Helm Allows A Specially Crafted JSON Schema To Cause A Stack Overflow

@@ -33,6 +33,15 @@ import (
 	chart "helm.sh/helm/v4/pkg/chart/v2"
 )
 
+// MaxDecompressedChartSize is the maximum size of a chart archive that will be
+// decompressed. This is the decompressed size of all the files.
+// The default value is 100 MiB.
+var MaxDecompressedChartSize int64 = 100 * 1024 * 1024 // Default 100 MiB
+
+// MaxDecompressedFileSize is the size of the largest file that Helm will attempt to load.
+// The size of the file is the decompressed version of it when it is stored in an archive.
+var MaxDecompressedFileSize int64 = 5 * 1024 * 1024 // Default 5 MiB
+
 var drivePathPattern = regexp.MustCompile(`^[a-zA-Z]:/`)
 
 // FileLoader loads a chart from a file
@@ -119,6 +128,7 @@ func LoadArchiveFiles(in io.Reader) ([]*BufferedFile, error) {
 
 	files := []*BufferedFile{}
 	tr := tar.NewReader(unzipped)
+	remainingSize := MaxDecompressedChartSize
 	for {
 		b := bytes.NewBuffer(nil)
 		hd, err := tr.Next()
@@ -178,10 +188,30 @@ func LoadArchiveFiles(in io.Reader) ([]*BufferedFile, error) {
 			return nil, errors.New("chart yaml not in base directory")
 		}
 
-		if _, err := io.Copy(b, tr); err != nil {
+		if hd.Size > remainingSize {
+			return nil, fmt.Errorf("decompressed chart is larger than the maximum size %d", MaxDecompressedChartSize)
+		}
+
+		if hd.Size > MaxDecompressedFileSize {
+			return nil, fmt.Errorf("decompressed chart file %q is larger than the maximum file size %d", hd.Name, MaxDecompressedFileSize)
+		}
+
+		limitedReader := io.LimitReader(tr, remainingSize)
+
+		bytesWritten, err := io.Copy(b, limitedReader)
+		if err != nil {
 			return nil, err
 		}
 
+		remainingSize -= bytesWritten
+		// When the bytesWritten are less than the file size it means the limit reader ended
+		// copying early. Here we report that error. This is important if the last file extracted
+		// is the one that goes over the limit. It assumes the Size stored in the tar header
+		// is correct, something many applications do.
+		if bytesWritten < hd.Size || remainingSize <= 0 {
+			return nil, fmt.Errorf("decompressed chart is larger than the maximum size %d", MaxDecompressedChartSize)
+		}
+
 		data := bytes.TrimPrefix(b.Bytes(), utf8bom)
 
 		files = append(files, &BufferedFile{Name: n, Data: data})

@@ -101,6 +101,10 @@ func LoadDir(dir string) (*chart.Chart, error) {
 			return fmt.Errorf("cannot load irregular file %s as it has file mode type bits set", name)
 		}
 
+		if fi.Size() > MaxDecompressedFileSize {
+			return fmt.Errorf("chart file %q is larger than the maximum file size %d", fi.Name(), MaxDecompressedFileSize)
+		}
+
 		data, err := os.ReadFile(name)
 		if err != nil {
 			return errors.Wrapf(err, "error reading %s", n)