package/lxc: fix CVE-2022-47952

lxc-user-nic in lxc through 5.0.1 is installed setuid root, and may
allow local users to infer whether any file exists, even within a
protected directory tree, because "Failed to open" often indicates that
a file does not exist, whereas "does not refer to a network namespace
path" often indicates that a file exists. NOTE: this is different from
CVE-2018-6556 because the CVE-2018-6556 fix design was based on the
premise that "we will report back to the user that the open() failed but
the user has no way of knowing why it failed"; however, in many
realistic cases, there are no plausible reasons for failing except that
the file does not exist.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/lxc/0005-Patching-an-incoming-CVE-CVE-2022-47952.patch

@@ -0,0 +1,73 @@
+From 1b0469530d7a38b8f8990e114b52530d1bf7f3b8 Mon Sep 17 00:00:00 2001
+From: Maher Azzouzi <maherazz04@gmail.com>
+Date: Sun, 25 Dec 2022 13:50:25 +0100
+Subject: [PATCH] Patching an incoming CVE (CVE-2022-47952)
+
+lxc-user-nic in lxc through 5.0.1 is installed setuid root, and may
+allow local users to infer whether any file exists, even within a
+protected directory tree, because "Failed to open" often indicates
+that a file does not exist, whereas "does not refer to a network
+namespace path" often indicates that a file exists. NOTE: this is
+different from CVE-2018-6556 because the CVE-2018-6556 fix design was
+based on the premise that "we will report back to the user that the
+open() failed but the user has no way of knowing why it failed";
+however, in many realistic cases, there are no plausible reasons for
+failing except that the file does not exist.
+
+PoC:
+> % ls /l
+> ls: cannot open directory '/l': Permission denied
+> % /usr/lib/x86_64-linux-gnu/lxc/lxc-user-nic delete lol lol /l/h/tt h h
+> cmd/lxc_user_nic.c: 1096: main: Failed to open "/l/h/tt" <----- file does not exist.
+> % /usr/lib/x86_64-linux-gnu/lxc/lxc-user-nic delete lol lol /l/h/t h h
+> cmd/lxc_user_nic.c: 1101: main: Path "/l/h/t" does not refer to a network namespace path <---- file exist!
+
+Signed-off-by: MaherAzzouzi <maherazz04@gmail.com>
+Acked-by: Serge Hallyn <serge@hallyn.com>
+
+[Retrieved from:
+https://github.com/lxc/lxc/commit/1b0469530d7a38b8f8990e114b52530d1bf7f3b8]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ src/lxc/cmd/lxc_user_nic.c | 15 ++++++---------
+ 1 file changed, 6 insertions(+), 9 deletions(-)
+
+diff --git a/src/lxc/cmd/lxc_user_nic.c b/src/lxc/cmd/lxc_user_nic.c
+index a91e2259d5..69bc6f17d1 100644
+--- a/src/lxc/cmd/lxc_user_nic.c
++++ b/src/lxc/cmd/lxc_user_nic.c
+@@ -1085,20 +1085,17 @@ int main(int argc, char *argv[])
+ 	} else if (request == LXC_USERNIC_DELETE) {
+ 		char opath[LXC_PROC_PID_FD_LEN];
+ 
+-		/* Open the path with O_PATH which will not trigger an actual
+-		 * open(). Don't report an errno to the caller to not leak
+-		 * information whether the path exists or not.
+-		 * When stracing setuid is stripped so this is not a concern
+-		 * either.
+-		 */
++		// Keep in mind CVE-2022-47952: It's crucial not to leak any
++		// information whether open() succeeded of failed.
++
+ 		netns_fd = open(args.pid, O_PATH | O_CLOEXEC);
+ 		if (netns_fd < 0) {
+-			usernic_error("Failed to open \"%s\"\n", args.pid);
++			usernic_error("Failed while opening netns file for \"%s\"\n", args.pid);
+ 			_exit(EXIT_FAILURE);
+ 		}
+ 
+ 		if (!fhas_fs_type(netns_fd, NSFS_MAGIC)) {
+-			usernic_error("Path \"%s\" does not refer to a network namespace path\n", args.pid);
++			usernic_error("Failed while opening netns file for \"%s\"\n", args.pid);
+ 			close(netns_fd);
+ 			_exit(EXIT_FAILURE);
+ 		}
+@@ -1112,7 +1109,7 @@ int main(int argc, char *argv[])
+ 		/* Now get an fd that we can use in setns() calls. */
+ 		ret = open(opath, O_RDONLY | O_CLOEXEC);
+ 		if (ret < 0) {
+-			CMD_SYSERROR("Failed to open \"%s\"\n", args.pid);
++			CMD_SYSERROR("Failed while opening netns file for \"%s\"\n", args.pid);
+ 			close(netns_fd);
+ 			_exit(EXIT_FAILURE);
+ 		}

package/lxc/lxc.mk

@@ -12,6 +12,9 @@ LXC_CPE_ID_VENDOR = linuxcontainers
 LXC_DEPENDENCIES = host-pkgconf
 LXC_INSTALL_STAGING = YES
 
+# 0005-Patching-an-incoming-CVE-CVE-2022-47952.patch
+LXC_IGNORE_CVES += CVE-2022-47952
+
 LXC_CONF_OPTS = \
 	--disable-apparmor \
 	--disable-examples \