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 * This file contains functions for reading and writing identity files, and
6 * for reading the passphrase from the user.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 *
14 *
15 * Copyright (c) 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 RCSID("$OpenBSD: authfile.c,v 1.50 2002/06/24 14:55:38 markus Exp $");
40
41 #pragma ident "%Z%%M% %I% %E% SMI"
42
43 #include <openssl/opensslconf.h>
44 #include <openssl/err.h>
45 #include <openssl/evp.h>
46 #include <openssl/pem.h>
47
48 #include "cipher.h"
49 #include "xmalloc.h"
50 #include "buffer.h"
51 #include "bufaux.h"
52 #include "key.h"
53 #include "ssh.h"
54 #include "log.h"
55 #include "authfile.h"
56 #include "rsa.h"
57
58 /* Version identification string for SSH v1 identity files. */
59 static const char authfile_id_string[] =
60 "SSH PRIVATE KEY FILE FORMAT 1.1\n";
61
62 /*
63 * Saves the authentication (private) key in a file, encrypting it with
64 * passphrase. The identification of the file (lowest 64 bits of n) will
65 * precede the key to provide identification of the key without needing a
66 * passphrase.
67 */
68
69 static int
70 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase,
71 const char *comment)
72 {
73 Buffer buffer, encrypted;
74 u_char buf[100], *cp;
75 int fd, i, cipher_num;
76 CipherContext ciphercontext;
77 Cipher *cipher;
78 u_int32_t rand;
79
80 /*
81 * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting
82 * to another cipher; otherwise use SSH_AUTHFILE_CIPHER.
83 */
84 cipher_num = (strcmp(passphrase, "") == 0) ?
85 SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER;
86 if ((cipher = cipher_by_number(cipher_num)) == NULL)
87 fatal("save_private_key_rsa: bad cipher");
88
89 /* This buffer is used to built the secret part of the private key. */
90 buffer_init(&buffer);
91
92 /* Put checkbytes for checking passphrase validity. */
93 rand = arc4random();
94 buf[0] = rand & 0xff;
95 buf[1] = (rand >> 8) & 0xff;
96 buf[2] = buf[0];
97 buf[3] = buf[1];
98 buffer_append(&buffer, buf, 4);
99
100 /*
101 * Store the private key (n and e will not be stored because they
102 * will be stored in plain text, and storing them also in encrypted
103 * format would just give known plaintext).
104 */
105 buffer_put_bignum(&buffer, key->rsa->d);
106 buffer_put_bignum(&buffer, key->rsa->iqmp);
107 buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */
108 buffer_put_bignum(&buffer, key->rsa->p); /* reverse from SSL q */
109
110 /* Pad the part to be encrypted until its size is a multiple of 8. */
111 while (buffer_len(&buffer) % 8 != 0)
112 buffer_put_char(&buffer, 0);
113
114 /* This buffer will be used to contain the data in the file. */
115 buffer_init(&encrypted);
116
117 /* First store keyfile id string. */
118 for (i = 0; authfile_id_string[i]; i++)
119 buffer_put_char(&encrypted, authfile_id_string[i]);
120 buffer_put_char(&encrypted, 0);
121
122 /* Store cipher type. */
123 buffer_put_char(&encrypted, cipher_num);
124 buffer_put_int(&encrypted, 0); /* For future extension */
125
126 /* Store public key. This will be in plain text. */
127 buffer_put_int(&encrypted, BN_num_bits(key->rsa->n));
128 buffer_put_bignum(&encrypted, key->rsa->n);
129 buffer_put_bignum(&encrypted, key->rsa->e);
130 buffer_put_cstring(&encrypted, comment);
131
132 /* Allocate space for the private part of the key in the buffer. */
133 cp = buffer_append_space(&encrypted, buffer_len(&buffer));
134
135 cipher_set_key_string(&ciphercontext, cipher, passphrase,
136 CIPHER_ENCRYPT);
137 cipher_crypt(&ciphercontext, cp,
138 buffer_ptr(&buffer), buffer_len(&buffer));
139 cipher_cleanup(&ciphercontext);
140 memset(&ciphercontext, 0, sizeof(ciphercontext));
141
142 /* Destroy temporary data. */
143 memset(buf, 0, sizeof(buf));
144 buffer_free(&buffer);
145
146 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
147 if (fd < 0) {
148 error("open %s failed: %s.", filename, strerror(errno));
149 return 0;
150 }
151 if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) !=
152 buffer_len(&encrypted)) {
153 error("write to key file %s failed: %s", filename,
154 strerror(errno));
155 buffer_free(&encrypted);
156 close(fd);
157 unlink(filename);
158 return 0;
159 }
160 close(fd);
161 buffer_free(&encrypted);
162 return 1;
163 }
164
165 /* save SSH v2 key in OpenSSL PEM format */
166 static int
167 key_save_private_pem(Key *key, const char *filename, const char *_passphrase,
168 const char *comment)
169 {
170 FILE *fp;
171 int fd;
172 int success = 0;
173 int len = strlen(_passphrase);
174 u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL;
175 const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL;
176
177 if (len > 0 && len <= 4) {
178 error("passphrase too short: have %d bytes, need > 4", len);
179 return 0;
180 }
181 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
182 if (fd < 0) {
183 error("open %s failed: %s.", filename, strerror(errno));
184 return 0;
185 }
186 fp = fdopen(fd, "w");
187 if (fp == NULL ) {
188 error("fdopen %s failed: %s.", filename, strerror(errno));
189 close(fd);
190 return 0;
191 }
192 switch (key->type) {
193 case KEY_DSA:
194 success = PEM_write_DSAPrivateKey(fp, key->dsa,
195 cipher, passphrase, len, NULL, NULL);
196 break;
197 case KEY_RSA:
198 success = PEM_write_RSAPrivateKey(fp, key->rsa,
199 cipher, passphrase, len, NULL, NULL);
200 break;
201 }
202 fclose(fp);
203 return success;
204 }
205
206 int
207 key_save_private(Key *key, const char *filename, const char *passphrase,
208 const char *comment)
209 {
210 switch (key->type) {
211 case KEY_RSA1:
212 return key_save_private_rsa1(key, filename, passphrase,
213 comment);
214 break;
215 case KEY_DSA:
216 case KEY_RSA:
217 return key_save_private_pem(key, filename, passphrase,
218 comment);
219 break;
220 default:
221 break;
222 }
223 error("key_save_private: cannot save key type %d", key->type);
224 return 0;
225 }
226
227 /*
228 * Loads the public part of the ssh v1 key file. Returns NULL if an error was
229 * encountered (the file does not exist or is not readable), and the key
230 * otherwise.
231 */
232
233 static Key *
234 key_load_public_rsa1(int fd, const char *filename, char **commentp)
235 {
236 Buffer buffer;
237 Key *pub;
238 char *cp;
239 int i;
240 off_t len;
241
242 len = lseek(fd, (off_t) 0, SEEK_END);
243 lseek(fd, (off_t) 0, SEEK_SET);
244
245 buffer_init(&buffer);
246 cp = buffer_append_space(&buffer, len);
247
248 if (read(fd, cp, (size_t) len) != (size_t) len) {
249 debug("Read from key file %.200s failed: %.100s", filename,
250 strerror(errno));
251 buffer_free(&buffer);
252 return NULL;
253 }
254
255 /* Check that it is at least big enough to contain the ID string. */
256 if (len < sizeof(authfile_id_string)) {
257 debug3("Not a RSA1 key file %.200s.", filename);
258 buffer_free(&buffer);
259 return NULL;
260 }
261 /*
262 * Make sure it begins with the id string. Consume the id string
263 * from the buffer.
264 */
265 for (i = 0; i < sizeof(authfile_id_string); i++)
266 if (buffer_get_char(&buffer) != authfile_id_string[i]) {
267 debug3("Not a RSA1 key file %.200s.", filename);
268 buffer_free(&buffer);
269 return NULL;
270 }
271 /* Skip cipher type and reserved data. */
272 (void) buffer_get_char(&buffer); /* cipher type */
273 (void) buffer_get_int(&buffer); /* reserved */
274
275 /* Read the public key from the buffer. */
276 (void) buffer_get_int(&buffer);
277 pub = key_new(KEY_RSA1);
278 buffer_get_bignum(&buffer, pub->rsa->n);
279 buffer_get_bignum(&buffer, pub->rsa->e);
280 if (commentp)
281 *commentp = buffer_get_string(&buffer, NULL);
282 /* The encrypted private part is not parsed by this function. */
283
284 buffer_free(&buffer);
285 return pub;
286 }
287
288 /* load public key from private-key file, works only for SSH v1 */
289 Key *
290 key_load_public_type(int type, const char *filename, char **commentp)
291 {
292 Key *pub;
293 int fd;
294
295 if (type == KEY_RSA1) {
296 fd = open(filename, O_RDONLY);
297 if (fd < 0)
298 return NULL;
299 pub = key_load_public_rsa1(fd, filename, commentp);
300 close(fd);
301 return pub;
302 }
303 return NULL;
304 }
305
306 /*
307 * Loads the private key from the file. Returns 0 if an error is encountered
308 * (file does not exist or is not readable, or passphrase is bad). This
309 * initializes the private key.
310 * Assumes we are called under uid of the owner of the file.
311 */
312
313 static Key *
314 key_load_private_rsa1(int fd, const char *filename, const char *passphrase,
315 char **commentp)
316 {
317 int i, check1, check2, cipher_type;
318 off_t len;
319 Buffer buffer, decrypted;
320 u_char *cp;
321 CipherContext ciphercontext;
322 Cipher *cipher;
323 Key *prv = NULL;
324
325 len = lseek(fd, (off_t) 0, SEEK_END);
326 lseek(fd, (off_t) 0, SEEK_SET);
327
328 buffer_init(&buffer);
329 cp = buffer_append_space(&buffer, len);
330
331 if (read(fd, cp, (size_t) len) != (size_t) len) {
332 debug("Read from key file %.200s failed: %.100s", filename,
333 strerror(errno));
334 buffer_free(&buffer);
335 close(fd);
336 return NULL;
337 }
338
339 /* Check that it is at least big enough to contain the ID string. */
340 if (len < sizeof(authfile_id_string)) {
341 debug3("Not a RSA1 key file %.200s.", filename);
342 buffer_free(&buffer);
343 close(fd);
344 return NULL;
345 }
346 /*
347 * Make sure it begins with the id string. Consume the id string
348 * from the buffer.
349 */
350 for (i = 0; i < sizeof(authfile_id_string); i++)
351 if (buffer_get_char(&buffer) != authfile_id_string[i]) {
352 debug3("Not a RSA1 key file %.200s.", filename);
353 buffer_free(&buffer);
354 close(fd);
355 return NULL;
356 }
357
358 /* Read cipher type. */
359 cipher_type = buffer_get_char(&buffer);
360 (void) buffer_get_int(&buffer); /* Reserved data. */
361
362 /* Read the public key from the buffer. */
363 (void) buffer_get_int(&buffer);
364 prv = key_new_private(KEY_RSA1);
365
366 buffer_get_bignum(&buffer, prv->rsa->n);
367 buffer_get_bignum(&buffer, prv->rsa->e);
368 if (commentp)
369 *commentp = buffer_get_string(&buffer, NULL);
370 else
371 xfree(buffer_get_string(&buffer, NULL));
372
373 /* Check that it is a supported cipher. */
374 cipher = cipher_by_number(cipher_type);
375 if (cipher == NULL) {
376 debug("Unsupported cipher %d used in key file %.200s.",
377 cipher_type, filename);
378 buffer_free(&buffer);
379 goto fail;
380 }
381 /* Initialize space for decrypted data. */
382 buffer_init(&decrypted);
383 cp = buffer_append_space(&decrypted, buffer_len(&buffer));
384
385 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */
386 cipher_set_key_string(&ciphercontext, cipher, passphrase,
387 CIPHER_DECRYPT);
388 cipher_crypt(&ciphercontext, cp,
389 buffer_ptr(&buffer), buffer_len(&buffer));
390 cipher_cleanup(&ciphercontext);
391 memset(&ciphercontext, 0, sizeof(ciphercontext));
392 buffer_free(&buffer);
393
394 check1 = buffer_get_char(&decrypted);
395 check2 = buffer_get_char(&decrypted);
396 if (check1 != buffer_get_char(&decrypted) ||
397 check2 != buffer_get_char(&decrypted)) {
398 if (strcmp(passphrase, "") != 0)
399 debug("Bad passphrase supplied for key file %.200s.",
400 filename);
401 /* Bad passphrase. */
402 buffer_free(&decrypted);
403 goto fail;
404 }
405 /* Read the rest of the private key. */
406 buffer_get_bignum(&decrypted, prv->rsa->d);
407 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */
408 /* in SSL and SSH v1 p and q are exchanged */
409 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */
410 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */
411
412 /* calculate p-1 and q-1 */
413 rsa_generate_additional_parameters(prv->rsa);
414
415 buffer_free(&decrypted);
416 close(fd);
417 return prv;
418
419 fail:
420 if (commentp)
421 xfree(*commentp);
422 close(fd);
423 key_free(prv);
424 return NULL;
425 }
426
427 Key *
428 key_load_private_pem(int fd, int type, const char *passphrase,
429 char **commentp)
430 {
431 FILE *fp;
432 EVP_PKEY *pk = NULL;
433 Key *prv = NULL;
434 char *name = "<no key>";
435
436 fp = fdopen(fd, "r");
437 if (fp == NULL) {
438 error("fdopen failed: %s", strerror(errno));
439 close(fd);
440 return NULL;
441 }
442 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase);
443 if (pk == NULL) {
444 debug("PEM_read_PrivateKey failed");
445 (void)ERR_get_error();
446 } else if (pk->type == EVP_PKEY_RSA &&
447 (type == KEY_UNSPEC||type==KEY_RSA)) {
448 prv = key_new(KEY_UNSPEC);
449 prv->rsa = EVP_PKEY_get1_RSA(pk);
450 prv->type = KEY_RSA;
451 name = "rsa w/o comment";
452 #ifdef DEBUG_PK
453 RSA_print_fp(stderr, prv->rsa, 8);
454 #endif
455 } else if (pk->type == EVP_PKEY_DSA &&
456 (type == KEY_UNSPEC||type==KEY_DSA)) {
457 prv = key_new(KEY_UNSPEC);
458 prv->dsa = EVP_PKEY_get1_DSA(pk);
459 prv->type = KEY_DSA;
460 name = "dsa w/o comment";
461 #ifdef DEBUG_PK
462 DSA_print_fp(stderr, prv->dsa, 8);
463 #endif
464 } else {
465 error("PEM_read_PrivateKey: mismatch or "
466 "unknown EVP_PKEY save_type %d", pk->save_type);
467 }
468 fclose(fp);
469 if (pk != NULL)
470 EVP_PKEY_free(pk);
471 if (prv != NULL && commentp)
472 *commentp = xstrdup(name);
473 debug("read PEM private key done: type %s",
474 prv ? key_type(prv) : "<unknown>");
475 return prv;
476 }
477
478 static int
479 key_perm_ok(int fd, const char *filename)
480 {
481 struct stat st;
482
483 if (fstat(fd, &st) < 0)
484 return 0;
485 /*
486 * if a key owned by the user is accessed, then we check the
487 * permissions of the file. if the key owned by a different user,
488 * then we don't care.
489 */
490 #ifdef HAVE_CYGWIN
491 if (check_ntsec(filename))
492 #endif
493 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) {
494 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
495 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @");
496 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
497 error("Permissions 0%3.3o for '%s' are too open.",
498 (int)(st.st_mode & 0777), filename);
499 error("It is recommended that your private key files are NOT accessible by others.");
500 error("This private key will be ignored.");
501 return 0;
502 }
503 return 1;
504 }
505
506 Key *
507 key_load_private_type(int type, const char *filename, const char *passphrase,
508 char **commentp)
509 {
510 int fd;
511
512 fd = open(filename, O_RDONLY);
513 if (fd < 0)
514 return NULL;
515 if (!key_perm_ok(fd, filename)) {
516 error("bad permissions: ignore key: %s", filename);
517 close(fd);
518 return NULL;
519 }
520 switch (type) {
521 case KEY_RSA1:
522 return key_load_private_rsa1(fd, filename, passphrase,
523 commentp);
524 /* closes fd */
525 break;
526 case KEY_DSA:
527 case KEY_RSA:
528 case KEY_UNSPEC:
529 return key_load_private_pem(fd, type, passphrase, commentp);
530 /* closes fd */
531 break;
532 default:
533 close(fd);
534 break;
535 }
536 return NULL;
537 }
538
539 Key *
540 key_load_private(const char *filename, const char *passphrase,
541 char **commentp)
542 {
543 Key *pub, *prv;
544 int fd;
545
546 fd = open(filename, O_RDONLY);
547 if (fd < 0)
548 return NULL;
549 if (!key_perm_ok(fd, filename)) {
550 error("bad permissions: ignore key: %s", filename);
551 close(fd);
552 return NULL;
553 }
554 pub = key_load_public_rsa1(fd, filename, commentp);
555 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */
556 if (pub == NULL) {
557 /* closes fd */
558 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL);
559 /* use the filename as a comment for PEM */
560 if (commentp && prv)
561 *commentp = xstrdup(filename);
562 } else {
563 /* it's a SSH v1 key if the public key part is readable */
564 key_free(pub);
565 /* closes fd */
566 prv = key_load_private_rsa1(fd, filename, passphrase, NULL);
567 }
568 return prv;
569 }
570
571 static int
572 key_try_load_public(Key *k, const char *filename, char **commentp)
573 {
574 FILE *f;
575 char line[4096];
576 char *cp;
577
578 f = fopen(filename, "r");
579 if (f != NULL) {
580 while (fgets(line, sizeof(line), f)) {
581 line[sizeof(line)-1] = '\0';
582 cp = line;
583 switch (*cp) {
584 case '#':
585 case '\n':
586 case '\0':
587 continue;
588 }
589 /* Skip leading whitespace. */
590 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
591 ;
592 if (*cp) {
593 if (key_read(k, &cp) == 1) {
594 if (commentp)
595 *commentp=xstrdup(filename);
596 fclose(f);
597 return 1;
598 }
599 }
600 }
601 fclose(f);
602 }
603 return 0;
604 }
605
606 /* load public key from ssh v1 private or any pubkey file */
607 Key *
608 key_load_public(const char *filename, char **commentp)
609 {
610 Key *pub;
611 char file[MAXPATHLEN];
612
613 pub = key_load_public_type(KEY_RSA1, filename, commentp);
614 if (pub != NULL)
615 return pub;
616 pub = key_new(KEY_UNSPEC);
617 if (key_try_load_public(pub, filename, commentp) == 1)
618 return pub;
619 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) &&
620 (strlcat(file, ".pub", sizeof file) < sizeof(file)) &&
621 (key_try_load_public(pub, file, commentp) == 1))
622 return pub;
623 key_free(pub);
624 return NULL;
625 }