Fix PDF decryption for 256-bit AES with V=5

This commit is contained in:
NoDRM 2023-08-02 18:13:42 +02:00
parent 7f6dd84389
commit e82d2b5c9c
2 changed files with 12 additions and 4 deletions

View File

@ -100,3 +100,4 @@ This is v10.0.9, a release candidate for v10.1.0. I don't expect there to be maj
## Fixes on master (not yet released): ## Fixes on master (not yet released):
- Fix a bug where decrypting a 40-bit RC4 pdf with R=2 didn't work. - Fix a bug where decrypting a 40-bit RC4 pdf with R=2 didn't work.
- Fix a bug where decrypting a 256-bit AES pdf with V=5 didn't work.

View File

@ -1366,8 +1366,7 @@ class PDFDocument(object):
def process_with_aes(self, key, encrypt, data, repetitions = 1, iv = None): def process_with_aes(self, key, encrypt, data, repetitions = 1, iv = None):
if iv is None: if iv is None:
keylen = len(key) iv = bytes(bytearray(16))
iv = bytes([0x00]*keylen)
aes = AES.new(key, AES.MODE_CBC, iv) aes = AES.new(key, AES.MODE_CBC, iv)
@ -1395,10 +1394,18 @@ class PDFDocument(object):
raise Exception("K1 < 32 ...") raise Exception("K1 < 32 ...")
#def process_with_aes(self, key: bytes, encrypt: bool, data: bytes, repetitions: int = 1, iv: bytes = None): #def process_with_aes(self, key: bytes, encrypt: bool, data: bytes, repetitions: int = 1, iv: bytes = None):
E = self.process_with_aes(K[:16], True, K1, 64, K[16:32]) E = self.process_with_aes(K[:16], True, K1, 64, K[16:32])
K = (hashlib.sha256, hashlib.sha384, hashlib.sha512)[sum(E) % 3](E).digest() E = bytearray(E)
E_mod_3 = 0
for i in range(16):
E_mod_3 += E[i]
E_mod_3 %= 3
K = (hashlib.sha256, hashlib.sha384, hashlib.sha512)[E_mod_3](E).digest()
if round_number >= 64: if round_number >= 64:
ch = int.from_bytes(E[-1:], "big", signed=False) ch = E[-1:][0] # get last byte
if ch <= round_number - 32: if ch <= round_number - 32:
done = True done = True