chunked: improve detection of root directory path

Signed-off-by: Giuseppe Scrivano <[email protected]>

pkg/chunked/storage_linux.go

@@ -1280,6 +1280,13 @@ func typeToOsMode(typ string) (os.FileMode, error) {
 	return 0, fmt.Errorf("unknown file type %q", typ)
 }
 
+// cleanAbsDirectory removes any ".." and "." from the path
+// and ensures it starts with a "/".  If the path refers to the root
+// directory, it returns "/".
+func cleanAbsDirectory(path string) string {
+	return filepath.Clean("/" + path)
+}
+
 func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, differOpts *graphdriver.DifferOptions) (graphdriver.DriverWithDifferOutput, error) {
 	defer c.layersCache.release()
 	defer func() {
@@ -1544,10 +1551,10 @@ func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, diff
 			}
 		}
 
-		r.Name = filepath.Clean(r.Name)
+		r.Name = cleanAbsDirectory(r.Name)
 		// do not modify the value of symlinks
 		if r.Linkname != "" && t != tar.TypeSymlink {
-			r.Linkname = filepath.Clean(r.Linkname)
+			r.Linkname = cleanAbsDirectory(r.Linkname)
 		}
 
 		if whiteoutConverter != nil {
@@ -1595,7 +1602,7 @@ func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, diff
 			}
 
 		case tar.TypeDir:
-			if r.Name == "" || r.Name == "." {
+			if r.Name == "/" {
 				output.RootDirMode = &mode
 			}
 			if err := safeMkdir(dirfd, mode, r.Name, r, options); err != nil {

pkg/chunked/storage_linux_test.go

@@ -211,3 +211,39 @@ func TestTypeToOsMode(t *testing.T) {
 		})
 	}
 }
+
+func TestCleanAbsDirectory(t *testing.T) {
+	tests := []struct {
+		path     string
+		expected string
+	}{
+		{"", "/"},
+		{"./", "/"},
+		{"../", "/"},
+		{"/../", "/"},
+		{"/./", "/"},
+		{"foo", "/foo"},
+		{"foo/bar", "/foo/bar"},
+		{"/foo/bar/../baz", "/foo/baz"},
+		{"/foo/./bar", "/foo/bar"},
+		{"/foo/bar/../../baz", "/baz"},
+		{"/././foo", "/foo"},
+		{"../foo", "/foo"},
+		{"./foo/bar/../..", "/"},
+		{"foo/..", "/"},
+		{"foo/../bar", "/bar"},
+		{"//foo//bar", "/foo/bar"},
+		{"foo/bar//baz/..", "/foo/bar"},
+		{"../..", "/"},
+		{".././..", "/"},
+		{"../../.", "/"},
+		{"/../../foo", "/foo"},
+		{"../foo/bar/../baz", "/foo/baz"},
+		{"../.././/.//../foo/./../bar/..", "/"},
+		{"a/../.././/.//../foo/./../bar/..", "/"},
+	}
+
+	for _, test := range tests {
+		assert.Equal(t, test.expected, cleanAbsDirectory(test.path), fmt.Sprintf("path %q failed", test.path))
+	}
+}