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"
38RCSID("$OpenBSD: cipher.c,v 1.52 2002/02/18 13:05:32 markus Exp $");
39RCSID("$FreeBSD: head/crypto/openssh/cipher.c 92559 2002-03-18 10:09:43Z des $");
40
41#include "xmalloc.h"
42#include "log.h"
43#include "cipher.h"
44
45#include <openssl/md5.h>
46#include "rijndael.h"
47
48static EVP_CIPHER *evp_ssh1_3des(void);
49static EVP_CIPHER *evp_ssh1_bf(void);
50static EVP_CIPHER *evp_rijndael(void);
51
52struct Cipher {
53 char *name;
54 int number; /* for ssh1 only */
55 u_int block_size;
56 u_int key_len;
57 EVP_CIPHER *(*evptype)(void);
58} ciphers[] = {
59 { "none", SSH_CIPHER_NONE, 8, 0, EVP_enc_null },
60 { "des", SSH_CIPHER_DES, 8, 8, EVP_des_cbc },
61 { "3des", SSH_CIPHER_3DES, 8, 16, evp_ssh1_3des },
62 { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, evp_ssh1_bf },
63
64 { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, EVP_des_ede3_cbc },
65 { "blowfish-cbc", SSH_CIPHER_SSH2, 8, 16, EVP_bf_cbc },
66 { "cast128-cbc", SSH_CIPHER_SSH2, 8, 16, EVP_cast5_cbc },
67 { "arcfour", SSH_CIPHER_SSH2, 8, 16, EVP_rc4 },
68 { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, evp_rijndael },
69 { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, evp_rijndael },
70 { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, evp_rijndael },
71
72 { NULL, SSH_CIPHER_ILLEGAL, 0, 0, NULL }
73};
74
75/*--*/
76
77u_int
78cipher_blocksize(Cipher *c)
79{
80 return (c->block_size);
81}
82u_int
83cipher_keylen(Cipher *c)
84{
85 return (c->key_len);
86}
87
88u_int
89cipher_mask_ssh1(int client)
90{
91 u_int mask = 0;
92 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
93 mask |= 1 << SSH_CIPHER_BLOWFISH;
94 if (client) {
95 mask |= 1 << SSH_CIPHER_DES;
96 }
97 return mask;
98}
99
100Cipher *
101cipher_by_name(const char *name)
102{
103 Cipher *c;
104 for (c = ciphers; c->name != NULL; c++)
105 if (strcasecmp(c->name, name) == 0)
106 return c;
107 return NULL;
108}
109
110Cipher *
111cipher_by_number(int id)
112{
113 Cipher *c;
114 for (c = ciphers; c->name != NULL; c++)
115 if (c->number == id)
116 return c;
117 return NULL;
118}
119
120#define CIPHER_SEP ","
121int
122ciphers_valid(const char *names)
123{
124 Cipher *c;
125 char *ciphers, *cp;
126 char *p;
127
128 if (names == NULL || strcmp(names, "") == 0)
129 return 0;
130 ciphers = cp = xstrdup(names);
131 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
132 (p = strsep(&cp, CIPHER_SEP))) {
133 c = cipher_by_name(p);
134 if (c == NULL || c->number != SSH_CIPHER_SSH2) {
135 debug("bad cipher %s [%s]", p, names);
136 xfree(ciphers);
137 return 0;
138 } else {
139 debug3("cipher ok: %s [%s]", p, names);
140 }
141 }
142 debug3("ciphers ok: [%s]", names);
143 xfree(ciphers);
144 return 1;
145}
146
147/*
148 * Parses the name of the cipher. Returns the number of the corresponding
149 * cipher, or -1 on error.
150 */
151
152int
153cipher_number(const char *name)
154{
155 Cipher *c;
156 if (name == NULL)
157 return -1;
158 c = cipher_by_name(name);
159 return (c==NULL) ? -1 : c->number;
160}
161
162char *
163cipher_name(int id)
164{
165 Cipher *c = cipher_by_number(id);
166 return (c==NULL) ? "<unknown>" : c->name;
167}
168
169void
170cipher_init(CipherContext *cc, Cipher *cipher,
171 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
172 int encrypt)
173{
174 static int dowarn = 1;
175 const EVP_CIPHER *type;
176 int klen;
177
178 if (cipher->number == SSH_CIPHER_DES) {
179 if (dowarn) {
180 error("Warning: use of DES is strongly discouraged "
181 "due to cryptographic weaknesses");
182 dowarn = 0;
183 }
184 if (keylen > 8)
185 keylen = 8;
186 }
187 cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
188
189 if (keylen < cipher->key_len)
190 fatal("cipher_init: key length %d is insufficient for %s.",
191 keylen, cipher->name);
192 if (iv != NULL && ivlen < cipher->block_size)
193 fatal("cipher_init: iv length %d is insufficient for %s.",
194 ivlen, cipher->name);
195 cc->cipher = cipher;
196
197 type = (*cipher->evptype)();
198
199 EVP_CIPHER_CTX_init(&cc->evp);
200 if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
201 (encrypt == CIPHER_ENCRYPT)) == 0)
202 fatal("cipher_init: EVP_CipherInit failed for %s",
203 cipher->name);
204 klen = EVP_CIPHER_CTX_key_length(&cc->evp);
205 if (klen > 0 && keylen != klen) {
206 debug("cipher_init: set keylen (%d -> %d)", klen, keylen);
207 if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
208 fatal("cipher_init: set keylen failed (%d -> %d)",
209 klen, keylen);
210 }
211 if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
212 fatal("cipher_init: EVP_CipherInit: set key failed for %s",
213 cipher->name);
214}
215
216void
217cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
218{
219 if (len % cc->cipher->block_size)
220 fatal("cipher_encrypt: bad plaintext length %d", len);
221 if (EVP_Cipher(&cc->evp, dest, (u_char *)src, len) == 0)
222 fatal("evp_crypt: EVP_Cipher failed");
223}
224
225void
226cipher_cleanup(CipherContext *cc)
227{
228 if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
229 error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
230}
231
232/*
233 * Selects the cipher, and keys if by computing the MD5 checksum of the
234 * passphrase and using the resulting 16 bytes as the key.
235 */
236
237void
238cipher_set_key_string(CipherContext *cc, Cipher *cipher,
239 const char *passphrase, int encrypt)
240{
241 MD5_CTX md;
242 u_char digest[16];
243
244 MD5_Init(&md);
245 MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
246 MD5_Final(digest, &md);
247
248 cipher_init(cc, cipher, digest, 16, NULL, 0, encrypt);
249
250 memset(digest, 0, sizeof(digest));
251 memset(&md, 0, sizeof(md));
252}
253
254/* Implementations for other non-EVP ciphers */
255
256/*
257 * This is used by SSH1:
258 *
259 * What kind of triple DES are these 2 routines?
260 *
261 * Why is there a redundant initialization vector?
262 *
263 * If only iv3 was used, then, this would till effect have been
264 * outer-cbc. However, there is also a private iv1 == iv2 which
265 * perhaps makes differential analysis easier. On the other hand, the
266 * private iv1 probably makes the CRC-32 attack ineffective. This is a
267 * result of that there is no longer any known iv1 to use when
268 * choosing the X block.
269 */
270struct ssh1_3des_ctx
271{
272 EVP_CIPHER_CTX k1, k2, k3;
273};
274static int
275ssh1_3des_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
276 int enc)
277{
278 struct ssh1_3des_ctx *c;
279 u_char *k1, *k2, *k3;
280
281 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
282 c = xmalloc(sizeof(*c));
283 EVP_CIPHER_CTX_set_app_data(ctx, c);
284 }
285 if (key == NULL)
286 return (1);
287 if (enc == -1)
288 enc = ctx->encrypt;
289 k1 = k2 = k3 = (u_char *) key;
290 k2 += 8;
291 if (EVP_CIPHER_CTX_key_length(ctx) >= 16+8) {
292 if (enc)
293 k3 += 16;
294 else
295 k1 += 16;
296 }
297 EVP_CIPHER_CTX_init(&c->k1);
298 EVP_CIPHER_CTX_init(&c->k2);
299 EVP_CIPHER_CTX_init(&c->k3);
300 if (EVP_CipherInit(&c->k1, EVP_des_cbc(), k1, NULL, enc) == 0 ||
301 EVP_CipherInit(&c->k2, EVP_des_cbc(), k2, NULL, !enc) == 0 ||
302 EVP_CipherInit(&c->k3, EVP_des_cbc(), k3, NULL, enc) == 0) {
303 memset(c, 0, sizeof(*c));
304 xfree(c);
305 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
306 return (0);
307 }
308 return (1);
309}
310static int
311ssh1_3des_cbc(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src, u_int len)
312{
313 struct ssh1_3des_ctx *c;
314
315 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
316 error("ssh1_3des_cbc: no context");
317 return (0);
318 }
319 if (EVP_Cipher(&c->k1, dest, (u_char *)src, len) == 0 ||
320 EVP_Cipher(&c->k2, dest, dest, len) == 0 ||
321 EVP_Cipher(&c->k3, dest, dest, len) == 0)
322 return (0);
323 return (1);
324}
325static int
326ssh1_3des_cleanup(EVP_CIPHER_CTX *ctx)
327{
328 struct ssh1_3des_ctx *c;
329
330 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
331 memset(c, 0, sizeof(*c));
332 xfree(c);
333 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
334 }
335 return (1);
336}
337static EVP_CIPHER *
338evp_ssh1_3des(void)
339{
340 static EVP_CIPHER ssh1_3des;
341
342 memset(&ssh1_3des, 0, sizeof(EVP_CIPHER));
343 ssh1_3des.nid = NID_undef;
344 ssh1_3des.block_size = 8;
345 ssh1_3des.iv_len = 0;
346 ssh1_3des.key_len = 16;
347 ssh1_3des.init = ssh1_3des_init;
348 ssh1_3des.cleanup = ssh1_3des_cleanup;
349 ssh1_3des.do_cipher = ssh1_3des_cbc;
350 ssh1_3des.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH;
351 return (&ssh1_3des);
352}
353
354/*
355 * SSH1 uses a variation on Blowfish, all bytes must be swapped before
356 * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
357 */
358static void
359swap_bytes(const u_char *src, u_char *dst, int n)
360{
361 u_char c[4];
362
363 /* Process 4 bytes every lap. */
364 for (n = n / 4; n > 0; n--) {
365 c[3] = *src++;
366 c[2] = *src++;
367 c[1] = *src++;
368 c[0] = *src++;
369
370 *dst++ = c[0];
371 *dst++ = c[1];
372 *dst++ = c[2];
373 *dst++ = c[3];
374 }
375}
376static int (*orig_bf)(EVP_CIPHER_CTX *, u_char *, const u_char *, u_int) = NULL;
377static int
378bf_ssh1_cipher(EVP_CIPHER_CTX *ctx, u_char *out, const u_char *in, u_int len)
379{
380 int ret;
381
382 swap_bytes(in, out, len);
383 ret = (*orig_bf)(ctx, out, out, len);
384 swap_bytes(out, out, len);
385 return (ret);
386}
387static EVP_CIPHER *
388evp_ssh1_bf(void)
389{
390 static EVP_CIPHER ssh1_bf;
391
392 memcpy(&ssh1_bf, EVP_bf_cbc(), sizeof(EVP_CIPHER));
393 orig_bf = ssh1_bf.do_cipher;
394 ssh1_bf.nid = NID_undef;
395 ssh1_bf.do_cipher = bf_ssh1_cipher;
396 ssh1_bf.key_len = 32;
397 return (&ssh1_bf);
398}
399
400/* RIJNDAEL */
401#define RIJNDAEL_BLOCKSIZE 16
402struct ssh_rijndael_ctx
403{
404 rijndael_ctx r_ctx;
405 u_char r_iv[RIJNDAEL_BLOCKSIZE];
406};
407
408static int
409ssh_rijndael_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
410 int enc)
411{
412 struct ssh_rijndael_ctx *c;
413
414 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
415 c = xmalloc(sizeof(*c));
416 EVP_CIPHER_CTX_set_app_data(ctx, c);
417 }
418 if (key != NULL) {
419 if (enc == -1)
420 enc = ctx->encrypt;
421 rijndael_set_key(&c->r_ctx, (u_char *)key,
422 8*EVP_CIPHER_CTX_key_length(ctx), enc);
423 }
424 if (iv != NULL)
425 memcpy(c->r_iv, iv, RIJNDAEL_BLOCKSIZE);
426 return (1);
427}
428static int
429ssh_rijndael_cbc(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
430 u_int len)
431{
432 struct ssh_rijndael_ctx *c;
433 u_char buf[RIJNDAEL_BLOCKSIZE];
434 u_char *cprev, *cnow, *plain, *ivp;
435 int i, j, blocks = len / RIJNDAEL_BLOCKSIZE;
436
437 if (len == 0)
438 return (1);
439 if (len % RIJNDAEL_BLOCKSIZE)
440 fatal("ssh_rijndael_cbc: bad len %d", len);
441 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
442 error("ssh_rijndael_cbc: no context");
443 return (0);
444 }
445 if (ctx->encrypt) {
446 cnow = dest;
447 plain = (u_char *)src;
448 cprev = c->r_iv;
449 for (i = 0; i < blocks; i++, plain+=RIJNDAEL_BLOCKSIZE,
450 cnow+=RIJNDAEL_BLOCKSIZE) {
451 for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
452 buf[j] = plain[j] ^ cprev[j];
453 rijndael_encrypt(&c->r_ctx, buf, cnow);
454 cprev = cnow;
455 }
456 memcpy(c->r_iv, cprev, RIJNDAEL_BLOCKSIZE);
457 } else {
458 cnow = (u_char *) (src+len-RIJNDAEL_BLOCKSIZE);
459 plain = dest+len-RIJNDAEL_BLOCKSIZE;
460
461 memcpy(buf, cnow, RIJNDAEL_BLOCKSIZE);
462 for (i = blocks; i > 0; i--, cnow-=RIJNDAEL_BLOCKSIZE,
463 plain-=RIJNDAEL_BLOCKSIZE) {
464 rijndael_decrypt(&c->r_ctx, cnow, plain);
465 ivp = (i == 1) ? c->r_iv : cnow-RIJNDAEL_BLOCKSIZE;
466 for (j = 0; j < RIJNDAEL_BLOCKSIZE; j++)
467 plain[j] ^= ivp[j];
468 }
469 memcpy(c->r_iv, buf, RIJNDAEL_BLOCKSIZE);
470 }
471 return (1);
472}
473static int
474ssh_rijndael_cleanup(EVP_CIPHER_CTX *ctx)
475{
476 struct ssh_rijndael_ctx *c;
477
478 if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
479 memset(c, 0, sizeof(*c));
480 xfree(c);
481 EVP_CIPHER_CTX_set_app_data(ctx, NULL);
482 }
483 return (1);
484}
485static EVP_CIPHER *
486evp_rijndael(void)
487{
488 static EVP_CIPHER rijndal_cbc;
489
490 memset(&rijndal_cbc, 0, sizeof(EVP_CIPHER));
491 rijndal_cbc.nid = NID_undef;
492 rijndal_cbc.block_size = RIJNDAEL_BLOCKSIZE;
493 rijndal_cbc.iv_len = RIJNDAEL_BLOCKSIZE;
494 rijndal_cbc.key_len = 16;
495 rijndal_cbc.init = ssh_rijndael_init;
496 rijndal_cbc.cleanup = ssh_rijndael_cleanup;
497 rijndal_cbc.do_cipher = ssh_rijndael_cbc;
498 rijndal_cbc.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
499 EVP_CIPH_ALWAYS_CALL_INIT;
500 return (&rijndal_cbc);
501}