/*
 * Copyright(C) 2009-2022 Internet Systems Consortium, Inc.("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * 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.
 *   PO Box 360
 *   Newmarket, NH 03857 USA
 *   <info@isc.org>
 *   http://www.isc.org/
 *
 */

/*Trying to figure out what we need to define to get things to work.
  It looks like we want/need the library but need the fdwatchcommand
  which may be a problem */

#include "dhcpd.h"

#include <sys/time.h>
#include <signal.h>

dhcp_context_t dhcp_gbl_ctx;
int shutdown_signal = 0;

#if defined (NSUPDATE)

/* This routine will open up the /etc/resolv.conf file and
 * send any nameservers it finds to the DNS client code.
 * It may be moved to be part of the dns client code instead
 * of being in the DHCP code
 */
isc_result_t
dhcp_dns_client_setservers(void)
{
	isc_result_t result;
	irs_resconf_t *resconf = NULL;
	isc_sockaddrlist_t *nameservers;
	isc_sockaddr_t *sa;

	result = irs_resconf_load(dhcp_gbl_ctx.mctx, _PATH_RESOLV_CONF,
				  &resconf);
	if (result != ISC_R_SUCCESS && result != ISC_R_FILENOTFOUND) {
		log_error("irs_resconf_load failed: %d.", result);
		return (result);
	}

	nameservers = irs_resconf_getnameservers(resconf);

	/* Initialize port numbers */
	for (sa = ISC_LIST_HEAD(*nameservers);
	     sa != NULL;
	     sa = ISC_LIST_NEXT(sa, link)) {
		switch (sa->type.sa.sa_family) {
		case AF_INET:
			sa->type.sin.sin_port = htons(NS_DEFAULTPORT);
			break;
		case AF_INET6:
			sa->type.sin6.sin6_port = htons(NS_DEFAULTPORT);
			break;
		default:
			break;
		}
	}

	result = dns_client_setservers(dhcp_gbl_ctx.dnsclient,
				       dns_rdataclass_in,
				       NULL, nameservers);
	if (result != ISC_R_SUCCESS) {
		log_error("dns_client_setservers failed: %d.",
			  result);
	}
	return (result);
}
#endif /* defined NSUPDATE */

void
isclib_cleanup(void)
{
#if defined (NSUPDATE)
	if (dhcp_gbl_ctx.dnsclient != NULL)
		dns_client_destroy((dns_client_t **)&dhcp_gbl_ctx.dnsclient);
#endif /* defined NSUPDATE */

	if (dhcp_gbl_ctx.task != NULL) {
		isc_task_shutdown(dhcp_gbl_ctx.task);
		isc_task_detach(&dhcp_gbl_ctx.task);
	}

	if (dhcp_gbl_ctx.timermgr != NULL)
		isc_timermgr_destroy(&dhcp_gbl_ctx.timermgr);

	if (dhcp_gbl_ctx.socketmgr != NULL)
		isc_socketmgr_destroy(&dhcp_gbl_ctx.socketmgr);

	if (dhcp_gbl_ctx.taskmgr != NULL)
		isc_taskmgr_destroy(&dhcp_gbl_ctx.taskmgr);

	if (dhcp_gbl_ctx.actx_started != ISC_FALSE) {
		isc_app_ctxfinish(dhcp_gbl_ctx.actx);
		dhcp_gbl_ctx.actx_started = ISC_FALSE;
	}

	if (dhcp_gbl_ctx.actx != NULL)
		isc_appctx_destroy(&dhcp_gbl_ctx.actx);

	if (dhcp_gbl_ctx.mctx != NULL)
		isc_mem_detach(&dhcp_gbl_ctx.mctx);

	return;
}

/* Installs a handler for a signal using sigaction */
static void
handle_signal(int sig, void (*handler)(int)) {
	struct sigaction sa;

	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = handler;
	sigfillset(&sa.sa_mask);
	if (sigaction(sig, &sa, NULL) != 0) {
		log_debug("handle_signal() failed for signal %d error: %s",
                          sig, strerror(errno));
	}
}

/* Callback passed to isc_app_ctxonrun
 *
 * BIND9 context code will invoke this handler once the context has
 * entered the running state.  We use it to set a global marker so that
 * we can tell if the context is running.  Several of the isc_app_
 * calls REQUIRE that the context is running and we need a way to
 * know that.
 *
 * We also check to see if we received a shutdown signal prior to
 * the context entering the run state.  If we did, then we can just
 * simply shut the context down now.  This closes the relatively
 * small window between start up and entering run via the call
 * to dispatch().
 *
 */
static void
set_ctx_running(isc_task_t *task, isc_event_t *event) {
    IGNORE_UNUSED(task);
	dhcp_gbl_ctx.actx_running = ISC_TRUE;

	if (shutdown_signal) {
		// We got signaled shutdown before we entered running state.
		// Now that we've reached running state, shut'er down.
		isc_app_ctxsuspend(dhcp_gbl_ctx.actx);
	}

        isc_event_free(&event);
}

isc_result_t
dhcp_context_create(int flags,
		    struct in_addr  *local4,
		    struct in6_addr *local6) {
	isc_result_t result;

	if ((flags & DHCP_CONTEXT_PRE_DB) != 0) {
		dhcp_gbl_ctx.actx_started = ISC_FALSE;
		dhcp_gbl_ctx.actx_running = ISC_FALSE;

		/*
		 * Set up the error messages, this isn't the right place
		 * for this call but it is convienent for now.
		 */
		result = dhcp_result_register();
		if (result != ISC_R_SUCCESS) {
			log_fatal("register_table() %s: %u", "failed", result);
		}

		memset(&dhcp_gbl_ctx, 0, sizeof (dhcp_gbl_ctx));

		isc_lib_register();

		/* get the current time for use as the random seed */
		gettimeofday(&cur_tv, (struct timezone *)0);
		isc_random_seed(cur_tv.tv_sec);

		/* we need to create the memory context before
		 * the lib inits in case we aren't doing NSUPDATE
		 * in which case dst needs a memory context
		 */
		result = isc_mem_create(0, 0, &dhcp_gbl_ctx.mctx);
		if (result != ISC_R_SUCCESS)
			goto cleanup;


#if defined (NSUPDATE)
		result = dns_lib_init();
		if (result != ISC_R_SUCCESS)
			goto cleanup;
#else /* defined NSUPDATE */
		/* The dst library is inited as part of dns_lib_init, we don't
		 * need it if NSUPDATE is enabled */
		result = dst_lib_init(dhcp_gbl_ctx.mctx, NULL, 0);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

#endif /* defined NSUPDATE */

		result = isc_appctx_create(dhcp_gbl_ctx.mctx,
					   &dhcp_gbl_ctx.actx);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		result = isc_taskmgr_createinctx(dhcp_gbl_ctx.mctx,
						 dhcp_gbl_ctx.actx,
						 1, 0,
						 &dhcp_gbl_ctx.taskmgr);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		result = isc_socketmgr_createinctx(dhcp_gbl_ctx.mctx,
						   dhcp_gbl_ctx.actx,
						   &dhcp_gbl_ctx.socketmgr);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		result = isc_timermgr_createinctx(dhcp_gbl_ctx.mctx,
						  dhcp_gbl_ctx.actx,
						  &dhcp_gbl_ctx.timermgr);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		result = isc_task_create(dhcp_gbl_ctx.taskmgr, 0,
					 &dhcp_gbl_ctx.task);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		result = isc_app_ctxstart(dhcp_gbl_ctx.actx);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		dhcp_gbl_ctx.actx_started = ISC_TRUE;

		// Install the onrun callback.
		result = isc_app_ctxonrun(dhcp_gbl_ctx.actx, dhcp_gbl_ctx.mctx,
					  dhcp_gbl_ctx.task, set_ctx_running,
					  dhcp_gbl_ctx.actx);
		if (result != ISC_R_SUCCESS)
			goto cleanup;

		/* Not all OSs support suppressing SIGPIPE through socket
		 * options, so set the sigal action to be ignore.  This allows
		 * broken connections to fail gracefully with EPIPE on writes */
		handle_signal(SIGPIPE, SIG_IGN);

		/* Reset handlers installed by isc_app_ctxstart()
		 * to default for control-c and kill */
		handle_signal(SIGINT, SIG_DFL);
		handle_signal(SIGTERM, SIG_DFL);
	}

#if defined (NSUPDATE)
	if ((flags & DHCP_CONTEXT_POST_DB) != 0) {
		/* Setting addresses only.
		 * All real work will be done later on if needed to avoid
		 * listening on ddns port if client/server was compiled with
		 * ddns support but not using it. */
		if (local4 != NULL) {
			dhcp_gbl_ctx.use_local4 = 1;
			isc_sockaddr_fromin(&dhcp_gbl_ctx.local4_sockaddr,
					    local4, 0);
		}

		if (local6 != NULL) {
			dhcp_gbl_ctx.use_local6 = 1;
			isc_sockaddr_fromin6(&dhcp_gbl_ctx.local6_sockaddr,
					     local6, 0);
		}

		if (!(flags & DHCP_DNS_CLIENT_LAZY_INIT)) {
			result = dns_client_init();
		}
	}
#endif /* defined NSUPDATE */

	return(ISC_R_SUCCESS);

 cleanup:
	/*
	 * Currently we don't try and cleanup, just return an error
	 * expecting that our caller will log the error and exit.
	 */

	return(result);
}

/*
 * Convert a string name into the proper structure for the isc routines
 *
 * Previously we allowed names without a trailing '.' however the current
 * dns and dst code requires the names to end in a period.  If the
 * name doesn't have a trailing period add one as part of creating
 * the dns name.
 */

isc_result_t
dhcp_isc_name(unsigned char   *namestr,
	      dns_fixedname_t *namefix,
	      dns_name_t     **name)
{
	size_t namelen;
	isc_buffer_t b;
	isc_result_t result;

	namelen = strlen((char *)namestr);
	isc_buffer_init(&b, namestr, namelen);
	isc_buffer_add(&b, namelen);
	dns_fixedname_init(namefix);
	*name = dns_fixedname_name(namefix);
	result = dns_name_fromtext(*name, &b, dns_rootname, 0, NULL);
	isc_buffer_invalidate(&b);
	return(result);
}

isc_result_t
isclib_make_dst_key(char          *inname,
		    char          *algorithm,
		    unsigned char *secret,
		    int            length,
		    dst_key_t    **dstkey)
{
	isc_result_t result;
	dns_name_t *name;
	dns_fixedname_t name0;
	isc_buffer_t b;
	unsigned int algorithm_code;

	isc_buffer_init(&b, secret, length);
	isc_buffer_add(&b, length);

	if (strcasecmp(algorithm, DHCP_HMAC_MD5_NAME) == 0) {
		algorithm_code =  DST_ALG_HMACMD5;
	} else if (strcasecmp(algorithm, DHCP_HMAC_SHA1_NAME) == 0) {
		algorithm_code =  DST_ALG_HMACSHA1;
	} else if (strcasecmp(algorithm, DHCP_HMAC_SHA224_NAME) == 0) {
		algorithm_code =  DST_ALG_HMACSHA224;
	} else if (strcasecmp(algorithm, DHCP_HMAC_SHA256_NAME) == 0) {
		algorithm_code =  DST_ALG_HMACSHA256;
	} else if (strcasecmp(algorithm, DHCP_HMAC_SHA384_NAME) == 0) {
		algorithm_code =  DST_ALG_HMACSHA384;
	} else if (strcasecmp(algorithm, DHCP_HMAC_SHA512_NAME) == 0) {
		algorithm_code =  DST_ALG_HMACSHA512;
	} else {
		return(DHCP_R_INVALIDARG);
	}

	result = dhcp_isc_name((unsigned char *)inname, &name0, &name);
	if (result != ISC_R_SUCCESS) {
		return(result);
	}

	return(dst_key_frombuffer(name, algorithm_code, DNS_KEYOWNER_ENTITY,
				  DNS_KEYPROTO_DNSSEC, dns_rdataclass_in,
				  &b, dhcp_gbl_ctx.mctx, dstkey));
}

/**
 * signal handler that initiates server shutdown
 *
 * @param signal signal code that we received
 */
void dhcp_signal_handler(int signal) {
	if (shutdown_signal != 0) {
		/* Already in shutdown. */
		return;
	}

	/* Possible race but does it matter? */
	shutdown_signal = signal;

	/* If the application context is running tell it to shut down */
	if (dhcp_gbl_ctx.actx_running == ISC_TRUE) {
		(void) isc_app_ctxsuspend(dhcp_gbl_ctx.actx);
	}
}

#if defined (NSUPDATE)
isc_result_t dns_client_init() {
	isc_result_t result;
	if (dhcp_gbl_ctx.dnsclient == NULL) {
		result = dns_client_createx2(dhcp_gbl_ctx.mctx,
					     dhcp_gbl_ctx.actx,
					     dhcp_gbl_ctx.taskmgr,
					     dhcp_gbl_ctx.socketmgr,
					     dhcp_gbl_ctx.timermgr,
					     0,
					     &dhcp_gbl_ctx.dnsclient,
					     (dhcp_gbl_ctx.use_local4 ?
					      &dhcp_gbl_ctx.local4_sockaddr
					      : NULL),
					     (dhcp_gbl_ctx.use_local6 ?
					      &dhcp_gbl_ctx.local6_sockaddr
					      : NULL));

		if (result != ISC_R_SUCCESS) {
			log_error("Unable to create DNS client context:"
				  " result: %d", result);
			return result;
		}

		/* If we can't set up the servers we may not be able to
		 * do DDNS but we should continue to try and perform
		 * our basic functions and let the user sort it out. */
		result = dhcp_dns_client_setservers();
		if (result != ISC_R_SUCCESS) {
			log_error("Unable to set resolver from resolv.conf; "
				  "startup continuing but DDNS support "
				  "may be affected: result %d", result);
		}
	}

	return ISC_R_SUCCESS;
}
#endif /* defined (NSUPDATE) */