allow .. in file and directory names

extractor.go

@@ -158,9 +158,14 @@ func (te *Extractor) Extract(reader io.Reader) error {
 		// Checks if the relative path matches or exceeds the root
 		// We check for matching because the outputPath function strips the original root
 		rel, err := fp.Rel(rootOutputPath, outputPath)
-		if err != nil || rel == "." || strings.Contains(rel, "..") {
+		if err != nil || rel == "." {
 			return errInvalidRootMultipleRoots
 		}
+		for _, e := range strings.Split(fp.ToSlash(rel), "/") {
+			if e == ".." {
+				return fmt.Errorf("relative path contains '..'")
+			}
+		}
 
 		switch header.Typeflag {
 		case tar.TypeDir:
@@ -211,7 +216,7 @@ func getRelativePath(rootName, tarPath string) (string, error) {
 	return tarPath[len(rootName)+1:], nil
 }
 
-// outputPath returns the path at which to place the relativeTarPath. Assumes the path is cleaned.
+// outputPath returns the directory path at which to place the file relativeTarPath. Assumes relativeTarPath is cleaned.
 func (te *Extractor) outputPath(basePlatformPath, relativeTarPath string) (string, error) {
 	elems := strings.Split(relativeTarPath, "/")
 

extractor_test.go

@@ -45,7 +45,7 @@ func init() {
 }
 
 func TestSingleFile(t *testing.T) {
-	fileName := "file"
+	fileName := "file..ext"
 	fileData := "file data"
 
 	testTarExtraction(t, nil, []tarEntry{
@@ -64,7 +64,7 @@ func TestSingleFile(t *testing.T) {
 }
 
 func TestSingleDirectory(t *testing.T) {
-	dirName := "dir"
+	dirName := "dir..sfx"
 
 	testTarExtraction(t, nil, []tarEntry{
 		&dirTarEntry{dirName},

sanitize.go

@@ -20,6 +20,9 @@ func validatePlatformPath(platformPath string) error {
 }
 
 func validatePathComponent(c string) error {
+	if c == ".." {
+		return fmt.Errorf("invalid platform path: path component cannot be '..'")
+	}
 	if strings.Contains(c, "\x00") {
 		return fmt.Errorf("invalid platform path: path components cannot contain null: %q", c)
 	}

sanitize_windows.go

@@ -38,6 +38,9 @@ func validatePathComponent(c string) error {
 		return fmt.Errorf("invalid platform path: path components cannot end with ' ' : %q", c)
 	}
 
+	if c == ".." {
+		return fmt.Errorf("invalid platform path: path component cannot be '..'")
+	}
 	// error on reserved characters
 	if strings.ContainsAny(c, reservedCharsStr) {
 		return fmt.Errorf("invalid platform path: path components cannot contain any of %s : %q", reservedCharsStr, c)