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

In selinux_ip_postroute() we perform access checks based on the
packet's security label.  For locally generated traffic we get the
packet's security label from the associated socket; this works in all
cases except for TCP SYN-ACK packets.  In the case of SYN-ACK packet's
the correct security label is stored in the connection's request_sock,
not the server's socket.  Unfortunately, at the point in time when
selinux_ip_postroute() is called we can't query the request_sock
directly, we need to recreate the label using the same logic that
originally labeled the associated request_sock.

See the inline comments for more explanation.

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 2013-12-04 16:10:51 -05:00
parent 4718006827
commit 446b802437
1 changed files with 53 additions and 15 deletions
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68
security/selinux/hooks.c
View File

@ -3847,6 +3847,30 @@ static int selinux_skb_peerlbl_sid(struct sk_buff *skb, u16 family, u32 *sid)
return 0;
}
/**
* selinux_conn_sid - Determine the child socket label for a connection
* @sk_sid: the parent socket's SID
* @skb_sid: the packet's SID
* @conn_sid: the resulting connection SID
*
* If @skb_sid is valid then the user:role:type information from @sk_sid is
* combined with the MLS information from @skb_sid in order to create
* @conn_sid. If @skb_sid is not valid then then @conn_sid is simply a copy
* of @sk_sid. Returns zero on success, negative values on failure.
*
*/
static int selinux_conn_sid(u32 sk_sid, u32 skb_sid, u32 *conn_sid)
{
int err = 0;
if (skb_sid != SECSID_NULL)
err = security_sid_mls_copy(sk_sid, skb_sid, conn_sid);
else
*conn_sid = sk_sid;
return err;
}
/* socket security operations */
static int socket_sockcreate_sid(const struct task_security_struct *tsec,
@ -4453,7 +4477,7 @@ static int selinux_inet_conn_request(struct sock *sk, struct sk_buff *skb,
struct sk_security_struct *sksec = sk->sk_security;
int err;
u16 family = sk->sk_family;
u32 newsid;
u32 connsid;
u32 peersid;
/* handle mapped IPv4 packets arriving via IPv6 sockets */
@ -4463,16 +4487,11 @@ static int selinux_inet_conn_request(struct sock *sk, struct sk_buff *skb,
err = selinux_skb_peerlbl_sid(skb, family, &peersid);
if (err)
return err;
if (peersid == SECSID_NULL) {
req->secid = sksec->sid;
req->peer_secid = SECSID_NULL;
} else {
err = security_sid_mls_copy(sksec->sid, peersid, &newsid);
if (err)
return err;
req->secid = newsid;
req->peer_secid = peersid;
}
err = selinux_conn_sid(sksec->sid, peersid, &connsid);
if (err)
return err;
req->secid = connsid;
req->peer_secid = peersid;
return selinux_netlbl_inet_conn_request(req, family);
}
@ -4846,12 +4865,12 @@ static unsigned int selinux_ip_postroute(struct sk_buff *skb, int ifindex,
if (!secmark_active && !peerlbl_active)
return NF_ACCEPT;
/* if the packet is being forwarded then get the peer label from the
* packet itself; otherwise check to see if it is from a local
* application or the kernel, if from an application get the peer label
* from the sending socket, otherwise use the kernel's sid */
sk = skb->sk;
if (sk == NULL) {
/* Without an associated socket the packet is either coming
* from the kernel or it is being forwarded; check the packet
* to determine which and if the packet is being forwarded
* query the packet directly to determine the security label. */
if (skb->skb_iif) {
secmark_perm = PACKET__FORWARD_OUT;
if (selinux_skb_peerlbl_sid(skb, family, &peer_sid))
@ -4860,7 +4879,26 @@ static unsigned int selinux_ip_postroute(struct sk_buff *skb, int ifindex,
secmark_perm = PACKET__SEND;
peer_sid = SECINITSID_KERNEL;
}
} else if (sk->sk_state == TCP_LISTEN) {
/* Locally generated packet but the associated socket is in the
* listening state which means this is a SYN-ACK packet. In
* this particular case the correct security label is assigned
* to the connection/request_sock but unfortunately we can't
* query the request_sock as it isn't queued on the parent
* socket until after the SYN-ACK packet is sent; the only
* viable choice is to regenerate the label like we do in
* selinux_inet_conn_request(). See also selinux_ip_output()
* for similar problems. */
u32 skb_sid;
struct sk_security_struct *sksec = sk->sk_security;
if (selinux_skb_peerlbl_sid(skb, family, &skb_sid))
return NF_DROP;
if (selinux_conn_sid(sksec->sid, skb_sid, &peer_sid))
return NF_DROP;
secmark_perm = PACKET__SEND;
} else {
/* Locally generated packet, fetch the security label from the
* associated socket. */
struct sk_security_struct *sksec = sk->sk_security;
peer_sid = sksec->sid;
secmark_perm = PACKET__SEND;