Limit marc field terminator search to first 2048 bytes

internal/magic/binary.go

@@ -139,6 +139,10 @@ func Marc(raw []byte, limit uint32) bool {
 		}
 	}
 
-	// Field terminator is present.
-	return bytes.Contains(raw, []byte{0x1E})
+	l := 2048
+	if len(raw) < l {
+		l = len(raw)
+	}
+	// Field terminator is present in first 2048 bytes.
+	return bytes.Contains(raw[:l], []byte{0x1E})
 }