/src/netbsd/src/crypto/external/bsd/openssh/dist/hostfile.c

  1/*	$NetBSD: hostfile.c,v 1.4 2011/07/25 03:03:10 christos Exp $	*/
  2/* $OpenBSD: hostfile.c,v 1.50 2010/12/04 13:31:37 djm Exp $ */
  3/*
  4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
  5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  6 *                    All rights reserved
  7 * Functions for manipulating the known hosts files.
  8 *
  9 * As far as I am concerned, the code I have written for this software
 10 * can be used freely for any purpose.  Any derived versions of this
 11 * software must be clearly marked as such, and if the derived work is
 12 * incompatible with the protocol description in the RFC file, it must be
 13 * called by a name other than "ssh" or "Secure Shell".
 14 *
 15 *
 16 * Copyright (c) 1999, 2000 Markus Friedl.  All rights reserved.
 17 * Copyright (c) 1999 Niels Provos.  All rights reserved.
 18 *
 19 * Redistribution and use in source and binary forms, with or without
 20 * modification, are permitted provided that the following conditions
 21 * are met:
 22 * 1. Redistributions of source code must retain the above copyright
 23 *    notice, this list of conditions and the following disclaimer.
 24 * 2. Redistributions in binary form must reproduce the above copyright
 25 *    notice, this list of conditions and the following disclaimer in the
 26 *    documentation and/or other materials provided with the distribution.
 27 *
 28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 38 */
 39
 40#include "includes.h"
 41__RCSID("$NetBSD: hostfile.c,v 1.4 2011/07/25 03:03:10 christos Exp $");
 42#include <sys/types.h>
 43
 44#include <netinet/in.h>
 45
 46#include <openssl/hmac.h>
 47#include <openssl/sha.h>
 48
 49#include <resolv.h>
 50#include <stdio.h>
 51#include <stdlib.h>
 52#include <string.h>
 53
 54#include "xmalloc.h"
 55#include "match.h"
 56#include "key.h"
 57#include "hostfile.h"
 58#include "log.h"
 59#include "misc.h"
 60
 61struct hostkeys {
 62	struct hostkey_entry *entries;
 63	u_int num_entries;
 64};
 65
 66static int
 67extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
 68{
 69	char *p, *b64salt;
 70	u_int b64len;
 71	int ret;
 72
 73	if (l < sizeof(HASH_MAGIC) - 1) {
 74		debug2("extract_salt: string too short");
 75		return (-1);
 76	}
 77	if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
 78		debug2("extract_salt: invalid magic identifier");
 79		return (-1);
 80	}
 81	s += sizeof(HASH_MAGIC) - 1;
 82	l -= sizeof(HASH_MAGIC) - 1;
 83	if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
 84		debug2("extract_salt: missing salt termination character");
 85		return (-1);
 86	}
 87
 88	b64len = p - s;
 89	/* Sanity check */
 90	if (b64len == 0 || b64len > 1024) {
 91		debug2("extract_salt: bad encoded salt length %u", b64len);
 92		return (-1);
 93	}
 94	b64salt = xmalloc(1 + b64len);
 95	memcpy(b64salt, s, b64len);
 96	b64salt[b64len] = '\0';
 97
 98	ret = __b64_pton(b64salt, salt, salt_len);
 99	xfree(b64salt);
100	if (ret == -1) {
101		debug2("extract_salt: salt decode error");
102		return (-1);
103	}
104	if (ret != SHA_DIGEST_LENGTH) {
105		debug2("extract_salt: expected salt len %d, got %d",
106		    SHA_DIGEST_LENGTH, ret);
107		return (-1);
108	}
109
110	return (0);
111}
112
113char *
114host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
115{
116	const EVP_MD *md = EVP_sha1();
117	HMAC_CTX mac_ctx;
118	char salt[256], result[256], uu_salt[512], uu_result[512];
119	static char encoded[1024];
120	u_int i, len;
121
122	len = EVP_MD_size(md);
123
124	if (name_from_hostfile == NULL) {
125		/* Create new salt */
126		for (i = 0; i < len; i++)
127			salt[i] = arc4random();
128	} else {
129		/* Extract salt from known host entry */
130		if (extract_salt(name_from_hostfile, src_len, salt,
131		    sizeof(salt)) == -1)
132			return (NULL);
133	}
134
135	HMAC_Init(&mac_ctx, salt, len, md);
136	HMAC_Update(&mac_ctx, host, strlen(host));
137	HMAC_Final(&mac_ctx, result, NULL);
138	HMAC_cleanup(&mac_ctx);
139
140	if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
141	    __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
142		fatal("host_hash: __b64_ntop failed");
143
144	snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
145	    HASH_DELIM, uu_result);
146
147	return (encoded);
148}
149
150/*
151 * Parses an RSA (number of bits, e, n) or DSA key from a string.  Moves the
152 * pointer over the key.  Skips any whitespace at the beginning and at end.
153 */
154
155int
156hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
157{
158	char *cp;
159
160	/* Skip leading whitespace. */
161	for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
162		;
163
164	if (key_read(ret, &cp) != 1)
165		return 0;
166
167	/* Skip trailing whitespace. */
168	for (; *cp == ' ' || *cp == '\t'; cp++)
169		;
170
171	/* Return results. */
172	*cpp = cp;
173	if (bitsp != NULL)
174		*bitsp = key_size(ret);
175	return 1;
176}
177
178static int
179hostfile_check_key(int bits, const Key *key, const char *host,
180    const char *filename, u_long linenum)
181{
182	if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
183		return 1;
184	if (bits != BN_num_bits(key->rsa->n)) {
185		logit("Warning: %s, line %lu: keysize mismatch for host %s: "
186		    "actual %d vs. announced %d.",
187		    filename, linenum, host, BN_num_bits(key->rsa->n), bits);
188		logit("Warning: replace %d with %d in %s, line %lu.",
189		    bits, BN_num_bits(key->rsa->n), filename, linenum);
190	}
191	return 1;
192}
193
194static HostkeyMarker
195check_markers(char **cpp)
196{
197	char marker[32], *sp, *cp = *cpp;
198	int ret = MRK_NONE;
199
200	while (*cp == '@') {
201		/* Only one marker is allowed */
202		if (ret != MRK_NONE)
203			return MRK_ERROR;
204		/* Markers are terminated by whitespace */
205		if ((sp = strchr(cp, ' ')) == NULL &&
206		    (sp = strchr(cp, '\t')) == NULL)
207			return MRK_ERROR;
208		/* Extract marker for comparison */
209		if (sp <= cp + 1 || sp >= cp + sizeof(marker))
210			return MRK_ERROR;
211		memcpy(marker, cp, sp - cp);
212		marker[sp - cp] = '\0';
213		if (strcmp(marker, CA_MARKER) == 0)
214			ret = MRK_CA;
215		else if (strcmp(marker, REVOKE_MARKER) == 0)
216			ret = MRK_REVOKE;
217		else
218			return MRK_ERROR;
219
220		/* Skip past marker and any whitespace that follows it */
221		cp = sp;
222		for (; *cp == ' ' || *cp == '\t'; cp++)
223			;
224	}
225	*cpp = cp;
226	return ret;
227}
228
229struct hostkeys *
230init_hostkeys(void)
231{
232	struct hostkeys *ret = xcalloc(1, sizeof(*ret));
233
234	ret->entries = NULL;
235	return ret;
236}
237
238void
239load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path)
240{
241	FILE *f;
242	char line[8192];
243	u_long linenum = 0, num_loaded = 0;
244	char *cp, *cp2, *hashed_host;
245	HostkeyMarker marker;
246	Key *key;
247	int kbits;
248
249	if ((f = fopen(path, "r")) == NULL)
250		return;
251	debug3("%s: loading entries for host \"%.100s\" from file \"%s\"",
252	    __func__, host, path);
253	while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) {
254		cp = line;
255
256		/* Skip any leading whitespace, comments and empty lines. */
257		for (; *cp == ' ' || *cp == '\t'; cp++)
258			;
259		if (!*cp || *cp == '#' || *cp == '\n')
260			continue;
261
262		if ((marker = check_markers(&cp)) == MRK_ERROR) {
263			verbose("%s: invalid marker at %s:%lu",
264			    __func__, path, linenum);
265			continue;
266		}
267
268		/* Find the end of the host name portion. */
269		for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
270			;
271
272		/* Check if the host name matches. */
273		if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
274			if (*cp != HASH_DELIM)
275				continue;
276			hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
277			if (hashed_host == NULL) {
278				debug("Invalid hashed host line %lu of %s",
279				    linenum, path);
280				continue;
281			}
282			if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
283				continue;
284		}
285
286		/* Got a match.  Skip host name. */
287		cp = cp2;
288
289		/*
290		 * Extract the key from the line.  This will skip any leading
291		 * whitespace.  Ignore badly formatted lines.
292		 */
293		key = key_new(KEY_UNSPEC);
294		if (!hostfile_read_key(&cp, &kbits, key)) {
295			key_free(key);
296			key = key_new(KEY_RSA1);
297			if (!hostfile_read_key(&cp, &kbits, key)) {
298				key_free(key);
299				continue;
300			}
301		}
302		if (!hostfile_check_key(kbits, key, host, path, linenum))
303			continue;
304
305		debug3("%s: found %skey type %s in file %s:%lu", __func__,
306		    marker == MRK_NONE ? "" :
307		    (marker == MRK_CA ? "ca " : "revoked "),
308		    key_type(key), path, linenum);
309		hostkeys->entries = xrealloc(hostkeys->entries,
310		    hostkeys->num_entries + 1, sizeof(*hostkeys->entries));
311		hostkeys->entries[hostkeys->num_entries].host = xstrdup(host);
312		hostkeys->entries[hostkeys->num_entries].file = xstrdup(path);
313		hostkeys->entries[hostkeys->num_entries].line = linenum;
314		hostkeys->entries[hostkeys->num_entries].key = key;
315		hostkeys->entries[hostkeys->num_entries].marker = marker;
316		hostkeys->num_entries++;
317		num_loaded++;
318	}
319	debug3("%s: loaded %lu keys", __func__, num_loaded);
320	fclose(f);
321	return;
322}	
323
324void
325free_hostkeys(struct hostkeys *hostkeys)
326{
327	u_int i;
328
329	for (i = 0; i < hostkeys->num_entries; i++) {
330		xfree(hostkeys->entries[i].host);
331		xfree(hostkeys->entries[i].file);
332		key_free(hostkeys->entries[i].key);
333		bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
334	}
335	if (hostkeys->entries != NULL)
336		xfree(hostkeys->entries);
337	hostkeys->entries = NULL;
338	hostkeys->num_entries = 0;
339	xfree(hostkeys);
340}
341
342static int
343check_key_not_revoked(struct hostkeys *hostkeys, Key *k)
344{
345	int is_cert = key_is_cert(k);
346	u_int i;
347
348	for (i = 0; i < hostkeys->num_entries; i++) {
349		if (hostkeys->entries[i].marker != MRK_REVOKE)
350			continue;
351		if (key_equal_public(k, hostkeys->entries[i].key))
352			return -1;
353		if (is_cert &&
354		    key_equal_public(k->cert->signature_key,
355		    hostkeys->entries[i].key))
356			return -1;
357	}
358	return 0;
359}
360
361/*
362 * Match keys against a specified key, or look one up by key type.
363 *
364 * If looking for a keytype (key == NULL) and one is found then return
365 * HOST_FOUND, otherwise HOST_NEW.
366 *
367 * If looking for a key (key != NULL):
368 *  1. If the key is a cert and a matching CA is found, return HOST_OK
369 *  2. If the key is not a cert and a matching key is found, return HOST_OK
370 *  3. If no key matches but a key with a different type is found, then
371 *     return HOST_CHANGED
372 *  4. If no matching keys are found, then return HOST_NEW.
373 *
374 * Finally, check any found key is not revoked.
375 */
376static HostStatus
377check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
378    Key *k, int keytype, const struct hostkey_entry **found)
379{
380	u_int i;
381	HostStatus end_return = HOST_NEW;
382	int want_cert = key_is_cert(k);
383	HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
384	int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2;
385
386	if (found != NULL)
387		*found = NULL;
388
389	for (i = 0; i < hostkeys->num_entries; i++) {
390		if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1)
391			continue;
392		if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1)
393			continue;
394		if (hostkeys->entries[i].marker != want_marker)
395			continue;
396		if (k == NULL) {
397			if (hostkeys->entries[i].key->type != keytype)
398				continue;
399			end_return = HOST_FOUND;
400			if (found != NULL)
401				*found = hostkeys->entries + i;
402			k = hostkeys->entries[i].key;
403			break;
404		}
405		if (want_cert) {
406			if (key_equal_public(k->cert->signature_key,
407			    hostkeys->entries[i].key)) {
408				/* A matching CA exists */
409				end_return = HOST_OK;
410				if (found != NULL)
411					*found = hostkeys->entries + i;
412				break;
413			}
414		} else {
415			if (key_equal(k, hostkeys->entries[i].key)) {
416				end_return = HOST_OK;
417				if (found != NULL)
418					*found = hostkeys->entries + i;
419				break;
420			}
421			/* A non-maching key exists */
422			end_return = HOST_CHANGED;
423			if (found != NULL)
424				*found = hostkeys->entries + i;
425		}
426	}
427	if (check_key_not_revoked(hostkeys, k) != 0) {
428		end_return = HOST_REVOKED;
429		if (found != NULL)
430			*found = NULL;
431	}
432	return end_return;
433}
434	
435HostStatus
436check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key,
437    const struct hostkey_entry **found)
438{
439	if (key == NULL)
440		fatal("no key to look up");
441	return check_hostkeys_by_key_or_type(hostkeys, key, 0, found);
442}
443
444int
445lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
446    const struct hostkey_entry **found)
447{
448	return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype,
449	    found) == HOST_FOUND);
450}
451
452/*
453 * Appends an entry to the host file.  Returns false if the entry could not
454 * be appended.
455 */
456
457int
458add_host_to_hostfile(const char *filename, const char *host, const Key *key,
459    int store_hash)
460{
461	FILE *f;
462	int success = 0;
463	char *hashed_host = NULL;
464
465	if (key == NULL)
466		return 1;	/* XXX ? */
467	f = fopen(filename, "a");
468	if (!f)
469		return 0;
470
471	if (store_hash) {
472		if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
473			error("add_host_to_hostfile: host_hash failed");
474			fclose(f);
475			return 0;
476		}
477	}
478	fprintf(f, "%s ", store_hash ? hashed_host : host);
479
480	if (key_write(key, f)) {
481		success = 1;
482	} else {
483		error("add_host_to_hostfile: saving key in %s failed", filename);
484	}
485	fprintf(f, "\n");
486	fclose(f);
487	return success;
488}