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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 1.31 2000/09/12 00:38:32 deraadt Exp $"); | |
39 | ||
40 | #include "ssh.h" | |
41 | #include "cipher.h" | |
42 | #include "xmalloc.h" | |
43 | ||
44 | #include <openssl/md5.h> | |
45 | ||
46 | /* | |
47 | * This is used by SSH1: | |
48 | * | |
49 | * What kind of triple DES are these 2 routines? | |
50 | * | |
51 | * Why is there a redundant initialization vector? | |
52 | * | |
53 | * If only iv3 was used, then, this would till effect have been | |
54 | * outer-cbc. However, there is also a private iv1 == iv2 which | |
55 | * perhaps makes differential analysis easier. On the other hand, the | |
56 | * private iv1 probably makes the CRC-32 attack ineffective. This is a | |
57 | * result of that there is no longer any known iv1 to use when | |
58 | * choosing the X block. | |
59 | */ | |
60 | void | |
61 | SSH_3CBC_ENCRYPT(des_key_schedule ks1, | |
62 | des_key_schedule ks2, des_cblock * iv2, | |
63 | des_key_schedule ks3, des_cblock * iv3, | |
64 | unsigned char *dest, unsigned char *src, | |
65 | unsigned int len) | |
66 | { | |
67 | des_cblock iv1; | |
68 | ||
69 | memcpy(&iv1, iv2, 8); | |
70 | ||
71 | des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT); | |
72 | memcpy(&iv1, dest + len - 8, 8); | |
73 | ||
74 | des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT); | |
75 | memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */ | |
76 | ||
77 | des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT); | |
78 | memcpy(iv3, dest + len - 8, 8); | |
79 | } | |
80 | ||
81 | void | |
82 | SSH_3CBC_DECRYPT(des_key_schedule ks1, | |
83 | des_key_schedule ks2, des_cblock * iv2, | |
84 | des_key_schedule ks3, des_cblock * iv3, | |
85 | unsigned char *dest, unsigned char *src, | |
86 | unsigned int len) | |
87 | { | |
88 | des_cblock iv1; | |
89 | ||
90 | memcpy(&iv1, iv2, 8); | |
91 | ||
92 | des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT); | |
93 | memcpy(iv3, src + len - 8, 8); | |
94 | ||
95 | des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT); | |
96 | memcpy(iv2, dest + len - 8, 8); | |
97 | ||
98 | des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT); | |
99 | /* memcpy(&iv1, iv2, 8); */ | |
100 | /* Note how iv1 == iv2 on entry and exit. */ | |
101 | } | |
102 | ||
103 | /* | |
104 | * SSH1 uses a variation on Blowfish, all bytes must be swapped before | |
105 | * and after encryption/decryption. Thus the swap_bytes stuff (yuk). | |
106 | */ | |
107 | static void | |
108 | swap_bytes(const unsigned char *src, unsigned char *dst_, int n) | |
109 | { | |
110 | /* dst must be properly aligned. */ | |
111 | u_int32_t *dst = (u_int32_t *) dst_; | |
112 | union { | |
113 | u_int32_t i; | |
114 | char c[4]; | |
115 | } t; | |
116 | ||
117 | /* Process 8 bytes every lap. */ | |
118 | for (n = n / 8; n > 0; n--) { | |
119 | t.c[3] = *src++; | |
120 | t.c[2] = *src++; | |
121 | t.c[1] = *src++; | |
122 | t.c[0] = *src++; | |
123 | *dst++ = t.i; | |
124 | ||
125 | t.c[3] = *src++; | |
126 | t.c[2] = *src++; | |
127 | t.c[1] = *src++; | |
128 | t.c[0] = *src++; | |
129 | *dst++ = t.i; | |
130 | } | |
131 | } | |
132 | ||
133 | /* | |
134 | * Names of all encryption algorithms. | |
135 | * These must match the numbers defined in cipher.h. | |
136 | */ | |
137 | static char *cipher_names[] = | |
138 | { | |
139 | "none", | |
140 | "idea", | |
141 | "des", | |
142 | "3des", | |
143 | "tss", | |
144 | "rc4", /* Alleged RC4 */ | |
145 | "blowfish", | |
146 | "reserved", | |
147 | "blowfish-cbc", | |
148 | "3des-cbc", | |
149 | "arcfour", | |
150 | "cast128-cbc" | |
151 | }; | |
152 | ||
153 | /* | |
154 | * Returns a bit mask indicating which ciphers are supported by this | |
155 | * implementation. The bit mask has the corresponding bit set of each | |
156 | * supported cipher. | |
157 | */ | |
158 | ||
159 | unsigned int | |
160 | cipher_mask1() | |
161 | { | |
162 | unsigned int mask = 0; | |
163 | mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ | |
164 | mask |= 1 << SSH_CIPHER_BLOWFISH; | |
165 | return mask; | |
166 | } | |
167 | unsigned int | |
168 | cipher_mask2() | |
169 | { | |
170 | unsigned int mask = 0; | |
171 | mask |= 1 << SSH_CIPHER_BLOWFISH_CBC; | |
172 | mask |= 1 << SSH_CIPHER_3DES_CBC; | |
173 | mask |= 1 << SSH_CIPHER_ARCFOUR; | |
174 | mask |= 1 << SSH_CIPHER_CAST128_CBC; | |
175 | return mask; | |
176 | } | |
177 | unsigned int | |
178 | cipher_mask() | |
179 | { | |
180 | return cipher_mask1() | cipher_mask2(); | |
181 | } | |
182 | ||
183 | /* Returns the name of the cipher. */ | |
184 | ||
185 | const char * | |
186 | cipher_name(int cipher) | |
187 | { | |
188 | if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) || | |
189 | cipher_names[cipher] == NULL) | |
190 | fatal("cipher_name: bad cipher name: %d", cipher); | |
191 | return cipher_names[cipher]; | |
192 | } | |
193 | ||
194 | /* Returns 1 if the name of the ciphers are valid. */ | |
195 | ||
196 | #define CIPHER_SEP "," | |
197 | int | |
198 | ciphers_valid(const char *names) | |
199 | { | |
200 | char *ciphers, *cp; | |
201 | char *p; | |
202 | int i; | |
203 | ||
204 | if (names == NULL || strcmp(names, "") == 0) | |
205 | return 0; | |
206 | ciphers = cp = xstrdup(names); | |
207 | for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; | |
208 | (p = strsep(&cp, CIPHER_SEP))) { | |
209 | i = cipher_number(p); | |
210 | if (i == -1 || !(cipher_mask2() & (1 << i))) { | |
211 | xfree(ciphers); | |
212 | return 0; | |
213 | } | |
214 | } | |
215 | xfree(ciphers); | |
216 | return 1; | |
217 | } | |
218 | ||
219 | /* | |
220 | * Parses the name of the cipher. Returns the number of the corresponding | |
221 | * cipher, or -1 on error. | |
222 | */ | |
223 | ||
224 | int | |
225 | cipher_number(const char *name) | |
226 | { | |
227 | int i; | |
228 | if (name == NULL) | |
229 | return -1; | |
230 | for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++) | |
231 | if (strcmp(cipher_names[i], name) == 0 && | |
232 | (cipher_mask() & (1 << i))) | |
233 | return i; | |
234 | return -1; | |
235 | } | |
236 | ||
237 | /* | |
238 | * Selects the cipher, and keys if by computing the MD5 checksum of the | |
239 | * passphrase and using the resulting 16 bytes as the key. | |
240 | */ | |
241 | ||
242 | void | |
243 | cipher_set_key_string(CipherContext *context, int cipher, const char *passphrase) | |
244 | { | |
245 | MD5_CTX md; | |
246 | unsigned char digest[16]; | |
247 | ||
248 | MD5_Init(&md); | |
249 | MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase)); | |
250 | MD5_Final(digest, &md); | |
251 | ||
252 | cipher_set_key(context, cipher, digest, 16); | |
253 | ||
254 | memset(digest, 0, sizeof(digest)); | |
255 | memset(&md, 0, sizeof(md)); | |
256 | } | |
257 | ||
258 | /* Selects the cipher to use and sets the key. */ | |
259 | ||
260 | void | |
261 | cipher_set_key(CipherContext *context, int cipher, const unsigned char *key, | |
262 | int keylen) | |
263 | { | |
264 | unsigned char padded[32]; | |
265 | ||
266 | /* Set cipher type. */ | |
267 | context->type = cipher; | |
268 | ||
269 | /* Get 32 bytes of key data. Pad if necessary. (So that code | |
270 | below does not need to worry about key size). */ | |
271 | memset(padded, 0, sizeof(padded)); | |
272 | memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded)); | |
273 | ||
274 | /* Initialize the initialization vector. */ | |
275 | switch (cipher) { | |
276 | case SSH_CIPHER_NONE: | |
277 | /* | |
278 | * Has to stay for authfile saving of private key with no | |
279 | * passphrase | |
280 | */ | |
281 | break; | |
282 | ||
283 | case SSH_CIPHER_3DES: | |
284 | /* | |
285 | * Note: the least significant bit of each byte of key is | |
286 | * parity, and must be ignored by the implementation. 16 | |
287 | * bytes of key are used (first and last keys are the same). | |
288 | */ | |
289 | if (keylen < 16) | |
290 | error("Key length %d is insufficient for 3DES.", keylen); | |
291 | des_set_key((void *) padded, context->u.des3.key1); | |
292 | des_set_key((void *) (padded + 8), context->u.des3.key2); | |
293 | if (keylen <= 16) | |
294 | des_set_key((void *) padded, context->u.des3.key3); | |
295 | else | |
296 | des_set_key((void *) (padded + 16), context->u.des3.key3); | |
297 | memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2)); | |
298 | memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3)); | |
299 | break; | |
300 | ||
301 | case SSH_CIPHER_BLOWFISH: | |
302 | if (keylen < 16) | |
303 | error("Key length %d is insufficient for blowfish.", keylen); | |
304 | BF_set_key(&context->u.bf.key, keylen, padded); | |
305 | memset(context->u.bf.iv, 0, 8); | |
306 | break; | |
307 | ||
308 | case SSH_CIPHER_3DES_CBC: | |
309 | case SSH_CIPHER_BLOWFISH_CBC: | |
310 | case SSH_CIPHER_ARCFOUR: | |
311 | case SSH_CIPHER_CAST128_CBC: | |
312 | fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher)); | |
313 | break; | |
314 | ||
315 | default: | |
316 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); | |
317 | } | |
318 | memset(padded, 0, sizeof(padded)); | |
319 | } | |
320 | ||
321 | void | |
322 | cipher_set_key_iv(CipherContext * context, int cipher, | |
323 | const unsigned char *key, int keylen, | |
324 | const unsigned char *iv, int ivlen) | |
325 | { | |
326 | /* Set cipher type. */ | |
327 | context->type = cipher; | |
328 | ||
329 | /* Initialize the initialization vector. */ | |
330 | switch (cipher) { | |
331 | case SSH_CIPHER_NONE: | |
332 | break; | |
333 | ||
334 | case SSH_CIPHER_3DES: | |
335 | case SSH_CIPHER_BLOWFISH: | |
336 | fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher)); | |
337 | break; | |
338 | ||
339 | case SSH_CIPHER_3DES_CBC: | |
340 | if (keylen < 24) | |
341 | error("Key length %d is insufficient for 3des-cbc.", keylen); | |
342 | des_set_key((void *) key, context->u.des3.key1); | |
343 | des_set_key((void *) (key+8), context->u.des3.key2); | |
344 | des_set_key((void *) (key+16), context->u.des3.key3); | |
345 | if (ivlen < 8) | |
346 | error("IV length %d is insufficient for 3des-cbc.", ivlen); | |
347 | memcpy(context->u.des3.iv3, (char *)iv, 8); | |
348 | break; | |
349 | ||
350 | case SSH_CIPHER_BLOWFISH_CBC: | |
351 | if (keylen < 16) | |
352 | error("Key length %d is insufficient for blowfish.", keylen); | |
353 | if (ivlen < 8) | |
354 | error("IV length %d is insufficient for blowfish.", ivlen); | |
355 | BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key); | |
356 | memcpy(context->u.bf.iv, (char *)iv, 8); | |
357 | break; | |
358 | ||
359 | case SSH_CIPHER_ARCFOUR: | |
360 | if (keylen < 16) | |
361 | error("Key length %d is insufficient for arcfour.", keylen); | |
362 | RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key); | |
363 | break; | |
364 | ||
365 | case SSH_CIPHER_CAST128_CBC: | |
366 | if (keylen < 16) | |
367 | error("Key length %d is insufficient for cast128.", keylen); | |
368 | if (ivlen < 8) | |
369 | error("IV length %d is insufficient for cast128.", ivlen); | |
370 | CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key); | |
371 | memcpy(context->u.cast.iv, (char *)iv, 8); | |
372 | break; | |
373 | ||
374 | default: | |
375 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); | |
376 | } | |
377 | } | |
378 | ||
379 | /* Encrypts data using the cipher. */ | |
380 | ||
381 | void | |
382 | cipher_encrypt(CipherContext *context, unsigned char *dest, | |
383 | const unsigned char *src, unsigned int len) | |
384 | { | |
385 | if ((len & 7) != 0) | |
386 | fatal("cipher_encrypt: bad plaintext length %d", len); | |
387 | ||
388 | switch (context->type) { | |
389 | case SSH_CIPHER_NONE: | |
390 | memcpy(dest, src, len); | |
391 | break; | |
392 | ||
393 | case SSH_CIPHER_3DES: | |
394 | SSH_3CBC_ENCRYPT(context->u.des3.key1, | |
395 | context->u.des3.key2, &context->u.des3.iv2, | |
396 | context->u.des3.key3, &context->u.des3.iv3, | |
397 | dest, (unsigned char *) src, len); | |
398 | break; | |
399 | ||
400 | case SSH_CIPHER_BLOWFISH: | |
401 | swap_bytes(src, dest, len); | |
402 | BF_cbc_encrypt(dest, dest, len, | |
403 | &context->u.bf.key, context->u.bf.iv, | |
404 | BF_ENCRYPT); | |
405 | swap_bytes(dest, dest, len); | |
406 | break; | |
407 | ||
408 | case SSH_CIPHER_BLOWFISH_CBC: | |
409 | BF_cbc_encrypt((void *)src, dest, len, | |
410 | &context->u.bf.key, context->u.bf.iv, | |
411 | BF_ENCRYPT); | |
412 | break; | |
413 | ||
414 | case SSH_CIPHER_3DES_CBC: | |
415 | des_ede3_cbc_encrypt(src, dest, len, | |
416 | context->u.des3.key1, context->u.des3.key2, | |
417 | context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT); | |
418 | break; | |
419 | ||
420 | case SSH_CIPHER_ARCFOUR: | |
421 | RC4(&context->u.rc4, len, (unsigned char *)src, dest); | |
422 | break; | |
423 | ||
424 | case SSH_CIPHER_CAST128_CBC: | |
425 | CAST_cbc_encrypt(src, dest, len, | |
426 | &context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT); | |
427 | break; | |
428 | ||
429 | default: | |
430 | fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type)); | |
431 | } | |
432 | } | |
433 | ||
434 | /* Decrypts data using the cipher. */ | |
435 | ||
436 | void | |
437 | cipher_decrypt(CipherContext *context, unsigned char *dest, | |
438 | const unsigned char *src, unsigned int len) | |
439 | { | |
440 | if ((len & 7) != 0) | |
441 | fatal("cipher_decrypt: bad ciphertext length %d", len); | |
442 | ||
443 | switch (context->type) { | |
444 | case SSH_CIPHER_NONE: | |
445 | memcpy(dest, src, len); | |
446 | break; | |
447 | ||
448 | case SSH_CIPHER_3DES: | |
449 | SSH_3CBC_DECRYPT(context->u.des3.key1, | |
450 | context->u.des3.key2, &context->u.des3.iv2, | |
451 | context->u.des3.key3, &context->u.des3.iv3, | |
452 | dest, (unsigned char *) src, len); | |
453 | break; | |
454 | ||
455 | case SSH_CIPHER_BLOWFISH: | |
456 | swap_bytes(src, dest, len); | |
457 | BF_cbc_encrypt((void *) dest, dest, len, | |
458 | &context->u.bf.key, context->u.bf.iv, | |
459 | BF_DECRYPT); | |
460 | swap_bytes(dest, dest, len); | |
461 | break; | |
462 | ||
463 | case SSH_CIPHER_BLOWFISH_CBC: | |
464 | BF_cbc_encrypt((void *) src, dest, len, | |
465 | &context->u.bf.key, context->u.bf.iv, | |
466 | BF_DECRYPT); | |
467 | break; | |
468 | ||
469 | case SSH_CIPHER_3DES_CBC: | |
470 | des_ede3_cbc_encrypt(src, dest, len, | |
471 | context->u.des3.key1, context->u.des3.key2, | |
472 | context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT); | |
473 | break; | |
474 | ||
475 | case SSH_CIPHER_ARCFOUR: | |
476 | RC4(&context->u.rc4, len, (unsigned char *)src, dest); | |
477 | break; | |
478 | ||
479 | case SSH_CIPHER_CAST128_CBC: | |
480 | CAST_cbc_encrypt(src, dest, len, | |
481 | &context->u.cast.key, context->u.cast.iv, CAST_DECRYPT); | |
482 | break; | |
483 | ||
484 | default: | |
485 | fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type)); | |
486 | } | |
487 | } |