Fix Golang Zip Slip Vulnerability

sdks/go/pkg/beam/core/runtime/xlangx/expansionx/download.go

@@ -139,6 +139,18 @@ func getLocalJar(url string) (string, error) {
 	return jarPath, nil
 }
 
+func validatePath(dest, filename string) (string, error) {
+	destPath := filepath.Join(dest, filename)
+	cleanDest := filepath.Clean(dest)
+	cleanPath := filepath.Clean(destPath)
+
+	rel, err := filepath.Rel(cleanDest, cleanPath)
+	if err != nil || strings.HasPrefix(rel, ".."+string(filepath.Separator)) || rel == ".." {
+		return "", fmt.Errorf("file path %q is outside destination directory %q", filename, dest)
+	}
+	return cleanPath, nil
+}
+
 func extractJar(source, dest string) error {
 	reader, err := zip.OpenReader(source)
 	if err != nil {
@@ -150,7 +162,10 @@ func extractJar(source, dest string) error {
 	}
 
 	for _, file := range reader.File {
-		fileName := filepath.Join(dest, file.Name)
+		fileName, err := validatePath(dest, file.Name)
+		if err != nil {
+			return fmt.Errorf("error validating file path (%s, %s): %w", dest, file.Name, err)
+		}
 		if file.FileInfo().IsDir() {
 			os.MkdirAll(fileName, 0700)
 			continue

sdks/go/pkg/beam/core/runtime/xlangx/expansionx/download_test.go

@@ -249,3 +249,28 @@ func TestGetPythonVersion(t *testing.T) {
 		}
 	}
 }
+
+func TestValidatePath(t *testing.T) {
+	dest := filepath.Clean("/tmp/cache")
+	tests := []struct {
+		name     string
+		filename string
+		wantErr  bool
+	}{
+		{"valid simple file", "Foo.class", false},
+		{"valid nested file", "org/apache/beam/Foo.class", false},
+		{"traversal attack", "../../etc/passwd", true},
+		{"partial directory prefix attack", "../cache_evil/evil.sh", true},
+		{"parent directory traversal", "..", true},
+		{"nested traversal attack", "foo/bar/../../../etc/passwd", true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := validatePath(dest, tc.filename)
+			if (err != nil) != tc.wantErr {
+				t.Errorf("validatePath(%q, %q) error = %v, wantErr %v", dest, tc.filename, err, tc.wantErr)
+			}
+		})
+	}
+}