[MLSXFRM]: Define new SELinux service routine

This defines a routine that combines the Type Enforcement portion of
one sid with the MLS portion from the other sid to arrive at a new
sid. This would be used to define a sid for a security association
that is to be negotiated by IKE as well as for determing the sid for
open requests and connection-oriented child sockets.

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

1 files changed, 69 insertions, 0 deletions

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 85e429884393..b00ec69f0ffd 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1817,6 +1817,75 @@ out:
 	return rc;
 }
 
+/*
+ * security_sid_mls_copy() - computes a new sid based on the given
+ * sid and the mls portion of mls_sid.
+ */
+int security_sid_mls_copy(u32 sid, u32 mls_sid, u32 *new_sid)
+{
+	struct context *context1;
+	struct context *context2;
+	struct context newcon;
+	char *s;
+	u32 len;
+	int rc = 0;
+
+	if (!ss_initialized) {
+		*new_sid = sid;
+		goto out;
+	}
+
+	context_init(&newcon);
+
+	POLICY_RDLOCK;
+	context1 = sidtab_search(&sidtab, sid);
+	if (!context1) {
+		printk(KERN_ERR "security_sid_mls_copy:  unrecognized SID "
+		       "%d\n", sid);
+		rc = -EINVAL;
+		goto out_unlock;
+	}
+
+	context2 = sidtab_search(&sidtab, mls_sid);
+	if (!context2) {
+		printk(KERN_ERR "security_sid_mls_copy:  unrecognized SID "
+		       "%d\n", mls_sid);
+		rc = -EINVAL;
+		goto out_unlock;
+	}
+
+	newcon.user = context1->user;
+	newcon.role = context1->role;
+	newcon.type = context1->type;
+	rc = mls_copy_context(&newcon, context2);
+	if (rc)
+		goto out_unlock;
+
+
+	/* Check the validity of the new context. */
+	if (!policydb_context_isvalid(&policydb, &newcon)) {
+		rc = convert_context_handle_invalid_context(&newcon);
+		if (rc)
+			goto bad;
+	}
+
+	rc = sidtab_context_to_sid(&sidtab, &newcon, new_sid);
+	goto out_unlock;
+
+bad:
+	if (!context_struct_to_string(&newcon, &s, &len)) {
+		audit_log(current->audit_context, GFP_ATOMIC, AUDIT_SELINUX_ERR,
+			  "security_sid_mls_copy: invalid context %s", s);
+		kfree(s);
+	}
+
+out_unlock:
+	POLICY_RDUNLOCK;
+	context_destroy(&newcon);
+out:
+	return rc;
+}
+
 struct selinux_audit_rule {
 	u32 au_seqno;
 	struct context au_ctxt;