commit 916a27901de01446bcf57ecca4783f6cff493309 Author: Kevin Cernekee <cernekee@chromium.org> Date: Tue Dec 5 15:42:41 2017 -0800 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> diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c index 36e14b1..a34f314 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> @@ -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;