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