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oauth.py
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oauth.py
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import base64
import secrets
from datetime import datetime, timedelta
from typing import Any, Dict, List, Optional, Union
from uuid import uuid4
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2
from fastapi.param_functions import Form
from fastapi.openapi.models import OAuthFlows as OAuthFlowsModel, OAuthFlowClientCredentials
from fastapi.security.utils import get_authorization_scheme_param
from starlette.requests import Request
from starlette.status import HTTP_401_UNAUTHORIZED, HTTP_403_FORBIDDEN
from pydantic import BaseModel
from jose import jwt
# To get a string like this run:
# openssl rand -hex 32
# SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30
fake_clients_db = {
"johnsmith": {
'secret': "John smith",
'active': True,
},
"janedoe": {
'secret': "Jane Doe",
'active': True,
}
}
def generate_client_credentials(audience: str, scopes: List[str]=None):
data = dict(
client_id=str(uuid4()),
client_secret=secrets.token_hex(32),
scopes=scopes
)
# Save to db, keyed using audience
return data
class Token(BaseModel):
access_token: str
token_type: str='bearer'
class OAuth2ClientRequestForm:
def __init__(
self,
grant_type: str = Form(None, regex="client_credentials"),
scope: str = Form("api"),
client_id: Optional[str] = Form(None),
client_secret: Optional[str] = Form(None),
):
self.grant_type = grant_type
self.scopes = scope.split()
self.client_id = client_id
self.client_secret = client_secret
class OAuth2ClientBearer(OAuth2):
def __init__(
self,
tokenUrl: str,
scheme_name: Optional[str]=None,
scopes: Optional[Dict[str, str]]=None,
description: Optional[str]=None,
):
if not scopes:
scopes = {}
flows = OAuthFlowsModel(clientCredentials={"tokenUrl": tokenUrl, "scopes": scopes})
super().__init__(
flows=flows,
scheme_name=scheme_name,
description=description,
)
async def __call__(self, request: Request) -> Optional[str]:
authorization: str = request.headers.get("Authorization")
scheme, param = get_authorization_scheme_param(authorization)
if not authorization or scheme.lower() != "bearer":
if self.auto_error:
raise HTTPException(
status_code=HTTP_401_UNAUTHORIZED,
detail="Not authenticated",
headers={"WWW-Authenticate": "Bearer"},
)
else:
return None
return param
oauth2 = OAuth2ClientBearer(tokenUrl="auth/token")
def authenticate(id: str, secret: str):
try:
client = fake_clients_db[id]
return client and client['secret'] == secret
except:
return None
def create_token(
request: Request,
form: OAuth2ClientRequestForm
) -> Token:
id = ""
secret = ""
if form.client_id and form.client_secret:
id = form.client_id
secret = form.client_secret
else:
auth_type, value = request.headers['authorization'].split()
if auth_type.lower() == "basic":
id, secret = base64.b64decode(value).decode('utf-8').split(":")
user = authenticate(id, secret)
if not user:
raise HTTPException(
status_code=status.HTTP_401_UNAUTHORIZED,
detail="Incorrect client credentials",
headers={"WWW-Authenticate": "Bearer"},
)
to_encode = {
'iss': f'https://{request.url.hostname}',
'sub': id,
'iat': datetime.utcnow(),
'scope': ','.join(form.scopes),
'exp': datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES),
}
encoded_jwt = jwt.encode(to_encode, secret, algorithm=ALGORITHM)
return Token(access_token=encoded_jwt)
async def auth_token(token: str=Depends(oauth2)):
credentials_exception = HTTPException(
status_code=status.HTTP_401_UNAUTHORIZED,
detail="Could not validate credentials",
headers={"WWW-Authenticate": "Bearer"},
)
try:
# TODO: use client to look up secret
subject_client = jwt.get_unverified_claims(token)
print(f'Subject: {subject_client}')
subject_id = subject_client['sub']
client = fake_clients_db[subject_id]
print(f'Client: {client}')
# TODO: check to see if client exists
secret = client['secret']
payload = jwt.decode(token, secret, algorithms=[ALGORITHM])
print(f'Payload: {payload}')
id: str = payload.get("sub", None)
if id is None:
raise credentials_exception
except BaseException as err: # JWTError
raise err
# raise credentials_exception
client = fake_clients_db[id]
if client and client['active']:
return client
else:
raise HTTPException(status_code=400, detail="Inactive client")