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Subject[PATCH AUTOSEL for 4.4 27/36] netfilter: xt_osf: Add missing permission checks
Date
From: Kevin Cernekee <cernekee@chromium.org>

[ Upstream commit 916a27901de01446bcf57ecca4783f6cff493309 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
net/netfilter/xt_osf.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c
index df8801e02a32..7eae0d0af89a 100644
--- a/net/netfilter/xt_osf.c
+++ b/net/netfilter/xt_osf.c
@@ -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>
@@ -69,6 +70,9 @@ static int xt_osf_add_callback(struct sock *ctnl, struct sk_buff *skb,
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;

@@ -112,6 +116,9 @@ static int xt_osf_remove_callback(struct sock *ctnl, struct sk_buff *skb,
struct xt_osf_finger *sf;
int err = -ENOENT;

+ if (!capable(CAP_NET_ADMIN))
+ return -EPERM;
+
if (!osf_attrs[OSF_ATTR_FINGER])
return -EINVAL;

--
2.11.0
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