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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("$Id$"); | |
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; | |
178 | char *p; | |
179 | int i; | |
180 | ||
181 | if (strcmp(names, "") == 0) | |
182 | return 0; | |
183 | ciphers = xstrdup(names); | |
184 | for ((p = strtok(ciphers, CIPHER_SEP)); p; (p = strtok(NULL, CIPHER_SEP))) { | |
185 | i = cipher_number(p); | |
186 | if (i == -1 || !(cipher_mask2() & (1 << i))) { | |
187 | xfree(ciphers); | |
188 | return 0; | |
189 | } | |
190 | } | |
191 | xfree(ciphers); | |
192 | return 1; | |
193 | } | |
194 | ||
195 | /* | |
196 | * Parses the name of the cipher. Returns the number of the corresponding | |
197 | * cipher, or -1 on error. | |
198 | */ | |
199 | ||
200 | int | |
201 | cipher_number(const char *name) | |
202 | { | |
203 | int i; | |
204 | for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++) | |
205 | if (strcmp(cipher_names[i], name) == 0 && | |
206 | (cipher_mask() & (1 << i))) | |
207 | return i; | |
208 | return -1; | |
209 | } | |
210 | ||
211 | /* | |
212 | * Selects the cipher, and keys if by computing the MD5 checksum of the | |
213 | * passphrase and using the resulting 16 bytes as the key. | |
214 | */ | |
215 | ||
216 | void | |
217 | cipher_set_key_string(CipherContext *context, int cipher, const char *passphrase) | |
218 | { | |
219 | MD5_CTX md; | |
220 | unsigned char digest[16]; | |
221 | ||
222 | MD5_Init(&md); | |
223 | MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase)); | |
224 | MD5_Final(digest, &md); | |
225 | ||
226 | cipher_set_key(context, cipher, digest, 16); | |
227 | ||
228 | memset(digest, 0, sizeof(digest)); | |
229 | memset(&md, 0, sizeof(md)); | |
230 | } | |
231 | ||
232 | /* Selects the cipher to use and sets the key. */ | |
233 | ||
234 | void | |
235 | cipher_set_key(CipherContext *context, int cipher, const unsigned char *key, | |
236 | int keylen) | |
237 | { | |
238 | unsigned char padded[32]; | |
239 | ||
240 | /* Set cipher type. */ | |
241 | context->type = cipher; | |
242 | ||
243 | /* Get 32 bytes of key data. Pad if necessary. (So that code | |
244 | below does not need to worry about key size). */ | |
245 | memset(padded, 0, sizeof(padded)); | |
246 | memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded)); | |
247 | ||
248 | /* Initialize the initialization vector. */ | |
249 | switch (cipher) { | |
250 | case SSH_CIPHER_NONE: | |
251 | /* | |
252 | * Has to stay for authfile saving of private key with no | |
253 | * passphrase | |
254 | */ | |
255 | break; | |
256 | ||
257 | case SSH_CIPHER_3DES: | |
258 | /* | |
259 | * Note: the least significant bit of each byte of key is | |
260 | * parity, and must be ignored by the implementation. 16 | |
261 | * bytes of key are used (first and last keys are the same). | |
262 | */ | |
263 | if (keylen < 16) | |
264 | error("Key length %d is insufficient for 3DES.", keylen); | |
265 | des_set_key((void *) padded, context->u.des3.key1); | |
266 | des_set_key((void *) (padded + 8), context->u.des3.key2); | |
267 | if (keylen <= 16) | |
268 | des_set_key((void *) padded, context->u.des3.key3); | |
269 | else | |
270 | des_set_key((void *) (padded + 16), context->u.des3.key3); | |
271 | memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2)); | |
272 | memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3)); | |
273 | break; | |
274 | ||
275 | case SSH_CIPHER_BLOWFISH: | |
276 | if (keylen < 16) | |
277 | error("Key length %d is insufficient for blowfish.", keylen); | |
278 | BF_set_key(&context->u.bf.key, keylen, padded); | |
279 | memset(context->u.bf.iv, 0, 8); | |
280 | break; | |
281 | ||
282 | case SSH_CIPHER_3DES_CBC: | |
283 | case SSH_CIPHER_BLOWFISH_CBC: | |
284 | case SSH_CIPHER_ARCFOUR: | |
285 | case SSH_CIPHER_CAST128_CBC: | |
286 | fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher)); | |
287 | break; | |
288 | ||
289 | default: | |
290 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); | |
291 | } | |
292 | memset(padded, 0, sizeof(padded)); | |
293 | } | |
294 | ||
295 | void | |
296 | cipher_set_key_iv(CipherContext * context, int cipher, | |
297 | const unsigned char *key, int keylen, | |
298 | const unsigned char *iv, int ivlen) | |
299 | { | |
300 | /* Set cipher type. */ | |
301 | context->type = cipher; | |
302 | ||
303 | /* Initialize the initialization vector. */ | |
304 | switch (cipher) { | |
305 | case SSH_CIPHER_NONE: | |
306 | break; | |
307 | ||
308 | case SSH_CIPHER_3DES: | |
309 | case SSH_CIPHER_BLOWFISH: | |
310 | fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher)); | |
311 | break; | |
312 | ||
313 | case SSH_CIPHER_3DES_CBC: | |
314 | if (keylen < 24) | |
315 | error("Key length %d is insufficient for 3des-cbc.", keylen); | |
316 | des_set_key((void *) key, context->u.des3.key1); | |
317 | des_set_key((void *) (key+8), context->u.des3.key2); | |
318 | des_set_key((void *) (key+16), context->u.des3.key3); | |
319 | if (ivlen < 8) | |
320 | error("IV length %d is insufficient for 3des-cbc.", ivlen); | |
321 | memcpy(context->u.des3.iv3, (char *)iv, 8); | |
322 | break; | |
323 | ||
324 | case SSH_CIPHER_BLOWFISH_CBC: | |
325 | if (keylen < 16) | |
326 | error("Key length %d is insufficient for blowfish.", keylen); | |
327 | if (ivlen < 8) | |
328 | error("IV length %d is insufficient for blowfish.", ivlen); | |
329 | BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key); | |
330 | memcpy(context->u.bf.iv, (char *)iv, 8); | |
331 | break; | |
332 | ||
333 | case SSH_CIPHER_ARCFOUR: | |
334 | if (keylen < 16) | |
335 | error("Key length %d is insufficient for arcfour.", keylen); | |
336 | RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key); | |
337 | break; | |
338 | ||
339 | case SSH_CIPHER_CAST128_CBC: | |
340 | if (keylen < 16) | |
341 | error("Key length %d is insufficient for cast128.", keylen); | |
342 | if (ivlen < 8) | |
343 | error("IV length %d is insufficient for cast128.", ivlen); | |
344 | CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key); | |
345 | memcpy(context->u.cast.iv, (char *)iv, 8); | |
346 | break; | |
347 | ||
348 | default: | |
349 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); | |
350 | } | |
351 | } | |
352 | ||
353 | /* Encrypts data using the cipher. */ | |
354 | ||
355 | void | |
356 | cipher_encrypt(CipherContext *context, unsigned char *dest, | |
357 | const unsigned char *src, unsigned int len) | |
358 | { | |
359 | if ((len & 7) != 0) | |
360 | fatal("cipher_encrypt: bad plaintext length %d", len); | |
361 | ||
362 | switch (context->type) { | |
363 | case SSH_CIPHER_NONE: | |
364 | memcpy(dest, src, len); | |
365 | break; | |
366 | ||
367 | case SSH_CIPHER_3DES: | |
368 | SSH_3CBC_ENCRYPT(context->u.des3.key1, | |
369 | context->u.des3.key2, &context->u.des3.iv2, | |
370 | context->u.des3.key3, &context->u.des3.iv3, | |
371 | dest, (unsigned char *) src, len); | |
372 | break; | |
373 | ||
374 | case SSH_CIPHER_BLOWFISH: | |
375 | swap_bytes(src, dest, len); | |
376 | BF_cbc_encrypt(dest, dest, len, | |
377 | &context->u.bf.key, context->u.bf.iv, | |
378 | BF_ENCRYPT); | |
379 | swap_bytes(dest, dest, len); | |
380 | break; | |
381 | ||
382 | case SSH_CIPHER_BLOWFISH_CBC: | |
383 | BF_cbc_encrypt((void *)src, dest, len, | |
384 | &context->u.bf.key, context->u.bf.iv, | |
385 | BF_ENCRYPT); | |
386 | break; | |
387 | ||
388 | case SSH_CIPHER_3DES_CBC: | |
389 | des_ede3_cbc_encrypt(src, dest, len, | |
390 | context->u.des3.key1, context->u.des3.key2, | |
391 | context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT); | |
392 | break; | |
393 | ||
394 | case SSH_CIPHER_ARCFOUR: | |
395 | RC4(&context->u.rc4, len, (unsigned char *)src, dest); | |
396 | break; | |
397 | ||
398 | case SSH_CIPHER_CAST128_CBC: | |
399 | CAST_cbc_encrypt(src, dest, len, | |
400 | &context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT); | |
401 | break; | |
402 | ||
403 | default: | |
404 | fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type)); | |
405 | } | |
406 | } | |
407 | ||
408 | /* Decrypts data using the cipher. */ | |
409 | ||
410 | void | |
411 | cipher_decrypt(CipherContext *context, unsigned char *dest, | |
412 | const unsigned char *src, unsigned int len) | |
413 | { | |
414 | if ((len & 7) != 0) | |
415 | fatal("cipher_decrypt: bad ciphertext length %d", len); | |
416 | ||
417 | switch (context->type) { | |
418 | case SSH_CIPHER_NONE: | |
419 | memcpy(dest, src, len); | |
420 | break; | |
421 | ||
422 | case SSH_CIPHER_3DES: | |
423 | SSH_3CBC_DECRYPT(context->u.des3.key1, | |
424 | context->u.des3.key2, &context->u.des3.iv2, | |
425 | context->u.des3.key3, &context->u.des3.iv3, | |
426 | dest, (unsigned char *) src, len); | |
427 | break; | |
428 | ||
429 | case SSH_CIPHER_BLOWFISH: | |
430 | swap_bytes(src, dest, len); | |
431 | BF_cbc_encrypt((void *) dest, dest, len, | |
432 | &context->u.bf.key, context->u.bf.iv, | |
433 | BF_DECRYPT); | |
434 | swap_bytes(dest, dest, len); | |
435 | break; | |
436 | ||
437 | case SSH_CIPHER_BLOWFISH_CBC: | |
438 | BF_cbc_encrypt((void *) src, dest, len, | |
439 | &context->u.bf.key, context->u.bf.iv, | |
440 | BF_DECRYPT); | |
441 | break; | |
442 | ||
443 | case SSH_CIPHER_3DES_CBC: | |
444 | des_ede3_cbc_encrypt(src, dest, len, | |
445 | context->u.des3.key1, context->u.des3.key2, | |
446 | context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT); | |
447 | break; | |
448 | ||
449 | case SSH_CIPHER_ARCFOUR: | |
450 | RC4(&context->u.rc4, len, (unsigned char *)src, dest); | |
451 | break; | |
452 | ||
453 | case SSH_CIPHER_CAST128_CBC: | |
454 | CAST_cbc_encrypt(src, dest, len, | |
455 | &context->u.cast.key, context->u.cast.iv, CAST_DECRYPT); | |
456 | break; | |
457 | ||
458 | default: | |
459 | fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type)); | |
460 | } | |
461 | } |