[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>

1 files changed, 166 insertions, 33 deletions

diff --git a/security/selinux/xfrm.c b/security/selinux/xfrm.c
index 6c985ce..a502b05 100644
--- a/security/selinux/xfrm.c
+++ b/security/selinux/xfrm.c
@@ -6,7 +6,12 @@
  *  Authors:  Serge Hallyn <sergeh@us.ibm.com>
  *	      Trent Jaeger <jaegert@us.ibm.com>
  *
+ *  Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
+ *
+ *           Granular IPSec Associations for use in MLS environments.
+ *
  *  Copyright (C) 2005 International Business Machines Corporation
+ *  Copyright (C) 2006 Trusted Computer Solutions, Inc.
  *
  *	This program is free software; you can redistribute it and/or modify
  *	it under the terms of the GNU General Public License version 2,
@@ -67,10 +72,10 @@ static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
 }
 
 /*
- * LSM hook implementation that authorizes that a socket can be used
- * with the corresponding xfrm_sec_ctx and direction.
+ * LSM hook implementation that authorizes that a flow can use
+ * a xfrm policy rule.
  */
-int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir)
+int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, u8 dir)
 {
 	int rc = 0;
 	u32 sel_sid = SECINITSID_UNLABELED;
@@ -84,27 +89,129 @@ int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir)
 		sel_sid = ctx->ctx_sid;
 	}
 
-	rc = avc_has_perm(sk_sid, sel_sid, SECCLASS_ASSOCIATION,
-			  ((dir == FLOW_DIR_IN) ? ASSOCIATION__RECVFROM :
-			   ((dir == FLOW_DIR_OUT) ?  ASSOCIATION__SENDTO :
-			    (ASSOCIATION__SENDTO | ASSOCIATION__RECVFROM))),
+	rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
+			  ASSOCIATION__POLMATCH,
 			  NULL);
 
 	return rc;
 }
 
 /*
+ * LSM hook implementation that authorizes that a state matches
+ * the given policy, flow combo.
+ */
+
+int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp,
+			struct flowi *fl)
+{
+	u32 state_sid;
+	u32 pol_sid;
+	int err;
+
+	if (x->security)
+		state_sid = x->security->ctx_sid;
+	else
+		state_sid = SECINITSID_UNLABELED;
+
+	if (xp->security)
+		pol_sid = xp->security->ctx_sid;
+	else
+		pol_sid = SECINITSID_UNLABELED;
+
+	err = avc_has_perm(state_sid, pol_sid, SECCLASS_ASSOCIATION,
+			  ASSOCIATION__POLMATCH,
+			  NULL);
+
+	if (err)
+		return 0;
+
+	return selinux_xfrm_flow_state_match(fl, x);
+}
+
+/*
+ * LSM hook implementation that authorizes that a particular outgoing flow
+ * can use a given security association.
+ */
+
+int selinux_xfrm_flow_state_match(struct flowi *fl, struct xfrm_state *xfrm)
+{
+	int rc = 0;
+	u32 sel_sid = SECINITSID_UNLABELED;
+	struct xfrm_sec_ctx *ctx;
+
+	/* Context sid is either set to label or ANY_ASSOC */
+	if ((ctx = xfrm->security)) {
+		if (!selinux_authorizable_ctx(ctx))
+			return 0;
+
+		sel_sid = ctx->ctx_sid;
+	}
+
+	rc = avc_has_perm(fl->secid, sel_sid, SECCLASS_ASSOCIATION,
+			  ASSOCIATION__SENDTO,
+			  NULL)? 0:1;
+
+	return rc;
+}
+
+/*
+ * LSM hook implementation that determines the sid for the session.
+ */
+
+int selinux_xfrm_decode_session(struct sk_buff *skb, struct flowi *fl)
+{
+	struct sec_path *sp;
+
+	fl->secid = SECSID_NULL;
+
+	if (skb == NULL)
+		return 0;
+
+	sp = skb->sp;
+	if (sp) {
+		int i, sid_set = 0;
+
+		for (i = sp->len-1; i >= 0; i--) {
+			struct xfrm_state *x = sp->xvec[i];
+			if (selinux_authorizable_xfrm(x)) {
+				struct xfrm_sec_ctx *ctx = x->security;
+
+				if (!sid_set) {
+					fl->secid = ctx->ctx_sid;
+					sid_set = 1;
+				}
+				else if (fl->secid != ctx->ctx_sid)
+					return -EINVAL;
+			}
+		}
+	}
+
+	return 0;
+}
+
+/*
  * Security blob allocation for xfrm_policy and xfrm_state
  * CTX does not have a meaningful value on input
  */
-static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp, struct xfrm_user_sec_ctx *uctx)
+static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp,
+	struct xfrm_user_sec_ctx *uctx, struct xfrm_sec_ctx *pol, u32 sid)
 {
 	int rc = 0;
 	struct task_security_struct *tsec = current->security;
-	struct xfrm_sec_ctx *ctx;
+	struct xfrm_sec_ctx *ctx = NULL;
+	char *ctx_str = NULL;
+	u32 str_len;
+	u32 ctx_sid;
+
+	BUG_ON(uctx && pol);
+
+	if (pol)
+		goto from_policy;
 
 	BUG_ON(!uctx);
-	BUG_ON(uctx->ctx_doi != XFRM_SC_ALG_SELINUX);
+
+	if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
+		return -EINVAL;
 
 	if (uctx->ctx_len >= PAGE_SIZE)
 		return -ENOMEM;
@@ -141,9 +248,41 @@ static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp, struct xfrm_us
 
 	return rc;
 
+from_policy:
+	BUG_ON(!pol);
+	rc = security_sid_mls_copy(pol->ctx_sid, sid, &ctx_sid);
+	if (rc)
+		goto out;
+
+	rc = security_sid_to_context(ctx_sid, &ctx_str, &str_len);
+	if (rc)
+		goto out;
+
+	*ctxp = ctx = kmalloc(sizeof(*ctx) +
+			      str_len,
+			      GFP_ATOMIC);
+
+	if (!ctx) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+
+	ctx->ctx_doi = XFRM_SC_DOI_LSM;
+	ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
+	ctx->ctx_sid = ctx_sid;
+	ctx->ctx_len = str_len;
+	memcpy(ctx->ctx_str,
+	       ctx_str,
+	       str_len);
+
+	goto out2;
+
 out:
 	*ctxp = NULL;
 	kfree(ctx);
+out2:
+	kfree(ctx_str);
 	return rc;
 }
 
@@ -157,7 +296,7 @@ int selinux_xfrm_policy_alloc(struct xfrm_policy *xp, struct xfrm_user_sec_ctx *
 
 	BUG_ON(!xp);
 
-	err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx);
+	err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, NULL, 0);
 	return err;
 }
 
@@ -217,13 +356,14 @@ int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
  * LSM hook implementation that allocs and transfers sec_ctx spec to
  * xfrm_state.
  */
-int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx)
+int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
+		struct xfrm_sec_ctx *pol, u32 secid)
 {
 	int err;
 
 	BUG_ON(!x);
 
-	err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx);
+	err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, pol, secid);
 	return err;
 }
 
@@ -329,38 +469,30 @@ int selinux_xfrm_state_delete(struct xfrm_state *x)
  * we need to check for unlabelled access since this may not have
  * gone thru the IPSec process.
  */
-int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb)
+int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
+				struct avc_audit_data *ad)
 {
 	int i, rc = 0;
 	struct sec_path *sp;
+	u32 sel_sid = SECINITSID_UNLABELED;
 
 	sp = skb->sp;
 
 	if (sp) {
-		/*
-		 * __xfrm_policy_check does not approve unless xfrm_policy_ok
-		 * says that spi's match for policy and the socket.
-		 *
-		 *  Only need to verify the existence of an authorizable sp.
-		 */
 		for (i = 0; i < sp->len; i++) {
 			struct xfrm_state *x = sp->xvec[i];
 
-			if (x && selinux_authorizable_xfrm(x))
-				goto accept;
+			if (x && selinux_authorizable_xfrm(x)) {
+				struct xfrm_sec_ctx *ctx = x->security;
+				sel_sid = ctx->ctx_sid;
+				break;
+			}
 		}
 	}
 
-	/* check SELinux sock for unlabelled access */
-	rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
-			  ASSOCIATION__RECVFROM, NULL);
-	if (rc)
-		goto drop;
-
-accept:
-	return 0;
+	rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
+			  ASSOCIATION__RECVFROM, ad);
 
-drop:
 	return rc;
 }
 
@@ -371,7 +503,8 @@ drop:
  * If we do have a authorizable security association, then it has already been
  * checked in xfrm_policy_lookup hook.
  */
-int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb)
+int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
+					struct avc_audit_data *ad)
 {
 	struct dst_entry *dst;
 	int rc = 0;
@@ -391,7 +524,7 @@ int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb)
 	}
 
 	rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
-			  ASSOCIATION__SENDTO, NULL);
+			  ASSOCIATION__SENDTO, ad);
 out:
 	return rc;
 }