dns.c

DHCP服务器源码

/* dns.c

   Domain Name Service subroutines. */

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 2001-2003 by Internet Software Consortium
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *   Internet Systems Consortium, Inc.
 *   950 Charter Street
 *   Redwood City, CA 94063
 *   <[e-mail]>
 *   http://www.isc.org/
 *
 * This software has been written for Internet Systems Consortium
 * by Ted Lemon in cooperation with Nominum, Inc.
 * To learn more about Internet Systems Consortium, see
 * ``http://www.isc.org/''.  To learn more about Nominum, Inc., see
 * ``http://www.nominum.com''.
 */

#ifndef lint
static char copyright[] =
"$Id: dns.c,v 1.35.2.16 2004/06/17 20:54:38 dhankins Exp $ Copyright (c) 2004 Internet Systems Consortium.  All rights reserved.\n";
#endif /* not lint */

#include "dhcpd.h"
#include "arpa/nameser.h"
#include "dst/md5.h"

/* This file is kind of a crutch for the BIND 8 nsupdate code, which has
 * itself been cruelly hacked from its original state.   What this code
 * does is twofold: first, it maintains a database of zone cuts that can
 * be used to figure out which server should be contacted to update any
 * given domain name.   Secondly, it maintains a set of named TSIG keys,
 * and associates those keys with zones.   When an update is requested for
 * a particular zone, the key associated with that zone is used for the
 * update.
 *
 * The way this works is that you define the domain name to which an
 * SOA corresponds, and the addresses of some primaries for that domain name:
 *
 *	zone FOO.COM {
 *	  primary 10.0.17.1;
 *	  secondary 10.0.22.1, 10.0.23.1;
 *	  key "FOO.COM Key";
 * 	}
 *
 * If an update is requested for GAZANGA.TOPANGA.FOO.COM, then the name
 * server looks in its database for a zone record for "GAZANGA.TOPANGA.FOO.COM",
 * doesn't find it, looks for one for "TOPANGA.FOO.COM", doesn't find *that*,
 * looks for "FOO.COM", finds it. So it
 * attempts the update to the primary for FOO.COM.   If that times out, it
 * tries the secondaries.   You can list multiple primaries if you have some
 * kind of magic name server that supports that.   You shouldn't list
 * secondaries that don't know how to forward updates (e.g., BIND 8 doesn't
 * support update forwarding, AFAIK).   If no TSIG key is listed, the update
 * is attempted without TSIG.
 *
 * The DHCP server tries to find an existing zone for any given name by
 * trying to look up a local zone structure for each domain containing
 * that name, all the way up to '.'.   If it finds one cached, it tries
 * to use that one to do the update.   That's why it tries to update
 * "FOO.COM" above, even though theoretically it should try GAZANGA...
 * and TOPANGA... first.
 *
 * If the update fails with a predefined or cached zone (we'll get to
 * those in a second), then it tries to find a more specific zone.   This
 * is done by looking first for an SOA for GAZANGA.TOPANGA.FOO.COM.   Then
 * an SOA for TOPANGA.FOO.COM is sought.   If during this search a predefined
 * or cached zone is found, the update fails - there's something wrong
 * somewhere.
 *
 * If a more specific zone _is_ found, that zone is cached for the length of
 * its TTL in the same database as that described above.   TSIG updates are
 * never done for cached zones - if you want TSIG updates you _must_
 * write a zone definition linking the key to the zone.   In cases where you
 * know for sure what the key is but do not want to hardcode the IP addresses
 * of the primary or secondaries, a zone declaration can be made that doesn't
 * include any primary or secondary declarations.   When the DHCP server
 * encounters this while hunting up a matching zone for a name, it looks up
 * the SOA, fills in the IP addresses, and uses that record for the update.
 * If the SOA lookup returns NXRRSET, a warning is printed and the zone is
 * discarded, TSIG key and all.   The search for the zone then continues as if
 * the zone record hadn't been found.   Zones without IP addresses don't
 * match when initially hunting for a predefined or cached zone to update.
 *
 * When an update is attempted and no predefined or cached zone is found
 * that matches any enclosing domain of the domain being updated, the DHCP
 * server goes through the same process that is done when the update to a
 * predefined or cached zone fails - starting with the most specific domain
 * name (GAZANGA.TOPANGA.FOO.COM) and moving to the least specific (the root),
 * it tries to look up an SOA record.   When it finds one, it creates a cached
 * zone and attempts an update, and gives up if the update fails.
 *
 * TSIG keys are defined like this:
 *
 *	key "FOO.COM Key" {
 *		algorithm HMAC-MD5.SIG-ALG.REG.INT;
 *		secret <Base64>;
 *	}
 *
 * <Base64> is a number expressed in base64 that represents the key.
 * It's also permissible to use a quoted string here - this will be
 * translated as the ASCII bytes making up the string, and will not
 * include any NUL termination.  The key name can be any text string,
 * and the key type must be one of the key types defined in the draft
 * or by the IANA.  Currently only the HMAC-MD5... key type is
 * supported.
 */

dns_zone_hash_t *dns_zone_hash;

#if defined (NSUPDATE)
isc_result_t find_tsig_key (ns_tsig_key **key, const char *zname,
			    struct dns_zone *zone)
{
	isc_result_t status;
	ns_tsig_key *tkey;

	if (!zone)
		return ISC_R_NOTFOUND;

	if (!zone -> key) {
		return ISC_R_KEY_UNKNOWN;
	}
	
	if ((!zone -> key -> name ||
	     strlen (zone -> key -> name) > NS_MAXDNAME) ||
	    (!zone -> key -> algorithm ||
	     strlen (zone -> key -> algorithm) > NS_MAXDNAME) ||
	    (!zone -> key) ||
	    (!zone -> key -> key) ||
	    (zone -> key -> key -> len == 0)) {
		return ISC_R_INVALIDKEY;
	}
	tkey = dmalloc (sizeof *tkey, MDL);
	if (!tkey) {
	      nomem:
		return ISC_R_NOMEMORY;
	}
	memset (tkey, 0, sizeof *tkey);
	tkey -> data = dmalloc (zone -> key -> key -> len, MDL);
	if (!tkey -> data) {
		dfree (tkey, MDL);
		goto nomem;
	}
	strcpy (tkey -> name, zone -> key -> name);
	strcpy (tkey -> alg, zone -> key -> algorithm);
	memcpy (tkey -> data,
		zone -> key -> key -> value, zone -> key -> key -> len);
	tkey -> len = zone -> key -> key -> len;
	*key = tkey;
	return ISC_R_SUCCESS;
}

void tkey_free (ns_tsig_key **key)
{
	if ((*key) -> data)
		dfree ((*key) -> data, MDL);
	dfree ((*key), MDL);
	*key = (ns_tsig_key *)0;
}
#endif

isc_result_t enter_dns_zone (struct dns_zone *zone)
{
	struct dns_zone *tz = (struct dns_zone *)0;

	if (dns_zone_hash) {
		dns_zone_hash_lookup (&tz,
				      dns_zone_hash, zone -> name, 0, MDL);
		if (tz == zone) {
			dns_zone_dereference (&tz, MDL);
			return ISC_R_SUCCESS;
		}
		if (tz) {
			dns_zone_hash_delete (dns_zone_hash,
					      zone -> name, 0, MDL);
			dns_zone_dereference (&tz, MDL);
		}
	} else {
		if (!dns_zone_new_hash (&dns_zone_hash, 1, MDL))
			return ISC_R_NOMEMORY;
	}
	dns_zone_hash_add (dns_zone_hash, zone -> name, 0, zone, MDL);
	return ISC_R_SUCCESS;
}

isc_result_t dns_zone_lookup (struct dns_zone **zone, const char *name)
{
	struct dns_zone *tz = (struct dns_zone *)0;
	int len;
	char *tname = (char *)0;
	isc_result_t status;

	if (!dns_zone_hash)
		return ISC_R_NOTFOUND;

	len = strlen (name);
	if (name [len - 1] != '.') {
		tname = dmalloc ((unsigned)len + 2, MDL);
		if (!tname)
			return ISC_R_NOMEMORY;;
		strcpy (tname, name);
		tname [len] = '.';
		tname [len + 1] = 0;
		name = tname;
	}
	if (!dns_zone_hash_lookup (zone, dns_zone_hash, name, 0, MDL))
		status = ISC_R_NOTFOUND;
	else
		status = ISC_R_SUCCESS;

	if (tname)
		dfree (tname, MDL);
	return status;
}

int dns_zone_dereference (ptr, file, line)
	struct dns_zone **ptr;
	const char *file;
	int line;
{
	int i;
	struct dns_zone *dns_zone;

	if (!ptr || !*ptr) {
		log_error ("%s(%d): null pointer", file, line);
#if defined (POINTER_DEBUG)
		abort ();
#else
		return 0;
#endif
	}

	dns_zone = *ptr;
	*ptr = (struct dns_zone *)0;
	--dns_zone -> refcnt;
	rc_register (file, line, ptr, dns_zone, dns_zone -> refcnt, 1, RC_MISC);
	if (dns_zone -> refcnt > 0)
		return 1;

	if (dns_zone -> refcnt < 0) {
		log_error ("%s(%d): negative refcnt!", file, line);
#if defined (DEBUG_RC_HISTORY)
		dump_rc_history (dns_zone);
#endif
#if defined (POINTER_DEBUG)
		abort ();
#else
		return 0;
#endif
	}

	if (dns_zone -> name)
		dfree (dns_zone -> name, file, line);
	if (dns_zone -> key)
		omapi_auth_key_dereference (&dns_zone -> key, file, line);
	if (dns_zone -> primary)
		option_cache_dereference (&dns_zone -> primary, file, line);
	if (dns_zone -> secondary)
		option_cache_dereference (&dns_zone -> secondary, file, line);
	dfree (dns_zone, file, line);
	return 1;
}

#if defined (NSUPDATE)
isc_result_t find_cached_zone (const char *dname, ns_class class,
			       char *zname, size_t zsize,
			       struct in_addr *addrs,
			       int naddrs, int *naddrout,
			       struct dns_zone **zcookie)
{
	isc_result_t status = ISC_R_NOTFOUND;
	const char *np;
	struct dns_zone *zone = (struct dns_zone *)0;
	struct data_string nsaddrs;
	int ix;

	/* The absence of the zcookie pointer indicates that we
	   succeeded previously, but the update itself failed, meaning
	   that we shouldn't use the cached zone. */
	if (!zcookie)
		return ISC_R_NOTFOUND;

	/* We can't look up a null zone. */
	if (!dname || !*dname)
		return ISC_R_INVALIDARG;

	/* For each subzone, try to find a cached zone. */
	for (np = dname; np; np = strchr (np, '.')) {
		np++;
		status = dns_zone_lookup (&zone, np);
		if (status == ISC_R_SUCCESS)
			break;
	}

	if (status != ISC_R_SUCCESS)
		return status;

	/* Make sure the zone is valid. */
	if (zone -> timeout && zone -> timeout < cur_time) {
		dns_zone_dereference (&zone, MDL);
		return ISC_R_CANCELED;
	}

	/* Make sure the zone name will fit. */
	if (strlen (zone -> name) > zsize) {
		dns_zone_dereference (&zone, MDL);
		return ISC_R_NOSPACE;
	}
	strcpy (zname, zone -> name);

	memset (&nsaddrs, 0, sizeof nsaddrs);
	ix = 0;

	if (zone -> primary) {
		if (evaluate_option_cache (&nsaddrs, (struct packet *)0,
					   (struct lease *)0,
					   (struct client_state *)0,
					   (struct option_state *)0,
					   (struct option_state *)0,
					   &global_scope,
					   zone -> primary, MDL)) {
			int ip = 0;
			while (ix < naddrs) {
				if (ip + 4 > nsaddrs.len)
					break;
				memcpy (&addrs [ix], &nsaddrs.data [ip], 4);
				ip += 4;
				ix++;
			}
			data_string_forget (&nsaddrs, MDL);
		}
	}
	if (zone -> secondary) {
		if (evaluate_option_cache (&nsaddrs, (struct packet *)0,
					   (struct lease *)0,
					   (struct client_state *)0,
					   (struct option_state *)0,
					   (struct option_state *)0,
					   &global_scope,
					   zone -> secondary, MDL)) {
			int ip = 0;
			while (ix < naddrs) {
				if (ip + 4 > nsaddrs.len)
					break;
				memcpy (&addrs [ix], &nsaddrs.data [ip], 4);
				ip += 4;
				ix++;
			}
			data_string_forget (&nsaddrs, MDL);
		}
	}

	/* It's not an error for zcookie to have a value here - actually,
	   it's quite likely, because res_nupdate cycles through all the
	   names in the update looking for their zones. */
	if (!*zcookie)
		dns_zone_reference (zcookie, zone, MDL);
	dns_zone_dereference (&zone, MDL);
	if (naddrout)
		*naddrout = ix;
	return ISC_R_SUCCESS;
}

void forget_zone (struct dns_zone **zone)
{
	dns_zone_dereference (zone, MDL);
}

void repudiate_zone (struct dns_zone **zone)
{
	/* XXX Currently we're not differentiating between a cached
	   XXX zone and a zone that's been repudiated, which means
	   XXX that if we reap cached zones, we blow away repudiated
	   XXX zones.   This isn't a big problem since we're not yet
	   XXX caching zones... :'} */

	(*zone) -> timeout = cur_time - 1;
	dns_zone_dereference (zone, MDL);
}

void cache_found_zone (ns_class class,
		       char *zname, struct in_addr *addrs, int naddrs)
{
	isc_result_t status = ISC_R_NOTFOUND;
	struct dns_zone *zone = (struct dns_zone *)0;
	struct data_string nsaddrs;
	int ix = strlen (zname);

	if (zname [ix - 1] == '.')
		ix = 0;

	/* See if there's already such a zone. */
	if (dns_zone_lookup (&zone, zname) == ISC_R_SUCCESS) {
		/* If it's not a dynamic zone, leave it alone. */
		if (!zone -> timeout)
			return;
		/* Address may have changed, so just blow it away. */
		if (zone -> primary)
			option_cache_dereference (&zone -> primary, MDL);
		if (zone -> secondary)
			option_cache_dereference (&zone -> secondary, MDL);
	} else if (!dns_zone_allocate (&zone, MDL))
		return;

	if (!zone -> name) {
		zone -> name =
			dmalloc (strlen (zname) + 1 + (ix != 0), MDL);
		if (!zone -> name) {
			dns_zone_dereference (&zone, MDL);
			return;
		}
		strcpy (zone -> name, zname);
		/* Add a trailing '.' if it was missing. */
		if (ix) {
			zone -> name [ix] = '.';
			zone -> name [ix + 1] = 0;
		}
	}

	/* XXX Need to get the lower-level code to push the actual zone
	   XXX TTL up to us. */
	zone -> timeout = cur_time + 1800;
	
	if (!option_cache_allocate (&zone -> primary, MDL)) {
		dns_zone_dereference (&zone, MDL);
		return;
	}
	if (!buffer_allocate (&zone -> primary -> data.buffer,
			      naddrs * sizeof (struct in_addr), MDL)) {
		dns_zone_dereference (&zone, MDL);
		return;
	}
	memcpy (zone -> primary -> data.buffer -> data,
		addrs, naddrs * sizeof *addrs);
	zone -> primary -> data.data =
		&zone -> primary -> data.buffer -> data [0];
	zone -> primary -> data.len = naddrs * sizeof *addrs;

	enter_dns_zone (zone);
}

/* Have to use TXT records for now. */
#define T_DHCID T_TXT

int get_dhcid (struct data_string *id,
	       int type, const u_int8_t *data, unsigned len)
{
	unsigned char buf[MD5_DIGEST_LENGTH];
	MD5_CTX md5;
	int i;

	/* Types can only be 0..(2^16)-1. */
	if (type < 0 || type > 65535)
		return 0;

	/* Hexadecimal MD5 digest plus two byte type and NUL. */
	if (!buffer_allocate (&id -> buffer,
			      (MD5_DIGEST_LENGTH * 2) + 3, MDL))
		return 0;
	id -> data = id -> buffer -> data;