auth.py

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import base64
import importlib
import logging
import threading
import time
from abc import ABC, abstractmethod
from functools import cached_property
from typing import Any

import requests
from requests import HTTPError, PreparedRequest, Session
from requests.auth import AuthBase

from pyiceberg.catalog.rest.response import TokenResponse, _handle_non_200_response
from pyiceberg.exceptions import OAuthError

AUTH_MANAGER = "auth.manager"

COLON = ":"
logger = logging.getLogger(__name__)


class AuthManager(ABC):
    """
    Abstract base class for Authentication Managers used to supply authorization headers to HTTP clients (e.g. requests.Session).

    Subclasses must implement the `auth_header` method to return an Authorization header value.
    """

    @abstractmethod
    def auth_header(self) -> str | None:
        """Return the Authorization header value, or None if not applicable."""


class NoopAuthManager(AuthManager):
    """Auth Manager implementation with no auth."""

    def auth_header(self) -> str | None:
        return None


class BasicAuthManager(AuthManager):
    """AuthManager implementation that supports basic password auth."""

    def __init__(self, username: str, password: str):
        credentials = f"{username}:{password}"
        self._token = base64.b64encode(credentials.encode()).decode()

    def auth_header(self) -> str:
        return f"Basic {self._token}"


class LegacyOAuth2AuthManager(AuthManager):
    """Legacy OAuth2 AuthManager implementation.

    This class exists for backward compatibility, and will be removed in
    PyIceberg 1.0.0 in favor of OAuth2AuthManager.
    """

    _session: Session
    _auth_url: str | None
    _token: str | None
    _credential: str | None
    _optional_oauth_params: dict[str, str] | None

    def __init__(
        self,
        session: Session,
        auth_url: str | None = None,
        credential: str | None = None,
        initial_token: str | None = None,
        optional_oauth_params: dict[str, str] | None = None,
    ):
        self._session = session
        self._auth_url = auth_url
        self._token = initial_token
        self._credential = credential
        self._optional_oauth_params = optional_oauth_params
        self._refresh_token()

    def _fetch_access_token(self, credential: str) -> str:
        if COLON in credential:
            client_id, client_secret = credential.split(COLON, maxsplit=1)
        else:
            client_id, client_secret = None, credential

        data = {"grant_type": "client_credentials", "client_id": client_id, "client_secret": client_secret}

        if self._optional_oauth_params:
            data.update(self._optional_oauth_params)

        if self._auth_url is None:
            raise ValueError("Cannot fetch access token from undefined auth_url")

        response = self._session.post(
            url=self._auth_url, data=data, headers={**self._session.headers, "Content-type": "application/x-www-form-urlencoded"}
        )
        try:
            response.raise_for_status()
        except HTTPError as exc:
            _handle_non_200_response(exc, {400: OAuthError, 401: OAuthError})

        return TokenResponse.model_validate_json(response.text).access_token

    def _refresh_token(self) -> None:
        if self._credential is not None:
            self._token = self._fetch_access_token(self._credential)

    def auth_header(self) -> str:
        return f"Bearer {self._token}"


class OAuth2TokenProvider:
    """Thread-safe OAuth2 token provider with token refresh support."""

    client_id: str
    client_secret: str
    token_url: str
    scope: str | None
    refresh_margin: int
    expires_in: int | None

    _token: str | None
    _expires_at: int
    _lock: threading.Lock

    def __init__(
        self,
        client_id: str,
        client_secret: str,
        token_url: str,
        scope: str | None = None,
        refresh_margin: int = 60,
        expires_in: int | None = None,
    ):
        self.client_id = client_id
        self.client_secret = client_secret
        self.token_url = token_url
        self.scope = scope
        self.refresh_margin = refresh_margin
        self.expires_in = expires_in

        self._token = None
        self._expires_at = 0
        self._lock = threading.Lock()

    @cached_property
    def _client_secret_header(self) -> str:
        creds = f"{self.client_id}:{self.client_secret}"
        creds_bytes = creds.encode("utf-8")
        b64_creds = base64.b64encode(creds_bytes).decode("utf-8")
        return f"Basic {b64_creds}"

    def _refresh_token(self) -> None:
        data = {"grant_type": "client_credentials"}
        if self.scope:
            data["scope"] = self.scope

        response = requests.post(self.token_url, data=data, headers={"Authorization": self._client_secret_header})
        response.raise_for_status()
        result = response.json()

        self._token = result["access_token"]
        expires_in = result.get("expires_in", self.expires_in)
        if expires_in is None:
            raise ValueError(
                "The expiration time of the Token must be provided by the Server in the Access Token Response in `expires_in` field, or by the PyIceberg Client."
            )
        self._expires_at = time.monotonic() + expires_in - self.refresh_margin

    def get_token(self) -> str:
        with self._lock:
            if not self._token or time.monotonic() >= self._expires_at:
                self._refresh_token()
            if self._token is None:
                raise ValueError("Authorization token is None after refresh")
            return self._token


class OAuth2AuthManager(AuthManager):
    """Auth Manager implementation that supports OAuth2 as defined in IETF RFC6749."""

    def __init__(
        self,
        client_id: str,
        client_secret: str,
        token_url: str,
        scope: str | None = None,
        refresh_margin: int = 60,
        expires_in: int | None = None,
    ):
        self.token_provider = OAuth2TokenProvider(
            client_id,
            client_secret,
            token_url,
            scope,
            refresh_margin,
            expires_in,
        )

    def auth_header(self) -> str:
        return f"Bearer {self.token_provider.get_token()}"


class GoogleAuthManager(AuthManager):
    """An auth manager that is responsible for handling Google credentials."""

    def __init__(self, credentials_path: str | None = None, scopes: list[str] | None = None):
        """
        Initialize GoogleAuthManager.

        Args:
            credentials_path: Optional path to Google credentials JSON file.
            scopes: Optional list of OAuth2 scopes.
        """
        try:
            import google.auth
            import google.auth.transport.requests
        except ImportError as e:
            raise ImportError("Google Auth libraries not found. Please install 'google-auth'.") from e

        if credentials_path:
            self.credentials, _ = google.auth.load_credentials_from_file(credentials_path, scopes=scopes)
        else:
            logger.info("Using Google Default Application Credentials")
            self.credentials, _ = google.auth.default(scopes=scopes)
        self._auth_request = google.auth.transport.requests.Request()

    def auth_header(self) -> str:
        self.credentials.refresh(self._auth_request)
        return f"Bearer {self.credentials.token}"


class AuthManagerAdapter(AuthBase):
    """A `requests.auth.AuthBase` adapter that integrates an `AuthManager` into a `requests.Session` to automatically attach the appropriate Authorization header to every request.

    This adapter is useful when working with `requests.Session.auth`
    and allows reuse of authentication strategies defined by `AuthManager`.
    This AuthManagerAdapter is only intended to be used against the REST Catalog
    Server that expects the Authorization Header.
    """

    def __init__(self, auth_manager: AuthManager):
        """
        Initialize AuthManagerAdapter.

        Args:
            auth_manager (AuthManager): An instance of an AuthManager subclass.
        """
        self.auth_manager = auth_manager

    def __call__(self, request: PreparedRequest) -> PreparedRequest:
        """
        Modify the outgoing request to include the Authorization header.

        Args:
            request (requests.PreparedRequest): The HTTP request being prepared.

        Returns:
            requests.PreparedRequest: The modified request with Authorization header.
        """
        if auth_header := self.auth_manager.auth_header():
            request.headers["Authorization"] = auth_header
        return request


class AuthManagerFactory:
    _registry: dict[str, type["AuthManager"]] = {}

    @classmethod
    def register(cls, name: str, auth_manager_class: type["AuthManager"]) -> None:
        """
        Register a string name to a known AuthManager class.

        Args:
            name (str): unique name like 'oauth2' to register the AuthManager with
            auth_manager_class (Type["AuthManager"]): Implementation of AuthManager

        Returns:
            None
        """
        cls._registry[name] = auth_manager_class

    @classmethod
    def create(cls, class_or_name: str, config: dict[str, Any]) -> AuthManager:
        """
        Create an AuthManager by name or fully-qualified class path.

        Args:
            class_or_name (str): Either a name like 'oauth2' or a full class path like 'my.module.CustomAuthManager'
            config (Dict[str, Any]): Configuration passed to the AuthManager constructor

        Returns:
            AuthManager: An instantiated AuthManager subclass
        """
        if class_or_name in cls._registry:
            manager_cls = cls._registry[class_or_name]
        else:
            try:
                module_path, class_name = class_or_name.rsplit(".", 1)
                module = importlib.import_module(module_path)
                manager_cls = getattr(module, class_name)
            except Exception as err:
                raise ValueError(f"Could not load AuthManager class for '{class_or_name}'") from err

        return manager_cls(**config)


AuthManagerFactory.register("noop", NoopAuthManager)
AuthManagerFactory.register("basic", BasicAuthManager)
AuthManagerFactory.register("legacyoauth2", LegacyOAuth2AuthManager)
AuthManagerFactory.register("oauth2", OAuth2AuthManager)
AuthManagerFactory.register("google", GoogleAuthManager)