Auth.py

############################ Copyrights and license ############################
#                                                                              #
# Copyright 2023 Enrico Minack <github@enrico.minack.dev>                      #
# Copyright 2023 Jirka Borovec <6035284+Borda@users.noreply.github.com>        #
# Copyright 2023 Trim21 <trim21.me@gmail.com>                                  #
# Copyright 2023 chantra <chantra@users.noreply.github.com>                    #
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################################################################################

import abc
import base64
import time
from abc import ABC
from datetime import datetime, timedelta, timezone
from typing import TYPE_CHECKING, Dict, Optional, Union

import jwt
from requests import utils

from github import Consts
from github.InstallationAuthorization import InstallationAuthorization
from github.Requester import Requester, WithRequester

if TYPE_CHECKING:
    from github.GithubIntegration import GithubIntegration

# For App authentication, time remaining before token expiration to request a new one
ACCESS_TOKEN_REFRESH_THRESHOLD_SECONDS = 20
TOKEN_REFRESH_THRESHOLD_TIMEDELTA = timedelta(seconds=ACCESS_TOKEN_REFRESH_THRESHOLD_SECONDS)


# add new implementations of github.Auth.Auth to docs/utilities.rst
class Auth(abc.ABC):
    """
    This class is the base class of all authentication methods for Requester.
    """

    @property
    @abc.abstractmethod
    def token_type(self) -> str:
        """
        The type of the auth token as used in the HTTP Authorization header, e.g. Bearer or Basic.

        :return: token type

        """

    @property
    @abc.abstractmethod
    def token(self) -> str:
        """
        The auth token as used in the HTTP Authorization header.

        :return: token

        """


class HTTPBasicAuth(Auth, abc.ABC):
    @property
    @abc.abstractmethod
    def username(self) -> str:
        """
        The username.
        """

    @property
    @abc.abstractmethod
    def password(self) -> str:
        """
        The password.
        """

    @property
    def token_type(self) -> str:
        return "Basic"

    @property
    def token(self) -> str:
        return base64.b64encode(f"{self.username}:{self.password}".encode()).decode("utf-8").replace("\n", "")


class Login(HTTPBasicAuth):
    """
    This class is used to authenticate with login and password.
    """

    def __init__(self, login: str, password: str):
        assert isinstance(login, str)
        assert len(login) > 0
        assert isinstance(password, str)
        assert len(password) > 0

        self._login = login
        self._password = password

    @property
    def login(self) -> str:
        return self._login

    @property
    def username(self) -> str:
        return self.login

    @property
    def password(self) -> str:
        return self._password


class Token(Auth):
    """
    This class is used to authenticate with a single constant token.
    """

    def __init__(self, token: str):
        assert isinstance(token, str)
        assert len(token) > 0
        self._token = token

    @property
    def token_type(self) -> str:
        return "token"

    @property
    def token(self) -> str:
        return self._token


class JWT(Auth, ABC):
    """
    This class is the base class to authenticate with a JSON Web Token (JWT).

    https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/generating-a-json-web-token-jwt-for-a-github-app

    """

    @property
    def token_type(self) -> str:
        return "Bearer"


class AppAuth(JWT):
    """
    This class is used to authenticate as a GitHub App.

    https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/authenticating-as-a-github-app

    """

    def __init__(
        self,
        app_id: Union[int, str],
        private_key: str,
        jwt_expiry: int = Consts.DEFAULT_JWT_EXPIRY,
        jwt_issued_at: int = Consts.DEFAULT_JWT_ISSUED_AT,
        jwt_algorithm: str = Consts.DEFAULT_JWT_ALGORITHM,
    ):
        assert isinstance(app_id, (int, str)), app_id
        if isinstance(app_id, str):
            assert len(app_id) > 0, "app_id must not be empty"
        assert isinstance(private_key, str)
        assert len(private_key) > 0, "private_key must not be empty"
        assert isinstance(jwt_expiry, int), jwt_expiry
        assert Consts.MIN_JWT_EXPIRY <= jwt_expiry <= Consts.MAX_JWT_EXPIRY, jwt_expiry

        self._app_id = app_id
        self._private_key = private_key
        self._jwt_expiry = jwt_expiry
        self._jwt_issued_at = jwt_issued_at
        self._jwt_algorithm = jwt_algorithm

    @property
    def app_id(self) -> Union[int, str]:
        return self._app_id

    @property
    def private_key(self) -> str:
        return self._private_key

    @property
    def token(self) -> str:
        return self.create_jwt()

    def get_installation_auth(
        self,
        installation_id: int,
        token_permissions: Optional[Dict[str, str]] = None,
        requester: Optional[Requester] = None,
    ) -> "AppInstallationAuth":
        """
        Creates a github.Auth.AppInstallationAuth instance for an installation.

        :param installation_id: installation id
        :param token_permissions: optional permissions
        :param requester: optional requester with app authentication
        :return:

        """
        return AppInstallationAuth(self, installation_id, token_permissions, requester)

    def create_jwt(self, expiration: Optional[int] = None) -> str:
        """
        Create a signed JWT
        https://docs.github.com/en/developers/apps/building-github-apps/authenticating-with-github-apps#authenticating-as-a-github-app

        :return string: jwt
        """
        if expiration is not None:
            assert isinstance(expiration, int), expiration
            assert Consts.MIN_JWT_EXPIRY <= expiration <= Consts.MAX_JWT_EXPIRY, expiration

        now = int(time.time())
        payload = {
            "iat": now + self._jwt_issued_at,
            "exp": now + (expiration if expiration is not None else self._jwt_expiry),
            "iss": self._app_id,
        }
        encrypted = jwt.encode(payload, key=self.private_key, algorithm=self._jwt_algorithm)

        if isinstance(encrypted, bytes):
            return encrypted.decode("utf-8")
        return encrypted


class AppAuthToken(JWT):
    """
    This class is used to authenticate as a GitHub App with a single constant JWT.

    https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/authenticating-as-a-github-app

    """

    def __init__(self, token: str):
        assert isinstance(token, str)
        assert len(token) > 0
        self._token = token

    @property
    def token(self) -> str:
        return self._token


class AppInstallationAuth(Auth, WithRequester["AppInstallationAuth"]):
    """
    This class is used to authenticate as a GitHub App Installation.

    https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/authenticating-as-a-github-app-installation

    """

    # used to fetch live access token when calling self.token
    __integration: Optional["GithubIntegration"] = None
    __installation_authorization: Optional[InstallationAuthorization] = None

    def __init__(
        self,
        app_auth: AppAuth,
        installation_id: int,
        token_permissions: Optional[Dict[str, str]] = None,
        requester: Optional[Requester] = None,
    ):
        super().__init__()

        assert isinstance(app_auth, AppAuth), app_auth
        assert isinstance(installation_id, int), installation_id
        assert token_permissions is None or isinstance(token_permissions, dict), token_permissions

        self._app_auth = app_auth
        self._installation_id = installation_id
        self._token_permissions = token_permissions

        if requester is not None:
            self.withRequester(requester)

    def withRequester(self, requester: Requester) -> "AppInstallationAuth":
        super().withRequester(requester.withAuth(self._app_auth))

        # imported here to avoid circular import
        from github.GithubIntegration import GithubIntegration

        self.__integration = GithubIntegration(**self.requester.kwargs)

        return self

    @property
    def app_id(self) -> Union[int, str]:
        return self._app_auth.app_id

    @property
    def private_key(self) -> str:
        return self._app_auth.private_key

    @property
    def installation_id(self) -> int:
        return self._installation_id

    @property
    def token_permissions(self) -> Optional[Dict[str, str]]:
        return self._token_permissions

    @property
    def token_type(self) -> str:
        return "token"

    @property
    def token(self) -> str:
        if self.__installation_authorization is None or self._is_expired:
            self.__installation_authorization = self._get_installation_authorization()
        return self.__installation_authorization.token

    @property
    def _is_expired(self) -> bool:
        assert self.__installation_authorization is not None
        token_expires_at = self.__installation_authorization.expires_at - TOKEN_REFRESH_THRESHOLD_TIMEDELTA
        return token_expires_at < datetime.now(timezone.utc)

    def _get_installation_authorization(self) -> InstallationAuthorization:
        assert self.__integration is not None, "Method withRequester(Requester) must be called first"
        return self.__integration.get_access_token(
            self._installation_id,
            permissions=self._token_permissions,
        )


class AppUserAuth(Auth, WithRequester["AppUserAuth"]):
    """
    This class is used to authenticate as a GitHub App on behalf of a user.

    https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/authenticating-with-a-github-app-on-behalf-of-a-user

    """

    _client_id: str
    _client_secret: str
    _token: str
    _type: str
    _scope: Optional[str]
    _expires_at: Optional[datetime]
    _refresh_token: Optional[str]
    _refresh_expires_at: Optional[datetime]

    # imported here to avoid circular import
    from github.ApplicationOAuth import ApplicationOAuth

    __app: ApplicationOAuth

    def __init__(
        self,
        client_id: str,
        client_secret: str,
        token: str,
        token_type: Optional[str] = None,
        expires_at: Optional[datetime] = None,
        refresh_token: Optional[str] = None,
        refresh_expires_at: Optional[datetime] = None,
        requester: Optional[Requester] = None,
    ) -> None:
        super().__init__()

        assert isinstance(client_id, str)
        assert len(client_id) > 0
        assert isinstance(client_secret, str)
        assert len(client_secret) > 0
        assert isinstance(token, str)
        assert len(token) > 0
        if token_type is not None:
            assert isinstance(token_type, str)
            assert len(token_type) > 0
        assert isinstance(token, str)
        if token_type is not None:
            assert isinstance(token_type, str)
            assert len(token_type) > 0
        if expires_at is not None:
            assert isinstance(expires_at, datetime)
        if refresh_token is not None:
            assert isinstance(refresh_token, str)
            assert len(refresh_token) > 0
        if refresh_expires_at is not None:
            assert isinstance(refresh_expires_at, datetime)

        self._client_id = client_id
        self._client_secret = client_secret
        self._token = token
        self._type = token_type or "bearer"
        self._expires_at = expires_at
        self._refresh_token = refresh_token
        self._refresh_expires_at = refresh_expires_at

        if requester is not None:
            self.withRequester(requester)

    @property
    def token_type(self) -> str:
        return self._type

    @property
    def token(self) -> str:
        if self._is_expired:
            self._refresh()
        return self._token

    def withRequester(self, requester: Requester) -> "AppUserAuth":
        super().withRequester(requester.withAuth(None))

        # imported here to avoid circular import
        from github.ApplicationOAuth import ApplicationOAuth

        self.__app = ApplicationOAuth(
            # take requester given to super().withRequester, not given to this method
            super().requester,
            headers={},
            attributes={
                "client_id": self._client_id,
                "client_secret": self._client_secret,
            },
            completed=False,
        )

        return self

    @property
    def _is_expired(self) -> bool:
        return self._expires_at is not None and self._expires_at < datetime.now(timezone.utc)

    def _refresh(self) -> None:
        if self._refresh_token is None:
            raise RuntimeError("Cannot refresh expired token because no refresh token has been provided")
        if self._refresh_expires_at is not None and self._refresh_expires_at < datetime.now(timezone.utc):
            raise RuntimeError("Cannot refresh expired token because refresh token also expired")

        # refresh token
        token = self.__app.refresh_access_token(self._refresh_token)

        # update this auth
        self._token = token.token
        self._type = token.type
        self._scope = token.scope
        self._expires_at = token.expires_at
        self._refresh_token = token.refresh_token
        self._refresh_expires_at = token.refresh_expires_at

    @property
    def expires_at(self) -> Optional[datetime]:
        return self._expires_at

    @property
    def refresh_token(self) -> Optional[str]:
        return self._refresh_token

    @property
    def refresh_expires_at(self) -> Optional[datetime]:
        return self._refresh_expires_at


class NetrcAuth(HTTPBasicAuth, WithRequester["NetrcAuth"]):
    """
    This class is used to authenticate via .netrc.
    """

    def __init__(self) -> None:
        super().__init__()

        self._login: Optional[str] = None
        self._password: Optional[str] = None

    @property
    def username(self) -> str:
        return self.login

    @property
    def login(self) -> str:
        assert self._login is not None, "Method withRequester(Requester) must be called first"
        return self._login

    @property
    def password(self) -> str:
        assert self._password is not None, "Method withRequester(Requester) must be called first"
        return self._password

    def withRequester(self, requester: Requester) -> "NetrcAuth":
        super().withRequester(requester)

        auth = utils.get_netrc_auth(requester.base_url, raise_errors=True)
        if auth is None:
            raise RuntimeError(f"Could not get credentials from netrc for host {requester.hostname}")

        self._login, self._password = auth

        return self