[openssh.git] / dns.c

/*	$OpenBSD: dns.c,v 1.13 2005/10/13 19:13:41 stevesk 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 <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"

RCSID("$OpenBSD: dns.c,v 1.13 2005/10/13 19:13:41 stevesk 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 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";
	}
}
#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, 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;
	}

	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;
}

/*
 * 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;

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

	if (getaddrinfo(hostname, "0", &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_hostkey_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;
			}
		}
	}

	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");
		success = 1;
	} else {
		error("dns_export_rr: unsupported algorithm");
	}

	return success;
}
Commit	Line	Data
adf8c40b	1	/* $OpenBSD: dns.c,v 1.13 2005/10/13 19:13:41 stevesk 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
	28
	29	#include "includes.h"
	30
21289cd0	31	#include <openssl/bn.h>
	32	#ifdef LWRES
	33	#include <lwres/netdb.h>
	34	#include <dns/result.h>
	35	#else /* LWRES */
	36	#include <netdb.h>
	37	#endif /* LWRES */
	38
	39	#include "xmalloc.h"
	40	#include "key.h"
	41	#include "dns.h"
	42	#include "log.h"
21289cd0	43
adf8c40b	44	RCSID("$OpenBSD: dns.c,v 1.13 2005/10/13 19:13:41 stevesk Exp $");
21289cd0	45
	46	#ifndef LWRES
	47	static const char *errset_text[] = {
	48	"success", /* 0 ERRSET_SUCCESS */
	49	"out of memory", /* 1 ERRSET_NOMEMORY */
	50	"general failure", /* 2 ERRSET_FAIL */
	51	"invalid parameter", /* 3 ERRSET_INVAL */
	52	"name does not exist", /* 4 ERRSET_NONAME */
	53	"data does not exist", /* 5 ERRSET_NODATA */
	54	};
	55
	56	static const char *
ca75d7de	57	dns_result_totext(unsigned int res)
21289cd0	58	{
ca75d7de	59	switch (res) {
21289cd0	60	case ERRSET_SUCCESS:
	61	return errset_text[ERRSET_SUCCESS];
	62	case ERRSET_NOMEMORY:
	63	return errset_text[ERRSET_NOMEMORY];
	64	case ERRSET_FAIL:
	65	return errset_text[ERRSET_FAIL];
	66	case ERRSET_INVAL:
	67	return errset_text[ERRSET_INVAL];
	68	case ERRSET_NONAME:
	69	return errset_text[ERRSET_NONAME];
	70	case ERRSET_NODATA:
	71	return errset_text[ERRSET_NODATA];
	72	default:
	73	return "unknown error";
	74	}
	75	}
	76	#endif /* LWRES */
	77
	78
	79	/*
	80	* Read SSHFP parameters from key buffer.
	81	*/
	82	static int
	83	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	84	u_char *digest, u_int digest_len, const Key *key)
21289cd0	85	{
	86	int success = 0;
	87
	88	switch (key->type) {
	89	case KEY_RSA:
	90	*algorithm = SSHFP_KEY_RSA;
	91	break;
	92	case KEY_DSA:
	93	*algorithm = SSHFP_KEY_DSA;
	94	break;
	95	default:
	96	*algorithm = SSHFP_KEY_RESERVED;
	97	}
	98
	99	if (*algorithm) {
	100	*digest_type = SSHFP_HASH_SHA1;
	101	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
	102	success = 1;
	103	} else {
	104	*digest_type = SSHFP_HASH_RESERVED;
	105	*digest = NULL;
	106	*digest_len = 0;
	107	success = 0;
	108	}
	109
	110	return success;
	111	}
	112
	113	/*
	114	* Read SSHFP parameters from rdata buffer.
	115	*/
	116	static int
	117	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	118	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	119	{
	120	int success = 0;
	121
	122	*algorithm = SSHFP_KEY_RESERVED;
	123	*digest_type = SSHFP_HASH_RESERVED;
	124
	125	if (rdata_len >= 2) {
	126	*algorithm = rdata[0];
	127	*digest_type = rdata[1];
	128	*digest_len = rdata_len - 2;
	129
	130	if (*digest_len > 0) {
	131	digest = (u_char ) xmalloc(*digest_len);
	132	memcpy(digest, rdata + 2, digest_len);
	133	} else {
	134	*digest = NULL;
	135	}
	136
	137	success = 1;
	138	}
	139
	140	return success;
	141	}
	142
4635e729	143	/*
	144	* Check if hostname is numerical.
	145	* Returns -1 if hostname is numeric, 0 otherwise
	146	*/
	147	static int
	148	is_numeric_hostname(const char *hostname)
	149	{
	150	struct addrinfo hints, *ai;
	151
	152	memset(&hints, 0, sizeof(hints));
	153	hints.ai_socktype = SOCK_DGRAM;
	154	hints.ai_flags = AI_NUMERICHOST;
	155
	156	if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
	157	freeaddrinfo(ai);
	158	return -1;
	159	}
	160
	161	return 0;
	162	}
21289cd0	163
	164	/*
	165	* Verify the given hostname, address and host key using DNS.
aff51935	166	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	167	*/
	168	int
	169	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	170	const Key hostkey, int flags)
21289cd0	171	{
2ceb8101	172	u_int counter;
21289cd0	173	int result;
21289cd0	174	struct rrsetinfo *fingerprints = NULL;
21289cd0	175
	176	u_int8_t hostkey_algorithm;
	177	u_int8_t hostkey_digest_type;
	178	u_char *hostkey_digest;
	179	u_int hostkey_digest_len;
	180
	181	u_int8_t dnskey_algorithm;
	182	u_int8_t dnskey_digest_type;
	183	u_char *dnskey_digest;
	184	u_int dnskey_digest_len;
	185
0161a13d	186	*flags = 0;
21289cd0	187
	188	debug3("verify_hostkey_dns");
	189	if (hostkey == NULL)
	190	fatal("No key to look up!");
	191
4635e729	192	if (is_numeric_hostname(hostname)) {
	193	debug("skipped DNS lookup for numerical hostname");
	194	return -1;
	195	}
	196
21289cd0	197	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	198	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	199	if (result) {
	200	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	201	return -1;
21289cd0	202	}
21289cd0	203
0161a13d	204	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	205	*flags \|= DNS_VERIFY_SECURE;
	206	debug("found %d secure fingerprints in DNS",
	207	fingerprints->rri_nrdatas);
	208	} else {
	209	debug("found %d insecure fingerprints in DNS",
	210	fingerprints->rri_nrdatas);
21289cd0	211	}
21289cd0	212
	213	/* Initialize host key parameters */
	214	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	215	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	216	error("Error calculating host key fingerprint.");
b414a17b	217	freerrset(fingerprints);
0161a13d	218	return -1;
21289cd0	219	}
21289cd0	220
0161a13d	221	if (fingerprints->rri_nrdatas)
	222	*flags \|= DNS_VERIFY_FOUND;
	223
adf8c40b	224	for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
21289cd0	225	/*
	226	* Extract the key from the answer. Ignore any badly
	227	* formatted fingerprints.
	228	*/
	229	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	230	&dnskey_digest, &dnskey_digest_len,
	231	fingerprints->rri_rdatas[counter].rdi_data,
	232	fingerprints->rri_rdatas[counter].rdi_length)) {
	233	verbose("Error parsing fingerprint from DNS.");
	234	continue;
	235	}
	236
	237	/* Check if the current key is the same as the given key */
	238	if (hostkey_algorithm == dnskey_algorithm &&
	239	hostkey_digest_type == dnskey_digest_type) {
	240
	241	if (hostkey_digest_len == dnskey_digest_len &&
	242	memcmp(hostkey_digest, dnskey_digest,
	243	hostkey_digest_len) == 0) {
	244
0161a13d	245	*flags \|= DNS_VERIFY_MATCH;
21289cd0	246	}
	247	}
	248	}
	249
	250	freerrset(fingerprints);
	251
0161a13d	252	if (*flags & DNS_VERIFY_FOUND)
	253	if (*flags & DNS_VERIFY_MATCH)
	254	debug("matching host key fingerprint found in DNS");
	255	else
	256	debug("mismatching host key fingerprint found in DNS");
	257	else
	258	debug("no host key fingerprint found in DNS");
21289cd0	259
0161a13d	260	return 0;
21289cd0	261	}
	262
	263
	264	/*
	265	* Export the fingerprint of a key as a DNS resource record
	266	*/
	267	int
0161a13d	268	export_dns_rr(const char hostname, const Key key, FILE *f, int generic)
21289cd0	269	{
	270	u_int8_t rdata_pubkey_algorithm = 0;
	271	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	272	u_char *rdata_digest;
	273	u_int rdata_digest_len;
	274
2ceb8101	275	u_int i;
21289cd0	276	int success = 0;
	277
	278	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
	279	&rdata_digest, &rdata_digest_len, key)) {
	280
	281	if (generic)
	282	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
	283	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
	284	rdata_pubkey_algorithm, rdata_digest_type);
	285	else
	286	fprintf(f, "%s IN SSHFP %d %d ", hostname,
	287	rdata_pubkey_algorithm, rdata_digest_type);
	288
	289	for (i = 0; i < rdata_digest_len; i++)
	290	fprintf(f, "%02x", rdata_digest[i]);
	291	fprintf(f, "\n");
	292	success = 1;
	293	} else {
	294	error("dns_export_rr: unsupported algorithm");
	295	}
	296
	297	return success;
	298	}