Fix zipfile decryption. The check for validity only worked on one

type of encrypted zip files.  Files using extended local headers
needed to compare the check byte against different values.  (according
to reading the infozip unzip crypt.c source code)

Fixes issue1003.

1 files changed, 11 insertions, 2 deletions

diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index eb00b34..6feabbf 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -186,6 +186,7 @@ class ZipInfo (object):
             'CRC',
             'compress_size',
             'file_size',
+            '_raw_time',
         )
 
     def __init__(self, filename="NoName", date_time=(1980,1,1,0,0,0)):
@@ -683,6 +684,7 @@ class ZipFile:
                 x.CRC, x.compress_size, x.file_size) = centdir[1:12]
             x.volume, x.internal_attr, x.external_attr = centdir[15:18]
             # Convert date/time code to (year, month, day, hour, min, sec)
+            x._raw_time = t
             x.date_time = ( (d>>9)+1980, (d>>5)&0xF, d&0x1F,
                                      t>>11, (t>>5)&0x3F, (t&0x1F) * 2 )
 
@@ -790,11 +792,18 @@ class ZipFile:
             # The first 12 bytes in the cypher stream is an encryption header
             #  used to strengthen the algorithm. The first 11 bytes are
             #  completely random, while the 12th contains the MSB of the CRC,
+            #  or the MSB of the file time depending on the header type
             #  and is used to check the correctness of the password.
             bytes = zef_file.read(12)
             h = map(zd, bytes[0:12])
-            if ord(h[11]) != ((zinfo.CRC>>24)&255):
-                raise RuntimeError, "Bad password for file %s" % name
+            if zinfo.flag_bits & 0x8:
+                # compare against the file type from extended local headers
+                check_byte = (zinfo._raw_time >> 8) & 0xff
+            else:
+                # compare against the CRC otherwise
+                check_byte = (zinfo.CRC >> 24) & 0xff
+            if ord(h[11]) != check_byte:
+                raise RuntimeError("Bad password for file", name)
 
         # build and return a ZipExtFile
         if zd is None: