SELinux: Fix SA selection semantics
Fix the selection of an SA for an outgoing packet to be at the same
context as the originating socket/flow. This eliminates the SELinux
policy's ability to use/sendto SAs with contexts other than the socket's.
With this patch applied, the SELinux policy will require one or more of the
following for a socket to be able to communicate with/without SAs:
1. To enable a socket to communicate without using labeled-IPSec SAs:
allow socket_t unlabeled_t:association { sendto recvfrom }
2. To enable a socket to communicate with labeled-IPSec SAs:
allow socket_t self:association { sendto };
allow socket_t peer_sa_t:association { recvfrom };
Signed-off-by: Venkat Yekkirala <vyekkirala@TrustedCS.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/xfrm.c b/security/selinux/xfrm.c
index 8fef742..9b77714 100644
--- a/security/selinux/xfrm.c
+++ b/security/selinux/xfrm.c
@@ -115,70 +115,39 @@
struct flowi *fl)
{
u32 state_sid;
- u32 pol_sid;
- int err;
+ int rc;
- if (xp->security) {
- if (!x->security)
- /* unlabeled SA and labeled policy can't match */
- return 0;
- else
- state_sid = x->security->ctx_sid;
- pol_sid = xp->security->ctx_sid;
- } else
+ if (!xp->security)
if (x->security)
/* unlabeled policy and labeled SA can't match */
return 0;
else
/* unlabeled policy and unlabeled SA match all flows */
return 1;
+ else
+ if (!x->security)
+ /* unlabeled SA and labeled policy can't match */
+ return 0;
+ else
+ if (!selinux_authorizable_xfrm(x))
+ /* Not a SELinux-labeled SA */
+ return 0;
- err = avc_has_perm(state_sid, pol_sid, SECCLASS_ASSOCIATION,
- ASSOCIATION__POLMATCH,
- NULL);
+ state_sid = x->security->ctx_sid;
- if (err)
+ if (fl->secid != state_sid)
return 0;
- err = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION,
+ rc = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__SENDTO,
NULL)? 0:1;
- return err;
-}
-
-/*
- * 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,
- struct xfrm_policy *xp)
-{
- int rc = 0;
- u32 sel_sid = SECINITSID_UNLABELED;
- struct xfrm_sec_ctx *ctx;
-
- if (!xp->security)
- if (!xfrm->security)
- return 1;
- else
- return 0;
- else
- if (!xfrm->security)
- return 0;
-
- /* 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;
+ /*
+ * We don't need a separate SA Vs. policy polmatch check
+ * since the SA is now of the same label as the flow and
+ * a flow Vs. policy polmatch check had already happened
+ * in selinux_xfrm_policy_lookup() above.
+ */
return rc;
}
@@ -481,6 +450,13 @@
}
}
+ /*
+ * This check even when there's no association involved is
+ * intended, according to Trent Jaeger, to make sure a
+ * process can't engage in non-ipsec communication unless
+ * explicitly allowed by policy.
+ */
+
rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__RECVFROM, ad);
@@ -492,10 +468,10 @@
* If we have no security association, then we need to determine
* whether the socket is allowed to send to an unlabelled destination.
* If we do have a authorizable security association, then it has already been
- * checked in xfrm_policy_lookup hook.
+ * checked in the selinux_xfrm_state_pol_flow_match hook above.
*/
int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
- struct avc_audit_data *ad)
+ struct avc_audit_data *ad, u8 proto)
{
struct dst_entry *dst;
int rc = 0;
@@ -514,6 +490,27 @@
}
}
+ switch (proto) {
+ case IPPROTO_AH:
+ case IPPROTO_ESP:
+ case IPPROTO_COMP:
+ /*
+ * We should have already seen this packet once before
+ * it underwent xfrm(s). No need to subject it to the
+ * unlabeled check.
+ */
+ goto out;
+ default:
+ break;
+ }
+
+ /*
+ * This check even when there's no association involved is
+ * intended, according to Trent Jaeger, to make sure a
+ * process can't engage in non-ipsec communication unless
+ * explicitly allowed by policy.
+ */
+
rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
ASSOCIATION__SENDTO, ad);
out: