From: Neil Brown <neilb@suse.de>
Date: Mon, 19 Mar 2007 23:03:28 +0000 (+1100)
Subject: sm-notify - drop privileges before receiving packets from network.
X-Git-Tag: nfs-utils-1-1-0-rc1~37
X-Git-Url: https://git.decadent.org.uk/gitweb/?a=commitdiff_plain;h=7ed3ed034b9cda6c51ee7b506b7f845b6effb861;p=nfs-utils.git

sm-notify - drop privileges before receiving packets from network.

If /var/lib/nfs/sm is owned by non-root, setuid to that uid
after opening sockets but before receiving answers.
---

diff --git a/utils/statd/sm-notify.8 b/utils/statd/sm-notify.8
index a1c10c3..dd03b8d 100644
--- a/utils/statd/sm-notify.8
+++ b/utils/statd/sm-notify.8
@@ -50,6 +50,22 @@ in
 .BR /var/lib/nfs/state ,
 and updated by
 .BR sm-notify .
+.SS Security
+.B sm-notify
+has little need for root privileges and so drops them as soon as
+possible.
+It continues to need to make changes to the
+.B sm
+and
+.B sm.bak
+directories so to be able to drop privileges, these must be writable
+by a non-privileged user.  If these directories are owned by a
+non-root user,
+.B sm-notify
+will drop privilege to match that user once it has created sockets for
+sending out request (for which it needs privileged) but before it
+processes any reply (which is the most likely source of possible
+privilege abuse).
 .SH OPTIONS
 .TP
 .BI -m " failtime
diff --git a/utils/statd/sm-notify.c b/utils/statd/sm-notify.c
index 0090137..c62e7eb 100644
--- a/utils/statd/sm-notify.c
+++ b/utils/statd/sm-notify.c
@@ -81,6 +81,7 @@ static void		addr_set_port(nsm_address *, int);
 static int		host_lookup(int, const char *, nsm_address *);
 void			nsm_log(int fac, const char *fmt, ...);
 static int		record_pid();
+static void		drop_privs(void);
 
 static struct nsm_host *	hosts = NULL;
 
@@ -243,6 +244,8 @@ notify(void)
 	if (opt_max_retry)
 		failtime = time(NULL) + opt_max_retry;
 
+	drop_privs();
+
 	while (hosts) {
 		struct pollfd	pfd;
 		time_t		now = time(NULL);
@@ -711,3 +714,31 @@ static int record_pid()
 	close(fd);
 	return 1;
 }
+
+/* Drop privileges to match owner of state-directory
+ * (in case a reply triggers some unknown bug).
+ */
+static void drop_privs(void)
+{
+	struct stat st;
+
+	if (stat(_SM_DIR_PATH, &st) == -1 &&
+	    stat(_SM_BASE_PATH, &st) == -1) {
+		st.st_uid = 0;
+		st.st_gid = 0;
+	}
+
+	if (st.st_uid == 0) {
+		nsm_log(LOG_WARNING,
+			"sm-notify running as root. chown %s to choose different user\n",
+		    _SM_DIR_PATH);
+		return;
+	}
+
+	setgroups(0, NULL);
+	if (setgid(st.st_gid) == -1
+	    || setuid(st.st_uid) == -1) {
+		nsm_log(LOG_ERR, "Fail to drop privileges");
+		exit(1);
+	}
+}