[openssh.git] / dns.c

/*	$OpenBSD: dns.c,v 1.11 2005/04/20 10:05:45 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"

#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 1.11 2005/04/20 10:05:45 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 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)
{
	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;

	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
4635e729	1	/* $OpenBSD: dns.c,v 1.11 2005/04/20 10:05:45 jakob 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"
	43	#include "uuencode.h"
	44
	45	extern char *__progname;
4635e729	46	RCSID("$OpenBSD: dns.c,v 1.11 2005/04/20 10:05:45 jakob Exp $");
21289cd0	47
	48	#ifndef LWRES
	49	static const char *errset_text[] = {
	50	"success", /* 0 ERRSET_SUCCESS */
	51	"out of memory", /* 1 ERRSET_NOMEMORY */
	52	"general failure", /* 2 ERRSET_FAIL */
	53	"invalid parameter", /* 3 ERRSET_INVAL */
	54	"name does not exist", /* 4 ERRSET_NONAME */
	55	"data does not exist", /* 5 ERRSET_NODATA */
	56	};
	57
	58	static const char *
ca75d7de	59	dns_result_totext(unsigned int res)
21289cd0	60	{
ca75d7de	61	switch (res) {
21289cd0	62	case ERRSET_SUCCESS:
	63	return errset_text[ERRSET_SUCCESS];
	64	case ERRSET_NOMEMORY:
	65	return errset_text[ERRSET_NOMEMORY];
	66	case ERRSET_FAIL:
	67	return errset_text[ERRSET_FAIL];
	68	case ERRSET_INVAL:
	69	return errset_text[ERRSET_INVAL];
	70	case ERRSET_NONAME:
	71	return errset_text[ERRSET_NONAME];
	72	case ERRSET_NODATA:
	73	return errset_text[ERRSET_NODATA];
	74	default:
	75	return "unknown error";
	76	}
	77	}
	78	#endif /* LWRES */
	79
	80
	81	/*
	82	* Read SSHFP parameters from key buffer.
	83	*/
	84	static int
	85	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	86	u_char *digest, u_int digest_len, const Key *key)
21289cd0	87	{
	88	int success = 0;
	89
	90	switch (key->type) {
	91	case KEY_RSA:
	92	*algorithm = SSHFP_KEY_RSA;
	93	break;
	94	case KEY_DSA:
	95	*algorithm = SSHFP_KEY_DSA;
	96	break;
	97	default:
	98	*algorithm = SSHFP_KEY_RESERVED;
	99	}
	100
	101	if (*algorithm) {
	102	*digest_type = SSHFP_HASH_SHA1;
	103	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
	104	success = 1;
	105	} else {
	106	*digest_type = SSHFP_HASH_RESERVED;
	107	*digest = NULL;
	108	*digest_len = 0;
	109	success = 0;
	110	}
	111
	112	return success;
	113	}
	114
	115	/*
	116	* Read SSHFP parameters from rdata buffer.
	117	*/
	118	static int
	119	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	120	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	121	{
	122	int success = 0;
	123
	124	*algorithm = SSHFP_KEY_RESERVED;
	125	*digest_type = SSHFP_HASH_RESERVED;
	126
	127	if (rdata_len >= 2) {
	128	*algorithm = rdata[0];
	129	*digest_type = rdata[1];
	130	*digest_len = rdata_len - 2;
	131
	132	if (*digest_len > 0) {
	133	digest = (u_char ) xmalloc(*digest_len);
	134	memcpy(digest, rdata + 2, digest_len);
	135	} else {
	136	*digest = NULL;
	137	}
	138
	139	success = 1;
	140	}
	141
	142	return success;
	143	}
	144
4635e729	145	/*
	146	* Check if hostname is numerical.
	147	* Returns -1 if hostname is numeric, 0 otherwise
	148	*/
	149	static int
	150	is_numeric_hostname(const char *hostname)
	151	{
	152	struct addrinfo hints, *ai;
	153
	154	memset(&hints, 0, sizeof(hints));
	155	hints.ai_socktype = SOCK_DGRAM;
	156	hints.ai_flags = AI_NUMERICHOST;
	157
	158	if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
	159	freeaddrinfo(ai);
	160	return -1;
	161	}
	162
	163	return 0;
	164	}
21289cd0	165
	166	/*
	167	* Verify the given hostname, address and host key using DNS.
aff51935	168	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	169	*/
	170	int
	171	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	172	const Key hostkey, int flags)
21289cd0	173	{
	174	int counter;
	175	int result;
	176	struct rrsetinfo *fingerprints = NULL;
21289cd0	177
	178	u_int8_t hostkey_algorithm;
	179	u_int8_t hostkey_digest_type;
	180	u_char *hostkey_digest;
	181	u_int hostkey_digest_len;
	182
	183	u_int8_t dnskey_algorithm;
	184	u_int8_t dnskey_digest_type;
	185	u_char *dnskey_digest;
	186	u_int dnskey_digest_len;
	187
0161a13d	188	*flags = 0;
21289cd0	189
	190	debug3("verify_hostkey_dns");
	191	if (hostkey == NULL)
	192	fatal("No key to look up!");
	193
4635e729	194	if (is_numeric_hostname(hostname)) {
	195	debug("skipped DNS lookup for numerical hostname");
	196	return -1;
	197	}
	198
21289cd0	199	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	200	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	201	if (result) {
	202	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	203	return -1;
21289cd0	204	}
21289cd0	205
0161a13d	206	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	207	*flags \|= DNS_VERIFY_SECURE;
	208	debug("found %d secure fingerprints in DNS",
	209	fingerprints->rri_nrdatas);
	210	} else {
	211	debug("found %d insecure fingerprints in DNS",
	212	fingerprints->rri_nrdatas);
21289cd0	213	}
21289cd0	214
	215	/* Initialize host key parameters */
	216	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	217	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	218	error("Error calculating host key fingerprint.");
b414a17b	219	freerrset(fingerprints);
0161a13d	220	return -1;
21289cd0	221	}
21289cd0	222
0161a13d	223	if (fingerprints->rri_nrdatas)
	224	*flags \|= DNS_VERIFY_FOUND;
	225
21289cd0	226	for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++) {
	227	/*
	228	* Extract the key from the answer. Ignore any badly
	229	* formatted fingerprints.
	230	*/
	231	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	232	&dnskey_digest, &dnskey_digest_len,
	233	fingerprints->rri_rdatas[counter].rdi_data,
	234	fingerprints->rri_rdatas[counter].rdi_length)) {
	235	verbose("Error parsing fingerprint from DNS.");
	236	continue;
	237	}
	238
	239	/* Check if the current key is the same as the given key */
	240	if (hostkey_algorithm == dnskey_algorithm &&
	241	hostkey_digest_type == dnskey_digest_type) {
	242
	243	if (hostkey_digest_len == dnskey_digest_len &&
	244	memcmp(hostkey_digest, dnskey_digest,
	245	hostkey_digest_len) == 0) {
	246
0161a13d	247	*flags \|= DNS_VERIFY_MATCH;
21289cd0	248	}
	249	}
	250	}
	251
	252	freerrset(fingerprints);
	253
0161a13d	254	if (*flags & DNS_VERIFY_FOUND)
	255	if (*flags & DNS_VERIFY_MATCH)
	256	debug("matching host key fingerprint found in DNS");
	257	else
	258	debug("mismatching host key fingerprint found in DNS");
	259	else
	260	debug("no host key fingerprint found in DNS");
21289cd0	261
0161a13d	262	return 0;
21289cd0	263	}
	264
	265
	266	/*
	267	* Export the fingerprint of a key as a DNS resource record
	268	*/
	269	int
0161a13d	270	export_dns_rr(const char hostname, const Key key, FILE *f, int generic)
21289cd0	271	{
	272	u_int8_t rdata_pubkey_algorithm = 0;
	273	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	274	u_char *rdata_digest;
	275	u_int rdata_digest_len;
	276
	277	int i;
	278	int success = 0;
	279
	280	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
	281	&rdata_digest, &rdata_digest_len, key)) {
	282
	283	if (generic)
	284	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
	285	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
	286	rdata_pubkey_algorithm, rdata_digest_type);
	287	else
	288	fprintf(f, "%s IN SSHFP %d %d ", hostname,
	289	rdata_pubkey_algorithm, rdata_digest_type);
	290
	291	for (i = 0; i < rdata_digest_len; i++)
	292	fprintf(f, "%02x", rdata_digest[i]);
	293	fprintf(f, "\n");
	294	success = 1;
	295	} else {
	296	error("dns_export_rr: unsupported algorithm");
	297	}
	298
	299	return success;
	300	}