From 2a4f2a8e3bfb944a2cd15ca58a917c61b08b5b6a Mon Sep 17 00:00:00 2001
From: Johannes Bauer <joe@johannes-bauer.com>
Date: Wed, 23 Oct 2019 22:29:40 +0200
Subject: [PATCH] Implemented client broadcasting again

Clients now broadcast their host UUID and magic number via UDP, but the
server does not respond nor would the client trigger anything if the
server did.
---
 client.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 global.h |  5 ++---
 msg.h    |  6 +++++-
 3 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/client.c b/client.c
index 425cb25..d38793f 100644
--- a/client.c
+++ b/client.c
@@ -152,6 +152,54 @@ static bool contact_keyserver_hostname(struct keyclient_t *keyclient, const char
 	return success;
 }
 
+static int create_udp_socket(void) {
+	int sd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sd < 0) {
+		log_libc(LLVL_ERROR, "Unable to create UDP server socket(2)");
+		return -1;
+	}
+	{
+		int value = 1;
+		if (setsockopt(sd, SOL_SOCKET, SO_BROADCAST, &value, sizeof(value))) {
+			log_libc(LLVL_ERROR, "Unable to set UDP socket in broadcast mode using setsockopt(2)");
+			close(sd);
+			return -1;
+		}
+	}
+	return sd;
+}
+
+static bool send_udp_broadcast_message(int sd, unsigned int port, const void *data, unsigned int length) {
+	struct sockaddr_in destination;
+	memset(&destination, 0, sizeof(struct sockaddr_in));
+	destination.sin_family = AF_INET;
+	destination.sin_port = htons(port);
+	destination.sin_addr.s_addr = htonl(INADDR_BROADCAST);
+
+	if (sendto(sd, data, length, 0, (struct sockaddr *)&destination, sizeof(struct sockaddr_in)) < 0) {
+		log_libc(LLVL_ERROR, "Unable to sendto(2)");
+		return false;
+	}
+	return true;
+}
+
+
+static bool broadcast_for_keyserver(struct keyclient_t *keyclient) {
+	int sd = create_udp_socket();
+	if (sd == -1) {
+		return false;
+	}
+
+	struct udp_query_t query;
+	memcpy(query.magic, UDP_MESSAGE_MAGIC, sizeof(query.magic));
+	memcpy(query.host_uuid, keyclient->keydb->hosts[0].host_uuid, 16);
+	while (true) {
+		send_udp_broadcast_message(sd, keyclient->opts->port, &query, sizeof(query));
+		sleep(1);
+	}
+	return true;
+}
+
 bool keyclient_start(const struct pgmopts_client_t *opts) {
 	/* Load key database first */
 	struct keyclient_t keyclient = {
@@ -197,7 +245,11 @@ bool keyclient_start(const struct pgmopts_client_t *opts) {
 				break;
 			}
 		} else {
-			/* TODO: Loop until keyserver found */
+			if (!broadcast_for_keyserver(&keyclient)) {
+				log_msg(LLVL_ERROR, "Failed to find key server using UDP broadcast.");
+				success = false;
+				break;
+			}
 		}
 	} while (false);
 
diff --git a/global.h b/global.h
index ebc3b37..3d6541b 100644
--- a/global.h
+++ b/global.h
@@ -25,10 +25,9 @@
 #define __GLOBAL_H__
 
 /* Magic is the prefix of announcement packages. It is the MD5SUM over the
- * CLIENT_PSK_IDENTITY. This only changes when the protocol that is spoken
+ * string "luksrku v2". This only changes when the protocol that is spoken
  * changes. */
-#define CLIENT_PSK_IDENTITY									"luksrku v2"
-#define CLIENT_ANNOUNCE_MAGIC								{ 0x46, 0xf2, 0xf6, 0xc6, 0x63, 0x12, 0x2e, 0x00, 0xa0, 0x8a, 0xae, 0x42, 0x0c, 0x51, 0xf5, 0x65 }
+#define UDP_MESSAGE_MAGIC									(const uint8_t[]){ 0x46, 0xf2, 0xf6, 0xc6, 0x63, 0x12, 0x2e, 0x00, 0xa0, 0x8a, 0xae, 0x42, 0x0c, 0x51, 0xf5, 0x65 }
 
 /* Size in bytes of the PSK that is used for TLS */
 #define PSK_SIZE_BYTES										32
diff --git a/msg.h b/msg.h
index 46d8a80..c937df4 100644
--- a/msg.h
+++ b/msg.h
@@ -27,11 +27,15 @@
 #include <stdint.h>
 #include "global.h"
 
-struct announcement_t {
+struct udp_query_t {
 	uint8_t magic[16];
 	uint8_t host_uuid[16];
 } __attribute__ ((packed));
 
+struct udp_response_t {
+	uint8_t magic[16];
+} __attribute__ ((packed));
+
 struct msg_t {
 	uint8_t volume_uuid[16];
 	uint8_t luks_passphrase_raw[LUKS_PASSPHRASE_RAW_SIZE_BYTES];