[openssh.git] / dns.c

/*	$OpenBSD: dns.c,v 1.17 2006/03/19 18:51:18 deraadt 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 <netdb.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 = 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;

	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_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
a92a0909	1	/* $OpenBSD: dns.c,v 1.17 2006/03/19 18:51:18 deraadt 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
21289cd0	30	#include <netdb.h>
21289cd0	31
	32	#include "xmalloc.h"
	33	#include "key.h"
	34	#include "dns.h"
	35	#include "log.h"
21289cd0	36
21289cd0	37	static const char *errset_text[] = {
	38	"success", /* 0 ERRSET_SUCCESS */
	39	"out of memory", /* 1 ERRSET_NOMEMORY */
	40	"general failure", /* 2 ERRSET_FAIL */
	41	"invalid parameter", /* 3 ERRSET_INVAL */
	42	"name does not exist", /* 4 ERRSET_NONAME */
	43	"data does not exist", /* 5 ERRSET_NODATA */
	44	};
	45
	46	static const char *
ca75d7de	47	dns_result_totext(unsigned int res)
21289cd0	48	{
ca75d7de	49	switch (res) {
21289cd0	50	case ERRSET_SUCCESS:
	51	return errset_text[ERRSET_SUCCESS];
	52	case ERRSET_NOMEMORY:
	53	return errset_text[ERRSET_NOMEMORY];
	54	case ERRSET_FAIL:
	55	return errset_text[ERRSET_FAIL];
	56	case ERRSET_INVAL:
	57	return errset_text[ERRSET_INVAL];
	58	case ERRSET_NONAME:
	59	return errset_text[ERRSET_NONAME];
	60	case ERRSET_NODATA:
	61	return errset_text[ERRSET_NODATA];
	62	default:
	63	return "unknown error";
	64	}
	65	}
21289cd0	66
	67	/*
	68	* Read SSHFP parameters from key buffer.
	69	*/
	70	static int
	71	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	72	u_char *digest, u_int digest_len, const Key *key)
21289cd0	73	{
	74	int success = 0;
	75
	76	switch (key->type) {
	77	case KEY_RSA:
	78	*algorithm = SSHFP_KEY_RSA;
	79	break;
	80	case KEY_DSA:
	81	*algorithm = SSHFP_KEY_DSA;
	82	break;
	83	default:
4d3434f7	84	algorithm = SSHFP_KEY_RESERVED; / 0 */
21289cd0	85	}
	86
	87	if (*algorithm) {
	88	*digest_type = SSHFP_HASH_SHA1;
	89	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
4d3434f7	90	if (*digest == NULL)
4d3434f7	91	fatal("dns_read_key: null from key_fingerprint_raw()");
21289cd0	92	success = 1;
	93	} else {
	94	*digest_type = SSHFP_HASH_RESERVED;
	95	*digest = NULL;
	96	*digest_len = 0;
	97	success = 0;
	98	}
	99
	100	return success;
	101	}
	102
	103	/*
	104	* Read SSHFP parameters from rdata buffer.
	105	*/
	106	static int
	107	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	108	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	109	{
	110	int success = 0;
	111
	112	*algorithm = SSHFP_KEY_RESERVED;
	113	*digest_type = SSHFP_HASH_RESERVED;
	114
	115	if (rdata_len >= 2) {
	116	*algorithm = rdata[0];
	117	*digest_type = rdata[1];
	118	*digest_len = rdata_len - 2;
	119
	120	if (*digest_len > 0) {
	121	digest = (u_char ) xmalloc(*digest_len);
	122	memcpy(digest, rdata + 2, digest_len);
	123	} else {
4d3434f7	124	*digest = xstrdup("");
21289cd0	125	}
	126
	127	success = 1;
	128	}
	129
	130	return success;
	131	}
	132
4635e729	133	/*
	134	* Check if hostname is numerical.
	135	* Returns -1 if hostname is numeric, 0 otherwise
	136	*/
	137	static int
	138	is_numeric_hostname(const char *hostname)
	139	{
	140	struct addrinfo hints, *ai;
	141
	142	memset(&hints, 0, sizeof(hints));
	143	hints.ai_socktype = SOCK_DGRAM;
	144	hints.ai_flags = AI_NUMERICHOST;
	145
	146	if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
	147	freeaddrinfo(ai);
	148	return -1;
	149	}
	150
	151	return 0;
	152	}
21289cd0	153
	154	/*
	155	* Verify the given hostname, address and host key using DNS.
aff51935	156	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	157	*/
	158	int
	159	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	160	const Key hostkey, int flags)
21289cd0	161	{
2ceb8101	162	u_int counter;
21289cd0	163	int result;
21289cd0	164	struct rrsetinfo *fingerprints = NULL;
21289cd0	165
	166	u_int8_t hostkey_algorithm;
	167	u_int8_t hostkey_digest_type;
	168	u_char *hostkey_digest;
	169	u_int hostkey_digest_len;
	170
	171	u_int8_t dnskey_algorithm;
	172	u_int8_t dnskey_digest_type;
	173	u_char *dnskey_digest;
	174	u_int dnskey_digest_len;
	175
0161a13d	176	*flags = 0;
21289cd0	177
8374cf6f	178	debug3("verify_host_key_dns");
21289cd0	179	if (hostkey == NULL)
	180	fatal("No key to look up!");
	181
4635e729	182	if (is_numeric_hostname(hostname)) {
	183	debug("skipped DNS lookup for numerical hostname");
	184	return -1;
	185	}
	186
21289cd0	187	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	188	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	189	if (result) {
	190	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	191	return -1;
21289cd0	192	}
21289cd0	193
0161a13d	194	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	195	*flags \|= DNS_VERIFY_SECURE;
	196	debug("found %d secure fingerprints in DNS",
	197	fingerprints->rri_nrdatas);
	198	} else {
	199	debug("found %d insecure fingerprints in DNS",
	200	fingerprints->rri_nrdatas);
21289cd0	201	}
21289cd0	202
	203	/* Initialize host key parameters */
	204	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	205	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	206	error("Error calculating host key fingerprint.");
b414a17b	207	freerrset(fingerprints);
0161a13d	208	return -1;
21289cd0	209	}
21289cd0	210
0161a13d	211	if (fingerprints->rri_nrdatas)
	212	*flags \|= DNS_VERIFY_FOUND;
	213
adf8c40b	214	for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
21289cd0	215	/*
	216	* Extract the key from the answer. Ignore any badly
	217	* formatted fingerprints.
	218	*/
	219	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	220	&dnskey_digest, &dnskey_digest_len,
	221	fingerprints->rri_rdatas[counter].rdi_data,
	222	fingerprints->rri_rdatas[counter].rdi_length)) {
	223	verbose("Error parsing fingerprint from DNS.");
	224	continue;
	225	}
	226
	227	/* Check if the current key is the same as the given key */
	228	if (hostkey_algorithm == dnskey_algorithm &&
	229	hostkey_digest_type == dnskey_digest_type) {
	230
	231	if (hostkey_digest_len == dnskey_digest_len &&
	232	memcmp(hostkey_digest, dnskey_digest,
	233	hostkey_digest_len) == 0) {
	234
0161a13d	235	*flags \|= DNS_VERIFY_MATCH;
21289cd0	236	}
21289cd0	237	}
4d3434f7	238	xfree(dnskey_digest);
21289cd0	239	}
21289cd0	240
4d3434f7	241	xfree(hostkey_digest); /* from key_fingerprint_raw() */
21289cd0	242	freerrset(fingerprints);
21289cd0	243
0161a13d	244	if (*flags & DNS_VERIFY_FOUND)
	245	if (*flags & DNS_VERIFY_MATCH)
	246	debug("matching host key fingerprint found in DNS");
	247	else
	248	debug("mismatching host key fingerprint found in DNS");
	249	else
	250	debug("no host key fingerprint found in DNS");
21289cd0	251
0161a13d	252	return 0;
21289cd0	253	}
21289cd0	254
21289cd0	255	/*
	256	* Export the fingerprint of a key as a DNS resource record
	257	*/
	258	int
0161a13d	259	export_dns_rr(const char hostname, const Key key, FILE *f, int generic)
21289cd0	260	{
	261	u_int8_t rdata_pubkey_algorithm = 0;
	262	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	263	u_char *rdata_digest;
	264	u_int rdata_digest_len;
	265
2ceb8101	266	u_int i;
21289cd0	267	int success = 0;
	268
	269	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
8374cf6f	270	&rdata_digest, &rdata_digest_len, key)) {
21289cd0	271
	272	if (generic)
	273	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
	274	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
	275	rdata_pubkey_algorithm, rdata_digest_type);
	276	else
	277	fprintf(f, "%s IN SSHFP %d %d ", hostname,
	278	rdata_pubkey_algorithm, rdata_digest_type);
	279
	280	for (i = 0; i < rdata_digest_len; i++)
	281	fprintf(f, "%02x", rdata_digest[i]);
	282	fprintf(f, "\n");
4d3434f7	283	xfree(rdata_digest); /* from key_fingerprint_raw() */
21289cd0	284	success = 1;
21289cd0	285	} else {
8374cf6f	286	error("export_dns_rr: unsupported algorithm");
21289cd0	287	}
	288
	289	return success;
	290	}