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 c529161cdbf8..99f3146b7337 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;