xref: /openssh-portable/hostfile.c (revision edd1d3a6)
1 /* $OpenBSD: hostfile.c,v 1.76 2019/07/07 01:05:00 dtucker 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 "ssherr.h"
61 #include "digest.h"
62 #include "hmac.h"
63 
64 struct hostkeys {
65 	struct hostkey_entry *entries;
66 	u_int num_entries;
67 };
68 
69 /* XXX hmac is too easy to dictionary attack; use bcrypt? */
70 
71 static int
extract_salt(const char * s,u_int l,u_char * salt,size_t salt_len)72 extract_salt(const char *s, u_int l, u_char *salt, size_t salt_len)
73 {
74 	char *p, *b64salt;
75 	u_int b64len;
76 	int ret;
77 
78 	if (l < sizeof(HASH_MAGIC) - 1) {
79 		debug2("extract_salt: string too short");
80 		return (-1);
81 	}
82 	if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
83 		debug2("extract_salt: invalid magic identifier");
84 		return (-1);
85 	}
86 	s += sizeof(HASH_MAGIC) - 1;
87 	l -= sizeof(HASH_MAGIC) - 1;
88 	if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
89 		debug2("extract_salt: missing salt termination character");
90 		return (-1);
91 	}
92 
93 	b64len = p - s;
94 	/* Sanity check */
95 	if (b64len == 0 || b64len > 1024) {
96 		debug2("extract_salt: bad encoded salt length %u", b64len);
97 		return (-1);
98 	}
99 	b64salt = xmalloc(1 + b64len);
100 	memcpy(b64salt, s, b64len);
101 	b64salt[b64len] = '\0';
102 
103 	ret = __b64_pton(b64salt, salt, salt_len);
104 	free(b64salt);
105 	if (ret == -1) {
106 		debug2("extract_salt: salt decode error");
107 		return (-1);
108 	}
109 	if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) {
110 		debug2("extract_salt: expected salt len %zd, got %d",
111 		    ssh_hmac_bytes(SSH_DIGEST_SHA1), ret);
112 		return (-1);
113 	}
114 
115 	return (0);
116 }
117 
118 char *
host_hash(const char * host,const char * name_from_hostfile,u_int src_len)119 host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
120 {
121 	struct ssh_hmac_ctx *ctx;
122 	u_char salt[256], result[256];
123 	char uu_salt[512], uu_result[512];
124 	static char encoded[1024];
125 	u_int len;
126 
127 	len = ssh_digest_bytes(SSH_DIGEST_SHA1);
128 
129 	if (name_from_hostfile == NULL) {
130 		/* Create new salt */
131 		arc4random_buf(salt, len);
132 	} else {
133 		/* Extract salt from known host entry */
134 		if (extract_salt(name_from_hostfile, src_len, salt,
135 		    sizeof(salt)) == -1)
136 			return (NULL);
137 	}
138 
139 	if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL ||
140 	    ssh_hmac_init(ctx, salt, len) < 0 ||
141 	    ssh_hmac_update(ctx, host, strlen(host)) < 0 ||
142 	    ssh_hmac_final(ctx, result, sizeof(result)))
143 		fatal("%s: ssh_hmac failed", __func__);
144 	ssh_hmac_free(ctx);
145 
146 	if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
147 	    __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
148 		fatal("%s: __b64_ntop failed", __func__);
149 
150 	snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
151 	    HASH_DELIM, uu_result);
152 
153 	return (encoded);
154 }
155 
156 /*
157  * Parses an RSA (number of bits, e, n) or DSA key from a string.  Moves the
158  * pointer over the key.  Skips any whitespace at the beginning and at end.
159  */
160 
161 int
hostfile_read_key(char ** cpp,u_int * bitsp,struct sshkey * ret)162 hostfile_read_key(char **cpp, u_int *bitsp, struct sshkey *ret)
163 {
164 	char *cp;
165 
166 	/* Skip leading whitespace. */
167 	for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
168 		;
169 
170 	if (sshkey_read(ret, &cp) != 0)
171 		return 0;
172 
173 	/* Skip trailing whitespace. */
174 	for (; *cp == ' ' || *cp == '\t'; cp++)
175 		;
176 
177 	/* Return results. */
178 	*cpp = cp;
179 	if (bitsp != NULL)
180 		*bitsp = sshkey_size(ret);
181 	return 1;
182 }
183 
184 static HostkeyMarker
check_markers(char ** cpp)185 check_markers(char **cpp)
186 {
187 	char marker[32], *sp, *cp = *cpp;
188 	int ret = MRK_NONE;
189 
190 	while (*cp == '@') {
191 		/* Only one marker is allowed */
192 		if (ret != MRK_NONE)
193 			return MRK_ERROR;
194 		/* Markers are terminated by whitespace */
195 		if ((sp = strchr(cp, ' ')) == NULL &&
196 		    (sp = strchr(cp, '\t')) == NULL)
197 			return MRK_ERROR;
198 		/* Extract marker for comparison */
199 		if (sp <= cp + 1 || sp >= cp + sizeof(marker))
200 			return MRK_ERROR;
201 		memcpy(marker, cp, sp - cp);
202 		marker[sp - cp] = '\0';
203 		if (strcmp(marker, CA_MARKER) == 0)
204 			ret = MRK_CA;
205 		else if (strcmp(marker, REVOKE_MARKER) == 0)
206 			ret = MRK_REVOKE;
207 		else
208 			return MRK_ERROR;
209 
210 		/* Skip past marker and any whitespace that follows it */
211 		cp = sp;
212 		for (; *cp == ' ' || *cp == '\t'; cp++)
213 			;
214 	}
215 	*cpp = cp;
216 	return ret;
217 }
218 
219 struct hostkeys *
init_hostkeys(void)220 init_hostkeys(void)
221 {
222 	struct hostkeys *ret = xcalloc(1, sizeof(*ret));
223 
224 	ret->entries = NULL;
225 	return ret;
226 }
227 
228 struct load_callback_ctx {
229 	const char *host;
230 	u_long num_loaded;
231 	struct hostkeys *hostkeys;
232 };
233 
234 static int
record_hostkey(struct hostkey_foreach_line * l,void * _ctx)235 record_hostkey(struct hostkey_foreach_line *l, void *_ctx)
236 {
237 	struct load_callback_ctx *ctx = (struct load_callback_ctx *)_ctx;
238 	struct hostkeys *hostkeys = ctx->hostkeys;
239 	struct hostkey_entry *tmp;
240 
241 	if (l->status == HKF_STATUS_INVALID) {
242 		/* XXX make this verbose() in the future */
243 		debug("%s:%ld: parse error in hostkeys file",
244 		    l->path, l->linenum);
245 		return 0;
246 	}
247 
248 	debug3("%s: found %skey type %s in file %s:%lu", __func__,
249 	    l->marker == MRK_NONE ? "" :
250 	    (l->marker == MRK_CA ? "ca " : "revoked "),
251 	    sshkey_type(l->key), l->path, l->linenum);
252 	if ((tmp = recallocarray(hostkeys->entries, hostkeys->num_entries,
253 	    hostkeys->num_entries + 1, sizeof(*hostkeys->entries))) == NULL)
254 		return SSH_ERR_ALLOC_FAIL;
255 	hostkeys->entries = tmp;
256 	hostkeys->entries[hostkeys->num_entries].host = xstrdup(ctx->host);
257 	hostkeys->entries[hostkeys->num_entries].file = xstrdup(l->path);
258 	hostkeys->entries[hostkeys->num_entries].line = l->linenum;
259 	hostkeys->entries[hostkeys->num_entries].key = l->key;
260 	l->key = NULL; /* steal it */
261 	hostkeys->entries[hostkeys->num_entries].marker = l->marker;
262 	hostkeys->num_entries++;
263 	ctx->num_loaded++;
264 
265 	return 0;
266 }
267 
268 void
load_hostkeys(struct hostkeys * hostkeys,const char * host,const char * path)269 load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path)
270 {
271 	int r;
272 	struct load_callback_ctx ctx;
273 
274 	ctx.host = host;
275 	ctx.num_loaded = 0;
276 	ctx.hostkeys = hostkeys;
277 
278 	if ((r = hostkeys_foreach(path, record_hostkey, &ctx, host, NULL,
279 	    HKF_WANT_MATCH|HKF_WANT_PARSE_KEY)) != 0) {
280 		if (r != SSH_ERR_SYSTEM_ERROR && errno != ENOENT)
281 			debug("%s: hostkeys_foreach failed for %s: %s",
282 			    __func__, path, ssh_err(r));
283 	}
284 	if (ctx.num_loaded != 0)
285 		debug3("%s: loaded %lu keys from %s", __func__,
286 		    ctx.num_loaded, host);
287 }
288 
289 void
free_hostkeys(struct hostkeys * hostkeys)290 free_hostkeys(struct hostkeys *hostkeys)
291 {
292 	u_int i;
293 
294 	for (i = 0; i < hostkeys->num_entries; i++) {
295 		free(hostkeys->entries[i].host);
296 		free(hostkeys->entries[i].file);
297 		sshkey_free(hostkeys->entries[i].key);
298 		explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
299 	}
300 	free(hostkeys->entries);
301 	explicit_bzero(hostkeys, sizeof(*hostkeys));
302 	free(hostkeys);
303 }
304 
305 static int
check_key_not_revoked(struct hostkeys * hostkeys,struct sshkey * k)306 check_key_not_revoked(struct hostkeys *hostkeys, struct sshkey *k)
307 {
308 	int is_cert = sshkey_is_cert(k);
309 	u_int i;
310 
311 	for (i = 0; i < hostkeys->num_entries; i++) {
312 		if (hostkeys->entries[i].marker != MRK_REVOKE)
313 			continue;
314 		if (sshkey_equal_public(k, hostkeys->entries[i].key))
315 			return -1;
316 		if (is_cert &&
317 		    sshkey_equal_public(k->cert->signature_key,
318 		    hostkeys->entries[i].key))
319 			return -1;
320 	}
321 	return 0;
322 }
323 
324 /*
325  * Match keys against a specified key, or look one up by key type.
326  *
327  * If looking for a keytype (key == NULL) and one is found then return
328  * HOST_FOUND, otherwise HOST_NEW.
329  *
330  * If looking for a key (key != NULL):
331  *  1. If the key is a cert and a matching CA is found, return HOST_OK
332  *  2. If the key is not a cert and a matching key is found, return HOST_OK
333  *  3. If no key matches but a key with a different type is found, then
334  *     return HOST_CHANGED
335  *  4. If no matching keys are found, then return HOST_NEW.
336  *
337  * Finally, check any found key is not revoked.
338  */
339 static HostStatus
check_hostkeys_by_key_or_type(struct hostkeys * hostkeys,struct sshkey * k,int keytype,const struct hostkey_entry ** found)340 check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
341     struct sshkey *k, int keytype, const struct hostkey_entry **found)
342 {
343 	u_int i;
344 	HostStatus end_return = HOST_NEW;
345 	int want_cert = sshkey_is_cert(k);
346 	HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
347 
348 	if (found != NULL)
349 		*found = NULL;
350 
351 	for (i = 0; i < hostkeys->num_entries; i++) {
352 		if (hostkeys->entries[i].marker != want_marker)
353 			continue;
354 		if (k == NULL) {
355 			if (hostkeys->entries[i].key->type != keytype)
356 				continue;
357 			end_return = HOST_FOUND;
358 			if (found != NULL)
359 				*found = hostkeys->entries + i;
360 			k = hostkeys->entries[i].key;
361 			break;
362 		}
363 		if (want_cert) {
364 			if (sshkey_equal_public(k->cert->signature_key,
365 			    hostkeys->entries[i].key)) {
366 				/* A matching CA exists */
367 				end_return = HOST_OK;
368 				if (found != NULL)
369 					*found = hostkeys->entries + i;
370 				break;
371 			}
372 		} else {
373 			if (sshkey_equal(k, hostkeys->entries[i].key)) {
374 				end_return = HOST_OK;
375 				if (found != NULL)
376 					*found = hostkeys->entries + i;
377 				break;
378 			}
379 			/* A non-maching key exists */
380 			end_return = HOST_CHANGED;
381 			if (found != NULL)
382 				*found = hostkeys->entries + i;
383 		}
384 	}
385 	if (check_key_not_revoked(hostkeys, k) != 0) {
386 		end_return = HOST_REVOKED;
387 		if (found != NULL)
388 			*found = NULL;
389 	}
390 	return end_return;
391 }
392 
393 HostStatus
check_key_in_hostkeys(struct hostkeys * hostkeys,struct sshkey * key,const struct hostkey_entry ** found)394 check_key_in_hostkeys(struct hostkeys *hostkeys, struct sshkey *key,
395     const struct hostkey_entry **found)
396 {
397 	if (key == NULL)
398 		fatal("no key to look up");
399 	return check_hostkeys_by_key_or_type(hostkeys, key, 0, found);
400 }
401 
402 int
lookup_key_in_hostkeys_by_type(struct hostkeys * hostkeys,int keytype,const struct hostkey_entry ** found)403 lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
404     const struct hostkey_entry **found)
405 {
406 	return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype,
407 	    found) == HOST_FOUND);
408 }
409 
410 static int
write_host_entry(FILE * f,const char * host,const char * ip,const struct sshkey * key,int store_hash)411 write_host_entry(FILE *f, const char *host, const char *ip,
412     const struct sshkey *key, int store_hash)
413 {
414 	int r, success = 0;
415 	char *hashed_host = NULL, *lhost;
416 
417 	lhost = xstrdup(host);
418 	lowercase(lhost);
419 
420 	if (store_hash) {
421 		if ((hashed_host = host_hash(lhost, NULL, 0)) == NULL) {
422 			error("%s: host_hash failed", __func__);
423 			free(lhost);
424 			return 0;
425 		}
426 		fprintf(f, "%s ", hashed_host);
427 	} else if (ip != NULL)
428 		fprintf(f, "%s,%s ", lhost, ip);
429 	else {
430 		fprintf(f, "%s ", lhost);
431 	}
432 	free(lhost);
433 	if ((r = sshkey_write(key, f)) == 0)
434 		success = 1;
435 	else
436 		error("%s: sshkey_write failed: %s", __func__, ssh_err(r));
437 	fputc('\n', f);
438 	return success;
439 }
440 
441 /*
442  * Appends an entry to the host file.  Returns false if the entry could not
443  * be appended.
444  */
445 int
add_host_to_hostfile(const char * filename,const char * host,const struct sshkey * key,int store_hash)446 add_host_to_hostfile(const char *filename, const char *host,
447     const struct sshkey *key, int store_hash)
448 {
449 	FILE *f;
450 	int success;
451 
452 	if (key == NULL)
453 		return 1;	/* XXX ? */
454 	f = fopen(filename, "a");
455 	if (!f)
456 		return 0;
457 	success = write_host_entry(f, host, NULL, key, store_hash);
458 	fclose(f);
459 	return success;
460 }
461 
462 struct host_delete_ctx {
463 	FILE *out;
464 	int quiet;
465 	const char *host;
466 	int *skip_keys; /* XXX split for host/ip? might want to ensure both */
467 	struct sshkey * const *keys;
468 	size_t nkeys;
469 	int modified;
470 };
471 
472 static int
host_delete(struct hostkey_foreach_line * l,void * _ctx)473 host_delete(struct hostkey_foreach_line *l, void *_ctx)
474 {
475 	struct host_delete_ctx *ctx = (struct host_delete_ctx *)_ctx;
476 	int loglevel = ctx->quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
477 	size_t i;
478 
479 	if (l->status == HKF_STATUS_MATCHED) {
480 		if (l->marker != MRK_NONE) {
481 			/* Don't remove CA and revocation lines */
482 			fprintf(ctx->out, "%s\n", l->line);
483 			return 0;
484 		}
485 
486 		/*
487 		 * If this line contains one of the keys that we will be
488 		 * adding later, then don't change it and mark the key for
489 		 * skipping.
490 		 */
491 		for (i = 0; i < ctx->nkeys; i++) {
492 			if (sshkey_equal(ctx->keys[i], l->key)) {
493 				ctx->skip_keys[i] = 1;
494 				fprintf(ctx->out, "%s\n", l->line);
495 				debug3("%s: %s key already at %s:%ld", __func__,
496 				    sshkey_type(l->key), l->path, l->linenum);
497 				return 0;
498 			}
499 		}
500 
501 		/*
502 		 * Hostname matches and has no CA/revoke marker, delete it
503 		 * by *not* writing the line to ctx->out.
504 		 */
505 		do_log2(loglevel, "%s%s%s:%ld: Removed %s key for host %s",
506 		    ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
507 		    l->path, l->linenum, sshkey_type(l->key), ctx->host);
508 		ctx->modified = 1;
509 		return 0;
510 	}
511 	/* Retain non-matching hosts and invalid lines when deleting */
512 	if (l->status == HKF_STATUS_INVALID) {
513 		do_log2(loglevel, "%s%s%s:%ld: invalid known_hosts entry",
514 		    ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
515 		    l->path, l->linenum);
516 	}
517 	fprintf(ctx->out, "%s\n", l->line);
518 	return 0;
519 }
520 
521 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)522 hostfile_replace_entries(const char *filename, const char *host, const char *ip,
523     struct sshkey **keys, size_t nkeys, int store_hash, int quiet, int hash_alg)
524 {
525 	int r, fd, oerrno = 0;
526 	int loglevel = quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
527 	struct host_delete_ctx ctx;
528 	char *fp, *temp = NULL, *back = NULL;
529 	mode_t omask;
530 	size_t i;
531 
532 	omask = umask(077);
533 
534 	memset(&ctx, 0, sizeof(ctx));
535 	ctx.host = host;
536 	ctx.quiet = quiet;
537 	if ((ctx.skip_keys = calloc(nkeys, sizeof(*ctx.skip_keys))) == NULL)
538 		return SSH_ERR_ALLOC_FAIL;
539 	ctx.keys = keys;
540 	ctx.nkeys = nkeys;
541 	ctx.modified = 0;
542 
543 	/*
544 	 * Prepare temporary file for in-place deletion.
545 	 */
546 	if ((r = asprintf(&temp, "%s.XXXXXXXXXXX", filename)) == -1 ||
547 	    (r = asprintf(&back, "%s.old", filename)) == -1) {
548 		r = SSH_ERR_ALLOC_FAIL;
549 		goto fail;
550 	}
551 
552 	if ((fd = mkstemp(temp)) == -1) {
553 		oerrno = errno;
554 		error("%s: mkstemp: %s", __func__, strerror(oerrno));
555 		r = SSH_ERR_SYSTEM_ERROR;
556 		goto fail;
557 	}
558 	if ((ctx.out = fdopen(fd, "w")) == NULL) {
559 		oerrno = errno;
560 		close(fd);
561 		error("%s: fdopen: %s", __func__, strerror(oerrno));
562 		r = SSH_ERR_SYSTEM_ERROR;
563 		goto fail;
564 	}
565 
566 	/* Remove all entries for the specified host from the file */
567 	if ((r = hostkeys_foreach(filename, host_delete, &ctx, host, ip,
568 	    HKF_WANT_PARSE_KEY)) != 0) {
569 		error("%s: hostkeys_foreach failed: %s", __func__, ssh_err(r));
570 		goto fail;
571 	}
572 
573 	/* Add the requested keys */
574 	for (i = 0; i < nkeys; i++) {
575 		if (ctx.skip_keys[i])
576 			continue;
577 		if ((fp = sshkey_fingerprint(keys[i], hash_alg,
578 		    SSH_FP_DEFAULT)) == NULL) {
579 			r = SSH_ERR_ALLOC_FAIL;
580 			goto fail;
581 		}
582 		do_log2(loglevel, "%s%sAdding new key for %s to %s: %s %s",
583 		    quiet ? __func__ : "", quiet ? ": " : "", host, filename,
584 		    sshkey_ssh_name(keys[i]), fp);
585 		free(fp);
586 		if (!write_host_entry(ctx.out, host, ip, keys[i], store_hash)) {
587 			r = SSH_ERR_INTERNAL_ERROR;
588 			goto fail;
589 		}
590 		ctx.modified = 1;
591 	}
592 	fclose(ctx.out);
593 	ctx.out = NULL;
594 
595 	if (ctx.modified) {
596 		/* Backup the original file and replace it with the temporary */
597 		if (unlink(back) == -1 && errno != ENOENT) {
598 			oerrno = errno;
599 			error("%s: unlink %.100s: %s", __func__,
600 			    back, strerror(errno));
601 			r = SSH_ERR_SYSTEM_ERROR;
602 			goto fail;
603 		}
604 		if (link(filename, back) == -1) {
605 			oerrno = errno;
606 			error("%s: link %.100s to %.100s: %s", __func__,
607 			    filename, back, strerror(errno));
608 			r = SSH_ERR_SYSTEM_ERROR;
609 			goto fail;
610 		}
611 		if (rename(temp, filename) == -1) {
612 			oerrno = errno;
613 			error("%s: rename \"%s\" to \"%s\": %s", __func__,
614 			    temp, filename, strerror(errno));
615 			r = SSH_ERR_SYSTEM_ERROR;
616 			goto fail;
617 		}
618 	} else {
619 		/* No changes made; just delete the temporary file */
620 		if (unlink(temp) != 0)
621 			error("%s: unlink \"%s\": %s", __func__,
622 			    temp, strerror(errno));
623 	}
624 
625 	/* success */
626 	r = 0;
627  fail:
628 	if (temp != NULL && r != 0)
629 		unlink(temp);
630 	free(temp);
631 	free(back);
632 	if (ctx.out != NULL)
633 		fclose(ctx.out);
634 	free(ctx.skip_keys);
635 	umask(omask);
636 	if (r == SSH_ERR_SYSTEM_ERROR)
637 		errno = oerrno;
638 	return r;
639 }
640 
641 static int
match_maybe_hashed(const char * host,const char * names,int * was_hashed)642 match_maybe_hashed(const char *host, const char *names, int *was_hashed)
643 {
644 	int hashed = *names == HASH_DELIM;
645 	const char *hashed_host;
646 	size_t nlen = strlen(names);
647 
648 	if (was_hashed != NULL)
649 		*was_hashed = hashed;
650 	if (hashed) {
651 		if ((hashed_host = host_hash(host, names, nlen)) == NULL)
652 			return -1;
653 		return nlen == strlen(hashed_host) &&
654 		    strncmp(hashed_host, names, nlen) == 0;
655 	}
656 	return match_hostname(host, names) == 1;
657 }
658 
659 int
hostkeys_foreach(const char * path,hostkeys_foreach_fn * callback,void * ctx,const char * host,const char * ip,u_int options)660 hostkeys_foreach(const char *path, hostkeys_foreach_fn *callback, void *ctx,
661     const char *host, const char *ip, u_int options)
662 {
663 	FILE *f;
664 	char *line = NULL, ktype[128];
665 	u_long linenum = 0;
666 	char *cp, *cp2;
667 	u_int kbits;
668 	int hashed;
669 	int s, r = 0;
670 	struct hostkey_foreach_line lineinfo;
671 	size_t linesize = 0, l;
672 
673 	memset(&lineinfo, 0, sizeof(lineinfo));
674 	if (host == NULL && (options & HKF_WANT_MATCH) != 0)
675 		return SSH_ERR_INVALID_ARGUMENT;
676 	if ((f = fopen(path, "r")) == NULL)
677 		return SSH_ERR_SYSTEM_ERROR;
678 
679 	debug3("%s: reading file \"%s\"", __func__, path);
680 	while (getline(&line, &linesize, f) != -1) {
681 		linenum++;
682 		line[strcspn(line, "\n")] = '\0';
683 
684 		free(lineinfo.line);
685 		sshkey_free(lineinfo.key);
686 		memset(&lineinfo, 0, sizeof(lineinfo));
687 		lineinfo.path = path;
688 		lineinfo.linenum = linenum;
689 		lineinfo.line = xstrdup(line);
690 		lineinfo.marker = MRK_NONE;
691 		lineinfo.status = HKF_STATUS_OK;
692 		lineinfo.keytype = KEY_UNSPEC;
693 
694 		/* Skip any leading whitespace, comments and empty lines. */
695 		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
696 			;
697 		if (!*cp || *cp == '#' || *cp == '\n') {
698 			if ((options & HKF_WANT_MATCH) == 0) {
699 				lineinfo.status = HKF_STATUS_COMMENT;
700 				if ((r = callback(&lineinfo, ctx)) != 0)
701 					break;
702 			}
703 			continue;
704 		}
705 
706 		if ((lineinfo.marker = check_markers(&cp)) == MRK_ERROR) {
707 			verbose("%s: invalid marker at %s:%lu",
708 			    __func__, path, linenum);
709 			if ((options & HKF_WANT_MATCH) == 0)
710 				goto bad;
711 			continue;
712 		}
713 
714 		/* Find the end of the host name portion. */
715 		for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
716 			;
717 		lineinfo.hosts = cp;
718 		*cp2++ = '\0';
719 
720 		/* Check if the host name matches. */
721 		if (host != NULL) {
722 			if ((s = match_maybe_hashed(host, lineinfo.hosts,
723 			    &hashed)) == -1) {
724 				debug2("%s: %s:%ld: bad host hash \"%.32s\"",
725 				    __func__, path, linenum, lineinfo.hosts);
726 				goto bad;
727 			}
728 			if (s == 1) {
729 				lineinfo.status = HKF_STATUS_MATCHED;
730 				lineinfo.match |= HKF_MATCH_HOST |
731 				    (hashed ? HKF_MATCH_HOST_HASHED : 0);
732 			}
733 			/* Try matching IP address if supplied */
734 			if (ip != NULL) {
735 				if ((s = match_maybe_hashed(ip, lineinfo.hosts,
736 				    &hashed)) == -1) {
737 					debug2("%s: %s:%ld: bad ip hash "
738 					    "\"%.32s\"", __func__, path,
739 					    linenum, lineinfo.hosts);
740 					goto bad;
741 				}
742 				if (s == 1) {
743 					lineinfo.status = HKF_STATUS_MATCHED;
744 					lineinfo.match |= HKF_MATCH_IP |
745 					    (hashed ? HKF_MATCH_IP_HASHED : 0);
746 				}
747 			}
748 			/*
749 			 * Skip this line if host matching requested and
750 			 * neither host nor address matched.
751 			 */
752 			if ((options & HKF_WANT_MATCH) != 0 &&
753 			    lineinfo.status != HKF_STATUS_MATCHED)
754 				continue;
755 		}
756 
757 		/* Got a match.  Skip host name and any following whitespace */
758 		for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
759 			;
760 		if (*cp2 == '\0' || *cp2 == '#') {
761 			debug2("%s:%ld: truncated before key type",
762 			    path, linenum);
763 			goto bad;
764 		}
765 		lineinfo.rawkey = cp = cp2;
766 
767 		if ((options & HKF_WANT_PARSE_KEY) != 0) {
768 			/*
769 			 * Extract the key from the line.  This will skip
770 			 * any leading whitespace.  Ignore badly formatted
771 			 * lines.
772 			 */
773 			if ((lineinfo.key = sshkey_new(KEY_UNSPEC)) == NULL) {
774 				error("%s: sshkey_new failed", __func__);
775 				r = SSH_ERR_ALLOC_FAIL;
776 				break;
777 			}
778 			if (!hostfile_read_key(&cp, &kbits, lineinfo.key)) {
779 				goto bad;
780 			}
781 			lineinfo.keytype = lineinfo.key->type;
782 			lineinfo.comment = cp;
783 		} else {
784 			/* Extract and parse key type */
785 			l = strcspn(lineinfo.rawkey, " \t");
786 			if (l <= 1 || l >= sizeof(ktype) ||
787 			    lineinfo.rawkey[l] == '\0')
788 				goto bad;
789 			memcpy(ktype, lineinfo.rawkey, l);
790 			ktype[l] = '\0';
791 			lineinfo.keytype = sshkey_type_from_name(ktype);
792 
793 			/*
794 			 * Assume legacy RSA1 if the first component is a short
795 			 * decimal number.
796 			 */
797 			if (lineinfo.keytype == KEY_UNSPEC && l < 8 &&
798 			    strspn(ktype, "0123456789") == l)
799 				goto bad;
800 
801 			/*
802 			 * Check that something other than whitespace follows
803 			 * the key type. This won't catch all corruption, but
804 			 * it does catch trivial truncation.
805 			 */
806 			cp2 += l; /* Skip past key type */
807 			for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
808 				;
809 			if (*cp2 == '\0' || *cp2 == '#') {
810 				debug2("%s:%ld: truncated after key type",
811 				    path, linenum);
812 				lineinfo.keytype = KEY_UNSPEC;
813 			}
814 			if (lineinfo.keytype == KEY_UNSPEC) {
815  bad:
816 				sshkey_free(lineinfo.key);
817 				lineinfo.key = NULL;
818 				lineinfo.status = HKF_STATUS_INVALID;
819 				if ((r = callback(&lineinfo, ctx)) != 0)
820 					break;
821 				continue;
822 			}
823 		}
824 		if ((r = callback(&lineinfo, ctx)) != 0)
825 			break;
826 	}
827 	sshkey_free(lineinfo.key);
828 	free(lineinfo.line);
829 	free(line);
830 	fclose(f);
831 	return r;
832 }
833