[openssh.git] / dns.c

/*	$OpenBSD: dns.c,v 1.15 2005/10/17 14:01:28 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>
#include <netdb.h>

#include "xmalloc.h"
#include "key.h"
#include "dns.h"
#include "log.h"

RCSID("$OpenBSD: dns.c,v 1.15 2005/10/17 14:01:28 stevesk Exp $");

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_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;
			}
		}
		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("dns_export_rr: unsupported algorithm");
	}

	return success;
}
Commit	Line	Data
7238b6e4	1	/* $OpenBSD: dns.c,v 1.15 2005/10/17 14:01:28 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>
21289cd0	32	#include <netdb.h>
21289cd0	33
	34	#include "xmalloc.h"
	35	#include "key.h"
	36	#include "dns.h"
	37	#include "log.h"
21289cd0	38
7238b6e4	39	RCSID("$OpenBSD: dns.c,v 1.15 2005/10/17 14:01:28 stevesk Exp $");
21289cd0	40
21289cd0	41	static const char *errset_text[] = {
	42	"success", /* 0 ERRSET_SUCCESS */
	43	"out of memory", /* 1 ERRSET_NOMEMORY */
	44	"general failure", /* 2 ERRSET_FAIL */
	45	"invalid parameter", /* 3 ERRSET_INVAL */
	46	"name does not exist", /* 4 ERRSET_NONAME */
	47	"data does not exist", /* 5 ERRSET_NODATA */
	48	};
	49
	50	static const char *
ca75d7de	51	dns_result_totext(unsigned int res)
21289cd0	52	{
ca75d7de	53	switch (res) {
21289cd0	54	case ERRSET_SUCCESS:
	55	return errset_text[ERRSET_SUCCESS];
	56	case ERRSET_NOMEMORY:
	57	return errset_text[ERRSET_NOMEMORY];
	58	case ERRSET_FAIL:
	59	return errset_text[ERRSET_FAIL];
	60	case ERRSET_INVAL:
	61	return errset_text[ERRSET_INVAL];
	62	case ERRSET_NONAME:
	63	return errset_text[ERRSET_NONAME];
	64	case ERRSET_NODATA:
	65	return errset_text[ERRSET_NODATA];
	66	default:
	67	return "unknown error";
	68	}
	69	}
21289cd0	70
	71	/*
	72	* Read SSHFP parameters from key buffer.
	73	*/
	74	static int
	75	dns_read_key(u_int8_t algorithm, u_int8_t digest_type,
0161a13d	76	u_char *digest, u_int digest_len, const Key *key)
21289cd0	77	{
	78	int success = 0;
	79
	80	switch (key->type) {
	81	case KEY_RSA:
	82	*algorithm = SSHFP_KEY_RSA;
	83	break;
	84	case KEY_DSA:
	85	*algorithm = SSHFP_KEY_DSA;
	86	break;
	87	default:
4d3434f7	88	algorithm = SSHFP_KEY_RESERVED; / 0 */
21289cd0	89	}
	90
	91	if (*algorithm) {
	92	*digest_type = SSHFP_HASH_SHA1;
	93	*digest = key_fingerprint_raw(key, SSH_FP_SHA1, digest_len);
4d3434f7	94	if (*digest == NULL)
4d3434f7	95	fatal("dns_read_key: null from key_fingerprint_raw()");
21289cd0	96	success = 1;
	97	} else {
	98	*digest_type = SSHFP_HASH_RESERVED;
	99	*digest = NULL;
	100	*digest_len = 0;
	101	success = 0;
	102	}
	103
	104	return success;
	105	}
	106
	107	/*
	108	* Read SSHFP parameters from rdata buffer.
	109	*/
	110	static int
	111	dns_read_rdata(u_int8_t algorithm, u_int8_t digest_type,
	112	u_char *digest, u_int digest_len, u_char *rdata, int rdata_len)
	113	{
	114	int success = 0;
	115
	116	*algorithm = SSHFP_KEY_RESERVED;
	117	*digest_type = SSHFP_HASH_RESERVED;
	118
	119	if (rdata_len >= 2) {
	120	*algorithm = rdata[0];
	121	*digest_type = rdata[1];
	122	*digest_len = rdata_len - 2;
	123
	124	if (*digest_len > 0) {
	125	digest = (u_char ) xmalloc(*digest_len);
	126	memcpy(digest, rdata + 2, digest_len);
	127	} else {
4d3434f7	128	*digest = xstrdup("");
21289cd0	129	}
	130
	131	success = 1;
	132	}
	133
	134	return success;
	135	}
	136
4635e729	137	/*
	138	* Check if hostname is numerical.
	139	* Returns -1 if hostname is numeric, 0 otherwise
	140	*/
	141	static int
	142	is_numeric_hostname(const char *hostname)
	143	{
	144	struct addrinfo hints, *ai;
	145
	146	memset(&hints, 0, sizeof(hints));
	147	hints.ai_socktype = SOCK_DGRAM;
	148	hints.ai_flags = AI_NUMERICHOST;
	149
	150	if (getaddrinfo(hostname, "0", &hints, &ai) == 0) {
	151	freeaddrinfo(ai);
	152	return -1;
	153	}
	154
	155	return 0;
	156	}
21289cd0	157
	158	/*
	159	* Verify the given hostname, address and host key using DNS.
aff51935	160	* Returns 0 if lookup succeeds, -1 otherwise
21289cd0	161	*/
	162	int
	163	verify_host_key_dns(const char hostname, struct sockaddr address,
0161a13d	164	const Key hostkey, int flags)
21289cd0	165	{
2ceb8101	166	u_int counter;
21289cd0	167	int result;
21289cd0	168	struct rrsetinfo *fingerprints = NULL;
21289cd0	169
	170	u_int8_t hostkey_algorithm;
	171	u_int8_t hostkey_digest_type;
	172	u_char *hostkey_digest;
	173	u_int hostkey_digest_len;
	174
	175	u_int8_t dnskey_algorithm;
	176	u_int8_t dnskey_digest_type;
	177	u_char *dnskey_digest;
	178	u_int dnskey_digest_len;
	179
0161a13d	180	*flags = 0;
21289cd0	181
	182	debug3("verify_hostkey_dns");
	183	if (hostkey == NULL)
	184	fatal("No key to look up!");
	185
4635e729	186	if (is_numeric_hostname(hostname)) {
	187	debug("skipped DNS lookup for numerical hostname");
	188	return -1;
	189	}
	190
21289cd0	191	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	192	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	193	if (result) {
	194	verbose("DNS lookup error: %s", dns_result_totext(result));
0161a13d	195	return -1;
21289cd0	196	}
21289cd0	197
0161a13d	198	if (fingerprints->rri_flags & RRSET_VALIDATED) {
	199	*flags \|= DNS_VERIFY_SECURE;
	200	debug("found %d secure fingerprints in DNS",
	201	fingerprints->rri_nrdatas);
	202	} else {
	203	debug("found %d insecure fingerprints in DNS",
	204	fingerprints->rri_nrdatas);
21289cd0	205	}
21289cd0	206
	207	/* Initialize host key parameters */
	208	if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
	209	&hostkey_digest, &hostkey_digest_len, hostkey)) {
	210	error("Error calculating host key fingerprint.");
b414a17b	211	freerrset(fingerprints);
0161a13d	212	return -1;
21289cd0	213	}
21289cd0	214
0161a13d	215	if (fingerprints->rri_nrdatas)
	216	*flags \|= DNS_VERIFY_FOUND;
	217
adf8c40b	218	for (counter = 0; counter < fingerprints->rri_nrdatas; counter++) {
21289cd0	219	/*
	220	* Extract the key from the answer. Ignore any badly
	221	* formatted fingerprints.
	222	*/
	223	if (!dns_read_rdata(&dnskey_algorithm, &dnskey_digest_type,
	224	&dnskey_digest, &dnskey_digest_len,
	225	fingerprints->rri_rdatas[counter].rdi_data,
	226	fingerprints->rri_rdatas[counter].rdi_length)) {
	227	verbose("Error parsing fingerprint from DNS.");
	228	continue;
	229	}
	230
	231	/* Check if the current key is the same as the given key */
	232	if (hostkey_algorithm == dnskey_algorithm &&
	233	hostkey_digest_type == dnskey_digest_type) {
	234
	235	if (hostkey_digest_len == dnskey_digest_len &&
	236	memcmp(hostkey_digest, dnskey_digest,
	237	hostkey_digest_len) == 0) {
	238
0161a13d	239	*flags \|= DNS_VERIFY_MATCH;
21289cd0	240	}
21289cd0	241	}
4d3434f7	242	xfree(dnskey_digest);
21289cd0	243	}
21289cd0	244
4d3434f7	245	xfree(hostkey_digest); /* from key_fingerprint_raw() */
21289cd0	246	freerrset(fingerprints);
21289cd0	247
0161a13d	248	if (*flags & DNS_VERIFY_FOUND)
	249	if (*flags & DNS_VERIFY_MATCH)
	250	debug("matching host key fingerprint found in DNS");
	251	else
	252	debug("mismatching host key fingerprint found in DNS");
	253	else
	254	debug("no host key fingerprint found in DNS");
21289cd0	255
0161a13d	256	return 0;
21289cd0	257	}
	258
	259
	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,
	275	&rdata_digest, &rdata_digest_len, key)) {
	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;
	290	} else {
	291	error("dns_export_rr: unsupported algorithm");
	292	}
	293
	294	return success;
	295	}