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Commit d8395c87 authored by Paul Moore's avatar Paul Moore
Browse files

selinux: Better local/forward check in selinux_ip_postroute() 



It turns out that checking to see if skb->sk is NULL is not a very good
indicator of a forwarded packet as some locally generated packets also have
skb->sk set to NULL.  Fix this by not only checking the skb->sk field but also
the IP[6]CB(skb)->flags field for the IP[6]SKB_FORWARDED flag.  While we are
at it, we are calling selinux_parse_skb() much earlier than we really should
resulting in potentially wasted cycles parsing packets for information we
might no use; so shuffle the code around a bit to fix this.

Signed-off-by: default avatarPaul Moore <paul.moore@hp.com>
Acked-by: default avatarJames Morris <jmorris@namei.org>
parent 948a7243

security/selinux/hooks.c

+81 −45
Original line number Diff line number Diff line
@@ -4070,20 +4070,28 @@ static int selinux_sock_rcv_skb_iptables_compat(struct sock *sk, 
}



static int selinux_sock_rcv_skb_compat(struct sock *sk, struct sk_buff *skb,

				       struct avc_audit_data *ad,

				       u16 family, char *addrp)

				       u16 family)

{

	int err;

	struct sk_security_struct *sksec = sk->sk_security;

	u32 peer_sid;

	u32 sk_sid = sksec->sid;

	struct avc_audit_data ad;

	char *addrp;



	AVC_AUDIT_DATA_INIT(&ad, NET);

	ad.u.net.netif = skb->iif;

	ad.u.net.family = family;

	err = selinux_parse_skb(skb, &ad, &addrp, 1, NULL);

	if (err)

		return err;



	if (selinux_compat_net)

		err = selinux_sock_rcv_skb_iptables_compat(sk, skb, ad,

		err = selinux_sock_rcv_skb_iptables_compat(sk, skb, &ad,

							   family, addrp);

	else

		err = avc_has_perm(sk_sid, skb->secmark, SECCLASS_PACKET,

				   PACKET__RECV, ad);

				   PACKET__RECV, &ad);

	if (err)

		return err;
@@ -4092,12 +4100,12 @@ static int selinux_sock_rcv_skb_compat(struct sock *sk, struct sk_buff *skb, 
		if (err)

			return err;

		err = avc_has_perm(sk_sid, peer_sid,

				   SECCLASS_PEER, PEER__RECV, ad);

				   SECCLASS_PEER, PEER__RECV, &ad);

	} else {

		err = selinux_netlbl_sock_rcv_skb(sksec, skb, family, ad);

		err = selinux_netlbl_sock_rcv_skb(sksec, skb, family, &ad);

		if (err)

			return err;

		err = selinux_xfrm_sock_rcv_skb(sksec->sid, skb, ad);

		err = selinux_xfrm_sock_rcv_skb(sksec->sid, skb, &ad);

	}



	return err;
@@ -4111,6 +4119,8 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb) 
	u32 sk_sid = sksec->sid;

	struct avc_audit_data ad;

	char *addrp;

	u8 secmark_active;

	u8 peerlbl_active;



	if (family != PF_INET && family != PF_INET6)

		return 0;
@@ -4119,6 +4129,18 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb) 
	if (family == PF_INET6 && skb->protocol == htons(ETH_P_IP))

		family = PF_INET;



	/* If any sort of compatibility mode is enabled then handoff processing

	 * to the selinux_sock_rcv_skb_compat() function to deal with the

	 * special handling.  We do this in an attempt to keep this function

	 * as fast and as clean as possible. */

	if (selinux_compat_net || !selinux_policycap_netpeer)

		return selinux_sock_rcv_skb_compat(sk, skb, family);



	secmark_active = selinux_secmark_enabled();

	peerlbl_active = netlbl_enabled() || selinux_xfrm_enabled();

	if (!secmark_active && !peerlbl_active)

		return 0;



	AVC_AUDIT_DATA_INIT(&ad, NET);

	ad.u.net.netif = skb->iif;

	ad.u.net.family = family;
@@ -4126,15 +4148,7 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb) 
	if (err)

		return err;



	/* If any sort of compatibility mode is enabled then handoff processing

	 * to the selinux_sock_rcv_skb_compat() function to deal with the

	 * special handling.  We do this in an attempt to keep this function

	 * as fast and as clean as possible. */

	if (selinux_compat_net || !selinux_policycap_netpeer)

		return selinux_sock_rcv_skb_compat(sk, skb, &ad,

						   family, addrp);



	if (netlbl_enabled() || selinux_xfrm_enabled()) {

	if (peerlbl_active) {

		u32 peer_sid;



		err = selinux_skb_peerlbl_sid(skb, family, &peer_sid);
@@ -4148,7 +4162,7 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb) 
				   PEER__RECV, &ad);

	}



	if (selinux_secmark_enabled()) {

	if (secmark_active) {

		err = avc_has_perm(sk_sid, skb->secmark, SECCLASS_PACKET,

				   PACKET__RECV, &ad);

		if (err)
@@ -4396,15 +4410,15 @@ static unsigned int selinux_ip_forward(struct sk_buff *skb, int ifindex, 
	if (!secmark_active && !peerlbl_active)

		return NF_ACCEPT;



	if (selinux_skb_peerlbl_sid(skb, family, &peer_sid) != 0)

		return NF_DROP;



	AVC_AUDIT_DATA_INIT(&ad, NET);

	ad.u.net.netif = ifindex;

	ad.u.net.family = family;

	if (selinux_parse_skb(skb, &ad, &addrp, 1, NULL) != 0)

		return NF_DROP;



	if (selinux_skb_peerlbl_sid(skb, family, &peer_sid) != 0)

		return NF_DROP;



	if (peerlbl_active)

		if (selinux_inet_sys_rcv_skb(ifindex, addrp, family,

					     peer_sid, &ad) != 0)
@@ -4505,30 +4519,36 @@ static int selinux_ip_postroute_iptables_compat(struct sock *sk, 


static unsigned int selinux_ip_postroute_compat(struct sk_buff *skb,

						int ifindex,

						struct avc_audit_data *ad,

						u16 family,

						char *addrp,

						u8 proto)

						u16 family)

{

	struct sock *sk = skb->sk;

	struct sk_security_struct *sksec;

	struct avc_audit_data ad;

	char *addrp;

	u8 proto;



	if (sk == NULL)

		return NF_ACCEPT;

	sksec = sk->sk_security;



	AVC_AUDIT_DATA_INIT(&ad, NET);

	ad.u.net.netif = ifindex;

	ad.u.net.family = family;

	if (selinux_parse_skb(skb, &ad, &addrp, 0, &proto))

		return NF_DROP;



	if (selinux_compat_net) {

		if (selinux_ip_postroute_iptables_compat(skb->sk, ifindex,

							 ad, family, addrp))

							 &ad, family, addrp))

			return NF_DROP;

	} else {

		if (avc_has_perm(sksec->sid, skb->secmark,

				 SECCLASS_PACKET, PACKET__SEND, ad))

				 SECCLASS_PACKET, PACKET__SEND, &ad))

			return NF_DROP;

	}



	if (selinux_policycap_netpeer)

		if (selinux_xfrm_postroute_last(sksec->sid, skb, ad, proto))

		if (selinux_xfrm_postroute_last(sksec->sid, skb, &ad, proto))

			return NF_DROP;



	return NF_ACCEPT;
@@ -4542,23 +4562,15 @@ static unsigned int selinux_ip_postroute(struct sk_buff *skb, int ifindex, 
	struct sock *sk;

	struct avc_audit_data ad;

	char *addrp;

	u8 proto;

	u8 secmark_active;

	u8 peerlbl_active;



	AVC_AUDIT_DATA_INIT(&ad, NET);

	ad.u.net.netif = ifindex;

	ad.u.net.family = family;

	if (selinux_parse_skb(skb, &ad, &addrp, 0, &proto))

		return NF_DROP;



	/* If any sort of compatibility mode is enabled then handoff processing

	 * to the selinux_ip_postroute_compat() function to deal with the

	 * special handling.  We do this in an attempt to keep this function

	 * as fast and as clean as possible. */

	if (selinux_compat_net || !selinux_policycap_netpeer)

		return selinux_ip_postroute_compat(skb, ifindex, &ad,

						   family, addrp, proto);

		return selinux_ip_postroute_compat(skb, ifindex, family);



	/* If skb->dst->xfrm is non-NULL then the packet is undergoing an IPsec

	 * packet transformation so allow the packet to pass without any checks
@@ -4574,21 +4586,45 @@ static unsigned int selinux_ip_postroute(struct sk_buff *skb, int ifindex, 
	if (!secmark_active && !peerlbl_active)

		return NF_ACCEPT;



	/* if the packet is locally generated (skb->sk != NULL) then use the

	 * socket's label as the peer label, otherwise the packet is being

	 * forwarded through this system and we need to fetch the peer label

	 * directly from the packet */

	/* 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) {

		struct sk_security_struct *sksec = sk->sk_security;

		peer_sid = sksec->sid;

	if (sk == NULL) {

		switch (family) {

		case PF_INET:

			if (IPCB(skb)->flags & IPSKB_FORWARDED)

				secmark_perm = PACKET__FORWARD_OUT;

			else

				secmark_perm = PACKET__SEND;

	} else {

			break;

		case PF_INET6:

			if (IP6CB(skb)->flags & IP6SKB_FORWARDED)

				secmark_perm = PACKET__FORWARD_OUT;

			else

				secmark_perm = PACKET__SEND;

			break;

		default:

			return NF_DROP;

		}

		if (secmark_perm == PACKET__FORWARD_OUT) {

			if (selinux_skb_peerlbl_sid(skb, family, &peer_sid))

				return NF_DROP;

		secmark_perm = PACKET__FORWARD_OUT;

		} else

			peer_sid = SECINITSID_KERNEL;

	} else {

		struct sk_security_struct *sksec = sk->sk_security;

		peer_sid = sksec->sid;

		secmark_perm = PACKET__SEND;

	}



	AVC_AUDIT_DATA_INIT(&ad, NET);

	ad.u.net.netif = ifindex;

	ad.u.net.family = family;

	if (selinux_parse_skb(skb, &ad, &addrp, 0, NULL))

		return NF_DROP;



	if (secmark_active)

		if (avc_has_perm(peer_sid, skb->secmark,

				 SECCLASS_PACKET, secmark_perm, &ad))