[PATCH] support for context based audit filtering

The following patch provides selinux interfaces that will allow the audit
system to perform filtering based on the process context (user, role, type,
sensitivity, and clearance).  These interfaces will allow the selinux
module to perform efficient matches based on lower level selinux constructs,
rather than relying on context retrievals and string comparisons within
the audit module.  It also allows for dominance checks on the mls portion
of the contexts that are impossible with only string comparisons.

Signed-off-by: Darrel Goeddel <dgoeddel@trustedcs.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

security/selinux/ss/mls.c

@@ -8,7 +8,7 @@
  *
  *	Support for enhanced MLS infrastructure.
  *
- * Copyright (C) 2004-2005 Trusted Computer Solutions, Inc.
+ * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
  */
 
 #include <linux/kernel.h>
@@ -384,6 +384,34 @@ out:
 	return rc;
 }
 
+/*
+ * Set the MLS fields in the security context structure
+ * `context' based on the string representation in
+ * the string `str'.  This function will allocate temporary memory with the
+ * given constraints of gfp_mask.
+ */
+int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
+{
+	char *tmpstr, *freestr;
+	int rc;
+
+	if (!selinux_mls_enabled)
+		return -EINVAL;
+
+	/* we need freestr because mls_context_to_sid will change
+	   the value of tmpstr */
+	tmpstr = freestr = kstrdup(str, gfp_mask);
+	if (!tmpstr) {
+		rc = -ENOMEM;
+	} else {
+		rc = mls_context_to_sid(':', &tmpstr, context,
+		                        NULL, SECSID_NULL);
+		kfree(freestr);
+	}
+
+	return rc;
+}
+
 /*
  * Copies the effective MLS range from `src' into `dst'.
  */