import base64 import enum import hashlib import json from dataclasses import dataclass from typing import Optional, Union import itsdangerous from app import config from app.log import LOG UNSUB_PREFIX = "un" class UnsubscribeAction(enum.Enum): UnsubscribeNewsletter = 1 DisableAlias = 2 DisableContact = 3 OriginalUnsubscribeMailto = 4 @dataclass class UnsubscribeOriginalData: alias_id: int recipient: str subject: str @dataclass class UnsubscribeData: action: UnsubscribeAction data: Union[UnsubscribeOriginalData, int] @dataclass class UnsubscribeLink: link: str via_email: bool class UnsubscribeEncoder: @staticmethod def encode( action: UnsubscribeAction, data: Union[int, UnsubscribeOriginalData], force_web: bool = False, ) -> UnsubscribeLink: if config.UNSUBSCRIBER and not force_web: return UnsubscribeLink(UnsubscribeEncoder.encode_mailto(action, data), True) return UnsubscribeLink(UnsubscribeEncoder.encode_url(action, data), False) @classmethod def encode_subject( cls, action: UnsubscribeAction, data: Union[int, UnsubscribeOriginalData] ) -> str: if ( action != UnsubscribeAction.OriginalUnsubscribeMailto and type(data) is not int ): raise ValueError(f"Data has to be an int for an action of type {action}") if action == UnsubscribeAction.OriginalUnsubscribeMailto: if type(data) is not UnsubscribeOriginalData: raise ValueError( f"Data has to be an UnsubscribeOriginalData for an action of type {action}" ) # Initial 0 is the version number. If we need to add support for extra use-cases we can bump up this number data = (0, data.alias_id, data.recipient, data.subject) payload = (action.value, data) serialized_data = ( base64.urlsafe_b64encode(json.dumps(payload).encode("utf-8")) .rstrip(b"=") .decode("utf-8") ) signed_data = cls._get_signer().sign(serialized_data).decode("utf-8") encoded_request = f"{UNSUB_PREFIX}.{signed_data}" if len(encoded_request) > 512: LOG.w("Encoded request is longer than 512 chars") return encoded_request @staticmethod def encode_mailto( action: UnsubscribeAction, data: Union[int, UnsubscribeOriginalData] ) -> str: subject = UnsubscribeEncoder.encode_subject(action, data) return f"mailto:{config.UNSUBSCRIBER}?subject={subject}" @staticmethod def encode_url( action: UnsubscribeAction, data: Union[int, UnsubscribeOriginalData] ) -> str: if action == UnsubscribeAction.DisableAlias: return f"{config.URL}/dashboard/unsubscribe/{data}" if action == UnsubscribeAction.DisableContact: return f"{config.URL}/dashboard/block_contact/{data}" if action in ( UnsubscribeAction.UnsubscribeNewsletter, UnsubscribeAction.OriginalUnsubscribeMailto, ): encoded = UnsubscribeEncoder.encode_subject(action, data) return f"{config.URL}/dashboard/unsubscribe/encoded?data={encoded}" @staticmethod def _get_signer() -> itsdangerous.Signer: return itsdangerous.Signer( config.UNSUBSCRIBE_SECRET, digest_method=hashlib.sha3_224 ) @classmethod def decode_subject(cls, data: str) -> Optional[UnsubscribeData]: if data.find(UNSUB_PREFIX) == -1: try: # subject has the format {alias.id}= if data.endswith("="): alias_id = int(data[:-1]) return UnsubscribeData(UnsubscribeAction.DisableAlias, alias_id) # {contact.id}_ elif data.endswith("_"): contact_id = int(data[:-1]) return UnsubscribeData(UnsubscribeAction.DisableContact, contact_id) # {user.id}* elif data.endswith("*"): user_id = int(data[:-1]) return UnsubscribeData( UnsubscribeAction.UnsubscribeNewsletter, user_id ) else: # some email providers might strip off the = suffix alias_id = int(data) return UnsubscribeData(UnsubscribeAction.DisableAlias, alias_id) except ValueError: return None signer = cls._get_signer() try: verified_data = signer.unsign(data[len(UNSUB_PREFIX) + 1 :]) except itsdangerous.BadSignature: return None try: padded_data = verified_data + (b"=" * (-len(verified_data) % 4)) payload = json.loads(base64.urlsafe_b64decode(padded_data)) except ValueError: return None action = UnsubscribeAction(payload[0]) action_data = payload[1] if action == UnsubscribeAction.OriginalUnsubscribeMailto: # Skip version number in action_data[0] for now it's always 0 action_data = UnsubscribeOriginalData( action_data[1], action_data[2], action_data[3] ) return UnsubscribeData(action, action_data)