1 /* $OpenBSD: hostfile.c,v 1.100 2025/11/25 00:57:04 djm 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 * Functions for manipulating the known hosts files.
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) 1999, 2000 Markus Friedl. All rights reserved.
16 * Copyright (c) 1999 Niels Provos. All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 * 1. Redistributions of source code must retain the above copyright
22 * notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 * notice, this list of conditions and the following disclaimer in the
25 * documentation and/or other materials provided with the distribution.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 #include "includes.h"
40
41 #include <sys/types.h>
42 #include <sys/stat.h>
43
44 #include <netinet/in.h>
45
46 #include <errno.h>
47 #include <resolv.h>
48 #include <stdarg.h>
49 #include <stdio.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #include <unistd.h>
53
54 #include "xmalloc.h"
55 #include "match.h"
56 #include "sshkey.h"
57 #include "hostfile.h"
58 #include "log.h"
59 #include "misc.h"
60 #include "pathnames.h"
61 #include "ssherr.h"
62 #include "digest.h"
63 #include "hmac.h"
64 #include "sshbuf.h"
65
66 /* XXX hmac is too easy to dictionary attack; use bcrypt? */
67
68 static int
extract_salt(const char * s,u_int l,u_char * salt,size_t salt_len)69 extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len)
70 {
71 char *p, *b64salt;
72 u_int b64len;
73 int ret;
74
75 if (l < sizeof(HASH_MAGIC) - 1) {
76 debug2("extract_salt: string too short");
77 return (-1);
78 }
79 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
80 debug2("extract_salt: invalid magic identifier");
81 return (-1);
82 }
83 s += sizeof(HASH_MAGIC) - 1;
84 l -= sizeof(HASH_MAGIC) - 1;
85 if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
86 debug2("extract_salt: missing salt termination character");
87 return (-1);
88 }
89
90 b64len = p - s;
91 /* Sanity check */
92 if (b64len == 0 || b64len > 1024) {
93 debug2("extract_salt: bad encoded salt length %u", b64len);
94 return (-1);
95 }
96 b64salt = xmalloc(1 + b64len);
97 memcpy(b64salt, s, b64len);
98 b64salt[b64len] = '\0';
99
100 ret = __b64_pton(b64salt, salt, salt_len);
101 free(b64salt);
102 if (ret == -1) {
103 debug2("extract_salt: salt decode error");
104 return (-1);
105 }
106 if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) {
107 debug2("extract_salt: expected salt len %zd, got %d",
108 ssh_hmac_bytes(SSH_DIGEST_SHA1), ret);
109 return (-1);
110 }
111
112 return (0);
113 }
114
115 char *
host_hash(const char * host,const char * name_from_hostfile,u_int src_len)116 host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
117 {
118 struct ssh_hmac_ctx *ctx;
119 u_char salt[256], result[256];
120 char uu_salt[512], uu_result[512];
121 char *encoded = NULL;
122 u_int len;
123
124 len = ssh_digest_bytes(SSH_DIGEST_SHA1);
125
126 if (name_from_hostfile == NULL) {
127 /* Create new salt */
128 arc4random_buf(salt, len);
129 } else {
130 /* Extract salt from known host entry */
131 if (extract_salt(name_from_hostfile, src_len, salt,
132 sizeof(salt)) == -1)
133 return (NULL);
134 }
135
136 if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL ||
137 ssh_hmac_init(ctx, salt, len) < 0 ||
138 ssh_hmac_update(ctx, host, strlen(host)) < 0 ||
139 ssh_hmac_final(ctx, result, sizeof(result)))
140 fatal_f("ssh_hmac failed");
141 ssh_hmac_free(ctx);
142
143 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
144 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
145 fatal_f("__b64_ntop failed");
146 xasprintf(&encoded, "%s%s%c%s", HASH_MAGIC, uu_salt, HASH_DELIM,
147 uu_result);
148
149 return (encoded);
150 }
151
152 /*
153 * Parses an RSA key from a string. Moves the pointer over the key.
154 * Skips any whitespace at the beginning and at end.
155 */
156
157 int
hostfile_read_key(char ** cpp,u_int * bitsp,struct sshkey * ret)158 hostfile_read_key(char **cpp, u_int *bitsp, struct sshkey *ret)
159 {
160 char *cp;
161
162 /* Skip leading whitespace. */
163 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
164 ;
165
166 if (sshkey_read(ret, &cp) != 0)
167 return 0;
168
169 /* Skip trailing whitespace. */
170 for (; *cp == ' ' || *cp == '\t'; cp++)
171 ;
172
173 /* Return results. */
174 *cpp = cp;
175 if (bitsp != NULL)
176 *bitsp = sshkey_size(ret);
177 return 1;
178 }
179
180 static HostkeyMarker
check_markers(char ** cpp)181 check_markers(char **cpp)
182 {
183 char marker[32], *sp, *cp = *cpp;
184 int ret = MRK_NONE;
185
186 while (*cp == '@') {
187 /* Only one marker is allowed */
188 if (ret != MRK_NONE)
189 return MRK_ERROR;
190 /* Markers are terminated by whitespace */
191 if ((sp = strchr(cp, ' ')) == NULL &&
192 (sp = strchr(cp, '\t')) == NULL)
193 return MRK_ERROR;
194 /* Extract marker for comparison */
195 if (sp <= cp + 1 || sp >= cp + sizeof(marker))
196 return MRK_ERROR;
197 memcpy(marker, cp, sp - cp);
198 marker[sp - cp] = '\0';
199 if (strcmp(marker, CA_MARKER) == 0)
200 ret = MRK_CA;
201 else if (strcmp(marker, REVOKE_MARKER) == 0)
202 ret = MRK_REVOKE;
203 else
204 return MRK_ERROR;
205
206 /* Skip past marker and any whitespace that follows it */
207 cp = sp;
208 for (; *cp == ' ' || *cp == '\t'; cp++)
209 ;
210 }
211 *cpp = cp;
212 return ret;
213 }
214
215 struct hostkeys *
init_hostkeys(void)216 init_hostkeys(void)
217 {
218 struct hostkeys *ret = xcalloc(1, sizeof(*ret));
219
220 ret->entries = NULL;
221 return ret;
222 }
223
224 struct load_callback_ctx {
225 const char *host;
226 u_long num_loaded;
227 struct hostkeys *hostkeys;
228 };
229
230 static int
record_hostkey(struct hostkey_foreach_line * l,void * _ctx)231 record_hostkey(struct hostkey_foreach_line *l, void *_ctx)
232 {
233 struct load_callback_ctx *ctx = (struct load_callback_ctx *)_ctx;
234 struct hostkeys *hostkeys = ctx->hostkeys;
235 struct hostkey_entry *tmp;
236
237 if (l->status == HKF_STATUS_INVALID) {
238 /* XXX make this verbose() in the future */
239 debug("%s:%ld: parse error in hostkeys file",
240 l->path, l->linenum);
241 return 0;
242 }
243
244 debug3_f("found %skey type %s in file %s:%lu",
245 l->marker == MRK_NONE ? "" :
246 (l->marker == MRK_CA ? "ca " : "revoked "),
247 sshkey_type(l->key), l->path, l->linenum);
248 if ((tmp = recallocarray(hostkeys->entries, hostkeys->num_entries,
249 hostkeys->num_entries + 1, sizeof(*hostkeys->entries))) == NULL)
250 return SSH_ERR_ALLOC_FAIL;
251 hostkeys->entries = tmp;
252 hostkeys->entries[hostkeys->num_entries].host = xstrdup(ctx->host);
253 hostkeys->entries[hostkeys->num_entries].file = xstrdup(l->path);
254 hostkeys->entries[hostkeys->num_entries].line = l->linenum;
255 hostkeys->entries[hostkeys->num_entries].key = l->key;
256 l->key = NULL; /* steal it */
257 hostkeys->entries[hostkeys->num_entries].marker = l->marker;
258 hostkeys->entries[hostkeys->num_entries].note = l->note;
259 hostkeys->num_entries++;
260 ctx->num_loaded++;
261
262 return 0;
263 }
264
265 void
load_hostkeys_file(struct hostkeys * hostkeys,const char * host,const char * path,FILE * f,u_int note)266 load_hostkeys_file(struct hostkeys *hostkeys, const char *host,
267 const char *path, FILE *f, u_int note)
268 {
269 int r;
270 struct load_callback_ctx ctx;
271
272 ctx.host = host;
273 ctx.num_loaded = 0;
274 ctx.hostkeys = hostkeys;
275
276 if ((r = hostkeys_foreach_file(path, f, record_hostkey, &ctx, host,
277 NULL, HKF_WANT_MATCH|HKF_WANT_PARSE_KEY, note)) != 0) {
278 if (r != SSH_ERR_SYSTEM_ERROR && errno != ENOENT)
279 debug_fr(r, "hostkeys_foreach failed for %s", path);
280 }
281 if (ctx.num_loaded != 0)
282 debug3_f("loaded %lu keys from %s", ctx.num_loaded, host);
283 }
284
285 void
load_hostkeys(struct hostkeys * hostkeys,const char * host,const char * path,u_int note)286 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path,
287 u_int note)
288 {
289 FILE *f;
290
291 if ((f = fopen(path, "r")) == NULL) {
292 debug_f("fopen %s: %s", path, strerror(errno));
293 return;
294 }
295
296 load_hostkeys_file(hostkeys, host, path, f, note);
297 fclose(f);
298 }
299
300 void
free_hostkeys(struct hostkeys * hostkeys)301 free_hostkeys(struct hostkeys *hostkeys)
302 {
303 u_int i;
304
305 for (i = 0; i < hostkeys->num_entries; i++) {
306 free(hostkeys->entries[i].host);
307 free(hostkeys->entries[i].file);
308 sshkey_free(hostkeys->entries[i].key);
309 explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
310 }
311 free(hostkeys->entries);
312 freezero(hostkeys, sizeof(*hostkeys));
313 }
314
315 static int
check_key_not_revoked(struct hostkeys * hostkeys,struct sshkey * k)316 check_key_not_revoked(struct hostkeys *hostkeys, struct sshkey *k)
317 {
318 int is_cert = sshkey_is_cert(k);
319 u_int i;
320
321 for (i = 0; i < hostkeys->num_entries; i++) {
322 if (hostkeys->entries[i].marker != MRK_REVOKE)
323 continue;
324 if (sshkey_equal_public(k, hostkeys->entries[i].key))
325 return -1;
326 if (is_cert && k != NULL &&
327 sshkey_equal_public(k->cert->signature_key,
328 hostkeys->entries[i].key))
329 return -1;
330 }
331 return 0;
332 }
333
334 /*
335 * Match keys against a specified key, or look one up by key type.
336 *
337 * If looking for a keytype (key == NULL) and one is found then return
338 * HOST_FOUND, otherwise HOST_NEW.
339 *
340 * If looking for a key (key != NULL):
341 * 1. If the key is a cert and a matching CA is found, return HOST_OK
342 * 2. If the key is not a cert and a matching key is found, return HOST_OK
343 * 3. If no key matches but a key with a different type is found, then
344 * return HOST_CHANGED
345 * 4. If no matching keys are found, then return HOST_NEW.
346 *
347 * Finally, check any found key is not revoked.
348 */
349 static HostStatus
check_hostkeys_by_key_or_type(struct hostkeys * hostkeys,struct sshkey * k,int keytype,int nid,const struct hostkey_entry ** found)350 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
351 struct sshkey *k, int keytype, int nid, const struct hostkey_entry **found)
352 {
353 u_int i;
354 HostStatus end_return = HOST_NEW;
355 int want_cert = sshkey_is_cert(k);
356 HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
357
358 if (found != NULL)
359 *found = NULL;
360
361 for (i = 0; i < hostkeys->num_entries; i++) {
362 if (hostkeys->entries[i].marker != want_marker)
363 continue;
364 if (k == NULL) {
365 if (hostkeys->entries[i].key->type != keytype)
366 continue;
367 if (nid != -1 &&
368 sshkey_type_plain(keytype) == KEY_ECDSA &&
369 hostkeys->entries[i].key->ecdsa_nid != nid)
370 continue;
371 end_return = HOST_FOUND;
372 if (found != NULL)
373 *found = hostkeys->entries + i;
374 k = hostkeys->entries[i].key;
375 break;
376 }
377 if (want_cert) {
378 if (sshkey_equal_public(k->cert->signature_key,
379 hostkeys->entries[i].key)) {
380 /* A matching CA exists */
381 end_return = HOST_OK;
382 if (found != NULL)
383 *found = hostkeys->entries + i;
384 break;
385 }
386 } else {
387 if (sshkey_equal(k, hostkeys->entries[i].key)) {
388 end_return = HOST_OK;
389 if (found != NULL)
390 *found = hostkeys->entries + i;
391 break;
392 }
393 /* A non-matching key exists */
394 end_return = HOST_CHANGED;
395 if (found != NULL)
396 *found = hostkeys->entries + i;
397 }
398 }
399 if (check_key_not_revoked(hostkeys, k) != 0) {
400 end_return = HOST_REVOKED;
401 if (found != NULL)
402 *found = NULL;
403 }
404 return end_return;
405 }
406
407 HostStatus
check_key_in_hostkeys(struct hostkeys * hostkeys,struct sshkey * key,const struct hostkey_entry ** found)408 check_key_in_hostkeys(struct hostkeys *hostkeys, struct sshkey *key,
409 const struct hostkey_entry **found)
410 {
411 if (key == NULL)
412 fatal("no key to look up");
413 return check_hostkeys_by_key_or_type(hostkeys, key, 0, -1, found);
414 }
415
416 int
lookup_key_in_hostkeys_by_type(struct hostkeys * hostkeys,int keytype,int nid,const struct hostkey_entry ** found)417 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, int nid,
418 const struct hostkey_entry **found)
419 {
420 return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, nid,
421 found) == HOST_FOUND);
422 }
423
424 int
lookup_marker_in_hostkeys(struct hostkeys * hostkeys,int want_marker)425 lookup_marker_in_hostkeys(struct hostkeys *hostkeys, int want_marker)
426 {
427 u_int i;
428
429 for (i = 0; i < hostkeys->num_entries; i++) {
430 if (hostkeys->entries[i].marker == (HostkeyMarker)want_marker)
431 return 1;
432 }
433 return 0;
434 }
435
436 static int
format_host_entry(struct sshbuf * entry,const char * host,const char * ip,const struct sshkey * key,int store_hash)437 format_host_entry(struct sshbuf *entry, const char *host, const char *ip,
438 const struct sshkey *key, int store_hash)
439 {
440 int r, success = 0;
441 char *hashed_host = NULL, *lhost;
442
443 lhost = xstrdup(host);
444 lowercase(lhost);
445
446 if (store_hash) {
447 if ((hashed_host = host_hash(lhost, NULL, 0)) == NULL) {
448 error_f("host_hash failed");
449 free(lhost);
450 return 0;
451 }
452 if ((r = sshbuf_putf(entry, "%s ", hashed_host)) != 0)
453 fatal_fr(r, "sshbuf_putf");
454 } else if (ip != NULL) {
455 if ((r = sshbuf_putf(entry, "%s,%s ", lhost, ip)) != 0)
456 fatal_fr(r, "sshbuf_putf");
457 } else {
458 if ((r = sshbuf_putf(entry, "%s ", lhost)) != 0)
459 fatal_fr(r, "sshbuf_putf");
460 }
461 free(hashed_host);
462 free(lhost);
463 if ((r = sshkey_format_text(key, entry)) == 0)
464 success = 1;
465 else
466 error_fr(r, "sshkey_write");
467 if ((r = sshbuf_putf(entry, "\n")) != 0)
468 fatal_fr(r, "sshbuf_putf");
469
470 /* If hashing is enabled, the IP address needs to go on its own line */
471 if (success && store_hash && ip != NULL)
472 success = format_host_entry(entry, ip, NULL, key, 1);
473 return success;
474 }
475
476 static int
write_host_entry(FILE * f,const char * host,const char * ip,const struct sshkey * key,int store_hash)477 write_host_entry(FILE *f, const char *host, const char *ip,
478 const struct sshkey *key, int store_hash)
479 {
480 int r, success = 0;
481 struct sshbuf *entry = NULL;
482
483 if ((entry = sshbuf_new()) == NULL)
484 fatal_f("allocation failed");
485 if ((r = format_host_entry(entry, host, ip, key, store_hash)) != 1) {
486 debug_f("failed to format host entry");
487 goto out;
488 }
489 if ((r = fwrite(sshbuf_ptr(entry), sshbuf_len(entry), 1, f)) != 1) {
490 error_f("fwrite: %s", strerror(errno));
491 goto out;
492 }
493 success = 1;
494 out:
495 sshbuf_free(entry);
496 return success;
497 }
498
499 /*
500 * Create user ~/.ssh directory if it doesn't exist and we want to write to it.
501 * If notify is set, a message will be emitted if the directory is created.
502 */
503 void
hostfile_create_user_ssh_dir(const char * filename,int notify)504 hostfile_create_user_ssh_dir(const char *filename, int notify)
505 {
506 char *dotsshdir = NULL, *p;
507 size_t len;
508 struct stat st;
509
510 if ((p = strrchr(filename, '/')) == NULL)
511 return;
512 len = p - filename;
513 dotsshdir = tilde_expand_filename("~/" _PATH_SSH_USER_DIR, getuid());
514 if (strlen(dotsshdir) > len || strncmp(filename, dotsshdir, len) != 0)
515 goto out; /* not ~/.ssh prefixed */
516 if (stat(dotsshdir, &st) == 0)
517 goto out; /* dir already exists */
518 else if (errno != ENOENT)
519 error("Could not stat %s: %s", dotsshdir, strerror(errno));
520 else {
521 #ifdef WITH_SELINUX
522 ssh_selinux_setfscreatecon(dotsshdir);
523 #endif
524 if (mkdir(dotsshdir, 0700) == -1)
525 error("Could not create directory '%.200s' (%s).",
526 dotsshdir, strerror(errno));
527 else if (notify)
528 logit("Created directory '%s'.", dotsshdir);
529 #ifdef WITH_SELINUX
530 ssh_selinux_setfscreatecon(NULL);
531 #endif
532 }
533 out:
534 free(dotsshdir);
535 }
536
537 /*
538 * Appends an entry to the host file. Returns false if the entry could not
539 * be appended.
540 */
541 int
add_host_to_hostfile(const char * filename,const char * host,const struct sshkey * key,int store_hash)542 add_host_to_hostfile(const char *filename, const char *host,
543 const struct sshkey *key, int store_hash)
544 {
545 FILE *f;
546 int success, addnl = 0;
547
548 if (key == NULL)
549 return 1; /* XXX ? */
550 hostfile_create_user_ssh_dir(filename, 0);
551 if ((f = fopen(filename, "a+")) == NULL)
552 return 0;
553 setvbuf(f, NULL, _IONBF, 0);
554 /* Make sure we have a terminating newline. */
555 if (fseek(f, -1L, SEEK_END) == 0 && fgetc(f) != '\n')
556 addnl = 1;
557 if (fseek(f, 0L, SEEK_END) != 0 || (addnl && fputc('\n', f) != '\n')) {
558 error("Failed to add terminating newline to %s: %s",
559 filename, strerror(errno));
560 fclose(f);
561 return 0;
562 }
563 success = write_host_entry(f, host, NULL, key, store_hash);
564 fclose(f);
565 return success;
566 }
567
568 struct host_delete_ctx {
569 FILE *out;
570 int quiet;
571 const char *host, *ip;
572 u_int *match_keys; /* mask of HKF_MATCH_* for this key */
573 struct sshkey * const *keys;
574 size_t nkeys;
575 int modified;
576 };
577
578 static int
host_delete(struct hostkey_foreach_line * l,void * _ctx)579 host_delete(struct hostkey_foreach_line *l, void *_ctx)
580 {
581 struct host_delete_ctx *ctx = (struct host_delete_ctx *)_ctx;
582 int loglevel = ctx->quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
583 size_t i;
584
585 /* Don't remove CA and revocation lines */
586 if (l->status == HKF_STATUS_MATCHED && l->marker == MRK_NONE) {
587 /*
588 * If this line contains one of the keys that we will be
589 * adding later, then don't change it and mark the key for
590 * skipping.
591 */
592 for (i = 0; i < ctx->nkeys; i++) {
593 if (!sshkey_equal(ctx->keys[i], l->key))
594 continue;
595 ctx->match_keys[i] |= l->match;
596 fprintf(ctx->out, "%s\n", l->line);
597 debug3_f("%s key already at %s:%ld",
598 sshkey_type(l->key), l->path, l->linenum);
599 return 0;
600 }
601
602 /*
603 * Hostname matches and has no CA/revoke marker, delete it
604 * by *not* writing the line to ctx->out.
605 */
606 do_log2(loglevel, "%s%s%s:%ld: Removed %s key for host %s",
607 ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
608 l->path, l->linenum, sshkey_type(l->key), ctx->host);
609 ctx->modified = 1;
610 return 0;
611 }
612 /* Retain non-matching hosts and invalid lines when deleting */
613 if (l->status == HKF_STATUS_INVALID) {
614 do_log2(loglevel, "%s%s%s:%ld: invalid known_hosts entry",
615 ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
616 l->path, l->linenum);
617 }
618 fprintf(ctx->out, "%s\n", l->line);
619 return 0;
620 }
621
622 int
hostfile_replace_entries(const char * filename,const char * host,const char * ip,struct sshkey ** keys,size_t nkeys,int store_hash,int quiet,int hash_alg)623 hostfile_replace_entries(const char *filename, const char *host, const char *ip,
624 struct sshkey **keys, size_t nkeys, int store_hash, int quiet, int hash_alg)
625 {
626 int r, fd, oerrno = 0;
627 int loglevel = quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
628 struct host_delete_ctx ctx;
629 char *fp = NULL, *temp = NULL, *back = NULL;
630 const char *what;
631 mode_t omask;
632 size_t i;
633 u_int want;
634
635 omask = umask(077);
636
637 memset(&ctx, 0, sizeof(ctx));
638 ctx.host = host;
639 ctx.ip = ip;
640 ctx.quiet = quiet;
641
642 if ((ctx.match_keys = calloc(nkeys, sizeof(*ctx.match_keys))) == NULL)
643 return SSH_ERR_ALLOC_FAIL;
644 ctx.keys = keys;
645 ctx.nkeys = nkeys;
646 ctx.modified = 0;
647
648 /*
649 * Prepare temporary file for in-place deletion.
650 */
651 if ((r = asprintf(&temp, "%s.XXXXXXXXXXX", filename)) == -1 ||
652 (r = asprintf(&back, "%s.old", filename)) == -1) {
653 r = SSH_ERR_ALLOC_FAIL;
654 goto fail;
655 }
656
657 if ((fd = mkstemp(temp)) == -1) {
658 oerrno = errno;
659 error_f("mkstemp: %s", strerror(oerrno));
660 r = SSH_ERR_SYSTEM_ERROR;
661 goto fail;
662 }
663 if ((ctx.out = fdopen(fd, "w")) == NULL) {
664 oerrno = errno;
665 close(fd);
666 error_f("fdopen: %s", strerror(oerrno));
667 r = SSH_ERR_SYSTEM_ERROR;
668 goto fail;
669 }
670
671 /* Remove stale/mismatching entries for the specified host */
672 if ((r = hostkeys_foreach(filename, host_delete, &ctx, host, ip,
673 HKF_WANT_PARSE_KEY, 0)) != 0) {
674 oerrno = errno;
675 error_fr(r, "hostkeys_foreach");
676 goto fail;
677 }
678
679 /* Re-add the requested keys */
680 want = HKF_MATCH_HOST | (ip == NULL ? 0 : HKF_MATCH_IP);
681 for (i = 0; i < nkeys; i++) {
682 if (keys[i] == NULL || (want & ctx.match_keys[i]) == want)
683 continue;
684 if ((fp = sshkey_fingerprint(keys[i], hash_alg,
685 SSH_FP_DEFAULT)) == NULL) {
686 r = SSH_ERR_ALLOC_FAIL;
687 goto fail;
688 }
689 /* write host/ip */
690 what = "";
691 if (ctx.match_keys[i] == 0) {
692 what = "Adding new key";
693 if (!write_host_entry(ctx.out, host, ip,
694 keys[i], store_hash)) {
695 r = SSH_ERR_INTERNAL_ERROR;
696 goto fail;
697 }
698 } else if ((want & ~ctx.match_keys[i]) == HKF_MATCH_HOST) {
699 what = "Fixing match (hostname)";
700 if (!write_host_entry(ctx.out, host, NULL,
701 keys[i], store_hash)) {
702 r = SSH_ERR_INTERNAL_ERROR;
703 goto fail;
704 }
705 } else if ((want & ~ctx.match_keys[i]) == HKF_MATCH_IP) {
706 what = "Fixing match (address)";
707 if (!write_host_entry(ctx.out, ip, NULL,
708 keys[i], store_hash)) {
709 r = SSH_ERR_INTERNAL_ERROR;
710 goto fail;
711 }
712 }
713 do_log2(loglevel, "%s%s%s for %s%s%s to %s: %s %s",
714 quiet ? __func__ : "", quiet ? ": " : "", what,
715 host, ip == NULL ? "" : ",", ip == NULL ? "" : ip, filename,
716 sshkey_ssh_name(keys[i]), fp);
717 free(fp);
718 fp = NULL;
719 ctx.modified = 1;
720 }
721 fclose(ctx.out);
722 ctx.out = NULL;
723
724 if (ctx.modified) {
725 /* Backup the original file and replace it with the temporary */
726 if (unlink(back) == -1 && errno != ENOENT) {
727 oerrno = errno;
728 error_f("unlink %.100s: %s", back, strerror(errno));
729 r = SSH_ERR_SYSTEM_ERROR;
730 goto fail;
731 }
732 if (link(filename, back) == -1) {
733 oerrno = errno;
734 error_f("link %.100s to %.100s: %s", filename,
735 back, strerror(errno));
736 r = SSH_ERR_SYSTEM_ERROR;
737 goto fail;
738 }
739 if (rename(temp, filename) == -1) {
740 oerrno = errno;
741 error_f("rename \"%s\" to \"%s\": %s", temp,
742 filename, strerror(errno));
743 r = SSH_ERR_SYSTEM_ERROR;
744 goto fail;
745 }
746 } else {
747 /* No changes made; just delete the temporary file */
748 if (unlink(temp) != 0)
749 error_f("unlink \"%s\": %s", temp, strerror(errno));
750 }
751
752 /* success */
753 r = 0;
754 fail:
755 if (temp != NULL && r != 0)
756 unlink(temp);
757 free(temp);
758 free(back);
759 free(fp);
760 if (ctx.out != NULL)
761 fclose(ctx.out);
762 free(ctx.match_keys);
763 umask(omask);
764 if (r == SSH_ERR_SYSTEM_ERROR)
765 errno = oerrno;
766 return r;
767 }
768
769 static int
match_maybe_hashed(const char * host,const char * names,int * was_hashed)770 match_maybe_hashed(const char *host, const char *names, int *was_hashed)
771 {
772 int hashed = *names == HASH_DELIM, ret;
773 char *hashed_host = NULL;
774 size_t nlen = strlen(names);
775
776 if (was_hashed != NULL)
777 *was_hashed = hashed;
778 if (hashed) {
779 if ((hashed_host = host_hash(host, names, nlen)) == NULL)
780 return -1;
781 ret = (nlen == strlen(hashed_host) &&
782 strncmp(hashed_host, names, nlen) == 0);
783 free(hashed_host);
784 return ret;
785 }
786 return match_hostname(host, names) == 1;
787 }
788
789 int
hostkeys_foreach_file(const char * path,FILE * f,hostkeys_foreach_fn * callback,void * ctx,const char * host,const char * ip,u_int options,u_int note)790 hostkeys_foreach_file(const char *path, FILE *f, hostkeys_foreach_fn *callback,
791 void *ctx, const char *host, const char *ip, u_int options, u_int note)
792 {
793 char *line = NULL, ktype[128];
794 u_long linenum = 0;
795 char *cp, *cp2;
796 u_int kbits;
797 int hashed;
798 int s, r = 0;
799 struct hostkey_foreach_line lineinfo;
800 size_t linesize = 0, l;
801
802 memset(&lineinfo, 0, sizeof(lineinfo));
803 if (host == NULL && (options & HKF_WANT_MATCH) != 0)
804 return SSH_ERR_INVALID_ARGUMENT;
805
806 while (getline(&line, &linesize, f) != -1) {
807 linenum++;
808 line[strcspn(line, "\n")] = '\0';
809
810 free(lineinfo.line);
811 sshkey_free(lineinfo.key);
812 memset(&lineinfo, 0, sizeof(lineinfo));
813 lineinfo.path = path;
814 lineinfo.linenum = linenum;
815 lineinfo.line = xstrdup(line);
816 lineinfo.marker = MRK_NONE;
817 lineinfo.status = HKF_STATUS_OK;
818 lineinfo.keytype = KEY_UNSPEC;
819 lineinfo.note = note;
820
821 /* Skip any leading whitespace, comments and empty lines. */
822 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
823 ;
824 if (!*cp || *cp == '#' || *cp == '\n') {
825 if ((options & HKF_WANT_MATCH) == 0) {
826 lineinfo.status = HKF_STATUS_COMMENT;
827 if ((r = callback(&lineinfo, ctx)) != 0)
828 break;
829 }
830 continue;
831 }
832
833 if ((lineinfo.marker = check_markers(&cp)) == MRK_ERROR) {
834 verbose_f("invalid marker at %s:%lu", path, linenum);
835 if ((options & HKF_WANT_MATCH) == 0)
836 goto bad;
837 continue;
838 }
839
840 /* Find the end of the host name portion. */
841 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
842 ;
843 if (*cp2 == '\0') {
844 verbose_f("truncated line at %s:%lu", path, linenum);
845 if ((options & HKF_WANT_MATCH) == 0)
846 goto bad;
847 continue;
848 }
849 lineinfo.hosts = cp;
850 *cp2++ = '\0';
851
852 /* Check if the host name matches. */
853 if (host != NULL) {
854 if ((s = match_maybe_hashed(host, lineinfo.hosts,
855 &hashed)) == -1) {
856 debug2_f("%s:%ld: bad host hash \"%.32s\"",
857 path, linenum, lineinfo.hosts);
858 goto bad;
859 }
860 if (s == 1) {
861 lineinfo.status = HKF_STATUS_MATCHED;
862 lineinfo.match |= HKF_MATCH_HOST |
863 (hashed ? HKF_MATCH_HOST_HASHED : 0);
864 }
865 /* Try matching IP address if supplied */
866 if (ip != NULL) {
867 if ((s = match_maybe_hashed(ip, lineinfo.hosts,
868 &hashed)) == -1) {
869 debug2_f("%s:%ld: bad ip hash "
870 "\"%.32s\"", path, linenum,
871 lineinfo.hosts);
872 goto bad;
873 }
874 if (s == 1) {
875 lineinfo.status = HKF_STATUS_MATCHED;
876 lineinfo.match |= HKF_MATCH_IP |
877 (hashed ? HKF_MATCH_IP_HASHED : 0);
878 }
879 }
880 /*
881 * Skip this line if host matching requested and
882 * neither host nor address matched.
883 */
884 if ((options & HKF_WANT_MATCH) != 0 &&
885 lineinfo.status != HKF_STATUS_MATCHED)
886 continue;
887 }
888
889 /* Got a match. Skip host name and any following whitespace */
890 for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
891 ;
892 if (*cp2 == '\0' || *cp2 == '#') {
893 debug2("%s:%ld: truncated before key type",
894 path, linenum);
895 goto bad;
896 }
897 lineinfo.rawkey = cp = cp2;
898
899 if ((options & HKF_WANT_PARSE_KEY) != 0) {
900 /*
901 * Extract the key from the line. This will skip
902 * any leading whitespace. Ignore badly formatted
903 * lines.
904 */
905 if ((lineinfo.key = sshkey_new(KEY_UNSPEC)) == NULL) {
906 error_f("sshkey_new failed");
907 r = SSH_ERR_ALLOC_FAIL;
908 break;
909 }
910 if (!hostfile_read_key(&cp, &kbits, lineinfo.key)) {
911 goto bad;
912 }
913 lineinfo.keytype = lineinfo.key->type;
914 lineinfo.comment = cp;
915 } else {
916 /* Extract and parse key type */
917 l = strcspn(lineinfo.rawkey, " \t");
918 if (l <= 1 || l >= sizeof(ktype) ||
919 lineinfo.rawkey[l] == '\0')
920 goto bad;
921 memcpy(ktype, lineinfo.rawkey, l);
922 ktype[l] = '\0';
923 lineinfo.keytype = sshkey_type_from_name(ktype);
924
925 /*
926 * Assume legacy RSA1 if the first component is a short
927 * decimal number.
928 */
929 if (lineinfo.keytype == KEY_UNSPEC && l < 8 &&
930 strspn(ktype, "0123456789") == l)
931 goto bad;
932
933 /*
934 * Check that something other than whitespace follows
935 * the key type. This won't catch all corruption, but
936 * it does catch trivial truncation.
937 */
938 cp2 += l; /* Skip past key type */
939 for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
940 ;
941 if (*cp2 == '\0' || *cp2 == '#') {
942 debug2("%s:%ld: truncated after key type",
943 path, linenum);
944 lineinfo.keytype = KEY_UNSPEC;
945 }
946 if (lineinfo.keytype == KEY_UNSPEC) {
947 bad:
948 sshkey_free(lineinfo.key);
949 lineinfo.key = NULL;
950 lineinfo.status = HKF_STATUS_INVALID;
951 if ((r = callback(&lineinfo, ctx)) != 0)
952 break;
953 continue;
954 }
955 }
956 if ((r = callback(&lineinfo, ctx)) != 0)
957 break;
958 }
959 sshkey_free(lineinfo.key);
960 free(lineinfo.line);
961 free(line);
962 return r;
963 }
964
965 int
hostkeys_foreach(const char * path,hostkeys_foreach_fn * callback,void * ctx,const char * host,const char * ip,u_int options,u_int note)966 hostkeys_foreach(const char *path, hostkeys_foreach_fn *callback, void *ctx,
967 const char *host, const char *ip, u_int options, u_int note)
968 {
969 FILE *f;
970 int r, oerrno;
971
972 if ((f = fopen(path, "r")) == NULL)
973 return SSH_ERR_SYSTEM_ERROR;
974
975 debug3_f("reading file \"%s\"", path);
976 r = hostkeys_foreach_file(path, f, callback, ctx, host, ip,
977 options, note);
978 oerrno = errno;
979 fclose(f);
980 errno = oerrno;
981 return r;
982 }
983