# Copyright 2021 AccelByte Inc
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""FastAPI module."""
from pydantic import BaseSettings
from typing import Callable, Optional, Union
from urllib.parse import urlparse
from fastapi import Depends, FastAPI, HTTPException, Request, Security
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer, APIKeyCookie
from .config import Config
from .async_client import NewAsyncClient
from .errors import Error as IAMError, ClientTokenGrantError, GetClientInformationError, \
StartLocalValidationError, TokenRevokedError, UserRevokedError, ValidateAndParseClaimsError, ValidatePermissionError
from .http_errors import InsufficientPermissions, InternalServerError, InvalidRefererHeader, UnauthorizedAccess
from .models import JWTClaims, Permission
# ---------- Exceptions ---------- #
[docs]class HTTPError(HTTPException):
def __init__(self, http_code: int, error_code: int, message: str, description: Optional[str] = None) -> None:
super().__init__(http_code, description)
self.code = http_code
self.error_code = error_code
self.message = message
self.description = description
# ---------- Extensions ---------- #
[docs]class Settings(BaseSettings):
"""IAM settings class.
"""
iam_base_url = ""
iam_client_id = ""
iam_client_secret = ""
iam_token_locations = ["headers", "cookies"]
iam_token_header_name = "Authorization"
iam_token_header_type = "Bearer"
iam_token_cookie_name = "access_token"
iam_token_cookie_path = "/"
iam_csrf_protection = True
iam_strict_referer = True
iam_cors_enable = False
iam_cors_origin = "*"
iam_cors_headers = "*"
iam_cors_methods = "*"
iam_cors_credentials = True
[docs]class IAM:
"""IAM FastAPI extensions class.
"""
def __init__(self, app: Union[FastAPI, None] = None, config: Settings = Settings()) -> None:
if app is not None:
self.init_app(app, config)
[docs] def init_app(self, app: FastAPI, config: Settings = Settings()) -> None:
"""Init IAM FastAPI extensions with FastAPI app.
Client token grant and local validation will be executed once here,
then the background thread will spawn to refresh token, jwks and revocation list.
Args:
app (Flask): Flask app instance
config (Settings): Configuration object
Raises:
IAMError: Error if the requirement configs are not set
"""
if not (
config.iam_base_url and config.iam_client_id and config.iam_client_secret
):
raise IAMError("IAM_BASE_URL, IAM_CLIENT_ID, IAM_CLIENT_SECRET need to set.")
self.config = config
self._set_default_errors(app)
if self.config.iam_cors_enable:
self._set_default_cors_headers(app)
# Grant token on FastAPI startup
@app.on_event("startup")
async def startup_event():
await self.grant_token()
def _set_default_errors(self, app: FastAPI) -> None:
@app.exception_handler(HTTPError)
def handle_http_error(request: Request, error: HTTPError):
return JSONResponse(
status_code=error.code,
content={'errorCode': error.error_code, 'errorMessage': f"{error.message}: {error.description}"}
)
@app.exception_handler(IAMError)
def handle_iam_error(request: Request, error: IAMError):
return JSONResponse(
status_code=InternalServerError[0],
content={'errorCode': InternalServerError[1], 'errorMessage': f"{InternalServerError[1]}: {str(error)}"}
)
def _set_default_cors_headers(self, app: FastAPI) -> None:
allowed_origin = self.config.iam_cors_origin.split(',')
allowed_headers = self.config.iam_cors_headers.split(',')
allowed_methods = self.config.iam_cors_methods.split(',')
allow_credentials = bool(self.config.iam_cors_credentials)
app.add_middleware(
CORSMiddleware,
allow_origins=allowed_origin,
allow_credentials=allow_credentials,
allow_methods=allowed_methods,
allow_headers=allowed_headers,
)
[docs] async def grant_token(self) -> None:
"""Generate oauth IAM token
Raises:
HTTPError: Unable to grant token
"""
config = Config(
BaseURL=self.config.iam_base_url,
ClientID=self.config.iam_client_id,
ClientSecret=self.config.iam_client_secret,
)
client = NewAsyncClient(config)
try:
await client.ClientTokenGrant()
await client.StartLocalValidation()
except (ClientTokenGrantError, StartLocalValidationError) as e:
# Cant get access token from IAM
raise HTTPError(*InternalServerError, description=f"unable to grant token: {str(e)}")
self.client = client
# ---------- Dependencies ---------- #
[docs]def token_required(csrf_protect: Union[bool, None] = None) -> Callable:
"""Validate token in the FastAPI request. This method support headers and cookies with based token.
Args:
csrf_protect (bool, None): Validate referer for CSRF protection
Raises:
IAMError: Error IAM init
HTTPError: Error if token is not found or invalid
Returns:
JWTClaims: JWT claims data
"""
async def _dependency(
request: Request,
bearer: Optional[HTTPAuthorizationCredentials] = Security(HTTPBearer(auto_error=False)),
cookie: Optional[str] = Security(APIKeyCookie(name="access_token", auto_error=False)),
) -> JWTClaims:
try:
iam = request.app.state.iam
except AttributeError:
raise IAMError(
"You must initialize a IAM with on fastapi "
"startup event before using this method"
)
access_token = ""
token_location = iam.config.iam_token_locations
for location in token_location:
# Get token from headers
if location == "headers":
if not bearer:
continue
header_parts = bearer.credentials.split()
access_token = header_parts[-1], "header"
# Get token from cookies
if location == "cookies":
if cookie:
access_token = cookie, "cookie"
if not access_token:
raise HTTPError(*UnauthorizedAccess, description=f"Missing access token in {' or '.join(token_location)}")
try:
jwt_claims = await iam.client.ValidateAndParseClaims(access_token[0])
except (ValidateAndParseClaimsError, UserRevokedError, TokenRevokedError) as e:
raise HTTPError(*UnauthorizedAccess, description=str(e))
if not jwt_claims:
raise HTTPError(*UnauthorizedAccess, description=f"Invalid access token")
# Validate referer header for cookie token
validate_referer = csrf_protect if csrf_protect is not None \
else iam.config.iam_csrf_protection
if access_token[1] == "cookie" and validate_referer:
if await validate_referer_header(request, jwt_claims) is not True:
raise HTTPError(*InvalidRefererHeader, description="Invalid referrer header")
return jwt_claims
return _dependency
[docs]def permission_required(
required_permission: Union[dict, Permission],
permission_resource: dict = {},
csrf_protect: Union[bool, None] = None
) -> Callable:
"""Validate permission in the token if it has required permission
Args:
required_permission (Union[dict, Permission]): The required permission
permission_resource (dict, optional): The placeholder replacement if any. Defaults to {}.
csrf_protect (Union[bool, None], optional): CSRF protect options. Defaults to None.
Raises:
IAMError: Error IAM init
HTTPError: Error if JWT claims data is not sufficient to access required permission and resource
Returns:
Callable: _description_
"""
async def _dependency(request: Request, jwt_claims: JWTClaims = Depends(token_required(csrf_protect))) -> None:
try:
iam = request.app.state.iam
except AttributeError:
raise IAMError(
"You must initialize a IAM with on fastapi "
"startup event before using this method"
)
permission_required = None
is_permitted = False
try:
if isinstance(required_permission, dict):
permission_required = Permission.loads(required_permission)
if not isinstance(permission_required, Permission):
raise ValueError('Invalid Permission')
is_permitted = await iam.client.ValidatePermission(
jwt_claims, permission_required, permission_resource
)
except (ValueError, ValidatePermissionError) as e:
raise HTTPError(*InternalServerError, description=f"unable to validate permission: {str(e)}")
if not is_permitted:
raise HTTPError(
*InsufficientPermissions, description="Access doesn't have required role permission(s)."
)
return _dependency