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1 | /* | |
2 | * | |
3 | * cipher.c | |
4 | * | |
5 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | * | |
7 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | * All rights reserved | |
9 | * | |
10 | * Created: Wed Apr 19 17:41:39 1995 ylo | |
11 | * | |
12 | */ | |
13 | ||
14 | #include "includes.h" | |
15 | RCSID("$OpenBSD: cipher.c,v 1.29 2000/07/10 16:30:25 ho Exp $"); | |
16 | ||
17 | #include "ssh.h" | |
18 | #include "cipher.h" | |
19 | #include "xmalloc.h" | |
20 | ||
21 | #include <openssl/md5.h> | |
22 | ||
23 | /* | |
24 | * This is used by SSH1: | |
25 | * | |
26 | * What kind of triple DES are these 2 routines? | |
27 | * | |
28 | * Why is there a redundant initialization vector? | |
29 | * | |
30 | * If only iv3 was used, then, this would till effect have been | |
31 | * outer-cbc. However, there is also a private iv1 == iv2 which | |
32 | * perhaps makes differential analysis easier. On the other hand, the | |
33 | * private iv1 probably makes the CRC-32 attack ineffective. This is a | |
34 | * result of that there is no longer any known iv1 to use when | |
35 | * choosing the X block. | |
36 | */ | |
37 | void | |
38 | SSH_3CBC_ENCRYPT(des_key_schedule ks1, | |
39 | des_key_schedule ks2, des_cblock * iv2, | |
40 | des_key_schedule ks3, des_cblock * iv3, | |
41 | unsigned char *dest, unsigned char *src, | |
42 | unsigned int len) | |
43 | { | |
44 | des_cblock iv1; | |
45 | ||
46 | memcpy(&iv1, iv2, 8); | |
47 | ||
48 | des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT); | |
49 | memcpy(&iv1, dest + len - 8, 8); | |
50 | ||
51 | des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT); | |
52 | memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */ | |
53 | ||
54 | des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT); | |
55 | memcpy(iv3, dest + len - 8, 8); | |
56 | } | |
57 | ||
58 | void | |
59 | SSH_3CBC_DECRYPT(des_key_schedule ks1, | |
60 | des_key_schedule ks2, des_cblock * iv2, | |
61 | des_key_schedule ks3, des_cblock * iv3, | |
62 | unsigned char *dest, unsigned char *src, | |
63 | unsigned int len) | |
64 | { | |
65 | des_cblock iv1; | |
66 | ||
67 | memcpy(&iv1, iv2, 8); | |
68 | ||
69 | des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT); | |
70 | memcpy(iv3, src + len - 8, 8); | |
71 | ||
72 | des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT); | |
73 | memcpy(iv2, dest + len - 8, 8); | |
74 | ||
75 | des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT); | |
76 | /* memcpy(&iv1, iv2, 8); */ | |
77 | /* Note how iv1 == iv2 on entry and exit. */ | |
78 | } | |
79 | ||
80 | /* | |
81 | * SSH1 uses a variation on Blowfish, all bytes must be swapped before | |
82 | * and after encryption/decryption. Thus the swap_bytes stuff (yuk). | |
83 | */ | |
84 | static void | |
85 | swap_bytes(const unsigned char *src, unsigned char *dst_, int n) | |
86 | { | |
87 | /* dst must be properly aligned. */ | |
88 | u_int32_t *dst = (u_int32_t *) dst_; | |
89 | union { | |
90 | u_int32_t i; | |
91 | char c[4]; | |
92 | } t; | |
93 | ||
94 | /* Process 8 bytes every lap. */ | |
95 | for (n = n / 8; n > 0; n--) { | |
96 | t.c[3] = *src++; | |
97 | t.c[2] = *src++; | |
98 | t.c[1] = *src++; | |
99 | t.c[0] = *src++; | |
100 | *dst++ = t.i; | |
101 | ||
102 | t.c[3] = *src++; | |
103 | t.c[2] = *src++; | |
104 | t.c[1] = *src++; | |
105 | t.c[0] = *src++; | |
106 | *dst++ = t.i; | |
107 | } | |
108 | } | |
109 | ||
110 | /* | |
111 | * Names of all encryption algorithms. | |
112 | * These must match the numbers defined in cipher.h. | |
113 | */ | |
114 | static char *cipher_names[] = | |
115 | { | |
116 | "none", | |
117 | "idea", | |
118 | "des", | |
119 | "3des", | |
120 | "tss", | |
121 | "rc4", | |
122 | "blowfish", | |
123 | "reserved", | |
124 | "blowfish-cbc", | |
125 | "3des-cbc", | |
126 | "arcfour", | |
127 | "cast128-cbc" | |
128 | }; | |
129 | ||
130 | /* | |
131 | * Returns a bit mask indicating which ciphers are supported by this | |
132 | * implementation. The bit mask has the corresponding bit set of each | |
133 | * supported cipher. | |
134 | */ | |
135 | ||
136 | unsigned int | |
137 | cipher_mask1() | |
138 | { | |
139 | unsigned int mask = 0; | |
140 | mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ | |
141 | mask |= 1 << SSH_CIPHER_BLOWFISH; | |
142 | return mask; | |
143 | } | |
144 | unsigned int | |
145 | cipher_mask2() | |
146 | { | |
147 | unsigned int mask = 0; | |
148 | mask |= 1 << SSH_CIPHER_BLOWFISH_CBC; | |
149 | mask |= 1 << SSH_CIPHER_3DES_CBC; | |
150 | mask |= 1 << SSH_CIPHER_ARCFOUR; | |
151 | mask |= 1 << SSH_CIPHER_CAST128_CBC; | |
152 | return mask; | |
153 | } | |
154 | unsigned int | |
155 | cipher_mask() | |
156 | { | |
157 | return cipher_mask1() | cipher_mask2(); | |
158 | } | |
159 | ||
160 | /* Returns the name of the cipher. */ | |
161 | ||
162 | const char * | |
163 | cipher_name(int cipher) | |
164 | { | |
165 | if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) || | |
166 | cipher_names[cipher] == NULL) | |
167 | fatal("cipher_name: bad cipher name: %d", cipher); | |
168 | return cipher_names[cipher]; | |
169 | } | |
170 | ||
171 | /* Returns 1 if the name of the ciphers are valid. */ | |
172 | ||
173 | #define CIPHER_SEP "," | |
174 | int | |
175 | ciphers_valid(const char *names) | |
176 | { | |
177 | char *ciphers, *cp; | |
178 | char *p; | |
179 | int i; | |
180 | ||
181 | if (names == NULL || strcmp(names, "") == 0) | |
182 | return 0; | |
183 | ciphers = cp = xstrdup(names); | |
184 | for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; | |
185 | (p = strsep(&cp, CIPHER_SEP))) { | |
186 | i = cipher_number(p); | |
187 | if (i == -1 || !(cipher_mask2() & (1 << i))) { | |
188 | xfree(ciphers); | |
189 | return 0; | |
190 | } | |
191 | } | |
192 | xfree(ciphers); | |
193 | return 1; | |
194 | } | |
195 | ||
196 | /* | |
197 | * Parses the name of the cipher. Returns the number of the corresponding | |
198 | * cipher, or -1 on error. | |
199 | */ | |
200 | ||
201 | int | |
202 | cipher_number(const char *name) | |
203 | { | |
204 | int i; | |
205 | if (name == NULL) | |
206 | return -1; | |
207 | for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++) | |
208 | if (strcmp(cipher_names[i], name) == 0 && | |
209 | (cipher_mask() & (1 << i))) | |
210 | return i; | |
211 | return -1; | |
212 | } | |
213 | ||
214 | /* | |
215 | * Selects the cipher, and keys if by computing the MD5 checksum of the | |
216 | * passphrase and using the resulting 16 bytes as the key. | |
217 | */ | |
218 | ||
219 | void | |
220 | cipher_set_key_string(CipherContext *context, int cipher, const char *passphrase) | |
221 | { | |
222 | MD5_CTX md; | |
223 | unsigned char digest[16]; | |
224 | ||
225 | MD5_Init(&md); | |
226 | MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase)); | |
227 | MD5_Final(digest, &md); | |
228 | ||
229 | cipher_set_key(context, cipher, digest, 16); | |
230 | ||
231 | memset(digest, 0, sizeof(digest)); | |
232 | memset(&md, 0, sizeof(md)); | |
233 | } | |
234 | ||
235 | /* Selects the cipher to use and sets the key. */ | |
236 | ||
237 | void | |
238 | cipher_set_key(CipherContext *context, int cipher, const unsigned char *key, | |
239 | int keylen) | |
240 | { | |
241 | unsigned char padded[32]; | |
242 | ||
243 | /* Set cipher type. */ | |
244 | context->type = cipher; | |
245 | ||
246 | /* Get 32 bytes of key data. Pad if necessary. (So that code | |
247 | below does not need to worry about key size). */ | |
248 | memset(padded, 0, sizeof(padded)); | |
249 | memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded)); | |
250 | ||
251 | /* Initialize the initialization vector. */ | |
252 | switch (cipher) { | |
253 | case SSH_CIPHER_NONE: | |
254 | /* | |
255 | * Has to stay for authfile saving of private key with no | |
256 | * passphrase | |
257 | */ | |
258 | break; | |
259 | ||
260 | case SSH_CIPHER_3DES: | |
261 | /* | |
262 | * Note: the least significant bit of each byte of key is | |
263 | * parity, and must be ignored by the implementation. 16 | |
264 | * bytes of key are used (first and last keys are the same). | |
265 | */ | |
266 | if (keylen < 16) | |
267 | error("Key length %d is insufficient for 3DES.", keylen); | |
268 | des_set_key((void *) padded, context->u.des3.key1); | |
269 | des_set_key((void *) (padded + 8), context->u.des3.key2); | |
270 | if (keylen <= 16) | |
271 | des_set_key((void *) padded, context->u.des3.key3); | |
272 | else | |
273 | des_set_key((void *) (padded + 16), context->u.des3.key3); | |
274 | memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2)); | |
275 | memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3)); | |
276 | break; | |
277 | ||
278 | case SSH_CIPHER_BLOWFISH: | |
279 | if (keylen < 16) | |
280 | error("Key length %d is insufficient for blowfish.", keylen); | |
281 | BF_set_key(&context->u.bf.key, keylen, padded); | |
282 | memset(context->u.bf.iv, 0, 8); | |
283 | break; | |
284 | ||
285 | case SSH_CIPHER_3DES_CBC: | |
286 | case SSH_CIPHER_BLOWFISH_CBC: | |
287 | case SSH_CIPHER_ARCFOUR: | |
288 | case SSH_CIPHER_CAST128_CBC: | |
289 | fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher)); | |
290 | break; | |
291 | ||
292 | default: | |
293 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); | |
294 | } | |
295 | memset(padded, 0, sizeof(padded)); | |
296 | } | |
297 | ||
298 | void | |
299 | cipher_set_key_iv(CipherContext * context, int cipher, | |
300 | const unsigned char *key, int keylen, | |
301 | const unsigned char *iv, int ivlen) | |
302 | { | |
303 | /* Set cipher type. */ | |
304 | context->type = cipher; | |
305 | ||
306 | /* Initialize the initialization vector. */ | |
307 | switch (cipher) { | |
308 | case SSH_CIPHER_NONE: | |
309 | break; | |
310 | ||
311 | case SSH_CIPHER_3DES: | |
312 | case SSH_CIPHER_BLOWFISH: | |
313 | fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher)); | |
314 | break; | |
315 | ||
316 | case SSH_CIPHER_3DES_CBC: | |
317 | if (keylen < 24) | |
318 | error("Key length %d is insufficient for 3des-cbc.", keylen); | |
319 | des_set_key((void *) key, context->u.des3.key1); | |
320 | des_set_key((void *) (key+8), context->u.des3.key2); | |
321 | des_set_key((void *) (key+16), context->u.des3.key3); | |
322 | if (ivlen < 8) | |
323 | error("IV length %d is insufficient for 3des-cbc.", ivlen); | |
324 | memcpy(context->u.des3.iv3, (char *)iv, 8); | |
325 | break; | |
326 | ||
327 | case SSH_CIPHER_BLOWFISH_CBC: | |
328 | if (keylen < 16) | |
329 | error("Key length %d is insufficient for blowfish.", keylen); | |
330 | if (ivlen < 8) | |
331 | error("IV length %d is insufficient for blowfish.", ivlen); | |
332 | BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key); | |
333 | memcpy(context->u.bf.iv, (char *)iv, 8); | |
334 | break; | |
335 | ||
336 | case SSH_CIPHER_ARCFOUR: | |
337 | if (keylen < 16) | |
338 | error("Key length %d is insufficient for arcfour.", keylen); | |
339 | RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key); | |
340 | break; | |
341 | ||
342 | case SSH_CIPHER_CAST128_CBC: | |
343 | if (keylen < 16) | |
344 | error("Key length %d is insufficient for cast128.", keylen); | |
345 | if (ivlen < 8) | |
346 | error("IV length %d is insufficient for cast128.", ivlen); | |
347 | CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key); | |
348 | memcpy(context->u.cast.iv, (char *)iv, 8); | |
349 | break; | |
350 | ||
351 | default: | |
352 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); | |
353 | } | |
354 | } | |
355 | ||
356 | /* Encrypts data using the cipher. */ | |
357 | ||
358 | void | |
359 | cipher_encrypt(CipherContext *context, unsigned char *dest, | |
360 | const unsigned char *src, unsigned int len) | |
361 | { | |
362 | if ((len & 7) != 0) | |
363 | fatal("cipher_encrypt: bad plaintext length %d", len); | |
364 | ||
365 | switch (context->type) { | |
366 | case SSH_CIPHER_NONE: | |
367 | memcpy(dest, src, len); | |
368 | break; | |
369 | ||
370 | case SSH_CIPHER_3DES: | |
371 | SSH_3CBC_ENCRYPT(context->u.des3.key1, | |
372 | context->u.des3.key2, &context->u.des3.iv2, | |
373 | context->u.des3.key3, &context->u.des3.iv3, | |
374 | dest, (unsigned char *) src, len); | |
375 | break; | |
376 | ||
377 | case SSH_CIPHER_BLOWFISH: | |
378 | swap_bytes(src, dest, len); | |
379 | BF_cbc_encrypt(dest, dest, len, | |
380 | &context->u.bf.key, context->u.bf.iv, | |
381 | BF_ENCRYPT); | |
382 | swap_bytes(dest, dest, len); | |
383 | break; | |
384 | ||
385 | case SSH_CIPHER_BLOWFISH_CBC: | |
386 | BF_cbc_encrypt((void *)src, dest, len, | |
387 | &context->u.bf.key, context->u.bf.iv, | |
388 | BF_ENCRYPT); | |
389 | break; | |
390 | ||
391 | case SSH_CIPHER_3DES_CBC: | |
392 | des_ede3_cbc_encrypt(src, dest, len, | |
393 | context->u.des3.key1, context->u.des3.key2, | |
394 | context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT); | |
395 | break; | |
396 | ||
397 | case SSH_CIPHER_ARCFOUR: | |
398 | RC4(&context->u.rc4, len, (unsigned char *)src, dest); | |
399 | break; | |
400 | ||
401 | case SSH_CIPHER_CAST128_CBC: | |
402 | CAST_cbc_encrypt(src, dest, len, | |
403 | &context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT); | |
404 | break; | |
405 | ||
406 | default: | |
407 | fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type)); | |
408 | } | |
409 | } | |
410 | ||
411 | /* Decrypts data using the cipher. */ | |
412 | ||
413 | void | |
414 | cipher_decrypt(CipherContext *context, unsigned char *dest, | |
415 | const unsigned char *src, unsigned int len) | |
416 | { | |
417 | if ((len & 7) != 0) | |
418 | fatal("cipher_decrypt: bad ciphertext length %d", len); | |
419 | ||
420 | switch (context->type) { | |
421 | case SSH_CIPHER_NONE: | |
422 | memcpy(dest, src, len); | |
423 | break; | |
424 | ||
425 | case SSH_CIPHER_3DES: | |
426 | SSH_3CBC_DECRYPT(context->u.des3.key1, | |
427 | context->u.des3.key2, &context->u.des3.iv2, | |
428 | context->u.des3.key3, &context->u.des3.iv3, | |
429 | dest, (unsigned char *) src, len); | |
430 | break; | |
431 | ||
432 | case SSH_CIPHER_BLOWFISH: | |
433 | swap_bytes(src, dest, len); | |
434 | BF_cbc_encrypt((void *) dest, dest, len, | |
435 | &context->u.bf.key, context->u.bf.iv, | |
436 | BF_DECRYPT); | |
437 | swap_bytes(dest, dest, len); | |
438 | break; | |
439 | ||
440 | case SSH_CIPHER_BLOWFISH_CBC: | |
441 | BF_cbc_encrypt((void *) src, dest, len, | |
442 | &context->u.bf.key, context->u.bf.iv, | |
443 | BF_DECRYPT); | |
444 | break; | |
445 | ||
446 | case SSH_CIPHER_3DES_CBC: | |
447 | des_ede3_cbc_encrypt(src, dest, len, | |
448 | context->u.des3.key1, context->u.des3.key2, | |
449 | context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT); | |
450 | break; | |
451 | ||
452 | case SSH_CIPHER_ARCFOUR: | |
453 | RC4(&context->u.rc4, len, (unsigned char *)src, dest); | |
454 | break; | |
455 | ||
456 | case SSH_CIPHER_CAST128_CBC: | |
457 | CAST_cbc_encrypt(src, dest, len, | |
458 | &context->u.cast.key, context->u.cast.iv, CAST_DECRYPT); | |
459 | break; | |
460 | ||
461 | default: | |
462 | fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type)); | |
463 | } | |
464 | } |