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selinux: handle TCP SYN-ACK packets correctly in selinux_ip_output()

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In selinux_ip_output() we always label packets based on the parent
socket.  While this approach works in almost all cases, it doesn't
work in the case of TCP SYN-ACK packets when the correct label is not
the label of the parent socket, but rather the label of the larval
socket represented by the request_sock struct.

Unfortunately, since the request_sock isn't queued on the parent
socket until *after* the SYN-ACK packet is sent, we can't lookup the
request_sock to determine the correct label for the packet; at this
point in time the best we can do is simply pass/NF_ACCEPT the packet.
It must be said that simply passing the packet without any explicit
labeling action, while far from ideal, is not terrible as the SYN-ACK
packet will inherit any IP option based labeling from the initial
connection request so the label *should* be correct and all our
access controls remain in place so we shouldn't have to worry about
information leaks.

Reported-by: Janak Desai <Janak.Desai@gtri.gatech.edu>
Tested-by: Janak Desai <Janak.Desai@gtri.gatech.edu>
Cc: stable@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
This commit is contained in:
Paul Moore 2013-12-03 11:14:04 -05:00
parent 8e645c345a
commit da2ea0d056
1 changed files with 23 additions and 2 deletions
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25
security/selinux/hooks.c
View file

@ -53,6 +53,7 @@
#include <net/ip.h> /* for local_port_range[] */
#include <net/sock.h>
#include <net/tcp.h> /* struct or_callable used in sock_rcv_skb */
#include <net/inet_connection_sock.h>
#include <net/net_namespace.h>
#include <net/netlabel.h>
#include <linux/uaccess.h>
@ -4731,6 +4732,7 @@ static unsigned int selinux_ipv6_forward(unsigned int hooknum,
static unsigned int selinux_ip_output(struct sk_buff *skb,
u16 family)
{
struct sock *sk;
u32 sid;
if (!netlbl_enabled())
@ -4739,8 +4741,27 @@ static unsigned int selinux_ip_output(struct sk_buff *skb,
/* we do this in the LOCAL_OUT path and not the POST_ROUTING path
* because we want to make sure we apply the necessary labeling
* before IPsec is applied so we can leverage AH protection */
if (skb->sk) {
struct sk_security_struct *sksec = skb->sk->sk_security;
sk = skb->sk;
if (sk) {
struct sk_security_struct *sksec;
if (sk->sk_state == TCP_LISTEN)
/* if the socket is the listening state then this
* packet is a SYN-ACK packet which means it needs to
* be labeled based on the connection/request_sock and
* not the parent socket. unfortunately, we can't
* lookup the request_sock yet as it isn't queued on
* the parent socket until after the SYN-ACK is sent.
* the "solution" is to simply pass the packet as-is
* as any IP option based labeling should be copied
* from the initial connection request (in the IP
* layer). it is far from ideal, but until we get a
* security label in the packet itself this is the
* best we can do. */
return NF_ACCEPT;
/* standard practice, label using the parent socket */
sksec = sk->sk_security;
sid = sksec->sid;
} else
sid = SECINITSID_KERNEL;