[PATCH] better credential patch

Here is a small improvement. We check for the type of message we receive
and udevsend seems not to need all the credential setup stuff, the
kernel will fill it for us.

udevd now refuses to start as non root, cause it doesn't make any sense.

1 files changed, 19 insertions, 6 deletions

diff --git a/udevd.c b/udevd.c
index 366c227a3b..14616b9824 100644
--- a/udevd.c
+++ b/udevd.c
@@ -252,16 +252,19 @@ static void handle_msg(int sock)
 	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 @@ static void handle_msg(int sock)
 	} else {
 		msg_queue_insert(msg);
 	}
+	return;
+
+skip:
+	free(msg);
+	return;
 }
 
 static void sig_handler(int signum)
@@ -316,6 +324,11 @@ int main(int argc, char *argv[])
 
 	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 @@ int main(int argc, char *argv[])
 
 	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;
 	}