Add synchronisation support for dhcpd - this allows for two dhcpd's

with the same configuration to be run on the same net and they will
keep their lease files/state in synch, and therefore allowing you to
run redundant dhcpd's. Synchronization code stolen from spamd, uses
an hmac key in /var/db/dhcpd.key if it exists.
ok krw@ deraadt@

1 files changed, 465 insertions, 0 deletions

diff --git a/usr.sbin/dhcpd/sync.c b/usr.sbin/dhcpd/sync.c
new file mode 100644
index 00000000000..58c776608c1
--- /dev/null
+++ b/usr.sbin/dhcpd/sync.c
@@ -0,0 +1,465 @@
+/*	$OpenBSD: sync.c,v 1.1 2008/05/07 12:19:20 beck Exp $	*/
+
+/*
+ * Copyright (c) 2008 Bob Beck <beck@openbsd.org>
+ * Copyright (c) 2006, 2007 Reyk Floeter <reyk@openbsd.org>
+ *
+ * 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
+ */
+
+#include <sys/param.h>
+#include <sys/stdint.h>
+#include <sys/file.h>
+#include <sys/wait.h>
+#include <sys/socket.h>
+#include <sys/resource.h>
+#include <sys/uio.h>
+#include <sys/ioctl.h>
+#include <sys/queue.h>
+
+
+#include <net/if.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#include <err.h>
+#include <errno.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sha1.h>
+#include <syslog.h>
+
+#include <netdb.h>
+
+#include <openssl/hmac.h>
+
+#include "dhcpd.h"
+#include "sync.h"
+
+int sync_debug;
+
+u_int32_t sync_counter;
+int syncfd;
+int sendmcast;
+
+struct sockaddr_in sync_in;
+struct sockaddr_in sync_out;
+static char *sync_key;
+
+struct sync_host {
+	LIST_ENTRY(sync_host)	h_entry;
+
+	char			*h_name;
+	struct sockaddr_in	sh_addr;
+};
+LIST_HEAD(synchosts, sync_host) sync_hosts = LIST_HEAD_INITIALIZER(sync_hosts);
+
+void	 sync_send(struct iovec *, int);
+void	 sync_addr(time_t, time_t, char *, u_int16_t);
+
+int
+sync_addhost(const char *name, u_short port)
+{
+	struct addrinfo hints, *res, *res0;
+	struct sync_host *shost;
+	struct sockaddr_in *addr = NULL;
+
+	bzero(&hints, sizeof(hints));
+	hints.ai_family = PF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	if (getaddrinfo(name, NULL, &hints, &res0) != 0)
+		return (EINVAL);
+	for (res = res0; res != NULL; res = res->ai_next) {
+		if (addr == NULL && res->ai_family == AF_INET) {
+			addr = (struct sockaddr_in *)res->ai_addr;
+			break;
+		}
+	}
+	if (addr == NULL) {
+		freeaddrinfo(res0);
+		return (EINVAL);
+	}
+	if ((shost = (struct sync_host *)
+	    calloc(1, sizeof(struct sync_host))) == NULL) {
+		freeaddrinfo(res0);
+		return (ENOMEM);
+	}
+	if ((shost->h_name = strdup(name)) == NULL) {
+		free(shost);
+		freeaddrinfo(res0);
+		return (ENOMEM);
+	}
+
+	shost->sh_addr.sin_family = AF_INET;
+	shost->sh_addr.sin_port = htons(port);
+	shost->sh_addr.sin_addr.s_addr = addr->sin_addr.s_addr;
+	freeaddrinfo(res0);
+
+	LIST_INSERT_HEAD(&sync_hosts, shost, h_entry);
+
+	if (sync_debug)
+		syslog_r(LOG_DEBUG, &sdata, "added dhcp sync host %s "
+		    "(address %s, port %d)\n", shost->h_name,
+		    inet_ntoa(shost->sh_addr.sin_addr), port);
+
+	return (0);
+}
+
+int
+sync_init(const char *iface, const char *baddr, u_short port)
+{
+	int one = 1;
+	u_int8_t ttl;
+	struct ifreq ifr;
+	struct ip_mreq mreq;
+	struct sockaddr_in *addr;
+	char ifnam[IFNAMSIZ], *ttlstr;
+	const char *errstr;
+	struct in_addr ina;
+
+	if (iface != NULL)
+		sendmcast++;
+
+	bzero(&ina, sizeof(ina));
+	if (baddr != NULL) {
+		if (inet_pton(AF_INET, baddr, &ina) != 1) {
+			ina.s_addr = htonl(INADDR_ANY);
+			if (iface == NULL)
+				iface = baddr;
+			else if (iface != NULL && strcmp(baddr, iface) != 0) {
+				fprintf(stderr, "multicast interface does "
+				    "not match");
+				return (-1);
+			}
+		}
+	}
+
+	sync_key = SHA1File(DHCP_SYNC_KEY, NULL);
+	if (sync_key == NULL) {
+		if (errno != ENOENT) {
+			fprintf(stderr, "failed to open sync key: %s\n",
+			    strerror(errno));
+			return (-1);
+		}
+		/* Use empty key by default */
+		sync_key = "";
+	}
+
+	syncfd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (syncfd == -1)
+		return (-1);
+
+	if (setsockopt(syncfd, SOL_SOCKET, SO_REUSEADDR, &one,
+	    sizeof(one)) == -1)
+		goto fail;
+
+	bzero(&sync_out, sizeof(sync_out));
+	sync_out.sin_family = AF_INET;
+	sync_out.sin_len = sizeof(sync_out);
+	sync_out.sin_addr.s_addr = ina.s_addr;
+	if (baddr == NULL && iface == NULL)
+		sync_out.sin_port = 0;
+	else
+		sync_out.sin_port = htons(port);
+
+	if (bind(syncfd, (struct sockaddr *)&sync_out, sizeof(sync_out)) == -1)
+		goto fail;
+
+	/* Don't use multicast messages */
+	if (iface == NULL)
+		return (syncfd);
+
+	strlcpy(ifnam, iface, sizeof(ifnam));
+	ttl = DHCP_SYNC_MCASTTTL;
+	if ((ttlstr = strchr(ifnam, ':')) != NULL) {
+		*ttlstr++ = '\0';
+		ttl = (u_int8_t)strtonum(ttlstr, 1, UINT8_MAX, &errstr);
+		if (errstr) {
+			fprintf(stderr, "invalid multicast ttl %s: %s",
+			    ttlstr, errstr);
+			goto fail;
+		}
+	}
+
+	bzero(&ifr, sizeof(ifr));
+	strlcpy(ifr.ifr_name, ifnam, sizeof(ifr.ifr_name));
+	if (ioctl(syncfd, SIOCGIFADDR, &ifr) == -1)
+		goto fail;
+
+	bzero(&sync_in, sizeof(sync_in));
+	addr = (struct sockaddr_in *)&ifr.ifr_addr;
+	sync_in.sin_family = AF_INET;
+	sync_in.sin_len = sizeof(sync_in);
+	sync_in.sin_addr.s_addr = addr->sin_addr.s_addr;
+	sync_in.sin_port = htons(port);
+
+	bzero(&mreq, sizeof(mreq));
+	sync_out.sin_addr.s_addr = inet_addr(DHCP_SYNC_MCASTADDR);
+	mreq.imr_multiaddr.s_addr = inet_addr(DHCP_SYNC_MCASTADDR);
+	mreq.imr_interface.s_addr = sync_in.sin_addr.s_addr;
+
+	if (setsockopt(syncfd, IPPROTO_IP,
+	    IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) == -1) {
+		fprintf(stderr, "failed to add multicast membership to %s: %s",
+		    DHCP_SYNC_MCASTADDR, strerror(errno));
+		goto fail;
+	}
+	if (setsockopt(syncfd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl,
+	    sizeof(ttl)) < 0) {
+		fprintf(stderr, "failed to set multicast ttl to "
+		    "%u: %s\n", ttl, strerror(errno));
+		setsockopt(syncfd, IPPROTO_IP,
+		    IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
+		goto fail;
+	}
+
+	if (sync_debug)
+		syslog_r(LOG_DEBUG, &sdata, "using multicast dhcp sync %smode "
+		    "(ttl %u, group %s, port %d)\n",
+		    sendmcast ? "" : "receive ",
+		    ttl, inet_ntoa(sync_out.sin_addr), port);
+
+	return (syncfd);
+
+ fail:
+	close(syncfd);
+	return (-1);
+}
+
+void
+sync_recv(void)
+{
+	struct dhcp_synchdr *hdr;
+	struct sockaddr_in addr;
+	struct dhcp_synctlv_hdr *tlv;
+	struct dhcp_synctlv_lease *lv;
+	struct lease	*lease;
+	u_int8_t buf[DHCP_SYNC_MAXSIZE];
+	u_int8_t hmac[2][DHCP_SYNC_HMAC_LEN];
+	struct lease l, *lp;
+	u_int8_t *p;
+	socklen_t addr_len;
+	ssize_t len;
+	u_int hmac_len;
+
+	bzero(&addr, sizeof(addr));
+	bzero(buf, sizeof(buf));
+
+	addr_len = sizeof(addr);
+	if ((len = recvfrom(syncfd, buf, sizeof(buf), 0,
+	    (struct sockaddr *)&addr, &addr_len)) < 1)
+		return;
+	if (addr.sin_addr.s_addr != htonl(INADDR_ANY) &&
+	    bcmp(&sync_in.sin_addr, &addr.sin_addr,
+	    sizeof(addr.sin_addr)) == 0)
+		return;
+
+	/* Ignore invalid or truncated packets */
+	hdr = (struct dhcp_synchdr *)buf;
+	if (len < sizeof(struct dhcp_synchdr) ||
+	    hdr->sh_version != DHCP_SYNC_VERSION ||
+	    hdr->sh_af != AF_INET ||
+	    len < ntohs(hdr->sh_length))
+		goto trunc;
+	len = ntohs(hdr->sh_length);
+
+	/* Compute and validate HMAC */
+	bcopy(hdr->sh_hmac, hmac[0], DHCP_SYNC_HMAC_LEN);
+	bzero(hdr->sh_hmac, DHCP_SYNC_HMAC_LEN);
+	HMAC(EVP_sha1(), sync_key, strlen(sync_key), buf, len,
+	    hmac[1], &hmac_len);
+	if (bcmp(hmac[0], hmac[1], DHCP_SYNC_HMAC_LEN) != 0)
+		goto trunc;
+
+	if (sync_debug)
+		syslog_r(LOG_DEBUG, &sdata,
+		    "%s(sync): received packet of %d bytes\n",
+		    inet_ntoa(addr.sin_addr), (int)len);
+
+	p = (u_int8_t *)(hdr + 1);
+	while (len) {
+		tlv = (struct dhcp_synctlv_hdr *)p;
+
+		if (len < sizeof(struct dhcp_synctlv_hdr) ||
+		    len < ntohs(tlv->st_length))
+			goto trunc;
+
+		switch (ntohs(tlv->st_type)) {
+		case DHCP_SYNC_LEASE:
+			lv = (struct dhcp_synctlv_lease *)tlv;
+			if (sizeof(*lv) > ntohs(tlv->st_length))
+				goto trunc;
+			if ((lease = find_lease_by_hw_addr(
+				    lv->hardware_addr.haddr,
+				    lv->hardware_addr.hlen)) == NULL) {
+				if ((lease = find_lease_by_hw_addr(
+					    lv->hardware_addr.haddr,
+					    lv->hardware_addr.hlen)) == NULL) {
+					lp = &l;
+					memset(lp, 0, sizeof(*lp));
+				} else
+					lp = lease;
+			} else
+				lp = lease;
+
+			lp = &l;
+			memset(lp, 0, sizeof(*lp));
+			lp->timestamp = ntohl(lv->timestamp);
+			lp->starts = ntohl(lv->starts);
+			lp->ends = ntohl(lv->ends);
+			memcpy(&lp->ip_addr, &lv->ip_addr,
+			    sizeof(lp->ip_addr));
+			memcpy(&lp->hardware_addr, &lv->hardware_addr,
+			    sizeof(lp->hardware_addr));
+			syslog_r(LOG_DEBUG, &sdata,
+			    "DHCP_SYNC_LEASE from %s for hw %s -> ip %s, "
+			    "start %d, end %d",
+			    inet_ntoa(addr.sin_addr),
+			    print_hw_addr(lp->hardware_addr.htype,
+				lp->hardware_addr.hlen,
+				lp->hardware_addr.haddr),
+			    piaddr(lp->ip_addr),
+			    lp->starts,
+			    lp->ends);
+			/* now whack the lease in there */
+			if (lease == NULL) {
+				enter_lease(lp);
+				write_leases();
+			}
+			else if (lease->ends < lp->ends)
+				supersede_lease(lease, lp, 1);
+			else if (lease->ends > lp->ends)
+				/*
+				 * our partner sent us a lease
+				 * that is older than what we have,
+				 * so re-educate them with what we
+				 * know is newer.
+				 */
+				sync_lease(lease);
+			break;
+		case DHCP_SYNC_END:
+			goto done;
+		default:
+			printf("invalid type: %d\n", ntohs(tlv->st_type));
+			goto trunc;
+		}
+		len -= ntohs(tlv->st_length);
+		p = ((u_int8_t *)tlv) + ntohs(tlv->st_length);
+	}
+
+ done:
+	return;
+
+ trunc:
+	if (sync_debug)
+		syslog_r(LOG_INFO, &sdata,
+		    "%s(sync): truncated or invalid packet\n",
+		    inet_ntoa(addr.sin_addr));
+}
+
+void
+sync_send(struct iovec *iov, int iovlen)
+{
+	struct sync_host *shost;
+	struct msghdr msg;
+
+	/* setup buffer */
+	bzero(&msg, sizeof(msg));
+	msg.msg_iov = iov;
+	msg.msg_iovlen = iovlen;
+
+	if (sendmcast) {
+		if (sync_debug)
+			syslog_r(LOG_DEBUG, &sdata,
+			    "sending multicast sync message\n");
+		msg.msg_name = &sync_out;
+		msg.msg_namelen = sizeof(sync_out);
+		sendmsg(syncfd, &msg, 0);
+	}
+
+	LIST_FOREACH(shost, &sync_hosts, h_entry) {
+		if (sync_debug)
+			syslog_r(LOG_DEBUG, &sdata,
+			    "sending sync message to %s (%s)\n",
+			    shost->h_name, inet_ntoa(shost->sh_addr.sin_addr));
+		msg.msg_name = &shost->sh_addr;
+		msg.msg_namelen = sizeof(shost->sh_addr);
+		sendmsg(syncfd, &msg, 0);
+	}
+}
+
+void
+sync_lease(struct lease *lease)
+{
+	struct iovec iov[3];
+	struct dhcp_synchdr hdr;
+	struct dhcp_synctlv_lease ld;
+	struct dhcp_synctlv_hdr end;
+	int i = 0;
+	HMAC_CTX ctx;
+	u_int hmac_len;
+
+	bzero(&hdr, sizeof(hdr));
+	bzero(&ld, sizeof(ld));
+
+	HMAC_CTX_init(&ctx);
+	HMAC_Init(&ctx, sync_key, strlen(sync_key), EVP_sha1());
+
+	/* Add DHCP sync packet header */
+	hdr.sh_version = DHCP_SYNC_VERSION;
+	hdr.sh_af = AF_INET;
+	hdr.sh_counter = sync_counter++;
+	hdr.sh_length = htons(sizeof(hdr) + sizeof(ld) + sizeof(end));
+	iov[i].iov_base = &hdr;
+	iov[i].iov_len = sizeof(hdr);
+	HMAC_Update(&ctx, iov[i].iov_base, iov[i].iov_len);
+	i++;
+
+	/* Add single DHCP sync address entry */
+	ld.type = htons(DHCP_SYNC_LEASE);
+	ld.length = htons(sizeof(ld));
+	ld.timestamp = htonl(lease->timestamp);
+	ld.starts = htonl(lease->starts);
+	ld.ends =  htonl(lease->ends);
+	memcpy(&ld.ip_addr, &lease->ip_addr, sizeof(ld.ip_addr));
+	memcpy(&ld.hardware_addr, &lease->hardware_addr,
+	    sizeof(ld.hardware_addr));
+	syslog_r(LOG_DEBUG, &sdata,
+	    "sending DHCP_SYNC_LEASE for hw %s -> ip %s, start %d, end %d",
+	    print_hw_addr(ld.hardware_addr.htype, ld.hardware_addr.hlen,
+		ld.hardware_addr.haddr),
+	    piaddr(lease->ip_addr),
+	    ntohl(ld.starts),
+	    ntohl(ld.ends));
+	iov[i].iov_base = &ld;
+	iov[i].iov_len = sizeof(ld);
+	HMAC_Update(&ctx, iov[i].iov_base, iov[i].iov_len);
+	i++;
+
+	/* Add end marker */
+	end.st_type = htons(DHCP_SYNC_END);
+	end.st_length = htons(sizeof(end));
+	iov[i].iov_base = &end;
+	iov[i].iov_len = sizeof(end);
+	HMAC_Update(&ctx, iov[i].iov_base, iov[i].iov_len);
+	i++;
+
+	HMAC_Final(&ctx, hdr.sh_hmac, &hmac_len);
+
+	/* Send message to the target hosts */
+	sync_send(iov, i);
+	HMAC_CTX_cleanup(&ctx);
+}