udevd - client access authorization

diff -Nru a/udevd.c b/udevd.c
@@ -216,6 +216,11 @@
 {
 	struct hotplug_msg *msg;
 	int retval;
+	struct msghdr smsg;
+	struct cmsghdr *cmsg;
+	struct iovec iov;
+	struct ucred *cred;
+	char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 
 	msg = msg_create();
 	if (msg == NULL) {

@@ -223,13 +228,30 @@
 		return;
 	}
 
-	retval = recv(sock, msg, sizeof(struct hotplug_msg), 0);
+	iov.iov_base = msg;
+	iov.iov_len = sizeof(struct hotplug_msg);
+
+	memset(&smsg, 0x00, sizeof(struct msghdr));
+	smsg.msg_iov = &iov;
+	smsg.msg_iovlen = 1;
+	smsg.msg_control = cred_msg;
+	smsg.msg_controllen = sizeof(cred_msg);
+
+	retval = recvmsg(sock, &smsg, 0);
 	if (retval <  0) {
 		if (errno != EINTR)
 			dbg("unable to receive message");
 		return;
 	}
-	
+	cmsg = CMSG_FIRSTHDR(&smsg);
+	cred = (struct ucred *) CMSG_DATA(cmsg);
+
+	if (cred->uid != 0) {
+		dbg("sender uid=%i, message ignored", cred->uid);
+		free(msg);
+		return;
+	}
+
 	if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 		dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 		free(msg);

@@ -283,6 +305,7 @@
 	struct sockaddr_un saddr;
 	socklen_t addrlen;
 	int retval;
+	const int on = 1;
 	struct sigaction act;
 
 	init_logging("udevd");

@@ -317,6 +340,9 @@
 		dbg("bind failed\n");
 		goto exit;
 	}
+
+	/* enable receiving of the sender credentials */
+	setsockopt(ssock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 
 	while (1) {
 		handle_msg(ssock);

diff -Nru a/udevsend.c b/udevsend.c
@@ -114,7 +114,7 @@
 
 int main(int argc, char* argv[])
 {
-	struct hotplug_msg message;
+	struct hotplug_msg msg;
 	char *action;
 	char *devpath;
 	char *subsystem;

@@ -128,6 +128,13 @@
 	struct sockaddr_un saddr;
 	socklen_t addrlen;
 	int started_daemon = 0;
+	struct iovec iov;
+	struct msghdr smsg;
+	char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
+	struct cmsghdr *cmsg;
+	struct ucred *cred;
+	
+
 
 #ifdef DEBUG
 	init_logging("udevsend");

@@ -169,12 +176,34 @@
 	strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 	addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 
-	size = build_hotplugmsg(&message, action, devpath, subsystem, seq);
-	
+	size = build_hotplugmsg(&msg, action, devpath, subsystem, seq);
+
+	/* prepare message with credentials to authenticate ourself */
+	iov.iov_base = &msg;
+	iov.iov_len = size;
+
+	smsg.msg_name = &saddr;
+	smsg.msg_namelen = addrlen;
+	smsg.msg_iov = &iov;
+	smsg.msg_iovlen = 1;
+	smsg.msg_control = cred_msg;
+	smsg.msg_controllen = CMSG_LEN(sizeof(struct ucred));;
+	smsg.msg_flags = 0;
+
+	cmsg = CMSG_FIRSTHDR(&smsg);
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_CREDENTIALS;
+	cmsg->cmsg_len = sizeof(cred_msg);
+	cred = (struct ucred *) CMSG_DATA(cmsg);
+	cred->uid = getuid();
+	cred->gid = getgid();
+	cred->pid = getpid();
+	cred->pid = getpid();
+
 	/* If we can't send, try to start daemon and resend message */
 	loop = UDEVSEND_CONNECT_RETRY;
 	while (loop--) {
-		retval = sendto(sock, &message, size, 0, (struct sockaddr *)&saddr, addrlen);
+		retval = sendmsg(sock, &smsg, 0);
 		if (retval != -1) {
 			retval = 0;
 			goto close_and_exit;

diff -Nru a/udevd.c b/udevd.c
@@ -252,16 +252,19 @@
 	cmsg = CMSG_FIRSTHDR(&smsg);
 	cred = (struct ucred *) CMSG_DATA(cmsg);
 
+	if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
+		dbg("no sender credentials received, message ignored");
+		goto skip;
+	}
+
 	if (cred->uid != 0) {
 		dbg("sender uid=%i, message ignored", cred->uid);
-		free(msg);
-		return;
+		goto skip;
 	}
 
 	if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 		dbg("message magic '%s' doesn't match, ignore it", msg->magic);
-		free(msg);
-		return;
+		goto skip;
 	}
 
 	/* if no seqnum is given, we move straight to exec queue */

@@ -271,6 +274,11 @@
 	} else {
 		msg_queue_insert(msg);
 	}
+	return;
+
+skip:
+	free(msg);
+	return;
 }
 
 static void sig_handler(int signum)

@@ -316,6 +324,11 @@
 
 	init_logging("udevd");
 
+	if (getuid() != 0) {
+		dbg("need to be root, exit");
+		exit(1);
+	}
+
 	/* set signal handler */
 	act.sa_handler = sig_handler;
 	sigemptyset (&act.sa_mask);

@@ -336,14 +349,14 @@
 
 	ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 	if (ssock == -1) {
-		dbg("error getting socket");
+		dbg("error getting socket, exit");
 		exit(1);
 	}
 
 	/* the bind takes care of ensuring only one copy running */
 	retval = bind(ssock, (struct sockaddr *) &saddr, addrlen);
 	if (retval < 0) {
-		dbg("bind failed\n");
+		dbg("bind failed, exit");
 		goto exit;
 	}
 

diff -Nru a/udevsend.c b/udevsend.c
@@ -133,13 +133,6 @@
 	struct sockaddr_un saddr;
 	socklen_t addrlen;
 	int started_daemon = 0;
-	struct iovec iov;
-	struct msghdr smsg;
-	char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
-	struct cmsghdr *cmsg;
-	struct ucred *cred;
-	
-
 
 #ifdef DEBUG
 	init_logging("udevsend");

@@ -183,32 +176,10 @@
 
 	size = build_hotplugmsg(&msg, action, devpath, subsystem, seq);
 
-	/* prepare message with credentials to authenticate ourself */
-	iov.iov_base = &msg;
-	iov.iov_len = size;
-
-	smsg.msg_name = &saddr;
-	smsg.msg_namelen = addrlen;
-	smsg.msg_iov = &iov;
-	smsg.msg_iovlen = 1;
-	smsg.msg_control = cred_msg;
-	smsg.msg_controllen = CMSG_LEN(sizeof(struct ucred));;
-	smsg.msg_flags = 0;
-
-	cmsg = CMSG_FIRSTHDR(&smsg);
-	cmsg->cmsg_level = SOL_SOCKET;
-	cmsg->cmsg_type = SCM_CREDENTIALS;
-	cmsg->cmsg_len = sizeof(cred_msg);
-	cred = (struct ucred *) CMSG_DATA(cmsg);
-	cred->uid = getuid();
-	cred->gid = getgid();
-	cred->pid = getpid();
-	cred->pid = getpid();
-
 	/* If we can't send, try to start daemon and resend message */
 	loop = UDEVSEND_CONNECT_RETRY;
 	while (loop--) {
-		retval = sendmsg(sock, &smsg, 0);
+		retval = sendto(sock, &msg, size, 0, (struct sockaddr *)&saddr, addrlen);
 		if (retval != -1) {
 			retval = 0;
 			goto close_and_exit;