1 files changed, 536 insertions, 20 deletions

diff --git a/wg-dynamic-client.c b/wg-dynamic-client.c
index 8554269..560c8d7 100644
--- a/wg-dynamic-client.c
+++ b/wg-dynamic-client.c
@@ -3,38 +3,554 @@
  * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
  */
 
-#include "netlink.h"
 #include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
 #include <string.h>
 #include <stdlib.h>
+#include <signal.h>
+#include <poll.h>
+
+#include <arpa/inet.h>
+#include <libmnl/libmnl.h>
+#include <linux/rtnetlink.h>
+
+#include "common.h"
+#include "dbg.h"
+#include "netlink.h"
+
+#define LEASE_CHECK_INTERVAL 1000 /* 1s is convenient for testing */
+#define LOW_PORT_START 214
+
+int DBG_LVL = 3;
+
+static const char *progname;
+static const char *wg_interface;
+static wg_device *device = NULL;
+static struct pollfd pollfds[1];
+static struct in6_addr our_lladdr = { 0 };
+static struct wg_combined_ip our_gaddr4 = { 0 };
+static struct wg_combined_ip our_gaddr6 = { 0 };
+static struct wg_dynamic_lease our_lease = { 0 };
+
+struct mnl_cb_data {
+	uint32_t ifindex;
+	struct in6_addr *lladdr;
+	struct wg_combined_ip *gaddr4;
+	struct wg_combined_ip *gaddr6;
+};
+
+static void usage()
+{
+	die("usage: %s <wg-interface>\n", progname);
+}
+
+int data_attr_cb(const struct nlattr *attr, void *data)
+{
+	const struct nlattr **tb = data;
+	int type = mnl_attr_get_type(attr);
+
+	/* skip unsupported attribute in user-space */
+	if (mnl_attr_type_valid(attr, IFA_MAX) < 0)
+		return MNL_CB_OK;
+
+	switch (type) {
+	case IFA_ADDRESS:
+		if (mnl_attr_validate(attr, MNL_TYPE_BINARY) < 0) {
+			perror("mnl_attr_validate");
+			return MNL_CB_ERROR;
+		}
+		break;
+	}
+	tb[type] = attr;
+	return MNL_CB_OK;
+}
+
+int data_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct nlattr *tb[IFA_MAX + 1] = {};
+	struct ifaddrmsg *ifa = mnl_nlmsg_get_payload(nlh);
+	struct mnl_cb_data *cb_data = (struct mnl_cb_data *)data;
+	unsigned char *addr;
+
+	if (ifa->ifa_index != cb_data->ifindex)
+		return MNL_CB_OK;
+
+	mnl_attr_parse(nlh, sizeof(*ifa), data_attr_cb, tb);
+
+	if (!tb[IFA_ADDRESS])
+		return MNL_CB_OK;
+
+	addr = mnl_attr_get_payload(tb[IFA_ADDRESS]);
+	char out[INET6_ADDRSTRLEN];
+	inet_ntop(ifa->ifa_family, addr, out, sizeof(out));
+	debug("index=%d, family=%d, addr=%s\n", ifa->ifa_index, ifa->ifa_family,
+	      out);
+
+	if (ifa->ifa_scope == RT_SCOPE_LINK) {
+		if (ifa->ifa_prefixlen != 128)
+			return MNL_CB_OK;
+		memcpy(cb_data->lladdr, addr, 16);
+	} else if (ifa->ifa_scope == RT_SCOPE_UNIVERSE) {
+		switch (ifa->ifa_family) {
+		case AF_INET:
+			cb_data->gaddr4->family = ifa->ifa_family;
+			memcpy(&cb_data->gaddr4->ip, addr, 4);
+			cb_data->gaddr4->cidr = ifa->ifa_prefixlen;
+			break;
+		case AF_INET6:
+			cb_data->gaddr6->family = ifa->ifa_family;
+			memcpy(&cb_data->gaddr6->ip, addr, 16);
+			cb_data->gaddr6->cidr = ifa->ifa_prefixlen;
+			break;
+		default:
+			die("Unknown address family: %u\n", ifa->ifa_family);
+		}
+	}
+
+	return MNL_CB_OK;
+}
+
+static void iface_update(uint16_t cmd, uint16_t flags, uint32_t ifindex,
+			 const struct wg_combined_ip *addr)
+{
+	struct mnl_socket *nl;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
+	unsigned int seq, portid;
+	struct ifaddrmsg *ifaddr; /* linux/if_addr.h */
+	int ret;
+
+	nl = mnl_socket_open(NETLINK_ROUTE);
+	if (nl == NULL)
+		fatal("mnl_socket_open");
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0)
+		fatal("mnl_socket_bind");
+
+	portid = mnl_socket_get_portid(nl);
+	seq = time(NULL);
+	nlh = mnl_nlmsg_put_header(buf);
+	nlh->nlmsg_seq = seq;
+	nlh->nlmsg_type = cmd;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
+	ifaddr = mnl_nlmsg_put_extra_header(nlh, sizeof(struct ifaddrmsg));
+	ifaddr->ifa_family = addr->family;
+	ifaddr->ifa_prefixlen = addr->cidr;
+	ifaddr->ifa_scope = RT_SCOPE_UNIVERSE; /* linux/rtnetlink.h */
+	ifaddr->ifa_index = ifindex;
+	mnl_attr_put(nlh, IFA_LOCAL, addr->family == AF_INET ? 4 : 16,
+		     &addr->ip);
+
+	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
+		fatal("mnl_socket_sendto");
+
+	do {
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+		if (ret <= MNL_CB_STOP)
+			break;
+		ret = mnl_cb_run(buf, ret, seq, portid, NULL, NULL);
+	} while (ret > 0);
+
+	if (ret == -1)
+		fatal("mnl_cb_run/mnl_socket_recvfrom");
+
+	mnl_socket_close(nl);
+}
+
+static void iface_remove_addr(uint32_t ifindex,
+			      const struct wg_combined_ip *addr)
+{
+	char ipstr[INET6_ADDRSTRLEN];
+	debug("removing %s/%u from interface %u\n",
+	      inet_ntop(addr->family, &addr->ip, ipstr, sizeof ipstr),
+	      addr->cidr, ifindex);
+	iface_update(RTM_DELADDR, 0, ifindex, addr);
+}
+
+static void iface_add_addr(uint32_t ifindex, const struct wg_combined_ip *addr)
+{
+	char ipstr[INET6_ADDRSTRLEN];
+	debug("adding %s/%u to interface %u\n",
+	      inet_ntop(addr->family, &addr->ip, ipstr, sizeof ipstr),
+	      addr->cidr, ifindex);
+	iface_update(RTM_NEWADDR, NLM_F_REPLACE | NLM_F_CREATE, ifindex, addr);
+}
+
+static bool get_and_validate_local_addrs(uint32_t ifindex,
+					 struct in6_addr *lladdr,
+					 struct wg_combined_ip *gaddr4,
+					 struct wg_combined_ip *gaddr6)
+{
+	struct mnl_cb_data cb_data = {
+		.ifindex = ifindex,
+		.lladdr = lladdr,
+		.gaddr4 = gaddr4,
+		.gaddr6 = gaddr6,
+	};
+
+	iface_get_all_addrs(AF_INET, data_cb, &cb_data);
+	iface_get_all_addrs(AF_INET6, data_cb, &cb_data);
+
+	return !IN6_IS_ADDR_UNSPECIFIED(cb_data.lladdr);
+}
+
+#if 0
+static void dump_leases()
+{
+	char ip4str[INET6_ADDRSTRLEN], ip6str[INET6_ADDRSTRLEN];
+	struct wg_dynamic_lease *l = &our_lease;
+
+	if (l->start == 0) {
+		debug("lease NONE\n");
+		return;
+	}
+
+	debug("lease %u %u %s/%u %s/%u\n", l->start + l->leasetime,
+	      l->start + l->leasetime - current_time(),
+	      inet_ntop(AF_INET, &l->ip4.ip.ip4, ip4str, INET6_ADDRSTRLEN),
+	      l->ip4.cidr,
+	      inet_ntop(AF_INET6, &l->ip6.ip.ip6, ip6str, INET6_ADDRSTRLEN),
+	      l->ip6.cidr);
+}
+#endif
+
+static int do_connect(int *fd)
+{
+	int res;
+	struct sockaddr_in6 our_addr = {
+		.sin6_family = AF_INET6,
+		.sin6_addr = our_lladdr,
+		.sin6_scope_id = device->ifindex,
+	};
+	struct sockaddr_in6 their_addr = {
+		.sin6_family = AF_INET6,
+		.sin6_port = htons(WG_DYNAMIC_PORT),
+		.sin6_scope_id = device->ifindex,
+	};
+
+	*fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (*fd < 0)
+		fatal("Creating a socket failed");
+
+	for (int port = LOW_PORT_START;; port++) {
+		our_addr.sin6_port = htons(port);
+		if (!bind(*fd, (struct sockaddr *)&our_addr, sizeof(our_addr)))
+			break;
+		if (errno != EADDRINUSE)
+			fatal("Binding socket failed");
+		if (port >= 1024)
+			die("No low ports available");
+	}
+
+	if (!inet_pton(AF_INET6, WG_DYNAMIC_ADDR, &their_addr.sin6_addr))
+		fatal("inet_pton()");
+	if (connect(*fd, (struct sockaddr *)&their_addr,
+		    sizeof(struct sockaddr_in6))) {
+		char out[INET6_ADDRSTRLEN];
+		if (!inet_ntop(their_addr.sin6_family, &their_addr.sin6_addr,
+			       out, sizeof out))
+			fatal("inet_ntop()");
+		debug("Connecting to [%s]:%u failed: %s\n", out,
+		      ntohs(their_addr.sin6_port), strerror(errno));
+		if (close(*fd))
+			debug("Closing socket failed: %s\n", strerror(errno));
+		*fd = -1;
+		return -1;
+	}
+
+	res = fcntl(*fd, F_GETFL, 0);
+	if (res < 0 || fcntl(*fd, F_SETFL, res | O_NONBLOCK) < 0)
+		fatal("Setting socket to nonblocking failed");
+
+	return 0;
+}
+
+static size_t connect_and_send(unsigned char *buf, size_t *len)
+{
+	size_t ret;
+	if (pollfds[0].fd < 0)
+		if (do_connect(&pollfds[0].fd))
+			return 0;
+	ret = send_message(pollfds[0].fd, buf, len);
+	return ret;
+}
+
+static bool request_ip(struct wg_dynamic_request *req,
+		       const struct wg_dynamic_lease *lease)
+{
+	unsigned char buf[MAX_RESPONSE_SIZE + 1];
+	char addrstr[INET6_ADDRSTRLEN];
+	size_t msglen;
+	size_t written;
+
+	msglen = 0;
+	msglen += print_to_buf((char *)buf, sizeof buf, msglen, "%s=%d\n",
+			       WG_DYNAMIC_KEY[WGKEY_REQUEST_IP], 1);
+
+	if (lease && lease->ip4.ip.ip4.s_addr) {
+		if (!inet_ntop(AF_INET, &lease->ip4.ip.ip4, addrstr,
+			       sizeof addrstr))
+			fatal("inet_ntop()");
+		msglen += print_to_buf((char *)buf, sizeof buf, msglen,
+				       "ipv4=%s/32\n", addrstr);
+	}
+	if (lease && !IN6_IS_ADDR_UNSPECIFIED(&lease->ip6.ip.ip6)) {
+		if (!inet_ntop(AF_INET6, &lease->ip6.ip.ip6, addrstr,
+			       sizeof addrstr))
+			fatal("inet_ntop()");
+		msglen += print_to_buf((char *)buf, sizeof buf, msglen,
+				       "ipv6=%s/128\n", addrstr);
+	}
+	/* nmsglen += print_to_buf((char *)buf, sizeof buf, msglen,
+	   "leasetime=%u\n", fixme); */
+
+	msglen += print_to_buf((char *)buf, sizeof buf, msglen, "\n");
+
+	written = connect_and_send(buf, &msglen);
+	if (msglen == 0)
+		return true;
+
+	debug("Socket %d blocking with %lu bytes to write, postponing\n",
+	      pollfds[0].fd, msglen);
+	send_later(req, buf + written, msglen);
+	return false;
+}
+
+static int maybe_refresh_lease(uint32_t now, struct wg_dynamic_lease *lease,
+			       struct wg_dynamic_request *req)
+{
+	if (now > lease->start + (lease->leasetime * 2) / 3) {
+		debug("Refreshing lease expiring on %u\n",
+		      lease->start + lease->leasetime);
+		request_ip(req, lease);
+		return 0;
+	}
+
+	return 1;
+}
+
+static bool lease_is_valid(uint32_t now, struct wg_dynamic_lease *lease)
+{
+	return now < lease->start + lease->leasetime;
+}
+
+static void maybe_remove_lease(uint32_t now, struct wg_dynamic_lease *lease)
+{
+	if (!lease_is_valid(now, lease))
+		memset(lease, 0, sizeof *lease);
+}
+
+static void check_leases(struct wg_dynamic_request *req)
+{
+	uint32_t now = current_time();
+
+	if (!lease_is_valid(now, &our_lease))
+		request_ip(req, NULL);
+	else {
+		maybe_remove_lease(now, &our_lease);
+		maybe_refresh_lease(now, &our_lease, req);
+	}
+}
+
+static int handle_received_lease(const struct wg_dynamic_request *req)
+{
+	uint32_t ret;
+	struct wg_dynamic_attr *attr;
+	struct wg_dynamic_lease *lease = &our_lease;
+	uint32_t now = current_time();
+	uint32_t lease_start = 0;
+	uint32_t curleasetime = lease->start + lease->leasetime;
+
+	attr = req->first;
+	while (attr) {
+		switch (attr->key) {
+		case WGKEY_IPV4:
+			memcpy(&lease->ip4, attr->value,
+			       sizeof(struct wg_combined_ip));
+			break;
+		case WGKEY_IPV6:
+			memcpy(&lease->ip6, attr->value,
+			       sizeof(struct wg_combined_ip));
+			break;
+		case WGKEY_LEASESTART:
+			memcpy(&lease_start, attr->value, sizeof(uint32_t));
+			break;
+		case WGKEY_LEASETIME:
+			memcpy(&lease->leasetime, attr->value,
+			       sizeof(uint32_t));
+			break;
+		case WGKEY_ERRNO:
+			memcpy(&ret, attr->value, sizeof(uint32_t));
+			if (ret) {
+				debug("Request IP failed with %ud from server\n",
+				      ret);
+				return -ret;
+			}
+			break;
+		case WGKEY_ERRMSG:
+			/* TODO: do something with the error message */
+			break;
+		default:
+			debug("Ignoring invalid attribute for request_ip: %d\n",
+			      attr->key);
+		}
+		attr = attr->next;
+	}
+
+	if (lease->leasetime == 0 ||
+	    (lease->ip4.ip.ip4.s_addr == 0 &&
+	     IN6_IS_ADDR_UNSPECIFIED(&lease->ip6.ip.ip6)))
+		return -EINVAL;
+
+	if (abs(now - lease_start) < 15)
+		lease->start = lease_start;
+	else
+		lease->start = now;
+
+	debug("Replacing lease %u -> %u\n", curleasetime,
+	      lease->start + lease->leasetime);
+
+	return 0;
+}
+
+static void cleanup()
+{
+	wg_free_device(device);
+	if (pollfds[0].fd >= 0)
+		if (close(pollfds[0].fd))
+			debug("Failed to close fd");
+}
+
+static bool handle_error(int fd, int ret)
+{
+	UNUSED(fd);
+	UNUSED(ret);
+
+	debug("Unable to parse response: %s\n", strerror(ret));
+
+	return true;
+}
+
+static void maybe_update_iface()
+{
+	if (memcmp(&our_gaddr4.ip, &our_lease.ip4.ip, sizeof our_gaddr4.ip) ||
+	    our_gaddr4.cidr != our_lease.ip4.cidr) {
+		if (our_gaddr4.ip.ip4.s_addr)
+			iface_remove_addr(device->ifindex, &our_gaddr4);
+		iface_add_addr(device->ifindex, &our_lease.ip4);
+		memcpy(&our_gaddr4, &our_lease.ip4, sizeof our_gaddr4);
+	}
+	if (memcmp(&our_gaddr6.ip, &our_lease.ip6.ip, sizeof our_gaddr6.ip) ||
+	    our_gaddr6.cidr != our_lease.ip6.cidr) {
+		if (!IN6_IS_ADDR_UNSPECIFIED(&our_gaddr6.ip.ip6))
+			iface_remove_addr(device->ifindex, &our_gaddr6);
+		iface_add_addr(device->ifindex, &our_lease.ip6);
+		memcpy(&our_gaddr6, &our_lease.ip6, sizeof our_gaddr6);
+	}
+}
+
+static bool handle_response(int fd, struct wg_dynamic_request *req)
+{
+	UNUSED(fd);
+
+#if 0
+	printf("Recieved response of type %s.\n", WG_DYNAMIC_KEY[req->cmd]);
+	struct wg_dynamic_attr *cur = req->first;
+	while (cur) {
+		printf("  with attr %s.\n", WG_DYNAMIC_KEY[cur->key]);
+		cur = cur->next;
+	}
+#endif
+
+	switch (req->cmd) {
+	case WGKEY_REQUEST_IP:
+		if (handle_received_lease(req) == 0)
+			maybe_update_iface();
+		break;
+	default:
+		debug("Unknown command: %d\n", req->cmd);
+		return true;
+	}
+
+	return true;
+}
 
 int main(int argc __attribute__((unused)), char *argv[] __attribute__((unused)))
 {
-	char *device_names, *device_name;
-	size_t len;
+	struct wg_dynamic_request req = { 0 };
+	uint32_t now = current_time();
+
+	progname = argv[0];
+	if (argc != 2)
+		usage();
+
+	wg_interface = argv[1];
+
+	if (wg_get_device(&device, wg_interface))
+		fatal("Unable to access interface %s", wg_interface);
+
+	if (atexit(cleanup))
+		die("Failed to set exit function\n");
+	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
+		fatal("Unable to ignore SIGPIPE");
+
+	if (!get_and_validate_local_addrs(device->ifindex, &our_lladdr,
+					  &our_gaddr4, &our_gaddr6))
+		die("%s needs to have an IPv6 link local address with prefixlen 128 assigned\n",
+		    wg_interface);
+	// TODO: verify that we have a peer matching the requirements (fe80::/128)?
 
-	device_names = wg_list_device_names();
-	if (!device_names) {
-		perror("Unable to get device names");
-		return 1;
+	char lladr_str[INET6_ADDRSTRLEN];
+	debug("%s: %s\n", wg_interface,
+	      inet_ntop(AF_INET6, &our_lladdr, lladr_str, sizeof lladr_str));
+
+	if (our_gaddr4.ip.ip4.s_addr ||
+	    !IN6_IS_ADDR_UNSPECIFIED(&our_gaddr6.ip.ip6)) {
+		our_lease.start = now;
+		our_lease.leasetime = 15;
+		memcpy(&our_lease.ip4, &our_gaddr4,
+		       sizeof(struct wg_combined_ip));
+		memcpy(&our_lease.ip6, &our_gaddr6,
+		       sizeof(struct wg_combined_ip));
 	}
-	wg_for_each_device_name(device_names, device_name, len) {
-		wg_device *device;
-		wg_peer *peer;
-		wg_key_b64_string key;
 
-		if (wg_get_device(&device, device_name) < 0) {
-			perror("Unable to get device");
+	/* TODO: use a blocking socket instead of the unnecessary
+	 * complexity of nonblocking */
+
+	pollfds[0] = (struct pollfd){.fd = -1, .events = POLLIN };
+	while (1) {
+		int nevents = poll(pollfds, 1, LEASE_CHECK_INTERVAL);
+
+		if (nevents == -1)
+			fatal("poll()");
+
+		if (nevents == 0) {
+			/* FIXME: if there's any risk for this path to
+			 * be starving, maybe do this regardless of
+			 * socket readiness? */
+			check_leases(&req);
 			continue;
 		}
-		wg_key_to_base64(key, device->public_key);
-		printf("%s has public key %s\n", device_name, key);
-		wg_for_each_peer(device, peer) {
-			wg_key_to_base64(key, peer->public_key);
-			printf(" - peer %s\n", key);
+
+		if (pollfds[0].revents & POLLOUT) {
+			pollfds[0].revents &= ~POLLOUT;
+			debug("sending, trying again with %lu bytes\n",
+			      req.buflen);
+			send_message(pollfds[0].fd, req.buf, &req.buflen);
+			if (!req.buflen)
+				close_connection(&pollfds[0].fd, &req);
+		}
+
+		if (pollfds[0].revents & POLLIN) {
+			pollfds[0].revents &= ~POLLIN;
+			if (handle_request(pollfds[0].fd, &req, handle_response,
+					   handle_error))
+				close_connection(&pollfds[0].fd, &req);
+			else if (req.buf)
+				pollfds[0].events |= POLLOUT;
 		}
-		wg_free_device(device);
 	}
-	free(device_names);
+
 	return 0;
 }