From 7b1cbec91a51a8d8f1546935d942744b0f5a274e Mon Sep 17 00:00:00 2001
From: "kay.sievers@vrfy.org" <kay.sievers@vrfy.org>
Date: Thu, 12 Feb 2004 01:23:59 -0800
Subject: [PATCH] [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.
---
 udevd.c    | 25 +++++++++++++++++++------
 udevsend.c | 31 +------------------------------
 2 files changed, 20 insertions(+), 36 deletions(-)

diff --git a/udevd.c b/udevd.c
index 366c227a..14616b98 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;
 	}
 
diff --git a/udevsend.c b/udevsend.c
index b26c7444..b2fbcbbc 100644
--- a/udevsend.c
+++ b/udevsend.c
@@ -133,13 +133,6 @@ int main(int argc, char* argv[])
 	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 @@ int main(int argc, char* argv[])
 
 	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;
-- 
2.39.5