1 files changed, 103 insertions, 0 deletions
diff --git a/lib/isc/fsaccess.c b/lib/isc/fsaccess.c
new file mode 100644
index 0000000..54bf38a
--- /dev/null
+++ b/lib/isc/fsaccess.c
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*! \file
+ * \brief
+ * This file contains the OS-independent functionality of the API.
+ */
+#include <stdbool.h>
+
+#include <isc/fsaccess.h>
+#include <isc/print.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, bool 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);
+}