diff options
| -rw-r--r-- | CHANGELOG.md | 2 | ||||
| -rwxr-xr-x | DeDRM_plugin/ineptpdf.py | 21 |
2 files changed, 17 insertions, 6 deletions
diff --git a/CHANGELOG.md b/CHANGELOG.md index 51478fb..b1e5816 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -99,4 +99,4 @@ 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): -- (none) +- Fix a bug where decrypting a 40-bit RC4 pdf with R=2 didn't work. diff --git a/DeDRM_plugin/ineptpdf.py b/DeDRM_plugin/ineptpdf.py index ab48130..e227ddc 100755 --- a/DeDRM_plugin/ineptpdf.py +++ b/DeDRM_plugin/ineptpdf.py @@ -1369,11 +1369,12 @@ class PDFDocument(object): keylen = len(key) iv = bytes([0x00]*keylen) + aes = AES.new(key, AES.MODE_CBC, iv) + if not encrypt: - plaintext = AES.new(key,AES.MODE_CBC,iv, True).decrypt(data) + plaintext = aes.decrypt(data) return plaintext else: - aes = AES.new(key, AES.MODE_CBC, iv, False) new_data = bytes(data * repetitions) crypt = aes.encrypt(new_data) return crypt @@ -1478,14 +1479,23 @@ class PDFDocument(object): EncMetadata = b'True' if (EncMetadata == ('False' or 'false') or V < 4) and R >= 4: hash.update(codecs.decode(b'ffffffff','hex')) + + # Finish hash: + hash = hash.digest() + if R >= 3: # 8 for _ in range(50): - hash = hashlib.md5(hash.digest()[:length//8]) - key = hash.digest()[:length//8] + hash = hashlib.md5(hash[:length//8]).digest() + if R == 2: + # R=2 only uses first five bytes. + key = hash[:5] + else: + key = hash[:length//8] + if R == 2: # Algorithm 3.4 - u1 = ARC4.new(key).decrypt(password) + u1 = ARC4.new(key).decrypt(self.PASSWORD_PADDING) elif R >= 3: # Algorithm 3.5 hash = hashlib.md5(self.PASSWORD_PADDING) # 2 @@ -1498,6 +1508,7 @@ class PDFDocument(object): k = b''.join(bytes([c ^ i]) for c in key ) x = ARC4.new(k).decrypt(x) u1 = x+x # 32bytes total + if R == 2: is_authenticated = (u1 == U) else: |