[PATCH 4/9] secid reconciliation-v04: Invoke LSM hook for outbound traffic

[Venkat Yekkirala <vyekkirala@trustedcs.com>]

Invoke the skb_flow_out LSM hook for outbound
traffic for secid reconciliation and flow control.

Signed-off-by: Venkat Yekkirala <vyekkirala@TrustedCS.com>
---
 net/netfilter/xt_CONNSECMARK.c |   72 ++++++++++++++++++++++++-------
 net/netfilter/xt_SECMARK.c     |   45 ++++++++++++++++++-
 2 files changed, 100 insertions(+), 17 deletions(-)

diff --git a/net/netfilter/xt_CONNSECMARK.c b/net/netfilter/xt_CONNSECMARK.c
index 4673862..cca4a0c 100644
--- a/net/netfilter/xt_CONNSECMARK.c
+++ b/net/netfilter/xt_CONNSECMARK.c
@@ -17,6 +17,8 @@
  */
 #include <linux/module.h>
 #include <linux/skbuff.h>
+#include <linux/security.h>
+#include <linux/netfilter_ipv6.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_CONNSECMARK.h>
 #include <net/netfilter/nf_conntrack_compat.h>
@@ -29,38 +31,78 @@ MODULE_DESCRIPTION("ip[6]tables CONNSECM
 MODULE_ALIAS("ipt_CONNSECMARK");
 MODULE_ALIAS("ip6t_CONNSECMARK");
 
+static inline int outbound(unsigned short family, unsigned int hooknum)
+{
+	if ((family == AF_INET &&
+		(hooknum == NF_IP_POST_ROUTING ||
+		 hooknum == NF_IP_LOCAL_OUT ||
+		 hooknum == NF_IP_FORWARD)) ||
+	    (family == AF_INET6 &&
+		(hooknum == NF_IP6_POST_ROUTING ||
+		 hooknum == NF_IP6_LOCAL_OUT ||
+		 hooknum == NF_IP6_FORWARD)))
+		return 1;
+	else
+		return 0;
+}
+
 /*
  * If the packet has a security mark and the connection does not, copy
  * the security mark from the packet to the connection.
  */
-static void secmark_save(struct sk_buff *skb)
+static void secmark_save(struct sk_buff *skb, unsigned int hooknum)
 {
 	if (skb->secmark) {
 		u32 *connsecmark;
 		enum ip_conntrack_info ctinfo;
 
 		connsecmark = nf_ct_get_secmark(skb, &ctinfo);
-		if (connsecmark && !*connsecmark)
+		if (connsecmark)
 			if (*connsecmark != skb->secmark)
 				*connsecmark = skb->secmark;
 	}
 }
 
 /*
- * If packet has no security mark, and the connection does, restore the
- * security mark from the connection to the packet.
+ * On the inbound, restore the security mark from the connection to the packet.
+ * On the outbound, filter based on the current secmark.
  */
-static void secmark_restore(struct sk_buff *skb)
+static unsigned int secmark_restore(struct sk_buff *skb, unsigned int hooknum,
+		   const struct net_device *in, unsigned short family)
 {
-	if (!skb->secmark) {
-		u32 *connsecmark;
-		enum ip_conntrack_info ctinfo;
-
-		connsecmark = nf_ct_get_secmark(skb, &ctinfo);
-		if (connsecmark && *connsecmark)
-			if (skb->secmark != *connsecmark)
-				skb->secmark = *connsecmark;
+	u32 *psecmark;
+	enum ip_conntrack_info ctinfo;
+
+	psecmark = nf_ct_get_secmark(skb, &ctinfo);
+
+	if (psecmark && *psecmark) {
+
+		/* Set secmark on inbound and filter it on outbound */
+		if (outbound(family, hooknum)) {
+			int err;
+
+			err = security_skb_flow_out(skb, *psecmark);
+			if (!err)
+				return NF_DROP;
+		} else
+			/* 
+			 * inbound:
+			 * loopback traffic should already be labeled
+			 * and any filtering on outbound should suffice
+			 */
+			if (in == &loopback_dev)
+				goto out;
+
+		/*
+		 * inbound or done with outbound check or no LSM hook
+		 * for outbound
+		 */
+		if (skb->secmark != *psecmark)
+			skb->secmark = *psecmark;
 	}
+
+out:
+	return XT_CONTINUE;
 }
 
 static unsigned int target(struct sk_buff **pskb, const struct net_device *in,
@@ -73,11 +115,11 @@ static unsigned int target(struct sk_buf
 
 	switch (info->mode) {
 	case CONNSECMARK_SAVE:
-		secmark_save(skb);
+		secmark_save(skb, hooknum);
 		break;
 
 	case CONNSECMARK_RESTORE:
-		secmark_restore(skb);
+		return secmark_restore(skb, hooknum, in, target->family);
 		break;
 
 	default:
diff --git a/net/netfilter/xt_SECMARK.c b/net/netfilter/xt_SECMARK.c
index add7521..9ecce66 100644
--- a/net/netfilter/xt_SECMARK.c
+++ b/net/netfilter/xt_SECMARK.c
@@ -15,8 +15,10 @@
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/selinux.h>
+#include <linux/security.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_SECMARK.h>
+#include <linux/netfilter_ipv6.h>
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("James Morris <jmorris@redhat.com>");
@@ -28,6 +30,21 @@ #define PFX "SECMARK: "
 
 static u8 mode;
 
+static inline int outbound(unsigned short family, unsigned int hooknum)
+{
+	if ((family == AF_INET &&
+		(hooknum == NF_IP_POST_ROUTING ||
+		 hooknum == NF_IP_LOCAL_OUT ||
+		 hooknum == NF_IP_FORWARD)) ||
+	    (family == AF_INET6 &&
+		(hooknum == NF_IP6_POST_ROUTING ||
+		 hooknum == NF_IP6_LOCAL_OUT ||
+		 hooknum == NF_IP6_FORWARD)))
+		return 1;
+	else
+		return 0;
+}
+
 static unsigned int target(struct sk_buff **pskb, const struct net_device *in,
 			   const struct net_device *out, unsigned int hooknum,
 			   const struct xt_target *target,
@@ -47,9 +64,33 @@ static unsigned int target(struct sk_buf
 		BUG();
 	}
 
-	if ((*pskb)->secmark != secmark)
-		(*pskb)->secmark = secmark;
+	if (secmark) {
+
+		/* Set secmark on inbound and filter it on outbound */
+		if (outbound(target->family, hooknum)) {
+			int err;
+
+			err = security_skb_flow_out(*pskb, secmark);
+			if (!err)
+				return NF_DROP;
+		} else
+			/*
+			 * inbound:
+			 * loopback traffic should already be labeled
+			 * and any filtering on outbound should suffice
+			 */
+			if (in == &loopback_dev)
+				goto out;
+
+		/* 
+		 * inbound or done with outbound check or no LSM hook
+		 * for outbound
+		 */
+		if ((*pskb)->secmark != secmark)
+			(*pskb)->secmark = secmark;
+	}
 
+out:
 	return XT_CONTINUE;
 }