Index: Lib/zipfile.py
===================================================================
--- Lib/zipfile.py	(revision 82848)
+++ Lib/zipfile.py	(working copy)
@@ -492,6 +492,15 @@
         self.mode = mode
         self.name = zipinfo.filename
 
+        if hasattr(zipinfo, 'CRC'):
+            self._expected_crc = zipinfo.CRC
+        else:
+            self._expected_crc = None
+        self._file_size = zipinfo.file_size
+        self._running_crc = crc32(b'') & 0xffffffff
+        self._crc_offset = 0
+        
+
     def readline(self, limit=-1):
         """Read and return a line from the stream.
 
@@ -613,6 +622,20 @@
             self._readbuffer = self._readbuffer[self._offset:] + data
             self._offset = 0
 
+        # Update the CRC. Don't checksum more than self._file_size bytes.
+        max_crc_offset = min(self._file_size, len(self._readbuffer))
+        if max_crc_offset > self._crc_offset:
+            self._running_crc = crc32(
+                self._readbuffer[self._crc_offset:max_crc_offset],
+                self._running_crc) & 0xffffffff
+            self._crc_offset = max_crc_offset
+            
+            #Check the CRC if we're at the end of the file
+            if (self._crc_offset == self._file_size and
+                self._expected_crc is not None and 
+                self._running_crc != self._expected_crc):
+                raise BadZipfile("Bad CRC-32 for file %r" % self.name)
+            
         # Read from buffer.
         data = self._readbuffer[self._offset: self._offset + n]
         self._offset += len(data)
Index: Lib/test/test_zipfile.py
===================================================================
--- Lib/test/test_zipfile.py	(revision 82848)
+++ Lib/test/test_zipfile.py	(working copy)
@@ -662,6 +662,17 @@
 
 
 class OtherTests(unittest.TestCase):
+    zip_with_bad_crc = (
+        b'PK\003\004\024\0\0\0\0\0 \213\212;:r'
+        b'\253\377\f\0\0\0\f\0\0\0\005\0\0\000af'
+        b'ilehello,AworldP'
+        b'K\001\002\024\003\024\0\0\0\0\0 \213\212;:'
+        b'r\253\377\f\0\0\0\f\0\0\0\005\0\0\0\0'
+        b'\0\0\0\0\0\0\0\200\001\0\0\0\000afi'
+        b'lePK\005\006\0\0\0\0\001\0\001\0003\000'
+        b'\0\0/\0\0\0\0\0')
+        
+    
     def test_unicode_filenames(self):
         with zipfile.ZipFile(TESTFN, "w") as zf:
             zf.writestr("foo.txt", "Test for unicode filename")
@@ -875,6 +886,24 @@
         with zipfile.ZipFile(TESTFN, mode="r") as zipfr:
             self.assertEqual(zipfr.comment, comment2)
 
+    def test_testzip_returns_file_with_bad_crc(self):
+        """Tests that files with bad CRCs return their name from testzip."""
+        with open(TESTFN, 'wb') as fp:
+            fp.write(self.zip_with_bad_crc)
+        
+        with zipfile.ZipFile(TESTFN, mode="r") as zipf:
+            #testzip returns the name of the first corrupt file, or None
+            self.assertEqual('afile', zipf.testzip())
+
+    def test_read_bad_crc_raises_BadZipfile(self):
+        """Tests that files with bad CRCs raise a BadZipfile exception when read."""
+        with open(TESTFN, 'wb') as fp:
+            fp.write(self.zip_with_bad_crc)
+            
+        with zipfile.ZipFile(TESTFN, mode="r") as zipf:
+            with zipf.open('afile', 'r') as corrupt_file:
+                self.assertRaises(zipfile.BadZipfile, corrupt_file.read)
+            
     def tearDown(self):
         unlink(TESTFN)
         unlink(TESTFN2)