[openssh.git] / dns.c

/*	$OpenBSD: dns.c,v 1.16 2005/10/17 14:13:35 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"
RCSID("$OpenBSD: dns.c,v 1.16 2005/10/17 14:13:35 stevesk Exp $");

#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
8374cf6f	1	/* $OpenBSD: dns.c,v 1.16 2005/10/17 14:13:35 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
21289cd0	28	#include "includes.h"
8374cf6f	29	RCSID("$OpenBSD: dns.c,v 1.16 2005/10/17 14:13:35 stevesk Exp $");
21289cd0	30
21289cd0	31	#include <netdb.h>
21289cd0	32
	33	#include "xmalloc.h"
	34	#include "key.h"
	35	#include "dns.h"
	36	#include "log.h"
21289cd0	37
21289cd0	38	static const char *errset_text[] = {
	39	"success", /* 0 ERRSET_SUCCESS */
	40	"out of memory", /* 1 ERRSET_NOMEMORY */
	41	"general failure", /* 2 ERRSET_FAIL */
	42	"invalid parameter", /* 3 ERRSET_INVAL */
	43	"name does not exist", /* 4 ERRSET_NONAME */
	44	"data does not exist", /* 5 ERRSET_NODATA */
	45	};
	46
	47	static const char *
ca75d7de	48	dns_result_totext(unsigned int res)
21289cd0	49	{
ca75d7de	50	switch (res) {
21289cd0	51	case ERRSET_SUCCESS:
	52	return errset_text[ERRSET_SUCCESS];
	53	case ERRSET_NOMEMORY:
	54	return errset_text[ERRSET_NOMEMORY];
	55	case ERRSET_FAIL:
	56	return errset_text[ERRSET_FAIL];
	57	case ERRSET_INVAL:
	58	return errset_text[ERRSET_INVAL];
	59	case ERRSET_NONAME:
	60	return errset_text[ERRSET_NONAME];
	61	case ERRSET_NODATA:
	62	return errset_text[ERRSET_NODATA];
	63	default:
	64	return "unknown error";
	65	}
	66	}
21289cd0	67
	68	/*
	69	* Read SSHFP parameters from key buffer.
	70	*/
	71	static int
	72	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	73	u_char *digest, u_int digest_len, const Key *key)
21289cd0	74	{
	75	int success = 0;
	76
	77	switch (key->type) {
	78	case KEY_RSA:
	79	*algorithm = SSHFP_KEY_RSA;
	80	break;
	81	case KEY_DSA:
	82	*algorithm = SSHFP_KEY_DSA;
	83	break;
	84	default:
4d3434f7	85	algorithm = SSHFP_KEY_RESERVED; / 0 */
21289cd0	86	}
	87
	88	if (*algorithm) {
	89	*digest_type = SSHFP_HASH_SHA1;
	90	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
4d3434f7	91	if (*digest == NULL)
4d3434f7	92	fatal("dns_read_key: null from key_fingerprint_raw()");
21289cd0	93	success = 1;
	94	} else {
	95	*digest_type = SSHFP_HASH_RESERVED;
	96	*digest = NULL;
	97	*digest_len = 0;
	98	success = 0;
	99	}
	100
	101	return success;
	102	}
	103
	104	/*
	105	* Read SSHFP parameters from rdata buffer.
	106	*/
	107	static int
	108	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	109	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	110	{
	111	int success = 0;
	112
	113	*algorithm = SSHFP_KEY_RESERVED;
	114	*digest_type = SSHFP_HASH_RESERVED;
	115
	116	if (rdata_len >= 2) {
	117	*algorithm = rdata[0];
	118	*digest_type = rdata[1];
	119	*digest_len = rdata_len - 2;
	120
	121	if (*digest_len > 0) {
	122	digest = (u_char ) xmalloc(*digest_len);
	123	memcpy(digest, rdata + 2, digest_len);
	124	} else {
4d3434f7	125	*digest = xstrdup("");
21289cd0	126	}
	127
	128	success = 1;
	129	}
	130
	131	return success;
	132	}
	133
4635e729	134	/*
	135	* Check if hostname is numerical.
	136	* Returns -1 if hostname is numeric, 0 otherwise
	137	*/
	138	static int
	139	is_numeric_hostname(const char *hostname)
	140	{
	141	struct addrinfo hints, *ai;
	142
	143	memset(&hints, 0, sizeof(hints));
	144	hints.ai_socktype = SOCK_DGRAM;
	145	hints.ai_flags = AI_NUMERICHOST;
	146
	147	if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
	148	freeaddrinfo(ai);
	149	return -1;
	150	}
	151
	152	return 0;
	153	}
21289cd0	154
	155	/*
	156	* Verify the given hostname, address and host key using DNS.
aff51935	157	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	158	*/
	159	int
	160	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	161	const Key hostkey, int flags)
21289cd0	162	{
2ceb8101	163	u_int counter;
21289cd0	164	int result;
21289cd0	165	struct rrsetinfo *fingerprints = NULL;
21289cd0	166
	167	u_int8_t hostkey_algorithm;
	168	u_int8_t hostkey_digest_type;
	169	u_char *hostkey_digest;
	170	u_int hostkey_digest_len;
	171
	172	u_int8_t dnskey_algorithm;
	173	u_int8_t dnskey_digest_type;
	174	u_char *dnskey_digest;
	175	u_int dnskey_digest_len;
	176
0161a13d	177	*flags = 0;
21289cd0	178
8374cf6f	179	debug3("verify_host_key_dns");
21289cd0	180	if (hostkey == NULL)
	181	fatal("No key to look up!");
	182
4635e729	183	if (is_numeric_hostname(hostname)) {
	184	debug("skipped DNS lookup for numerical hostname");
	185	return -1;
	186	}
	187
21289cd0	188	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	189	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	190	if (result) {
	191	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	192	return -1;
21289cd0	193	}
21289cd0	194
0161a13d	195	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	196	*flags \|= DNS_VERIFY_SECURE;
	197	debug("found %d secure fingerprints in DNS",
	198	fingerprints->rri_nrdatas);
	199	} else {
	200	debug("found %d insecure fingerprints in DNS",
	201	fingerprints->rri_nrdatas);
21289cd0	202	}
21289cd0	203
	204	/* Initialize host key parameters */
	205	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	206	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	207	error("Error calculating host key fingerprint.");
b414a17b	208	freerrset(fingerprints);
0161a13d	209	return -1;
21289cd0	210	}
21289cd0	211
0161a13d	212	if (fingerprints->rri_nrdatas)
	213	*flags \|= DNS_VERIFY_FOUND;
	214
adf8c40b	215	for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
21289cd0	216	/*
	217	* Extract the key from the answer. Ignore any badly
	218	* formatted fingerprints.
	219	*/
	220	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	221	&dnskey_digest, &dnskey_digest_len,
	222	fingerprints->rri_rdatas[counter].rdi_data,
	223	fingerprints->rri_rdatas[counter].rdi_length)) {
	224	verbose("Error parsing fingerprint from DNS.");
	225	continue;
	226	}
	227
	228	/* Check if the current key is the same as the given key */
	229	if (hostkey_algorithm == dnskey_algorithm &&
	230	hostkey_digest_type == dnskey_digest_type) {
	231
	232	if (hostkey_digest_len == dnskey_digest_len &&
	233	memcmp(hostkey_digest, dnskey_digest,
	234	hostkey_digest_len) == 0) {
	235
0161a13d	236	*flags \|= DNS_VERIFY_MATCH;
21289cd0	237	}
21289cd0	238	}
4d3434f7	239	xfree(dnskey_digest);
21289cd0	240	}
21289cd0	241
4d3434f7	242	xfree(hostkey_digest); /* from key_fingerprint_raw() */
21289cd0	243	freerrset(fingerprints);
21289cd0	244
0161a13d	245	if (*flags & DNS_VERIFY_FOUND)
	246	if (*flags & DNS_VERIFY_MATCH)
	247	debug("matching host key fingerprint found in DNS");
	248	else
	249	debug("mismatching host key fingerprint found in DNS");
	250	else
	251	debug("no host key fingerprint found in DNS");
21289cd0	252
0161a13d	253	return 0;
21289cd0	254	}
21289cd0	255
21289cd0	256	/*
	257	* Export the fingerprint of a key as a DNS resource record
	258	*/
	259	int
0161a13d	260	export_dns_rr(const char hostname, const Key key, FILE *f, int generic)
21289cd0	261	{
	262	u_int8_t rdata_pubkey_algorithm = 0;
	263	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	264	u_char *rdata_digest;
	265	u_int rdata_digest_len;
	266
2ceb8101	267	u_int i;
21289cd0	268	int success = 0;
	269
	270	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
8374cf6f	271	&rdata_digest, &rdata_digest_len, key)) {
21289cd0	272
	273	if (generic)
	274	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
	275	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
	276	rdata_pubkey_algorithm, rdata_digest_type);
	277	else
	278	fprintf(f, "%s IN SSHFP %d %d ", hostname,
	279	rdata_pubkey_algorithm, rdata_digest_type);
	280
	281	for (i = 0; i < rdata_digest_len; i++)
	282	fprintf(f, "%02x", rdata_digest[i]);
	283	fprintf(f, "\n");
4d3434f7	284	xfree(rdata_digest); /* from key_fingerprint_raw() */
21289cd0	285	success = 1;
21289cd0	286	} else {
8374cf6f	287	error("export_dns_rr: unsupported algorithm");
21289cd0	288	}
	289
	290	return success;
	291	}