app-MAIL-temp/app/alias_suffix.py

from __future__ import annotations
import json
from dataclasses import asdict, dataclass
from typing import Optional

import itsdangerous
from app import config
from app.log import LOG
from app.models import User


signer = itsdangerous.TimestampSigner(config.CUSTOM_ALIAS_SECRET)


@dataclass
class AliasSuffix:
    # whether this is a custom domain
    is_custom: bool
    # Suffix
    suffix: str
    # Suffix signature
    signed_suffix: str
    # whether this is a premium SL domain. Not apply to custom domain
    is_premium: bool
    # can be either Custom or SL domain
    domain: str
    # if custom domain, whether the custom domain has MX verified, i.e. can receive emails
    mx_verified: bool = True

    def serialize(self):
        return json.dumps(asdict(self))

    @classmethod
    def deserialize(cls, data: str) -> AliasSuffix:
        return AliasSuffix(**json.loads(data))


def check_suffix_signature(signed_suffix: str) -> Optional[str]:
    # hypothesis: user will click on the button in the 600 secs
    try:
        return signer.unsign(signed_suffix, max_age=600).decode()
    except itsdangerous.BadSignature:
        return None


def verify_prefix_suffix(user: User, alias_prefix, alias_suffix) -> bool:
    """verify if user could create an alias with the given prefix and suffix"""
    if not alias_prefix or not alias_suffix:  # should be caught on frontend
        return False

    user_custom_domains = [cd.domain for cd in user.verified_custom_domains()]

    # make sure alias_suffix is either .random_word@simplelogin.co or @my-domain.com
    alias_suffix = alias_suffix.strip()
    # alias_domain_prefix is either a .random_word or ""
    alias_domain_prefix, alias_domain = alias_suffix.split("@", 1)

    # alias_domain must be either one of user custom domains or built-in domains
    if alias_domain not in user.available_alias_domains():
        LOG.e("wrong alias suffix %s, user %s", alias_suffix, user)
        return False

    # SimpleLogin domain case:
    # 1) alias_suffix must start with "." and
    # 2) alias_domain_prefix must come from the word list
    if (
        alias_domain in user.available_sl_domains()
        and alias_domain not in user_custom_domains
        # when DISABLE_ALIAS_SUFFIX is true, alias_domain_prefix is empty
        and not config.DISABLE_ALIAS_SUFFIX
    ):

        if not alias_domain_prefix.startswith("."):
            LOG.e("User %s submits a wrong alias suffix %s", user, alias_suffix)
            return False

    else:
        if alias_domain not in user_custom_domains:
            if not config.DISABLE_ALIAS_SUFFIX:
                LOG.e("wrong alias suffix %s, user %s", alias_suffix, user)
                return False

            if alias_domain not in user.available_sl_domains():
                LOG.e("wrong alias suffix %s, user %s", alias_suffix, user)
                return False

    return True


def get_alias_suffixes(user: User) -> [AliasSuffix]:
    """
    Similar to as get_available_suffixes() but also return custom domain that doesn't have MX set up.
    """
    user_custom_domains = user.verified_custom_domains()

    alias_suffixes: [AliasSuffix] = []

    # put custom domain first
    # for each user domain, generate both the domain and a random suffix version
    for custom_domain in user_custom_domains:
        if custom_domain.random_prefix_generation:
            suffix = "." + user.get_random_alias_suffix() + "@" + custom_domain.domain
            alias_suffix = AliasSuffix(
                is_custom=True,
                suffix=suffix,
                signed_suffix=signer.sign(suffix).decode(),
                is_premium=False,
                domain=custom_domain.domain,
                mx_verified=custom_domain.verified,
            )
            if user.default_alias_custom_domain_id == custom_domain.id:
                alias_suffixes.insert(0, alias_suffix)
            else:
                alias_suffixes.append(alias_suffix)

        suffix = "@" + custom_domain.domain
        alias_suffix = AliasSuffix(
            is_custom=True,
            suffix=suffix,
            signed_suffix=signer.sign(suffix).decode(),
            is_premium=False,
            domain=custom_domain.domain,
            mx_verified=custom_domain.verified,
        )

        # put the default domain to top
        # only if random_prefix_generation isn't enabled
        if (
            user.default_alias_custom_domain_id == custom_domain.id
            and not custom_domain.random_prefix_generation
        ):
            alias_suffixes.insert(0, alias_suffix)
        else:
            alias_suffixes.append(alias_suffix)

    # then SimpleLogin domain
    for sl_domain in user.get_sl_domains():
        suffix = (
            (
                ""
                if config.DISABLE_ALIAS_SUFFIX
                else "." + user.get_random_alias_suffix()
            )
            + "@"
            + sl_domain.domain
        )
        alias_suffix = AliasSuffix(
            is_custom=False,
            suffix=suffix,
            signed_suffix=signer.sign(suffix).decode(),
            is_premium=sl_domain.premium_only,
            domain=sl_domain.domain,
            mx_verified=True,
        )

        # put the default domain to top
        if user.default_alias_public_domain_id == sl_domain.id:
            alias_suffixes.insert(0, alias_suffix)
        else:
            alias_suffixes.append(alias_suffix)

    return alias_suffixes