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selinux: Better local/forward check in selinux_ip_postroute()
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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: Paul Moore <[email protected]>
Acked-by: James Morris <[email protected]>
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@pcmoore
pcmoore committed Oct 10, 2008
1 parent 948a724 commit d8395c8
Showing 1 changed file with 81 additions and 45 deletions.
126 changes: 81 additions & 45 deletions security/selinux/hooks.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -4119,22 +4129,26 @@ 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;
err = selinux_parse_skb(skb, &ad, &addrp, 1, NULL);
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);
Expand All @@ -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)
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
Expand All @@ -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
Expand All @@ -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) {
if (sk == NULL) {
switch (family) {
case PF_INET:
if (IPCB(skb)->flags & IPSKB_FORWARDED)
secmark_perm = PACKET__FORWARD_OUT;
else
secmark_perm = PACKET__SEND;
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;
} else
peer_sid = SECINITSID_KERNEL;
} else {
struct sk_security_struct *sksec = sk->sk_security;
peer_sid = sksec->sid;
secmark_perm = PACKET__SEND;
} else {
if (selinux_skb_peerlbl_sid(skb, family, &peer_sid))
return NF_DROP;
secmark_perm = PACKET__FORWARD_OUT;
}

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))
Expand Down

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