subpath: creation for splitting locale-root

Change-Id: Ia339dc1d1291ef52fbec3c928537721ed7410694
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

1 files changed, 128 insertions, 0 deletions

diff --git a/src/subpath.c b/src/subpath.c
new file mode 100644
index 00000000..a8441638
--- /dev/null
+++ b/src/subpath.c
@@ -0,0 +1,128 @@
+/*
+ Copyright 2015 IoT.bzh
+
+ author: José Bollo <jose.bollo@iot.bzh>
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <assert.h>
+#include <limits.h>
+#include <string.h>
+#include <ctype.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <dirent.h>
+
+#include "subpath.h"
+
+/* a valid subpath is a relative path not looking deeper than root using .. */
+int subpath_is_valid(const char *path)
+{
+	int l = 0, i = 0;
+
+	/* absolute path is not valid */
+	if (path[i] == '/')
+		return 0;
+
+	/* inspect the path */
+	while(path[i]) {
+		switch(path[i++]) {
+		case '.':
+			if (!path[i])
+				break;
+			if (path[i] == '/') {
+				i++;
+				break;
+			}
+			if (path[i++] == '.') {
+				if (!path[i]) {
+					l--;
+					break;
+				}
+				if (path[i++] == '/') {
+					l--;
+					break;
+				}
+			}
+		default:
+			while(path[i] && path[i] != '/')
+				i++;
+			if (l >= 0)
+				l++;
+		case '/':
+			break;
+		}
+	}
+	return l >= 0;
+}
+
+/*
+ * Return the path or NULL is not valid.
+ * Ensure that the path doesn't start with '/' and that
+ * it does not contains sequence of '..' going deeper than
+ * root.
+ * Returns the path or NULL in case of
+ * invalid path.
+ */
+const char *subpath(const char *path)
+{
+	return path && subpath_is_valid(path) ? (path[0] ? path : ".") : NULL;
+}
+
+/*
+ * Normalizes and checks the 'path'.
+ * Removes any starting '/' and checks that 'path'
+ * does not contains sequence of '..' going deeper than
+ * root.
+ * Returns the normalized path or NULL in case of
+ * invalid path.
+ */
+const char *subpath_force(const char *path)
+{
+	while(path && *path == '/')
+		path++;
+	return subpath(path);
+}
+
+#if defined(TEST_subpath)
+#include <stdio.h>
+void t(const char *subpath, int validity) {
+  printf("%s -> %d = %d, %s\n", subpath, validity, subpath_is_valid(subpath), subpath_is_valid(subpath)==validity ? "ok" : "NOT OK");
+}
+int main() {
+  t("/",0);
+  t("..",0);
+  t(".",1);
+  t("../a",0);
+  t("a/..",1);
+  t("a/../////..",0);
+  t("a/../b/..",1);
+  t("a/b/c/..",1);
+  t("a/b/c/../..",1);
+  t("a/b/c/../../..",1);
+  t("a/b/c/../../../.",1);
+  t("./..a/././..b/..c/./.././.././../.",1);
+  t("./..a/././..b/..c/./.././.././.././..",0);
+  t("./..a//.//./..b/..c/./.././/./././///.././.././a/a/a/a/a",1);
+  return 0;
+}
+#endif
+