| Message ID | 20180131130451.22182-2-kleber.souza@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [SRU,T,X,A,B,1/1] netfilter: xt_osf: Add missing permission checks | expand |
On 31.01.2018 14:04, Kleber Sacilotto de Souza wrote: > From: Kevin Cernekee <cernekee@chromium.org> > > 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> > > CVE-2017-17450 > (cherry picked from commit 916a27901de01446bcf57ecca4783f6cff493309) > Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.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 647d989a01e6..de49ff18963a 100644 > --- a/net/netfilter/xt_osf.c > +++ b/net/netfilter/xt_osf.c > @@ -20,6 +20,7 @@ > #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 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; > > @@ -113,6 +117,9 @@ 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; > >
diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c index 647d989a01e6..de49ff18963a 100644 --- a/net/netfilter/xt_osf.c +++ b/net/netfilter/xt_osf.c @@ -20,6 +20,7 @@ #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 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; @@ -113,6 +117,9 @@ 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;