[MLSXFRM]: Flow based matching of xfrm policy and state

This implements a seemless mechanism for xfrm policy selection and
state matching based on the flow sid. This also includes the necessary
SELinux enforcement pieces.

Signed-off-by: Venkat Yekkirala <vyekkirala@TrustedCS.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/security.h

@@ -31,6 +31,7 @@
 #include <linux/msg.h>
 #include <linux/sched.h>
 #include <linux/key.h>
+#include <linux/xfrm.h>
 
 struct ctl_table;
 
@@ -825,9 +826,8 @@ struct swap_info_struct;
  *	used by the XFRM system.
  *	@sec_ctx contains the security context information being provided by
  *	the user-level policy update program (e.g., setkey).
- *	Allocate a security structure to the xp->security field.
- *	The security field is initialized to NULL when the xfrm_policy is
- *	allocated.
+ *	Allocate a security structure to the xp->security field; the security
+ *	field is initialized to NULL when the xfrm_policy is allocated.
  *	Return 0 if operation was successful (memory to allocate, legal context)
  * @xfrm_policy_clone_security:
  *	@old contains an existing xfrm_policy in the SPD.
@@ -846,9 +846,14 @@ struct swap_info_struct;
  *	Database by the XFRM system.
  *	@sec_ctx contains the security context information being provided by
  *	the user-level SA generation program (e.g., setkey or racoon).
- *	Allocate a security structure to the x->security field.  The
- *	security field is initialized to NULL when the xfrm_state is
- *	allocated.
+ *	@polsec contains the security context information associated with a xfrm
+ *	policy rule from which to take the base context. polsec must be NULL
+ *	when sec_ctx is specified.
+ *	@secid contains the secid from which to take the mls portion of the context.
+ *	Allocate a security structure to the x->security field; the security
+ *	field is initialized to NULL when the xfrm_state is allocated. Set the
+ *	context to correspond to either sec_ctx or polsec, with the mls portion
+ *	taken from secid in the latter case.
  *	Return 0 if operation was successful (memory to allocate, legal context).
  * @xfrm_state_free_security:
  *	@x contains the xfrm_state.
@@ -859,13 +864,26 @@ struct swap_info_struct;
  * @xfrm_policy_lookup:
  *	@xp contains the xfrm_policy for which the access control is being
  *	checked.
- *	@sk_sid contains the sock security label that is used to authorize
+ *	@fl_secid contains the flow security label that is used to authorize
  *	access to the policy xp.
  *	@dir contains the direction of the flow (input or output).
- *	Check permission when a sock selects a xfrm_policy for processing
+ *	Check permission when a flow selects a xfrm_policy for processing
  *	XFRMs on a packet.  The hook is called when selecting either a
  *	per-socket policy or a generic xfrm policy.
  *	Return 0 if permission is granted.
+ * @xfrm_state_pol_flow_match:
+ *	@x contains the state to match.
+ *	@xp contains the policy to check for a match.
+ *	@fl contains the flow to check for a match.
+ *	Return 1 if there is a match.
+ * @xfrm_flow_state_match:
+ *	@fl contains the flow key to match.
+ *	@xfrm points to the xfrm_state to match.
+ *	Return 1 if there is a match.
+ * @xfrm_decode_session:
+ *	@skb points to skb to decode.
+ *	@fl points to the flow key to set.
+ *	Return 0 if successful decoding.
  *
  * Security hooks affecting all Key Management operations
  *
@@ -1343,10 +1361,16 @@ struct security_operations {
 	int (*xfrm_policy_clone_security) (struct xfrm_policy *old, struct xfrm_policy *new);
 	void (*xfrm_policy_free_security) (struct xfrm_policy *xp);
 	int (*xfrm_policy_delete_security) (struct xfrm_policy *xp);
-	int (*xfrm_state_alloc_security) (struct xfrm_state *x, struct xfrm_user_sec_ctx *sec_ctx);
+	int (*xfrm_state_alloc_security) (struct xfrm_state *x,
+		struct xfrm_user_sec_ctx *sec_ctx, struct xfrm_sec_ctx *polsec,
+		u32 secid);
 	void (*xfrm_state_free_security) (struct xfrm_state *x);
 	int (*xfrm_state_delete_security) (struct xfrm_state *x);
-	int (*xfrm_policy_lookup)(struct xfrm_policy *xp, u32 sk_sid, u8 dir);
+	int (*xfrm_policy_lookup)(struct xfrm_policy *xp, u32 fl_secid, u8 dir);
+	int (*xfrm_state_pol_flow_match)(struct xfrm_state *x,
+			struct xfrm_policy *xp, struct flowi *fl);
+	int (*xfrm_flow_state_match)(struct flowi *fl, struct xfrm_state *xfrm);
+	int (*xfrm_decode_session)(struct sk_buff *skb, struct flowi *fl);
 #endif	/* CONFIG_SECURITY_NETWORK_XFRM */
 
 	/* key management security hooks */
@@ -3050,9 +3074,18 @@ static inline int security_xfrm_policy_delete(struct xfrm_policy *xp)
 	return security_ops->xfrm_policy_delete_security(xp);
 }
 
-static inline int security_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *sec_ctx)
+static inline int security_xfrm_state_alloc(struct xfrm_state *x,
+			struct xfrm_user_sec_ctx *sec_ctx)
+{
+	return security_ops->xfrm_state_alloc_security(x, sec_ctx, NULL, 0);
+}
+
+static inline int security_xfrm_state_alloc_acquire(struct xfrm_state *x,
+				struct xfrm_sec_ctx *polsec, u32 secid)
 {
-	return security_ops->xfrm_state_alloc_security(x, sec_ctx);
+	if (!polsec)
+		return 0;
+	return security_ops->xfrm_state_alloc_security(x, NULL, polsec, secid);
 }
 
 static inline int security_xfrm_state_delete(struct xfrm_state *x)
@@ -3065,9 +3098,25 @@ static inline void security_xfrm_state_free(struct xfrm_state *x)
 	security_ops->xfrm_state_free_security(x);
 }
 
-static inline int security_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir)
+static inline int security_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, u8 dir)
+{
+	return security_ops->xfrm_policy_lookup(xp, fl_secid, dir);
+}
+
+static inline int security_xfrm_state_pol_flow_match(struct xfrm_state *x,
+			struct xfrm_policy *xp, struct flowi *fl)
+{
+	return security_ops->xfrm_state_pol_flow_match(x, xp, fl);
+}
+
+static inline int security_xfrm_flow_state_match(struct flowi *fl, struct xfrm_state *xfrm)
+{
+	return security_ops->xfrm_flow_state_match(fl, xfrm);
+}
+
+static inline int security_xfrm_decode_session(struct sk_buff *skb, struct flowi *fl)
 {
-	return security_ops->xfrm_policy_lookup(xp, sk_sid, dir);
+	return security_ops->xfrm_decode_session(skb, fl);
 }
 #else	/* CONFIG_SECURITY_NETWORK_XFRM */
 static inline int security_xfrm_policy_alloc(struct xfrm_policy *xp, struct xfrm_user_sec_ctx *sec_ctx)
@@ -3089,7 +3138,14 @@ static inline int security_xfrm_policy_delete(struct xfrm_policy *xp)
 	return 0;
 }
 
-static inline int security_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *sec_ctx)
+static inline int security_xfrm_state_alloc(struct xfrm_state *x,
+					struct xfrm_user_sec_ctx *sec_ctx)
+{
+	return 0;
+}
+
+static inline int security_xfrm_state_alloc_acquire(struct xfrm_state *x,
+					struct xfrm_sec_ctx *polsec, u32 secid)
 {
 	return 0;
 }
@@ -3103,10 +3159,28 @@ static inline int security_xfrm_state_delete(struct xfrm_state *x)
 	return 0;
 }
 
-static inline int security_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir)
+static inline int security_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, u8 dir)
 {
 	return 0;
 }
+
+static inline int security_xfrm_state_pol_flow_match(struct xfrm_state *x,
+			struct xfrm_policy *xp, struct flowi *fl)
+{
+	return 1;
+}
+
+static inline int security_xfrm_flow_state_match(struct flowi *fl,
+                                struct xfrm_state *xfrm)
+{
+	return 1;
+}
+
+static inline int security_xfrm_decode_session(struct sk_buff *skb, struct flowi *fl)
+{
+	return 0;
+}
+
 #endif	/* CONFIG_SECURITY_NETWORK_XFRM */
 
 #ifdef CONFIG_KEYS

include/net/flow.h

@@ -86,10 +86,10 @@ struct flowi {
 #define FLOW_DIR_FWD	2
 
 struct sock;
-typedef void (*flow_resolve_t)(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
+typedef void (*flow_resolve_t)(struct flowi *key, u16 family, u8 dir,
 			       void **objp, atomic_t **obj_refp);
 
-extern void *flow_cache_lookup(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
+extern void *flow_cache_lookup(struct flowi *key, u16 family, u8 dir,
 	 		       flow_resolve_t resolver);
 extern void flow_cache_flush(void);
 extern atomic_t flow_cache_genid;

net/core/flow.c

@@ -32,7 +32,6 @@ struct flow_cache_entry {
 	u8			dir;
 	struct flowi		key;
 	u32			genid;
-	u32			sk_sid;
 	void			*object;
 	atomic_t		*object_ref;
 };
@@ -165,7 +164,7 @@ static int flow_key_compare(struct flowi *key1, struct flowi *key2)
 	return 0;
 }
 
-void *flow_cache_lookup(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
+void *flow_cache_lookup(struct flowi *key, u16 family, u8 dir,
 			flow_resolve_t resolver)
 {
 	struct flow_cache_entry *fle, **head;
@@ -189,7 +188,6 @@ void *flow_cache_lookup(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
 	for (fle = *head; fle; fle = fle->next) {
 		if (fle->family == family &&
 		    fle->dir == dir &&
-		    fle->sk_sid == sk_sid &&
 		    flow_key_compare(key, &fle->key) == 0) {
 			if (fle->genid == atomic_read(&flow_cache_genid)) {
 				void *ret = fle->object;
@@ -214,7 +212,6 @@ void *flow_cache_lookup(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
 			*head = fle;
 			fle->family = family;
 			fle->dir = dir;
-			fle->sk_sid = sk_sid;
 			memcpy(&fle->key, key, sizeof(*key));
 			fle->object = NULL;
 			flow_count(cpu)++;
@@ -226,7 +223,7 @@ void *flow_cache_lookup(struct flowi *key, u32 sk_sid, u16 family, u8 dir,
 		void *obj;
 		atomic_t *obj_ref;
 
-		resolver(key, sk_sid, family, dir, &obj, &obj_ref);
+		resolver(key, family, dir, &obj, &obj_ref);
 
 		if (fle) {
 			fle->genid = atomic_read(&flow_cache_genid);

net/xfrm/xfrm_policy.c

@@ -597,7 +597,7 @@ EXPORT_SYMBOL(xfrm_policy_walk);
 
 /* Find policy to apply to this flow. */
 
-static void xfrm_policy_lookup(struct flowi *fl, u32 sk_sid, u16 family, u8 dir,
+static void xfrm_policy_lookup(struct flowi *fl, u16 family, u8 dir,
 			       void **objp, atomic_t **obj_refp)
 {
 	struct xfrm_policy *pol;
@@ -613,7 +613,7 @@ static void xfrm_policy_lookup(struct flowi *fl, u32 sk_sid, u16 family, u8 dir,
 		match = xfrm_selector_match(sel, fl, family);
 
 		if (match) {
- 			if (!security_xfrm_policy_lookup(pol, sk_sid, dir)) {
+ 			if (!security_xfrm_policy_lookup(pol, fl->secid, dir)) {
 				xfrm_pol_hold(pol);
 				break;
 			}
@@ -641,7 +641,7 @@ static inline int policy_to_flow_dir(int dir)
 	};
 }
 
-static struct xfrm_policy *xfrm_sk_policy_lookup(struct sock *sk, int dir, struct flowi *fl, u32 sk_sid)
+static struct xfrm_policy *xfrm_sk_policy_lookup(struct sock *sk, int dir, struct flowi *fl)
 {
 	struct xfrm_policy *pol;
 
@@ -652,7 +652,7 @@ static struct xfrm_policy *xfrm_sk_policy_lookup(struct sock *sk, int dir, struc
  		int err = 0;
 
 		if (match)
-		  err = security_xfrm_policy_lookup(pol, sk_sid, policy_to_flow_dir(dir));
+		  err = security_xfrm_policy_lookup(pol, fl->secid, policy_to_flow_dir(dir));
 
  		if (match && !err)
 			xfrm_pol_hold(pol);
@@ -862,19 +862,20 @@ int xfrm_lookup(struct dst_entry **dst_p, struct flowi *fl,
 	u32 genid;
 	u16 family;
 	u8 dir = policy_to_flow_dir(XFRM_POLICY_OUT);
-	u32 sk_sid = security_sk_sid(sk, fl, dir);
+
+	fl->secid = security_sk_sid(sk, fl, dir);
 restart:
 	genid = atomic_read(&flow_cache_genid);
 	policy = NULL;
 	if (sk && sk->sk_policy[1])
-		policy = xfrm_sk_policy_lookup(sk, XFRM_POLICY_OUT, fl, sk_sid);
+		policy = xfrm_sk_policy_lookup(sk, XFRM_POLICY_OUT, fl);
 
 	if (!policy) {
 		/* To accelerate a bit...  */
 		if ((dst_orig->flags & DST_NOXFRM) || !xfrm_policy_list[XFRM_POLICY_OUT])
 			return 0;
 
-		policy = flow_cache_lookup(fl, sk_sid, dst_orig->ops->family,
+		policy = flow_cache_lookup(fl, dst_orig->ops->family,
 					   dir, xfrm_policy_lookup);
 	}
 
@@ -1032,13 +1033,15 @@ int
 xfrm_decode_session(struct sk_buff *skb, struct flowi *fl, unsigned short family)
 {
 	struct xfrm_policy_afinfo *afinfo = xfrm_policy_get_afinfo(family);
+	int err;
 
 	if (unlikely(afinfo == NULL))
 		return -EAFNOSUPPORT;
 
 	afinfo->decode_session(skb, fl);
+	err = security_xfrm_decode_session(skb, fl);
 	xfrm_policy_put_afinfo(afinfo);
-	return 0;
+	return err;
 }
 EXPORT_SYMBOL(xfrm_decode_session);
 
@@ -1058,14 +1061,11 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 	struct xfrm_policy *pol;
 	struct flowi fl;
 	u8 fl_dir = policy_to_flow_dir(dir);
-	u32 sk_sid;
 
 	if (xfrm_decode_session(skb, &fl, family) < 0)
 		return 0;
 	nf_nat_decode_session(skb, &fl, family);
 
-	sk_sid = security_sk_sid(sk, &fl, fl_dir);
-
 	/* First, check used SA against their selectors. */
 	if (skb->sp) {
 		int i;
@@ -1079,10 +1079,10 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 
 	pol = NULL;
 	if (sk && sk->sk_policy[dir])
-		pol = xfrm_sk_policy_lookup(sk, dir, &fl, sk_sid);
+		pol = xfrm_sk_policy_lookup(sk, dir, &fl);
 
 	if (!pol)
-		pol = flow_cache_lookup(&fl, sk_sid, family, fl_dir,
+		pol = flow_cache_lookup(&fl, family, fl_dir,
 					xfrm_policy_lookup);
 
 	if (!pol)
@@ -1298,6 +1298,8 @@ int xfrm_bundle_ok(struct xfrm_dst *first, struct flowi *fl, int family)
 
 		if (fl && !xfrm_selector_match(&dst->xfrm->sel, fl, family))
 			return 0;
+		if (fl && !security_xfrm_flow_state_match(fl, dst->xfrm))
+			return 0;
 		if (dst->xfrm->km.state != XFRM_STATE_VALID)
 			return 0;
 

net/xfrm/xfrm_state.c

@@ -367,7 +367,7 @@ xfrm_state_find(xfrm_address_t *daddr, xfrm_address_t *saddr,
 			 */
 			if (x->km.state == XFRM_STATE_VALID) {
 				if (!xfrm_selector_match(&x->sel, fl, family) ||
-				    !xfrm_sec_ctx_match(pol->security, x->security))
+				    !security_xfrm_state_pol_flow_match(x, pol, fl))
 					continue;
 				if (!best ||
 				    best->km.dying > x->km.dying ||
@@ -379,7 +379,7 @@ xfrm_state_find(xfrm_address_t *daddr, xfrm_address_t *saddr,
 			} else if (x->km.state == XFRM_STATE_ERROR ||
 				   x->km.state == XFRM_STATE_EXPIRED) {
  				if (xfrm_selector_match(&x->sel, fl, family) &&
-				    xfrm_sec_ctx_match(pol->security, x->security))
+				    security_xfrm_state_pol_flow_match(x, pol, fl))
 					error = -ESRCH;
 			}
 		}
@@ -403,6 +403,14 @@ xfrm_state_find(xfrm_address_t *daddr, xfrm_address_t *saddr,
 		 * to current session. */
 		xfrm_init_tempsel(x, fl, tmpl, daddr, saddr, family);
 
+		error = security_xfrm_state_alloc_acquire(x, pol->security, fl->secid);
+		if (error) {
+			x->km.state = XFRM_STATE_DEAD;
+			xfrm_state_put(x);
+			x = NULL;
+			goto out;
+		}
+
 		if (km_query(x, tmpl, pol) == 0) {
 			x->km.state = XFRM_STATE_ACQ;
 			list_add_tail(&x->bydst, xfrm_state_bydst+h);