[openssh.git] / dns.c

/*	$OpenBSD: dns.c,v 1.4 2003/05/14 23:29:22 jakob Exp $	*/

/*
 * Copyright (c) 2003 Wesley Griffin. All rights reserved.
 * Copyright (c) 2003 Jakob Schlyter. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include "includes.h"

#ifdef DNS
#include <openssl/bn.h>
#ifdef LWRES
#include <lwres/netdb.h>
#include <dns/result.h>
#else /* LWRES */
#include <netdb.h>
#endif /* LWRES */

#include "xmalloc.h"
#include "key.h"
#include "dns.h"
#include "log.h"
#include "uuencode.h"

extern char *__progname;
RCSID("$OpenBSD: dns.c,v 1.4 2003/05/14 23:29:22 jakob Exp $");

#ifndef LWRES
static const char *errset_text[] = {
	"success",		/* 0 ERRSET_SUCCESS */
	"out of memory",	/* 1 ERRSET_NOMEMORY */
	"general failure",	/* 2 ERRSET_FAIL */
	"invalid parameter",	/* 3 ERRSET_INVAL */
	"name does not exist",	/* 4 ERRSET_NONAME */
	"data does not exist",	/* 5 ERRSET_NODATA */
};

static const char *
dns_result_totext(unsigned int error)
{
	switch (error) {
	case ERRSET_SUCCESS:
		return errset_text[ERRSET_SUCCESS];
	case ERRSET_NOMEMORY:
		return errset_text[ERRSET_NOMEMORY];
	case ERRSET_FAIL:
		return errset_text[ERRSET_FAIL];
	case ERRSET_INVAL:
		return errset_text[ERRSET_INVAL];
	case ERRSET_NONAME:
		return errset_text[ERRSET_NONAME];
	case ERRSET_NODATA:
		return errset_text[ERRSET_NODATA];
	default:
		return "unknown error";
	}
}
#endif /* LWRES */


/*
 * Read SSHFP parameters from key buffer.
 */
static int
dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
    u_char **digest, u_int *digest_len, Key *key)
{
	int success = 0;

	switch (key->type) {
	case KEY_RSA:
		*algorithm = SSHFP_KEY_RSA;
		break;
	case KEY_DSA:
		*algorithm = SSHFP_KEY_DSA;
		break;
	default:
		*algorithm = SSHFP_KEY_RESERVED;
	}

	if (*algorithm) {
		*digest_type = SSHFP_HASH_SHA1;
		*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
		success = 1;
	} else {
		*digest_type = SSHFP_HASH_RESERVED;
		*digest = NULL;
		*digest_len = 0;
		success = 0;
	}

	return success;
}

/*
 * Read SSHFP parameters from rdata buffer.
 */
static int
dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
    u_char **digest, u_int *digest_len, u_char *rdata, int rdata_len)
{
	int success = 0;

	*algorithm = SSHFP_KEY_RESERVED;
	*digest_type = SSHFP_HASH_RESERVED;

	if (rdata_len >= 2) {
		*algorithm = rdata[0];
		*digest_type = rdata[1];
		*digest_len = rdata_len - 2;

		if (*digest_len > 0) {
			*digest = (u_char *) xmalloc(*digest_len);
			memcpy(*digest, rdata + 2, *digest_len);
		} else {
			*digest = NULL;
		}

		success = 1;
	}

	return success;
}


/*
 * Verify the given hostname, address and host key using DNS.
 * Returns 0 if key verifies or -1 if key does NOT verify
 */
int
verify_host_key_dns(const char *hostname, struct sockaddr *address,
    Key *hostkey)
{
	int counter;
	int result;
	struct rrsetinfo *fingerprints = NULL;
	int failures = 0;

	u_int8_t hostkey_algorithm;
	u_int8_t hostkey_digest_type;
	u_char *hostkey_digest;
	u_int hostkey_digest_len;

	u_int8_t dnskey_algorithm;
	u_int8_t dnskey_digest_type;
	u_char *dnskey_digest;
	u_int dnskey_digest_len;


	debug3("verify_hostkey_dns");
	if (hostkey == NULL)
		fatal("No key to look up!");

	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	    DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	if (result) {
		verbose("DNS lookup error: %s", dns_result_totext(result));
		return DNS_VERIFY_ERROR;
	}

#ifdef DNSSEC
	/* Only accept validated answers */
	if (!fingerprints->rri_flags & RRSET_VALIDATED) {
		error("Ignored unvalidated fingerprint from DNS.");
		return DNS_VERIFY_ERROR;
	}
#endif

	debug("found %d fingerprints in DNS", fingerprints->rri_nrdatas);

	/* Initialize host key parameters */
	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	    &hostkey_digest, &hostkey_digest_len, hostkey)) {
		error("Error calculating host key fingerprint.");
		return DNS_VERIFY_ERROR;
	}

	for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++)  {
		/*
		 * Extract the key from the answer. Ignore any badly
		 * formatted fingerprints.
		 */
		if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
		    &dnskey_digest, &dnskey_digest_len,
		    fingerprints->rri_rdatas[counter].rdi_data,
		    fingerprints->rri_rdatas[counter].rdi_length)) {
			verbose("Error parsing fingerprint from DNS.");
			continue;
		}

		/* Check if the current key is the same as the given key */
		if (hostkey_algorithm == dnskey_algorithm &&
		    hostkey_digest_type == dnskey_digest_type) {

			if (hostkey_digest_len == dnskey_digest_len &&
			    memcmp(hostkey_digest, dnskey_digest,
			    hostkey_digest_len) == 0) {

				/* Matching algoritm and digest. */
				freerrset(fingerprints);
#ifdef DNSSEC
				debug("matching host key fingerprint found in DNS");
				return DNS_VERIFY_OK;
#else
				logit("Matching host key fingerprint found in DNS.");
				return DNS_VERIFY_ERROR;
#endif
			} else {
				/* Correct algorithm but bad digest */
				debug("verify_hostkey_dns: failed");
				failures++;
			}
		}
	}

	freerrset(fingerprints);

	if (failures) {
		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
		error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
		error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
		error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
		error("It is also possible that the %s host key has just been changed.",
		    key_type(hostkey));
		error("Please contact your system administrator.");
		return DNS_VERIFY_FAILED;
	}

	debug("fingerprints found in DNS, but none of them matched");

	return DNS_VERIFY_ERROR;
}


/*
 * Export the fingerprint of a key as a DNS resource record
 */
int
export_dns_rr(const char *hostname, Key *key, FILE *f, int generic)
{
	u_int8_t rdata_pubkey_algorithm = 0;
	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	u_char *rdata_digest;
	u_int rdata_digest_len;

	int i;
	int success = 0;

	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
			 &rdata_digest, &rdata_digest_len, key)) {

		if (generic)
			fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
			    DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
			    rdata_pubkey_algorithm, rdata_digest_type);
		else
			fprintf(f, "%s IN SSHFP %d %d ", hostname,
			    rdata_pubkey_algorithm, rdata_digest_type);

		for (i = 0; i < rdata_digest_len; i++)
			fprintf(f, "%02x", rdata_digest[i]);
		fprintf(f, "\n");
		success = 1;
	} else {
		error("dns_export_rr: unsupported algorithm");
	}

	return success;
}

#endif /* DNS */
Commit	Line	Data
21289cd0	1	/* $OpenBSD: dns.c,v 1.4 2003/05/14 23:29:22 jakob Exp $ */
	2
	3	/*
	4	* Copyright (c) 2003 Wesley Griffin. All rights reserved.
	5	* Copyright (c) 2003 Jakob Schlyter. All rights reserved.
	6	*
	7	* Redistribution and use in source and binary forms, with or without
	8	* modification, are permitted provided that the following conditions
	9	* are met:
	10	* 1. Redistributions of source code must retain the above copyright
	11	* notice, this list of conditions and the following disclaimer.
	12	* 2. Redistributions in binary form must reproduce the above copyright
	13	* notice, this list of conditions and the following disclaimer in the
	14	* documentation and/or other materials provided with the distribution.
	15	*
	16	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	17	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	18	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	19	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	20	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	21	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	22	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	23	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	24	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	25	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	26	*/
	27
	28
	29	#include "includes.h"
	30
	31	#ifdef DNS
	32	#include <openssl/bn.h>
	33	#ifdef LWRES
	34	#include <lwres/netdb.h>
	35	#include <dns/result.h>
	36	#else /* LWRES */
	37	#include <netdb.h>
	38	#endif /* LWRES */
	39
	40	#include "xmalloc.h"
	41	#include "key.h"
	42	#include "dns.h"
	43	#include "log.h"
	44	#include "uuencode.h"
	45
	46	extern char *__progname;
	47	RCSID("$OpenBSD: dns.c,v 1.4 2003/05/14 23:29:22 jakob Exp $");
	48
	49	#ifndef LWRES
	50	static const char *errset_text[] = {
	51	"success", /* 0 ERRSET_SUCCESS */
	52	"out of memory", /* 1 ERRSET_NOMEMORY */
	53	"general failure", /* 2 ERRSET_FAIL */
	54	"invalid parameter", /* 3 ERRSET_INVAL */
	55	"name does not exist", /* 4 ERRSET_NONAME */
	56	"data does not exist", /* 5 ERRSET_NODATA */
	57	};
	58
	59	static const char *
	60	dns_result_totext(unsigned int error)
	61	{
	62	switch (error) {
	63	case ERRSET_SUCCESS:
	64	return errset_text[ERRSET_SUCCESS];
65	case ERRSET_NOMEMORY:
66	return errset_text[ERRSET_NOMEMORY];
67	case ERRSET_FAIL:
68	return errset_text[ERRSET_FAIL];
69	case ERRSET_INVAL:
70	return errset_text[ERRSET_INVAL];
71	case ERRSET_NONAME:
72	return errset_text[ERRSET_NONAME];
73	case ERRSET_NODATA:
74	return errset_text[ERRSET_NODATA];
75	default:
76	return "unknown error";
77	}
78	}
79	#endif /* LWRES */
80
81
82	/*
83	* Read SSHFP parameters from key buffer.
84	*/
85	static int
86	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
87	u_char *digest, u_int digest_len, Key *key)
88	{
89	int success = 0;
90
91	switch (key->type) {
92	case KEY_RSA:
93	*algorithm = SSHFP_KEY_RSA;
94	break;
95	case KEY_DSA:
96	*algorithm = SSHFP_KEY_DSA;
97	break;
98	default:
99	*algorithm = SSHFP_KEY_RESERVED;
100	}
101
102	if (*algorithm) {
103	*digest_type = SSHFP_HASH_SHA1;
104	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
105	success = 1;
106	} else {
107	*digest_type = SSHFP_HASH_RESERVED;
108	*digest = NULL;
109	*digest_len = 0;
110	success = 0;
111	}
112
113	return success;
114	}
115
116	/*
117	* Read SSHFP parameters from rdata buffer.
118	*/
119	static int
120	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
121	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
122	{
123	int success = 0;
124
125	*algorithm = SSHFP_KEY_RESERVED;
126	*digest_type = SSHFP_HASH_RESERVED;
127
128	if (rdata_len >= 2) {
129	*algorithm = rdata[0];
130	*digest_type = rdata[1];
131	*digest_len = rdata_len - 2;
132
133	if (*digest_len > 0) {
134	digest = (u_char ) xmalloc(*digest_len);
135	memcpy(digest, rdata + 2, digest_len);
136	} else {
137	*digest = NULL;
138	}
139
140	success = 1;
141	}
142
143	return success;
144	}
145
146
147	/*
148	* Verify the given hostname, address and host key using DNS.
149	* Returns 0 if key verifies or -1 if key does NOT verify
150	*/
151	int
152	verify_host_key_dns(const char hostname, struct sockaddr address,
153	Key *hostkey)
154	{
155	int counter;
156	int result;
157	struct rrsetinfo *fingerprints = NULL;
158	int failures = 0;
159
160	u_int8_t hostkey_algorithm;
161	u_int8_t hostkey_digest_type;
162	u_char *hostkey_digest;
163	u_int hostkey_digest_len;
164
165	u_int8_t dnskey_algorithm;
166	u_int8_t dnskey_digest_type;
167	u_char *dnskey_digest;
168	u_int dnskey_digest_len;
169
170
171	debug3("verify_hostkey_dns");
172	if (hostkey == NULL)
173	fatal("No key to look up!");
174
175	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
176	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
177	if (result) {
178	verbose("DNS lookup error: %s", dns_result_totext(result));
179	return DNS_VERIFY_ERROR;
180	}
181
182	#ifdef DNSSEC
183	/* Only accept validated answers */
184	if (!fingerprints->rri_flags & RRSET_VALIDATED) {
185	error("Ignored unvalidated fingerprint from DNS.");
186	return DNS_VERIFY_ERROR;
187	}
188	#endif
189
190	debug("found %d fingerprints in DNS", fingerprints->rri_nrdatas);
191
192	/* Initialize host key parameters */
193	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
194	&hostkey_digest, &hostkey_digest_len, hostkey)) {
195	error("Error calculating host key fingerprint.");
196	return DNS_VERIFY_ERROR;
197	}
198
199	for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++) {
200	/*
201	* Extract the key from the answer. Ignore any badly
202	* formatted fingerprints.
203	*/
204	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
205	&dnskey_digest, &dnskey_digest_len,
206	fingerprints->rri_rdatas[counter].rdi_data,
207	fingerprints->rri_rdatas[counter].rdi_length)) {
208	verbose("Error parsing fingerprint from DNS.");
209	continue;
210	}
211
212	/* Check if the current key is the same as the given key */
213	if (hostkey_algorithm == dnskey_algorithm &&
214	hostkey_digest_type == dnskey_digest_type) {
215
216	if (hostkey_digest_len == dnskey_digest_len &&
217	memcmp(hostkey_digest, dnskey_digest,
218	hostkey_digest_len) == 0) {
219
220	/* Matching algoritm and digest. */
221	freerrset(fingerprints);
222	#ifdef DNSSEC
223	debug("matching host key fingerprint found in DNS");
224	return DNS_VERIFY_OK;
225	#else
226	logit("Matching host key fingerprint found in DNS.");
227	return DNS_VERIFY_ERROR;
228	#endif
229	} else {
230	/* Correct algorithm but bad digest */
231	debug("verify_hostkey_dns: failed");
232	failures++;
233	}
234	}
235	}
236
237	freerrset(fingerprints);
238
239	if (failures) {
240	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
241	error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
242	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
243	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
244	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
245	error("It is also possible that the %s host key has just been changed.",
246	key_type(hostkey));
247	error("Please contact your system administrator.");
248	return DNS_VERIFY_FAILED;
249	}
250
251	debug("fingerprints found in DNS, but none of them matched");
252
253	return DNS_VERIFY_ERROR;
254	}
255
256
257	/*
258	* Export the fingerprint of a key as a DNS resource record
259	*/
260	int
261	export_dns_rr(const char hostname, Key key, FILE *f, int generic)
262	{
263	u_int8_t rdata_pubkey_algorithm = 0;
264	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
265	u_char *rdata_digest;
266	u_int rdata_digest_len;
267
268	int i;
269	int success = 0;
270
271	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
272	&rdata_digest, &rdata_digest_len, key)) {
273
274	if (generic)
275	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
276	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
277	rdata_pubkey_algorithm, rdata_digest_type);
278	else
279	fprintf(f, "%s IN SSHFP %d %d ", hostname,
280	rdata_pubkey_algorithm, rdata_digest_type);
281
282	for (i = 0; i < rdata_digest_len; i++)
283	fprintf(f, "%02x", rdata_digest[i]);
284	fprintf(f, "\n");
285	success = 1;
286	} else {
287	error("dns_export_rr: unsupported algorithm");
288	}
289
290	return success;
291	}
292
293	#endif /* DNS */