[openssh.git] / dns.c

/* $OpenBSD: dns.c,v 1.20 2006/07/08 21:47:12 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 <sys/types.h>
#include <sys/socket.h>

#if defined(HAVE_NETDB_H)
# include <netdb.h>
#endif

#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;

	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
5b04a8bf	1	/* $OpenBSD: dns.c,v 1.20 2006/07/08 21:47:12 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"
21289cd0	29
5b04a8bf	30	#include <sys/types.h>
	31	#include <sys/socket.h>
	32
c8dfff33	33	#if defined(HAVE_NETDB_H)
	34	# include <netdb.h>
	35	#endif
21289cd0	36
	37	#include "xmalloc.h"
	38	#include "key.h"
	39	#include "dns.h"
	40	#include "log.h"
21289cd0	41
21289cd0	42	static const char *errset_text[] = {
	43	"success", /* 0 ERRSET_SUCCESS */
	44	"out of memory", /* 1 ERRSET_NOMEMORY */
	45	"general failure", /* 2 ERRSET_FAIL */
	46	"invalid parameter", /* 3 ERRSET_INVAL */
	47	"name does not exist", /* 4 ERRSET_NONAME */
	48	"data does not exist", /* 5 ERRSET_NODATA */
	49	};
	50
	51	static const char *
ca75d7de	52	dns_result_totext(unsigned int res)
21289cd0	53	{
ca75d7de	54	switch (res) {
21289cd0	55	case ERRSET_SUCCESS:
	56	return errset_text[ERRSET_SUCCESS];
	57	case ERRSET_NOMEMORY:
	58	return errset_text[ERRSET_NOMEMORY];
	59	case ERRSET_FAIL:
	60	return errset_text[ERRSET_FAIL];
	61	case ERRSET_INVAL:
	62	return errset_text[ERRSET_INVAL];
	63	case ERRSET_NONAME:
	64	return errset_text[ERRSET_NONAME];
	65	case ERRSET_NODATA:
	66	return errset_text[ERRSET_NODATA];
	67	default:
	68	return "unknown error";
	69	}
	70	}
21289cd0	71
	72	/*
	73	* Read SSHFP parameters from key buffer.
	74	*/
	75	static int
	76	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	77	u_char *digest, u_int digest_len, const Key *key)
21289cd0	78	{
	79	int success = 0;
	80
	81	switch (key->type) {
	82	case KEY_RSA:
	83	*algorithm = SSHFP_KEY_RSA;
	84	break;
	85	case KEY_DSA:
	86	*algorithm = SSHFP_KEY_DSA;
	87	break;
	88	default:
4d3434f7	89	algorithm = SSHFP_KEY_RESERVED; / 0 */
21289cd0	90	}
	91
	92	if (*algorithm) {
	93	*digest_type = SSHFP_HASH_SHA1;
	94	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
4d3434f7	95	if (*digest == NULL)
4d3434f7	96	fatal("dns_read_key: null from key_fingerprint_raw()");
21289cd0	97	success = 1;
	98	} else {
	99	*digest_type = SSHFP_HASH_RESERVED;
	100	*digest = NULL;
	101	*digest_len = 0;
	102	success = 0;
	103	}
	104
	105	return success;
	106	}
	107
	108	/*
	109	* Read SSHFP parameters from rdata buffer.
	110	*/
	111	static int
	112	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	113	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	114	{
	115	int success = 0;
	116
	117	*algorithm = SSHFP_KEY_RESERVED;
	118	*digest_type = SSHFP_HASH_RESERVED;
	119
	120	if (rdata_len >= 2) {
	121	*algorithm = rdata[0];
	122	*digest_type = rdata[1];
	123	*digest_len = rdata_len - 2;
	124
	125	if (*digest_len > 0) {
	126	digest = (u_char ) xmalloc(*digest_len);
	127	memcpy(digest, rdata + 2, digest_len);
	128	} else {
6cfe93ec	129	digest = (u_char )xstrdup("");
21289cd0	130	}
	131
	132	success = 1;
	133	}
	134
	135	return success;
	136	}
	137
4635e729	138	/*
	139	* Check if hostname is numerical.
	140	* Returns -1 if hostname is numeric, 0 otherwise
	141	*/
	142	static int
	143	is_numeric_hostname(const char *hostname)
	144	{
	145	struct addrinfo hints, *ai;
	146
	147	memset(&hints, 0, sizeof(hints));
	148	hints.ai_socktype = SOCK_DGRAM;
	149	hints.ai_flags = AI_NUMERICHOST;
	150
	151	if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
	152	freeaddrinfo(ai);
	153	return -1;
	154	}
	155
	156	return 0;
	157	}
21289cd0	158
	159	/*
	160	* Verify the given hostname, address and host key using DNS.
aff51935	161	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	162	*/
	163	int
	164	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	165	const Key hostkey, int flags)
21289cd0	166	{
2ceb8101	167	u_int counter;
21289cd0	168	int result;
21289cd0	169	struct rrsetinfo *fingerprints = NULL;
21289cd0	170
	171	u_int8_t hostkey_algorithm;
	172	u_int8_t hostkey_digest_type;
	173	u_char *hostkey_digest;
	174	u_int hostkey_digest_len;
	175
	176	u_int8_t dnskey_algorithm;
	177	u_int8_t dnskey_digest_type;
	178	u_char *dnskey_digest;
	179	u_int dnskey_digest_len;
	180
0161a13d	181	*flags = 0;
21289cd0	182
8374cf6f	183	debug3("verify_host_key_dns");
21289cd0	184	if (hostkey == NULL)
	185	fatal("No key to look up!");
	186
4635e729	187	if (is_numeric_hostname(hostname)) {
	188	debug("skipped DNS lookup for numerical hostname");
	189	return -1;
	190	}
	191
21289cd0	192	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	193	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	194	if (result) {
	195	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	196	return -1;
21289cd0	197	}
21289cd0	198
0161a13d	199	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	200	*flags \|= DNS_VERIFY_SECURE;
	201	debug("found %d secure fingerprints in DNS",
	202	fingerprints->rri_nrdatas);
	203	} else {
	204	debug("found %d insecure fingerprints in DNS",
	205	fingerprints->rri_nrdatas);
21289cd0	206	}
21289cd0	207
	208	/* Initialize host key parameters */
	209	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	210	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	211	error("Error calculating host key fingerprint.");
b414a17b	212	freerrset(fingerprints);
0161a13d	213	return -1;
21289cd0	214	}
21289cd0	215
0161a13d	216	if (fingerprints->rri_nrdatas)
	217	*flags \|= DNS_VERIFY_FOUND;
	218
adf8c40b	219	for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
21289cd0	220	/*
	221	* Extract the key from the answer. Ignore any badly
	222	* formatted fingerprints.
	223	*/
	224	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	225	&dnskey_digest, &dnskey_digest_len,
	226	fingerprints->rri_rdatas[counter].rdi_data,
	227	fingerprints->rri_rdatas[counter].rdi_length)) {
	228	verbose("Error parsing fingerprint from DNS.");
	229	continue;
	230	}
	231
	232	/* Check if the current key is the same as the given key */
	233	if (hostkey_algorithm == dnskey_algorithm &&
	234	hostkey_digest_type == dnskey_digest_type) {
	235
	236	if (hostkey_digest_len == dnskey_digest_len &&
	237	memcmp(hostkey_digest, dnskey_digest,
	238	hostkey_digest_len) == 0) {
	239
0161a13d	240	*flags \|= DNS_VERIFY_MATCH;
21289cd0	241	}
21289cd0	242	}
4d3434f7	243	xfree(dnskey_digest);
21289cd0	244	}
21289cd0	245
4d3434f7	246	xfree(hostkey_digest); /* from key_fingerprint_raw() */
21289cd0	247	freerrset(fingerprints);
21289cd0	248
0161a13d	249	if (*flags & DNS_VERIFY_FOUND)
	250	if (*flags & DNS_VERIFY_MATCH)
	251	debug("matching host key fingerprint found in DNS");
	252	else
	253	debug("mismatching host key fingerprint found in DNS");
	254	else
	255	debug("no host key fingerprint found in DNS");
21289cd0	256
0161a13d	257	return 0;
21289cd0	258	}
21289cd0	259
21289cd0	260	/*
	261	* Export the fingerprint of a key as a DNS resource record
	262	*/
	263	int
0161a13d	264	export_dns_rr(const char hostname, const Key key, FILE *f, int generic)
21289cd0	265	{
	266	u_int8_t rdata_pubkey_algorithm = 0;
	267	u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;
	268	u_char *rdata_digest;
	269	u_int rdata_digest_len;
	270
2ceb8101	271	u_int i;
21289cd0	272	int success = 0;
	273
	274	if (dns_read_key(&rdata_pubkey_algorithm, &rdata_digest_type,
8374cf6f	275	&rdata_digest, &rdata_digest_len, key)) {
21289cd0	276
	277	if (generic)
	278	fprintf(f, "%s IN TYPE%d \\# %d %02x %02x ", hostname,
	279	DNS_RDATATYPE_SSHFP, 2 + rdata_digest_len,
	280	rdata_pubkey_algorithm, rdata_digest_type);
	281	else
	282	fprintf(f, "%s IN SSHFP %d %d ", hostname,
	283	rdata_pubkey_algorithm, rdata_digest_type);
	284
	285	for (i = 0; i < rdata_digest_len; i++)
	286	fprintf(f, "%02x", rdata_digest[i]);
	287	fprintf(f, "\n");
4d3434f7	288	xfree(rdata_digest); /* from key_fingerprint_raw() */
21289cd0	289	success = 1;
21289cd0	290	} else {
8374cf6f	291	error("export_dns_rr: unsupported algorithm");
21289cd0	292	}
	293
	294	return success;
	295	}