OS-independent filesystem permissions

lib/isc/fsaccess.c

@@ -0,0 +1,82 @@
+/*
+ * This file contains the OS-independent functionality of the API.
+ */
+#include <isc/fsaccess.h>
+#include <isc/result.h>
+#include <isc/util.h>
+
+/*
+ * Shorthand.  Maybe ISC__FSACCESS_PERMISSIONBITS should not even be in
+ * <isc/fsaccess.h>.  Could check consistency with sizeof(isc_fsaccess_t)
+ * and the number of bits in each function.
+ */
+#define STEP		(ISC__FSACCESS_PERMISSIONBITS)
+#define GROUP		(STEP)
+#define OTHER		(STEP * 2)
+
+void
+isc_fsaccess_add(int trustee, int permission, isc_fsaccess_t *access) {
+	REQUIRE(trustee <= 0x7);
+	REQUIRE(permission <= 0xFF);
+
+	if ((trustee & ISC_FSACCESS_OWNER) != 0)
+		*access |= permission;
+
+	if ((trustee & ISC_FSACCESS_GROUP) != 0)
+		*access |= (permission << GROUP);
+
+	if ((trustee & ISC_FSACCESS_OTHER) != 0)
+		*access |= (permission << OTHER);
+}
+
+void
+isc_fsaccess_remove(int trustee, int permission, isc_fsaccess_t *access) {
+	REQUIRE(trustee <= 0x7);
+	REQUIRE(permission <= 0xFF);
+
+
+	if ((trustee & ISC_FSACCESS_OWNER) != 0)
+		*access &= ~permission;
+
+	if ((trustee & ISC_FSACCESS_GROUP) != 0)
+		*access &= ~(permission << GROUP);
+
+	if ((trustee & ISC_FSACCESS_OTHER) != 0)
+		*access &= ~(permission << OTHER);
+}
+
+static isc_result_t
+check_bad_bits(isc_fsaccess_t access, isc_boolean_t is_dir) {
+	isc_fsaccess_t bits;
+
+	/*
+	 * Check for disallowed user bits.
+	 */
+	if (is_dir)
+		bits = ISC_FSACCESS_READ |
+		       ISC_FSACCESS_WRITE |
+		       ISC_FSACCESS_EXECUTE;
+	else
+		bits = ISC_FSACCESS_CREATECHILD |
+		       ISC_FSACCESS_ACCESSCHILD |
+		       ISC_FSACCESS_DELETECHILD |
+		       ISC_FSACCESS_LISTDIRECTORY;
+
+	/*
+	 * Set group bad bits.
+	 */
+	bits |= bits << STEP;
+	/*
+	 * Set other bad bits.
+	 */
+	bits |= bits << STEP;
+
+	if ((access & bits) != 0) {
+		if (is_dir)
+			return (ISC_R_NOTFILE);
+		else
+			return (ISC_R_NOTDIRECTORY);
+	}
+
+	return (ISC_R_SUCCESS);
+}