PLT-7407: Back-end plugins (#7409)

* tie back-end plugins together

* fix comment typo

* add tests and a bit of polish

* tests and polish

* add test, don't let backend executable paths escape the plugin directory

utils/extract.go

@@ -13,19 +13,16 @@ import (
 )
 
 // ExtractTarGz takes in an io.Reader containing the bytes for a .tar.gz file and
-// a destination string to extract to. A list of the file and directory names that
-// were extracted is returned.
-func ExtractTarGz(gzipStream io.Reader, dst string) ([]string, error) {
+// a destination string to extract to.
+func ExtractTarGz(gzipStream io.Reader, dst string) error {
 	uncompressedStream, err := gzip.NewReader(gzipStream)
 	if err != nil {
-		return nil, fmt.Errorf("ExtractTarGz: NewReader failed: %s", err.Error())
+		return fmt.Errorf("ExtractTarGz: NewReader failed: %s", err.Error())
 	}
 	defer uncompressedStream.Close()
 
 	tarReader := tar.NewReader(uncompressedStream)
 
-	filenames := []string{}
-
 	for true {
 		header, err := tarReader.Next()
 
@@ -34,50 +31,46 @@ func ExtractTarGz(gzipStream io.Reader, dst string) ([]string, error) {
 		}
 
 		if err != nil {
-			return nil, fmt.Errorf("ExtractTarGz: Next() failed: %s", err.Error())
+			return fmt.Errorf("ExtractTarGz: Next() failed: %s", err.Error())
 		}
 
 		switch header.Typeflag {
 		case tar.TypeDir:
 			if PathTraversesUpward(header.Name) {
-				return nil, fmt.Errorf("ExtractTarGz: path attempts to traverse upwards")
+				return fmt.Errorf("ExtractTarGz: path attempts to traverse upwards")
 			}
 
 			path := filepath.Join(dst, header.Name)
 			if err := os.Mkdir(path, 0744); err != nil && !os.IsExist(err) {
-				return nil, fmt.Errorf("ExtractTarGz: Mkdir() failed: %s", err.Error())
+				return fmt.Errorf("ExtractTarGz: Mkdir() failed: %s", err.Error())
 			}
-
-			filenames = append(filenames, header.Name)
 		case tar.TypeReg:
 			if PathTraversesUpward(header.Name) {
-				return nil, fmt.Errorf("ExtractTarGz: path attempts to traverse upwards")
+				return fmt.Errorf("ExtractTarGz: path attempts to traverse upwards")
 			}
 
 			path := filepath.Join(dst, header.Name)
 			dir := filepath.Dir(path)
 
 			if err := os.MkdirAll(dir, 0744); err != nil {
-				return nil, fmt.Errorf("ExtractTarGz: MkdirAll() failed: %s", err.Error())
+				return fmt.Errorf("ExtractTarGz: MkdirAll() failed: %s", err.Error())
 			}
 
-			outFile, err := os.Create(path)
+			outFile, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, os.FileMode(header.Mode))
 			if err != nil {
-				return nil, fmt.Errorf("ExtractTarGz: Create() failed: %s", err.Error())
+				return fmt.Errorf("ExtractTarGz: Create() failed: %s", err.Error())
 			}
 			defer outFile.Close()
 			if _, err := io.Copy(outFile, tarReader); err != nil {
-				return nil, fmt.Errorf("ExtractTarGz: Copy() failed: %s", err.Error())
+				return fmt.Errorf("ExtractTarGz: Copy() failed: %s", err.Error())
 			}
-
-			filenames = append(filenames, header.Name)
 		default:
-			return nil, fmt.Errorf(
+			return fmt.Errorf(
 				"ExtractTarGz: unknown type: %v in %v",
 				header.Typeflag,
 				header.Name)
 		}
 	}
 
-	return filenames, nil
+	return nil
 }