Path traversal changes

Author: cx-aniket-shinde

internal/services/osinstaller/linux-mac-utils.go

@@ -7,43 +7,64 @@ import (
 	"compress/gzip"
 	"fmt"
 	"io"
-	"io/fs"
 	"log"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"syscall"
 
 	"github.com/checkmarx/ast-cli/internal/logger"
 )
 
-const dirDefault int = 0755
+// dirDefault is the permission bits applied to directories created during extraction.
+const dirDefault os.FileMode = 0755
+
+// maxExtractBytes caps how many bytes a single tar entry may expand to,
+// preventing decompression-bomb (tar-bomb) attacks.
+const maxExtractBytes int64 = 500 * 1024 * 1024 // 500 MB
 
 // UnzipOrExtractFiles Extracts all the files from the tar.gz file
 func UnzipOrExtractFiles(installationConfiguration *InstallationConfiguration) error {
 	logger.PrintIfVerbose("Extracting files in: " + installationConfiguration.WorkingDir())
 	filePath := filepath.Join(installationConfiguration.WorkingDir(), installationConfiguration.FileName)
+
 	gzipStream, err := os.Open(filePath)
 	if err != nil {
 		fmt.Println("error when open file ", filePath, err)
 		return err
 	}
+	defer gzipStream.Close()
+
 	uncompressedStream, err := gzip.NewReader(gzipStream)
 	if err != nil {
 		log.Println("ExtractTarGz: NewReader failed ", err)
 		return err
 	}
+	defer uncompressedStream.Close()
 
-	tarReader := tar.NewReader(uncompressedStream)
+	return extractFiles(installationConfiguration, tar.NewReader(uncompressedStream))
+}
 
-	err = extractFiles(installationConfiguration, tarReader)
-	if err != nil {
-		return err
+// safeJoin validates that name is a relative path and that the resolved
+// destination stays inside workingDir, preventing path traversal attacks.
+func safeJoin(workingDir, name string) (string, error) {
+	if name == "" || name == "." {
+		return "", fmt.Errorf("illegal file path (empty or dot): %s", name)
 	}
-	return nil
+	if filepath.IsAbs(name) {
+		return "", fmt.Errorf("illegal file path (absolute): %s", name)
+	}
+	dst := filepath.Join(workingDir, name)
+	cleanBase := filepath.Clean(workingDir) + string(os.PathSeparator)
+	if !strings.HasPrefix(dst, cleanBase) {
+		return "", fmt.Errorf("illegal file path (traversal): %s", name)
+	}
+	return dst, nil
 }
 
 func extractFiles(installationConfiguration *InstallationConfiguration, tarReader *tar.Reader) error {
+	workingDir := installationConfiguration.WorkingDir()
 	for {
 		header, err := tarReader.Next()
 
@@ -52,36 +73,49 @@ func extractFiles(installationConfiguration *InstallationConfiguration, tarReade
 		}
 
 		if err != nil {
-			log.Fatalf("ExtractTarGz: Next() failed: %s", err.Error())
+			return fmt.Errorf("ExtractTarGz: Next() failed: %w", err)
 		}
 
 		switch header.Typeflag {
 		case tar.TypeDir:
-			if err := os.Mkdir(header.Name, os.FileMode(dirDefault)); err != nil {
-				log.Fatalf("ExtractTarGz: Mkdir() failed: %s", err.Error())
+			dst, err := safeJoin(workingDir, header.Name)
+			if err != nil {
+				return err
 			}
+			if err := os.MkdirAll(dst, dirDefault); err != nil {
+				return fmt.Errorf("ExtractTarGz: Mkdir() failed: %w", err)
+			}
+
 		case tar.TypeReg:
-			extractedFilePath := filepath.Join(installationConfiguration.WorkingDir(), header.Name)
-			outFile, err := os.Create(extractedFilePath)
+			extractedFilePath, err := safeJoin(workingDir, header.Name)
 			if err != nil {
-				log.Fatalf("ExtractTarGz: Create() failed: %s", err.Error())
+				return err
 			}
-			if _, err = io.Copy(outFile, tarReader); err != nil {
-				log.Fatalf("ExtractTarGz: Copy() failed: %s", err.Error())
+			if err := os.MkdirAll(filepath.Dir(extractedFilePath), dirDefault); err != nil {
+				return fmt.Errorf("ExtractTarGz: MkdirAll() failed: %w", err)
 			}
-			err = outFile.Close()
+			outFile, err := os.Create(extractedFilePath)
 			if err != nil {
+				return fmt.Errorf("ExtractTarGz: Create() failed: %w", err)
+			}
+			if _, err = io.Copy(outFile, io.LimitReader(tarReader, maxExtractBytes)); err != nil {
+				_ = outFile.Close()
+				return fmt.Errorf("ExtractTarGz: Copy() failed: %w", err)
+			}
+			if err = outFile.Close(); err != nil {
 				return err
 			}
-			err = os.Chmod(extractedFilePath, fs.ModePerm)
-			if err != nil {
+			// Preserve only the executable bit from the archive entry; never grant world-write.
+			mode := os.FileMode(0644)
+			if header.FileInfo().Mode()&0111 != 0 {
+				mode = 0755
+			}
+			if err = os.Chmod(extractedFilePath, mode); err != nil {
 				return err
 			}
+
 		default:
-			log.Fatalf(
-				"ExtractTarGz: uknown type: %v in %s",
-				header.Typeflag,
-				header.Name)
+			log.Printf("ExtractTarGz: unknown type: %v in %s", header.Typeflag, header.Name)
 		}
 	}
 	return nil