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kfxdrm: Traipse through the kfx-zip more efficiently

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We only need to read the magic bytes headers to identify files of the
correct type.  Avoid slurping the entire contents out of the zip if it's
the wrong file.
This commit is contained in:
Conrad Meyer 2018-04-05 10:32:59 -07:00
parent 85e3db8f7c
commit 4400d8d1d4
1 changed files with 12 additions and 5 deletions
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17
DeDRM_calibre_plugin/DeDRM_plugin/kfxdedrm.py
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@ -36,8 +36,11 @@ class KFXZipBook:
def processBook(self, totalpids):
with zipfile.ZipFile(self.infile, 'r') as zf:
for filename in zf.namelist():
data = zf.read(filename)
if data.startswith('\xeaDRMION\xee'):
with zf.open(filename) as fh:
data = fh.read(8)
if data != '\xeaDRMION\xee':
continue
data += fh.read()
if self.voucher is None:
self.decrypt_voucher(totalpids)
print u'Decrypting KFX DRMION: {0}'.format(filename)
@ -51,9 +54,13 @@ class KFXZipBook:
def decrypt_voucher(self, totalpids):
with zipfile.ZipFile(self.infile, 'r') as zf:
for info in zf.infolist():
if info.file_size < 0x10000:
data = zf.read(info.filename)
if data.startswith('\xe0\x01\x00\xea') and 'ProtectedData' in data:
with zf.open(info.filename) as fh:
data = fh.read(4)
if data != '\xe0\x01\x00\xea':
continue
data += fh.read()
if 'ProtectedData' in data:
break # found DRM voucher
else:
raise Exception(u'The .kfx-zip archive contains an encrypted DRMION file without a DRM voucher')