dns.c - third_party/openssh-portable - Git at Google

 /*	$OpenBSD: dns.c,v 1.6 2003/06/11 10:18:47 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"

 #ifdef DNS
 #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 1.6 2003/06/11 10:18:47 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 error)
 {
 	switch (error) {
 	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, 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;
 }


 /*
  * Verify the given hostname, address and host key using DNS.
  * Returns 0 if key verifies or -1 if key does NOT verify
  */
 int
 verify_host_key_dns(const char *hostname, struct sockaddr *address,
     Key *hostkey)
 {
 	int counter;
 	int result;
 	struct rrsetinfo *fingerprints = NULL;
 	int failures = 0;

 	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;


 	debug3("verify_hostkey_dns");
 	if (hostkey == NULL)
 		fatal("No key to look up!");

 	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
 	    DNS_RDATATYPE_SSHFP, 0, &fingerprints);
 	if (result) {
 		verbose("DNS lookup error: %s", dns_result_totext(result));
 		return DNS_VERIFY_ERROR;
 	}

 #ifdef DNSSEC
 	/* Only accept validated answers */
 	if (!fingerprints->rri_flags & RRSET_VALIDATED) {
 		error("Ignored unvalidated fingerprint from DNS.");
 		freerrset(fingerprints);
 		return DNS_VERIFY_ERROR;
 	}
 #endif

 	debug("found %d 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 DNS_VERIFY_ERROR;
 	}

 	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) {

 				/* Matching algoritm and digest. */
 				freerrset(fingerprints);
 				debug("matching host key fingerprint found in DNS");
 				return DNS_VERIFY_OK;
 			} else {
 				/* Correct algorithm but bad digest */
 				debug("verify_hostkey_dns: failed");
 				failures++;
 			}
 		}
 	}

 	freerrset(fingerprints);

 	if (failures) {
 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 		error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
 		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 		error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
 		error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
 		error("It is also possible that the %s host key has just been changed.",
 		    key_type(hostkey));
 		error("Please contact your system administrator.");
 		return DNS_VERIFY_FAILED;
 	}

 	debug("fingerprints found in DNS, but none of them matched");

 	return DNS_VERIFY_ERROR;
 }


 /*
  * Export the fingerprint of a key as a DNS resource record
  */
 int
 export_dns_rr(const char *hostname, 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;
 }

 #endif /* DNS */
	/* $OpenBSD: dns.c,v 1.6 2003/06/11 10:18:47 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"

	#ifdef DNS
	#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 1.6 2003/06/11 10:18:47 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 error)
	{
	switch (error) {
	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, 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;
	}


	/*
	* Verify the given hostname, address and host key using DNS.
	* Returns 0 if key verifies or -1 if key does NOT verify
	*/
	int
	verify_host_key_dns(const char hostname, struct sockaddr address,
	Key *hostkey)
	{
	int counter;
	int result;
	struct rrsetinfo *fingerprints = NULL;
	int failures = 0;

	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;


	debug3("verify_hostkey_dns");
	if (hostkey == NULL)
	fatal("No key to look up!");

	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
	DNS_RDATATYPE_SSHFP, 0, &fingerprints);
	if (result) {
	verbose("DNS lookup error: %s", dns_result_totext(result));
	return DNS_VERIFY_ERROR;
	}

	#ifdef DNSSEC
	/* Only accept validated answers */
	if (!fingerprints->rri_flags & RRSET_VALIDATED) {
	error("Ignored unvalidated fingerprint from DNS.");
	freerrset(fingerprints);
	return DNS_VERIFY_ERROR;
	}
	#endif

	debug("found %d 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 DNS_VERIFY_ERROR;
	}

	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) {

	/* Matching algoritm and digest. */
	freerrset(fingerprints);
	debug("matching host key fingerprint found in DNS");
	return DNS_VERIFY_OK;
	} else {
	/* Correct algorithm but bad digest */
	debug("verify_hostkey_dns: failed");
	failures++;
	}
	}
	}

	freerrset(fingerprints);

	if (failures) {
	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
	error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
	error("It is also possible that the %s host key has just been changed.",
	key_type(hostkey));
	error("Please contact your system administrator.");
	return DNS_VERIFY_FAILED;
	}

	debug("fingerprints found in DNS, but none of them matched");

	return DNS_VERIFY_ERROR;
	}


	/*
	* Export the fingerprint of a key as a DNS resource record
	*/
	int
	export_dns_rr(const char hostname, 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;
	}

	#endif /* DNS */