278 | fatal("cipher_encrypt: bad plaintext length %d", len); | |
279 | #ifdef SSH_OLD_EVP | |
280 | EVP_Cipher(&cc->evp, dest, (u_char *)src, len); | |
281 | #else | |
282 | if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0) | |
283 | fatal("evp_crypt: EVP_Cipher failed"); | |
284 | #endif | |
285 | } | |
286 | ||
287 | void | |
288 | cipher_cleanup(CipherContext *cc) | |
289 | { | |
290 | #ifdef SSH_OLD_EVP | |
291 | EVP_CIPHER_CTX_cleanup(&cc->evp); | |
292 | #else | |
293 | if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0) | |
294 | error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed"); | |
295 | #endif | |
296 | } | |
297 | ||
298 | /* | |
299 | * Selects the cipher, and keys if by computing the MD5 checksum of the | |
300 | * passphrase and using the resulting 16 bytes as the key. | |
301 | */ | |
302 | ||
303 | void | |
304 | cipher_set_key_string(CipherContext *cc, Cipher *cipher, | |
305 | const char *passphrase, int do_encrypt) | |
306 | { | |
307 | MD5_CTX md; | |
308 | u_char digest[16]; | |
309 | ||
310 | MD5_Init(&md); | |
311 | MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase)); | |
312 | MD5_Final(digest, &md); | |
313 | ||
314 | cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt); | |
315 | ||
316 | memset(digest, 0, sizeof(digest)); | |
317 | memset(&md, 0, sizeof(md)); | |
318 | } | |
319 | ||
320 | /* | |
321 | * Exports an IV from the CipherContext required to export the key | |
322 | * state back from the unprivileged child to the privileged parent | |
323 | * process. | |
324 | */ | |
325 | ||
326 | int | |
327 | cipher_get_keyiv_len(const CipherContext *cc) | |
328 | { | |
329 | Cipher *c = cc->cipher; | |
330 | int ivlen; | |
331 | ||
332 | if (c->number == SSH_CIPHER_3DES) | |
333 | ivlen = 24; | |
334 | else | |
335 | ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp); | |
336 | return (ivlen); | |
337 | } | |
338 | ||
339 | void | |
340 | cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len) | |
341 | { | |
342 | Cipher *c = cc->cipher; | |
343 | int evplen; | |
344 | ||
345 | switch (c->number) { | |
346 | case SSH_CIPHER_SSH2: | |
347 | case SSH_CIPHER_DES: | |
348 | case SSH_CIPHER_BLOWFISH: | |
349 | evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); | |
350 | if (evplen == 0) | |
351 | return; | |
352 | if (evplen != len) | |
353 | fatal("%s: wrong iv length %d != %d", __func__, | |
354 | evplen, len); | |
355 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
356 | if (c->evptype == evp_rijndael) | |
357 | ssh_rijndael_iv(&cc->evp, 0, iv, len); | |
358 | else | |
359 | #endif | |
360 | if (c->evptype == evp_aes_128_ctr) | |
361 | ssh_aes_ctr_iv(&cc->evp, 0, iv, len); | |
362 | else | |
363 | memcpy(iv, cc->evp.iv, len); | |
364 | break; | |
365 | case SSH_CIPHER_3DES: | |
366 | ssh1_3des_iv(&cc->evp, 0, iv, 24); | |
367 | break; | |
368 | default: | |
369 | fatal("%s: bad cipher %d", __func__, c->number); | |
370 | } | |
371 | } | |
372 | ||
373 | void | |
374 | cipher_set_keyiv(CipherContext *cc, u_char *iv) | |
375 | { | |
376 | Cipher *c = cc->cipher; | |
377 | int evplen = 0; | |
378 | ||
379 | switch (c->number) { | |
380 | case SSH_CIPHER_SSH2: | |
381 | case SSH_CIPHER_DES: | |
382 | case SSH_CIPHER_BLOWFISH: | |
383 | evplen = EVP_CIPHER_CTX_iv_length(&cc->evp); | |
384 | if (evplen == 0) | |
385 | return; | |
386 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
387 | if (c->evptype == evp_rijndael) | |
388 | ssh_rijndael_iv(&cc->evp, 1, iv, evplen); | |
389 | else | |
390 | #endif | |
391 | if (c->evptype == evp_aes_128_ctr) | |
392 | ssh_aes_ctr_iv(&cc->evp, 1, iv, evplen); | |
393 | else | |
394 | memcpy(cc->evp.iv, iv, evplen); | |
395 | break; | |
396 | case SSH_CIPHER_3DES: | |
397 | ssh1_3des_iv(&cc->evp, 1, iv, 24); | |
398 | break; | |
399 | default: | |
400 | fatal("%s: bad cipher %d", __func__, c->number); | |
401 | } | |
402 | } | |
403 | ||
404 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
405 | #define EVP_X_STATE(evp) &(evp).c | |
406 | #define EVP_X_STATE_LEN(evp) sizeof((evp).c) | |
407 | #else | |
408 | #define EVP_X_STATE(evp) (evp).cipher_data | |
409 | #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size | |
410 | #endif | |
411 | ||
412 | int | |
413 | cipher_get_keycontext(const CipherContext *cc, u_char *dat) | |
414 | { | |
415 | Cipher *c = cc->cipher; | |
416 | int plen = 0; | |
417 | ||
418 | if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { | |
419 | plen = EVP_X_STATE_LEN(cc->evp); | |
420 | if (dat == NULL) | |
421 | return (plen); | |
422 | memcpy(dat, EVP_X_STATE(cc->evp), plen); | |
423 | } | |
424 | return (plen); | |
425 | } | |
426 | ||
427 | void | |
428 | cipher_set_keycontext(CipherContext *cc, u_char *dat) | |
429 | { | |
430 | Cipher *c = cc->cipher; | |
431 | int plen; | |
432 | ||
433 | if (c->evptype == EVP_rc4 || c->evptype == EVP_acss) { | |
434 | plen = EVP_X_STATE_LEN(cc->evp); | |
435 | memcpy(EVP_X_STATE(cc->evp), dat, plen); | |
436 | } | |
437 | } |