def initialize(self, password=''):
if not self.encryption:
self.is_printable = self.is_modifiable = self.is_extractable = True
return
(docid, param) = self.encryption
if literal_name(param.get('Filter')) != 'Standard':
raise PDFEncryptionError('Unknown filter: param=%r' % param)
V = int_value(param.get('V', 0))
if not (V == 1 or V == 2):
raise PDFEncryptionError('Unknown algorithm: param=%r' % param)
length = int_value(param.get('Length', 40)) # Key length (bits)
O = str_value(param['O'])
R = int_value(param['R']) # Revision
if 5 <= R:
raise PDFEncryptionError('Unknown revision: %r' % R)
U = str_value(param['U'])
P = int_value(param['P'])
self.is_printable = bool(P & 4)
self.is_modifiable = bool(P & 8)
self.is_extractable = bool(P & 16)
# Algorithm 3.2
password = (password+self.PASSWORD_PADDING)[:32] # 1
hash = md5.md5(password) # 2
hash.update(O) # 3
hash.update(struct.pack('<l', P)) # 4
hash.update(docid[0]) # 5
if 4 <= R:
# 6
raise PDFNotImplementedError('Revision 4 encryption is currently unsupported')
if 3 <= R:
# 8
for _ in range(50):
hash = md5.md5(hash.digest()[:length/8])
key = hash.digest()[:length/8]
if R == 2:
# Algorithm 3.4
u1 = Arcfour(key).process(self.PASSWORD_PADDING)
elif R == 3:
# Algorithm 3.5
hash = md5.md5(self.PASSWORD_PADDING) # 2
hash.update(docid[0]) # 3
x = Arcfour(key).process(hash.digest()[:16]) # 4
for i in range(1,19+1):
k = ''.join( chr(ord(c) ^ i) for c in key )
x = Arcfour(k).process(x)
u1 = x+x # 32bytes total
if R == 2:
is_authenticated = (u1 == U)
else:
is_authenticated = (u1[:16] == U[:16])
if not is_authenticated:
raise PDFPasswordIncorrect
self.decrypt_key = key
self.decipher = self.decrypt_rc4 # XXX may be AES
return
def search(entry, level):
entry = dict_value(entry)
if 'Title' in entry:
if 'A' in entry or 'Dest' in entry:
title = decode_text(str_value(entry['Title']))
dest = entry.get('Dest')
action = entry.get('A')
se = entry.get('SE')
yield (level, title, dest, action, se)
if 'First' in entry and 'Last' in entry:
for x in search(entry['First'], level+1):
yield x
if 'Next' in entry:
for x in search(entry['Next'], level):
yield x
return
