[openssh.git] / dns.c

/* $OpenBSD: dns.c,v 1.25 2008/06/12 00:03:49 dtucker 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"

#include <sys/types.h>
#include <sys/socket.h>

#include <netdb.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>

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

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 res)
{
	switch (res) {
	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";
	}
}

/*
 * 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, const 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; /* 0 */
	}

	if (*algorithm) {
		*digest_type = SSHFP_HASH_SHA1;
		*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
		if (*digest == NULL)
			fatal("dns_read_key: null from key_fingerprint_raw()");
		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 = (u_char *)xstrdup("");
		}

		success = 1;
	}

	return success;
}

/*
 * Check if hostname is numerical.
 * Returns -1 if hostname is numeric, 0 otherwise
 */
static int
is_numeric_hostname(const char *hostname)
{
	struct addrinfo hints, *ai;

	/*
	 * We shouldn't ever get a null host but if we do then log an error
	 * and return -1 which stops DNS key fingerprint processing.
	 */
	if (hostname == NULL) {
		error("is_numeric_hostname called with NULL hostname");
		return -1;
	}

	memset(&hints, 0, sizeof(hints));
	hints.ai_socktype = SOCK_DGRAM;
	hints.ai_flags = AI_NUMERICHOST;

	if (getaddrinfo(hostname, NULL, &hints, &ai) == 0) {
		freeaddrinfo(ai);
		return -1;
	}

	return 0;
}

/*
 * Verify the given hostname, address and host key using DNS.
 * Returns 0 if lookup succeeds, -1 otherwise
 */
int
verify_host_key_dns(const char *hostname, struct sockaddr *address,
    const Key *hostkey, int *flags)
{
	u_int counter;
	int result;
	struct rrsetinfo *fingerprints = NULL;

	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;

	*flags = 0;

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

	if (is_numeric_hostname(hostname)) {
		debug("skipped DNS lookup for numerical hostname");
		return -1;
	}

	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	    DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	if (result) {
		verbose("DNS lookup error: %s", dns_result_totext(result));
		return -1;
	}

	if (fingerprints->rri_flags & RRSET_VALIDATED) {
		*flags |= DNS_VERIFY_SECURE;
		debug("found %d secure fingerprints in DNS",
		    fingerprints->rri_nrdatas);
	} else {
		debug("found %d insecure 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.");
		freerrset(fingerprints);
		return -1;
	}

	if (fingerprints->rri_nrdatas)
		*flags |= DNS_VERIFY_FOUND;

	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) {

				*flags |= DNS_VERIFY_MATCH;
			}
		}
		xfree(dnskey_digest);
	}

	xfree(hostkey_digest); /* from key_fingerprint_raw() */
	freerrset(fingerprints);

	if (*flags & DNS_VERIFY_FOUND)
		if (*flags & DNS_VERIFY_MATCH)
			debug("matching host key fingerprint found in DNS");
		else
			debug("mismatching host key fingerprint found in DNS");
	else
		debug("no host key fingerprint found in DNS");

	return 0;
}

/*
 * Export the fingerprint of a key as a DNS resource record
 */
int
export_dns_rr(const char *hostname, const 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;

	u_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");
		xfree(rdata_digest); /* from key_fingerprint_raw() */
		success = 1;
	} else {
		error("export_dns_rr: unsupported algorithm");
	}

	return success;
}
Commit	Line	Data
c5daf22b	1	/* $OpenBSD: dns.c,v 1.25 2008/06/12 00:03:49 dtucker Exp $ */
21289cd0	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
21289cd0	28	#include "includes.h"
21289cd0	29
5b04a8bf	30	#include <sys/types.h>
	31	#include <sys/socket.h>
	32
28cb0a43	33	#include <netdb.h>
24436b92	34	#include <stdarg.h>
cf851879	35	#include <stdio.h>
00146caa	36	#include <string.h>
21289cd0	37
	38	#include "xmalloc.h"
	39	#include "key.h"
	40	#include "dns.h"
	41	#include "log.h"
21289cd0	42
21289cd0	43	static const char *errset_text[] = {
	44	"success", /* 0 ERRSET_SUCCESS */
	45	"out of memory", /* 1 ERRSET_NOMEMORY */
	46	"general failure", /* 2 ERRSET_FAIL */
	47	"invalid parameter", /* 3 ERRSET_INVAL */
	48	"name does not exist", /* 4 ERRSET_NONAME */
	49	"data does not exist", /* 5 ERRSET_NODATA */
	50	};
	51
	52	static const char *
ca75d7de	53	dns_result_totext(unsigned int res)
21289cd0	54	{
ca75d7de	55	switch (res) {
21289cd0	56	case ERRSET_SUCCESS:
	57	return errset_text[ERRSET_SUCCESS];
	58	case ERRSET_NOMEMORY:
	59	return errset_text[ERRSET_NOMEMORY];
	60	case ERRSET_FAIL:
	61	return errset_text[ERRSET_FAIL];
	62	case ERRSET_INVAL:
	63	return errset_text[ERRSET_INVAL];
	64	case ERRSET_NONAME:
	65	return errset_text[ERRSET_NONAME];
	66	case ERRSET_NODATA:
	67	return errset_text[ERRSET_NODATA];
	68	default:
	69	return "unknown error";
	70	}
	71	}
21289cd0	72
	73	/*
	74	* Read SSHFP parameters from key buffer.
	75	*/
	76	static int
	77	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	78	u_char *digest, u_int digest_len, const Key *key)
21289cd0	79	{
	80	int success = 0;
	81
	82	switch (key->type) {
	83	case KEY_RSA:
	84	*algorithm = SSHFP_KEY_RSA;
	85	break;
	86	case KEY_DSA:
	87	*algorithm = SSHFP_KEY_DSA;
	88	break;
	89	default:
4d3434f7	90	algorithm = SSHFP_KEY_RESERVED; / 0 */
21289cd0	91	}
	92
	93	if (*algorithm) {
	94	*digest_type = SSHFP_HASH_SHA1;
	95	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
4d3434f7	96	if (*digest == NULL)
4d3434f7	97	fatal("dns_read_key: null from key_fingerprint_raw()");
21289cd0	98	success = 1;
	99	} else {
	100	*digest_type = SSHFP_HASH_RESERVED;
	101	*digest = NULL;
	102	*digest_len = 0;
	103	success = 0;
	104	}
	105
	106	return success;
	107	}
	108
	109	/*
	110	* Read SSHFP parameters from rdata buffer.
	111	*/
	112	static int
	113	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	114	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	115	{
	116	int success = 0;
	117
	118	*algorithm = SSHFP_KEY_RESERVED;
	119	*digest_type = SSHFP_HASH_RESERVED;
	120
	121	if (rdata_len >= 2) {
	122	*algorithm = rdata[0];
	123	*digest_type = rdata[1];
	124	*digest_len = rdata_len - 2;
	125
	126	if (*digest_len > 0) {
	127	digest = (u_char ) xmalloc(*digest_len);
	128	memcpy(digest, rdata + 2, digest_len);
	129	} else {
6cfe93ec	130	digest = (u_char )xstrdup("");
21289cd0	131	}
	132
	133	success = 1;
	134	}
	135
	136	return success;
	137	}
	138
4635e729	139	/*
	140	* Check if hostname is numerical.
	141	* Returns -1 if hostname is numeric, 0 otherwise
	142	*/
	143	static int
	144	is_numeric_hostname(const char *hostname)
	145	{
	146	struct addrinfo hints, *ai;
	147
c5daf22b	148	/*
	149	* We shouldn't ever get a null host but if we do then log an error
	150	* and return -1 which stops DNS key fingerprint processing.
	151	*/
	152	if (hostname == NULL) {
	153	error("is_numeric_hostname called with NULL hostname");
	154	return -1;
	155	}
	156
4635e729	157	memset(&hints, 0, sizeof(hints));
	158	hints.ai_socktype = SOCK_DGRAM;
	159	hints.ai_flags = AI_NUMERICHOST;
	160
c5daf22b	161	if (getaddrinfo(hostname, NULL, &hints, &ai) == 0) {
4635e729	162	freeaddrinfo(ai);
	163	return -1;
	164	}
	165
	166	return 0;
	167	}
21289cd0	168
	169	/*
	170	* Verify the given hostname, address and host key using DNS.
aff51935	171	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	172	*/
	173	int
	174	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	175	const Key hostkey, int flags)
21289cd0	176	{
2ceb8101	177	u_int counter;
21289cd0	178	int result;
21289cd0	179	struct rrsetinfo *fingerprints = NULL;
21289cd0	180
	181	u_int8_t hostkey_algorithm;
	182	u_int8_t hostkey_digest_type;
	183	u_char *hostkey_digest;
	184	u_int hostkey_digest_len;
	185
	186	u_int8_t dnskey_algorithm;
	187	u_int8_t dnskey_digest_type;
	188	u_char *dnskey_digest;
	189	u_int dnskey_digest_len;
	190
0161a13d	191	*flags = 0;
21289cd0	192
8374cf6f	193	debug3("verify_host_key_dns");
21289cd0	194	if (hostkey == NULL)
	195	fatal("No key to look up!");
	196
4635e729	197	if (is_numeric_hostname(hostname)) {
	198	debug("skipped DNS lookup for numerical hostname");
	199	return -1;
	200	}
	201
21289cd0	202	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	203	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	204	if (result) {
	205	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	206	return -1;
21289cd0	207	}
21289cd0	208
0161a13d	209	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	210	*flags \|= DNS_VERIFY_SECURE;
	211	debug("found %d secure fingerprints in DNS",
	212	fingerprints->rri_nrdatas);
	213	} else {
	214	debug("found %d insecure fingerprints in DNS",
	215	fingerprints->rri_nrdatas);
21289cd0	216	}
21289cd0	217
	218	/* Initialize host key parameters */
	219	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	220	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	221	error("Error calculating host key fingerprint.");
b414a17b	222	freerrset(fingerprints);
0161a13d	223	return -1;
21289cd0	224	}
21289cd0	225
0161a13d	226	if (fingerprints->rri_nrdatas)
	227	*flags \|= DNS_VERIFY_FOUND;
	228
4f6e2ba9	229	for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
21289cd0	230	/*
	231	* Extract the key from the answer. Ignore any badly
	232	* formatted fingerprints.
	233	*/
	234	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	235	&dnskey_digest, &dnskey_digest_len,
	236	fingerprints->rri_rdatas[counter].rdi_data,
	237	fingerprints->rri_rdatas[counter].rdi_length)) {
	238	verbose("Error parsing fingerprint from DNS.");
	239	continue;
	240	}
	241
	242	/* Check if the current key is the same as the given key */
	243	if (hostkey_algorithm == dnskey_algorithm &&
	244	hostkey_digest_type == dnskey_digest_type) {
	245
	246	if (hostkey_digest_len == dnskey_digest_len &&
	247	memcmp(hostkey_digest, dnskey_digest,
	248	hostkey_digest_len) == 0) {
	249
0161a13d	250	*flags \|= DNS_VERIFY_MATCH;
21289cd0	251	}
21289cd0	252	}
4d3434f7	253	xfree(dnskey_digest);
21289cd0	254	}
21289cd0	255
4d3434f7	256	xfree(hostkey_digest); /* from key_fingerprint_raw() */
21289cd0	257	freerrset(fingerprints);
21289cd0	258
0161a13d	259	if (*flags & DNS_VERIFY_FOUND)
	260	if (*flags & DNS_VERIFY_MATCH)
	261	debug("matching host key fingerprint found in DNS");
	262	else
	263	debug("mismatching host key fingerprint found in DNS");
	264	else
	265	debug("no host key fingerprint found in DNS");
21289cd0	266
0161a13d	267	return 0;
21289cd0	268	}
21289cd0	269
21289cd0	270	/*
	271	* Export the fingerprint of a key as a DNS resource record
	272	*/
	273	int
0161a13d	274	export_dns_rr(const char hostname, const Key key, FILE *f, int generic)
21289cd0	275	{
	276	u_int8_t rdata_pubkey_algorithm = 0;
	277	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	278	u_char *rdata_digest;
	279	u_int rdata_digest_len;
	280
2ceb8101	281	u_int i;
21289cd0	282	int success = 0;
	283
	284	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
8374cf6f	285	&rdata_digest, &rdata_digest_len, key)) {
21289cd0	286
	287	if (generic)
	288	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
	289	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
	290	rdata_pubkey_algorithm, rdata_digest_type);
	291	else
	292	fprintf(f, "%s IN SSHFP %d %d ", hostname,
	293	rdata_pubkey_algorithm, rdata_digest_type);
	294
	295	for (i = 0; i < rdata_digest_len; i++)
	296	fprintf(f, "%02x", rdata_digest[i]);
	297	fprintf(f, "\n");
4d3434f7	298	xfree(rdata_digest); /* from key_fingerprint_raw() */
21289cd0	299	success = 1;
21289cd0	300	} else {
8374cf6f	301	error("export_dns_rr: unsupported algorithm");
21289cd0	302	}
	303
	304	return success;
	305	}