Commit 916a2790 authored Dec 05, 2017 by Kevin Cernekee Committed by Pablo Neira Ayuso Dec 06, 2017

netfilter: xt_osf: Add missing permission checks



The capability check in nfnetlink_rcv() verifies that the caller
has CAP_NET_ADMIN in the namespace that "owns" the netlink socket.
However, xt_osf_fingers is shared by all net namespaces on the
system.  An unprivileged user can create user and net namespaces
in which he holds CAP_NET_ADMIN to bypass the netlink_net_capable()
check:

    vpnns -- nfnl_osf -f /tmp/pf.os

    vpnns -- nfnl_osf -f /tmp/pf.os -d

These non-root operations successfully modify the systemwide OS
fingerprint list.  Add new capable() checks so that they can't.

Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent 6ab40511

net/netfilter/xt_osf.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -19,6 +19,7 @@
		#include <linux/module.h>
		#include <linux/kernel.h>

		#include <linux/capability.h>
		#include <linux/if.h>
		#include <linux/inetdevice.h>
		#include <linux/ip.h>
		@@ -70,6 +71,9 @@ static int xt_osf_add_callback(struct net net, struct sock ctnl,
		struct xt_osf_finger kf = NULL, sf;
		int err = 0;

		if (!capable(CAP_NET_ADMIN))
		return -EPERM;

		if (!osf_attrs[OSF_ATTR_FINGER])
		return -EINVAL;

		@@ -115,6 +119,9 @@ static int xt_osf_remove_callback(struct net net, struct sock ctnl,
		struct xt_osf_finger *sf;
		int err = -ENOENT;

		if (!capable(CAP_NET_ADMIN))
		return -EPERM;

		if (!osf_attrs[OSF_ATTR_FINGER])
		return -EINVAL;

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