From cf599f6f6f1c392d8f12936982a370d533782195 Mon Sep 17 00:00:00 2001
From: Zackery Spytz <zspytz@gmail.com>
Date: Mon, 13 May 2019 01:50:52 -0600
Subject: bpo-6584: Add a BadGzipFile exception to the gzip module. (GH-13022)
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Co-Authored-By: Filip Gruszczyński <gruszczy@gmail.com>
Co-Authored-By: Michele Orrù <maker@tumbolandia.net>
---
 Lib/gzip.py | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

(limited to 'Lib/gzip.py')

diff --git a/Lib/gzip.py b/Lib/gzip.py
index 7c86187419..2968f475ef 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -11,7 +11,7 @@ import builtins
 import io
 import _compression
 
-__all__ = ["GzipFile", "open", "compress", "decompress"]
+__all__ = ["BadGzipFile", "GzipFile", "open", "compress", "decompress"]
 
 FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16
 
@@ -112,6 +112,11 @@ class _PaddedFile:
     def seekable(self):
         return True  # Allows fast-forwarding even in unseekable streams
 
+
+class BadGzipFile(OSError):
+    """Exception raised in some cases for invalid gzip files."""
+
+
 class GzipFile(_compression.BaseStream):
     """The GzipFile class simulates most of the methods of a file object with
     the exception of the truncate() method.
@@ -413,12 +418,12 @@ class _GzipReader(_compression.DecompressReader):
             return False
 
         if magic != b'\037\213':
-            raise OSError('Not a gzipped file (%r)' % magic)
+            raise BadGzipFile('Not a gzipped file (%r)' % magic)
 
         (method, flag,
          self._last_mtime) = struct.unpack("<BBIxx", self._read_exact(8))
         if method != 8:
-            raise OSError('Unknown compression method')
+            raise BadGzipFile('Unknown compression method')
 
         if flag & FEXTRA:
             # Read & discard the extra field, if present
@@ -502,10 +507,10 @@ class _GzipReader(_compression.DecompressReader):
         # stored is the true file size mod 2**32.
         crc32, isize = struct.unpack("<II", self._read_exact(8))
         if crc32 != self._crc:
-            raise OSError("CRC check failed %s != %s" % (hex(crc32),
-                                                         hex(self._crc)))
+            raise BadGzipFile("CRC check failed %s != %s" % (hex(crc32),
+                                                             hex(self._crc)))
         elif isize != (self._stream_size & 0xffffffff):
-            raise OSError("Incorrect length of data produced")
+            raise BadGzipFile("Incorrect length of data produced")
 
         # Gzip files can be padded with zeroes and still have archives.
         # Consume all zero bytes and set the file position to the first
-- 
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