app-MAIL-temp/app/handler/unsubscribe_encoder.py

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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) > 256:
LOG.e("Encoded request is longer than 256 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)