def read(encryption_entry: DictionaryObject,
first_id_entry: bytes) -> "Encryption":
filter = encryption_entry.get("/Filter")
if filter != "/Standard":
raise NotImplementedError(
"only Standard PDF encryption handler is available")
if "/SubFilter" in encryption_entry:
raise NotImplementedError("/SubFilter NOT supported")
StmF = "/V2"
StrF = "/V2"
EFF = "/V2"
V = encryption_entry.get("/V", 0)
if V not in (1, 2, 3, 4, 5):
raise NotImplementedError("Encryption V=%d NOT supported" % V)
if V >= 4:
filters = encryption_entry["/CF"]
StmF = encryption_entry.get("/StmF", "/Identity")
StrF = encryption_entry.get("/StrF", "/Identity")
EFF = encryption_entry.get("/EFF", StmF)
if StmF != "/Identity":
StmF = filters[StmF]["/CFM"] # type: ignore
if StrF != "/Identity":
StrF = filters[StrF]["/CFM"] # type: ignore
if EFF != "/Identity":
EFF = filters[EFF]["/CFM"] # type: ignore
allowed_methods = ("/Identity", "/V2", "/AESV2", "/AESV3")
if StmF not in allowed_methods:
raise NotImplementedError("StmF Method {StmF} NOT supported!")
if StrF not in allowed_methods:
raise NotImplementedError(f"StrF Method {StrF} NOT supported!")
if EFF not in allowed_methods:
raise NotImplementedError(f"EFF Method {EFF} NOT supported!")
R = cast(int, encryption_entry["/R"])
return Encryption(V, R, encryption_entry, first_id_entry, StmF, StrF,
EFF)
def __init__(
self,
algV: int,
algR: int,
entry: DictionaryObject,
first_id_entry: bytes,
StmF: str,
StrF: str,
EFF: str,
) -> None:
# See TABLE 3.18 Entries common to all encryption dictionaries
self.algV = algV
self.algR = algR
self.entry = entry
self.key_size = entry.get("/Length", 40)
self.id1_entry = first_id_entry
self.StmF = StmF
self.StrF = StrF
self.EFF = EFF
# 1 => owner password
# 2 => user password
self._password_type = PasswordType.NOT_DECRYPTED
self._key: Optional[bytes] = None
