1 /* $OpenBSD: cipher.c,v 1.121 2024/05/17 02:39:11 jsg Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose. Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 *
13 *
14 * Copyright (c) 1999 Niels Provos. All rights reserved.
15 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38 #include "includes.h"
39
40 #include <sys/types.h>
41
42 #include <string.h>
43 #include <stdarg.h>
44 #include <stdio.h>
45
46 #include "cipher.h"
47 #include "misc.h"
48 #include "sshbuf.h"
49 #include "ssherr.h"
50 #include "digest.h"
51
52 #include "openbsd-compat/openssl-compat.h"
53
54 #ifndef WITH_OPENSSL
55 #define EVP_CIPHER_CTX void
56 #endif
57
58 struct sshcipher_ctx {
59 int plaintext;
60 int encrypt;
61 EVP_CIPHER_CTX *evp;
62 struct chachapoly_ctx *cp_ctx;
63 struct aesctr_ctx ac_ctx; /* XXX union with evp? */
64 const struct sshcipher *cipher;
65 };
66
67 struct sshcipher {
68 char *name;
69 u_int block_size;
70 u_int key_len;
71 u_int iv_len; /* defaults to block_size */
72 u_int auth_len;
73 u_int flags;
74 #define CFLAG_CBC (1<<0)
75 #define CFLAG_CHACHAPOLY (1<<1)
76 #define CFLAG_AESCTR (1<<2)
77 #define CFLAG_NONE (1<<3)
78 #define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */
79 #ifdef WITH_OPENSSL
80 const EVP_CIPHER *(*evptype)(void);
81 #else
82 void *ignored;
83 #endif
84 };
85
86 static const struct sshcipher ciphers[] = {
87 #ifdef WITH_OPENSSL
88 #ifndef OPENSSL_NO_DES
89 { "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc },
90 #endif
91 { "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc },
92 { "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc },
93 { "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
94 { "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr },
95 { "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr },
96 { "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr },
97 { "aes128-gcm@openssh.com",
98 16, 16, 12, 16, 0, EVP_aes_128_gcm },
99 { "aes256-gcm@openssh.com",
100 16, 32, 12, 16, 0, EVP_aes_256_gcm },
101 #else
102 { "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL },
103 { "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL },
104 { "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL },
105 #endif
106 { "chacha20-poly1305@openssh.com",
107 8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL },
108 { "none", 8, 0, 0, 0, CFLAG_NONE, NULL },
109
110 { NULL, 0, 0, 0, 0, 0, NULL }
111 };
112
113 /*--*/
114
115 /* Returns a comma-separated list of supported ciphers. */
116 char *
cipher_alg_list(char sep,int auth_only)117 cipher_alg_list(char sep, int auth_only)
118 {
119 char *tmp, *ret = NULL;
120 size_t nlen, rlen = 0;
121 const struct sshcipher *c;
122
123 for (c = ciphers; c->name != NULL; c++) {
124 if ((c->flags & CFLAG_INTERNAL) != 0)
125 continue;
126 if (auth_only && c->auth_len == 0)
127 continue;
128 if (ret != NULL)
129 ret[rlen++] = sep;
130 nlen = strlen(c->name);
131 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
132 free(ret);
133 return NULL;
134 }
135 ret = tmp;
136 memcpy(ret + rlen, c->name, nlen + 1);
137 rlen += nlen;
138 }
139 return ret;
140 }
141
142 const char *
compression_alg_list(int compression)143 compression_alg_list(int compression)
144 {
145 #ifdef WITH_ZLIB
146 return compression ? "zlib@openssh.com,zlib,none" :
147 "none,zlib@openssh.com,zlib";
148 #else
149 return "none";
150 #endif
151 }
152
153 u_int
cipher_blocksize(const struct sshcipher * c)154 cipher_blocksize(const struct sshcipher *c)
155 {
156 return (c->block_size);
157 }
158
159 u_int
cipher_keylen(const struct sshcipher * c)160 cipher_keylen(const struct sshcipher *c)
161 {
162 return (c->key_len);
163 }
164
165 u_int
cipher_seclen(const struct sshcipher * c)166 cipher_seclen(const struct sshcipher *c)
167 {
168 if (strcmp("3des-cbc", c->name) == 0)
169 return 14;
170 return cipher_keylen(c);
171 }
172
173 u_int
cipher_authlen(const struct sshcipher * c)174 cipher_authlen(const struct sshcipher *c)
175 {
176 return (c->auth_len);
177 }
178
179 u_int
cipher_ivlen(const struct sshcipher * c)180 cipher_ivlen(const struct sshcipher *c)
181 {
182 /*
183 * Default is cipher block size, except for chacha20+poly1305 that
184 * needs no IV. XXX make iv_len == -1 default?
185 */
186 return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
187 c->iv_len : c->block_size;
188 }
189
190 u_int
cipher_is_cbc(const struct sshcipher * c)191 cipher_is_cbc(const struct sshcipher *c)
192 {
193 return (c->flags & CFLAG_CBC) != 0;
194 }
195
196 u_int
cipher_ctx_is_plaintext(struct sshcipher_ctx * cc)197 cipher_ctx_is_plaintext(struct sshcipher_ctx *cc)
198 {
199 return cc->plaintext;
200 }
201
202 const struct sshcipher *
cipher_by_name(const char * name)203 cipher_by_name(const char *name)
204 {
205 const struct sshcipher *c;
206 for (c = ciphers; c->name != NULL; c++)
207 if (strcmp(c->name, name) == 0)
208 return c;
209 return NULL;
210 }
211
212 #define CIPHER_SEP ","
213 int
ciphers_valid(const char * names)214 ciphers_valid(const char *names)
215 {
216 const struct sshcipher *c;
217 char *cipher_list, *cp;
218 char *p;
219
220 if (names == NULL || strcmp(names, "") == 0)
221 return 0;
222 if ((cipher_list = cp = strdup(names)) == NULL)
223 return 0;
224 for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
225 (p = strsep(&cp, CIPHER_SEP))) {
226 c = cipher_by_name(p);
227 if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) {
228 free(cipher_list);
229 return 0;
230 }
231 }
232 free(cipher_list);
233 return 1;
234 }
235
236 const char *
cipher_warning_message(const struct sshcipher_ctx * cc)237 cipher_warning_message(const struct sshcipher_ctx *cc)
238 {
239 if (cc == NULL || cc->cipher == NULL)
240 return NULL;
241 /* XXX repurpose for CBC warning */
242 return NULL;
243 }
244
245 int
cipher_init(struct sshcipher_ctx ** ccp,const struct sshcipher * cipher,const u_char * key,u_int keylen,const u_char * iv,u_int ivlen,int do_encrypt)246 cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher,
247 const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
248 int do_encrypt)
249 {
250 struct sshcipher_ctx *cc = NULL;
251 int ret = SSH_ERR_INTERNAL_ERROR;
252 #ifdef WITH_OPENSSL
253 const EVP_CIPHER *type;
254 int klen;
255 #endif
256
257 *ccp = NULL;
258 if ((cc = calloc(sizeof(*cc), 1)) == NULL)
259 return SSH_ERR_ALLOC_FAIL;
260
261 cc->plaintext = (cipher->flags & CFLAG_NONE) != 0;
262 cc->encrypt = do_encrypt;
263
264 if (keylen < cipher->key_len ||
265 (iv != NULL && ivlen < cipher_ivlen(cipher))) {
266 ret = SSH_ERR_INVALID_ARGUMENT;
267 goto out;
268 }
269
270 cc->cipher = cipher;
271 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
272 cc->cp_ctx = chachapoly_new(key, keylen);
273 ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT;
274 goto out;
275 }
276 if ((cc->cipher->flags & CFLAG_NONE) != 0) {
277 ret = 0;
278 goto out;
279 }
280 #ifndef WITH_OPENSSL
281 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
282 aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen);
283 aesctr_ivsetup(&cc->ac_ctx, iv);
284 ret = 0;
285 goto out;
286 }
287 ret = SSH_ERR_INVALID_ARGUMENT;
288 goto out;
289 #else /* WITH_OPENSSL */
290 type = (*cipher->evptype)();
291 if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) {
292 ret = SSH_ERR_ALLOC_FAIL;
293 goto out;
294 }
295 if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv,
296 (do_encrypt == CIPHER_ENCRYPT)) == 0) {
297 ret = SSH_ERR_LIBCRYPTO_ERROR;
298 goto out;
299 }
300 if (cipher_authlen(cipher) &&
301 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
302 -1, (u_char *)iv)) {
303 ret = SSH_ERR_LIBCRYPTO_ERROR;
304 goto out;
305 }
306 klen = EVP_CIPHER_CTX_key_length(cc->evp);
307 if (klen > 0 && keylen != (u_int)klen) {
308 if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) {
309 ret = SSH_ERR_LIBCRYPTO_ERROR;
310 goto out;
311 }
312 }
313 if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) {
314 ret = SSH_ERR_LIBCRYPTO_ERROR;
315 goto out;
316 }
317 ret = 0;
318 #endif /* WITH_OPENSSL */
319 out:
320 if (ret == 0) {
321 /* success */
322 *ccp = cc;
323 } else {
324 if (cc != NULL) {
325 #ifdef WITH_OPENSSL
326 EVP_CIPHER_CTX_free(cc->evp);
327 #endif /* WITH_OPENSSL */
328 freezero(cc, sizeof(*cc));
329 }
330 }
331 return ret;
332 }
333
334 /*
335 * cipher_crypt() operates as following:
336 * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
337 * These bytes are treated as additional authenticated data for
338 * authenticated encryption modes.
339 * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
340 * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
341 * This tag is written on encryption and verified on decryption.
342 * Both 'aadlen' and 'authlen' can be set to 0.
343 */
344 int
cipher_crypt(struct sshcipher_ctx * cc,u_int seqnr,u_char * dest,const u_char * src,u_int len,u_int aadlen,u_int authlen)345 cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest,
346 const u_char *src, u_int len, u_int aadlen, u_int authlen)
347 {
348 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
349 return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src,
350 len, aadlen, authlen, cc->encrypt);
351 }
352 if ((cc->cipher->flags & CFLAG_NONE) != 0) {
353 memcpy(dest, src, aadlen + len);
354 return 0;
355 }
356 #ifndef WITH_OPENSSL
357 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
358 if (aadlen)
359 memcpy(dest, src, aadlen);
360 aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen,
361 dest + aadlen, len);
362 return 0;
363 }
364 return SSH_ERR_INVALID_ARGUMENT;
365 #else
366 if (authlen) {
367 u_char lastiv[1];
368
369 if (authlen != cipher_authlen(cc->cipher))
370 return SSH_ERR_INVALID_ARGUMENT;
371 /* increment IV */
372 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
373 1, lastiv))
374 return SSH_ERR_LIBCRYPTO_ERROR;
375 /* set tag on decryption */
376 if (!cc->encrypt &&
377 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG,
378 authlen, (u_char *)src + aadlen + len))
379 return SSH_ERR_LIBCRYPTO_ERROR;
380 }
381 if (aadlen) {
382 if (authlen &&
383 EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0)
384 return SSH_ERR_LIBCRYPTO_ERROR;
385 memcpy(dest, src, aadlen);
386 }
387 if (len % cc->cipher->block_size)
388 return SSH_ERR_INVALID_ARGUMENT;
389 if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen,
390 len) < 0)
391 return SSH_ERR_LIBCRYPTO_ERROR;
392 if (authlen) {
393 /* compute tag (on encrypt) or verify tag (on decrypt) */
394 if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0)
395 return cc->encrypt ?
396 SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID;
397 if (cc->encrypt &&
398 !EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG,
399 authlen, dest + aadlen + len))
400 return SSH_ERR_LIBCRYPTO_ERROR;
401 }
402 return 0;
403 #endif
404 }
405
406 /* Extract the packet length, including any decryption necessary beforehand */
407 int
cipher_get_length(struct sshcipher_ctx * cc,u_int * plenp,u_int seqnr,const u_char * cp,u_int len)408 cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr,
409 const u_char *cp, u_int len)
410 {
411 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
412 return chachapoly_get_length(cc->cp_ctx, plenp, seqnr,
413 cp, len);
414 if (len < 4)
415 return SSH_ERR_MESSAGE_INCOMPLETE;
416 *plenp = PEEK_U32(cp);
417 return 0;
418 }
419
420 void
cipher_free(struct sshcipher_ctx * cc)421 cipher_free(struct sshcipher_ctx *cc)
422 {
423 if (cc == NULL)
424 return;
425 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
426 chachapoly_free(cc->cp_ctx);
427 cc->cp_ctx = NULL;
428 } else if ((cc->cipher->flags & CFLAG_AESCTR) != 0)
429 explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx));
430 #ifdef WITH_OPENSSL
431 EVP_CIPHER_CTX_free(cc->evp);
432 cc->evp = NULL;
433 #endif
434 freezero(cc, sizeof(*cc));
435 }
436
437 int
cipher_get_keyiv(struct sshcipher_ctx * cc,u_char * iv,size_t len)438 cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len)
439 {
440 #ifdef WITH_OPENSSL
441 const struct sshcipher *c = cc->cipher;
442 int evplen;
443 #endif
444
445 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
446 if (len != 0)
447 return SSH_ERR_INVALID_ARGUMENT;
448 return 0;
449 }
450 if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
451 if (len != sizeof(cc->ac_ctx.ctr))
452 return SSH_ERR_INVALID_ARGUMENT;
453 memcpy(iv, cc->ac_ctx.ctr, len);
454 return 0;
455 }
456 if ((cc->cipher->flags & CFLAG_NONE) != 0)
457 return 0;
458
459 #ifdef WITH_OPENSSL
460 evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
461 if (evplen == 0)
462 return 0;
463 else if (evplen < 0)
464 return SSH_ERR_LIBCRYPTO_ERROR;
465 if ((size_t)evplen != len)
466 return SSH_ERR_INVALID_ARGUMENT;
467 if (cipher_authlen(c)) {
468 if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
469 len, iv))
470 return SSH_ERR_LIBCRYPTO_ERROR;
471 } else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len))
472 return SSH_ERR_LIBCRYPTO_ERROR;
473 #endif
474 return 0;
475 }
476
477 int
cipher_set_keyiv(struct sshcipher_ctx * cc,const u_char * iv,size_t len)478 cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len)
479 {
480 #ifdef WITH_OPENSSL
481 const struct sshcipher *c = cc->cipher;
482 int evplen = 0;
483 #endif
484
485 if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
486 return 0;
487 if ((cc->cipher->flags & CFLAG_NONE) != 0)
488 return 0;
489
490 #ifdef WITH_OPENSSL
491 evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
492 if (evplen <= 0)
493 return SSH_ERR_LIBCRYPTO_ERROR;
494 if ((size_t)evplen != len)
495 return SSH_ERR_INVALID_ARGUMENT;
496 if (cipher_authlen(c)) {
497 /* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */
498 if (!EVP_CIPHER_CTX_ctrl(cc->evp,
499 EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv))
500 return SSH_ERR_LIBCRYPTO_ERROR;
501 } else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen))
502 return SSH_ERR_LIBCRYPTO_ERROR;
503 #endif
504 return 0;
505 }
506