FastAPI Basic Authentication - Based on https://fastapi.tiangolo.com/tutorial/security/oauth2-jwt/

fastapi_basic.py

from typing import Optional
import base64
from passlib.context import CryptContext
from datetime import datetime, timedelta

import jwt
from jwt import PyJWTError

from pydantic import BaseModel

from fastapi import Depends, FastAPI, HTTPException
from fastapi.encoders import jsonable_encoder
from fastapi.security import OAuth2PasswordRequestForm, OAuth2
from fastapi.security.base import SecurityBase
from fastapi.security.utils import get_authorization_scheme_param
from fastapi.openapi.docs import get_swagger_ui_html
from fastapi.openapi.models import OAuthFlows as OAuthFlowsModel
from fastapi.openapi.utils import get_openapi

from starlette.status import HTTP_403_FORBIDDEN
from starlette.responses import RedirectResponse, Response, JSONResponse
from starlette.requests import Request


# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "[email protected]",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    }
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: str = None


class User(BaseModel):
    username: str
    email: str = None
    full_name: str = None
    disabled: bool = None


class UserInDB(User):
    hashed_password: str


class OAuth2PasswordBearerCookie(OAuth2):
    def __init__(
        self,
        tokenUrl: str,
        scheme_name: str = None,
        scopes: dict = None,
        auto_error: bool = True,
    ):
        if not scopes:
            scopes = {}
        flows = OAuthFlowsModel(password={"tokenUrl": tokenUrl, "scopes": scopes})
        super().__init__(flows=flows, scheme_name=scheme_name, auto_error=auto_error)

    async def __call__(self, request: Request) -> Optional[str]:
        header_authorization: str = request.headers.get("Authorization")
        cookie_authorization: str = request.cookies.get("Authorization")

        header_scheme, header_param = get_authorization_scheme_param(
            header_authorization
        )
        cookie_scheme, cookie_param = get_authorization_scheme_param(
            cookie_authorization
        )

        if header_scheme.lower() == "bearer":
            authorization = True
            scheme = header_scheme
            param = header_param

        elif cookie_scheme.lower() == "bearer":
            authorization = True
            scheme = cookie_scheme
            param = cookie_param

        else:
            authorization = False

        if not authorization or scheme.lower() != "bearer":
            if self.auto_error:
                raise HTTPException(
                    status_code=HTTP_403_FORBIDDEN, detail="Not authenticated"
                )
            else:
                return None
        return param


class BasicAuth(SecurityBase):
    def __init__(self, scheme_name: str = None, auto_error: bool = True):
        self.scheme_name = scheme_name or self.__class__.__name__
        self.auto_error = auto_error

    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() != "basic":
            if self.auto_error:
                raise HTTPException(
                    status_code=HTTP_403_FORBIDDEN, detail="Not authenticated"
                )
            else:
                return None
        return param


basic_auth = BasicAuth(auto_error=False)

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearerCookie(tokenUrl="/token")

app = FastAPI(docs_url=None, redoc_url=None, openapi_url=None)


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(*, data: dict, expires_delta: timedelta = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(token: str = Depends(oauth2_scheme)):
    credentials_exception = HTTPException(
        status_code=HTTP_403_FORBIDDEN, detail="Could not validate credentials"
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_data = TokenData(username=username)
    except PyJWTError:
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    return user


async def get_current_active_user(current_user: User = Depends(get_current_user)):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.get("/")
async def homepage():
    return "Welcome to the security test!"


@app.post("/token", response_model=Token)
async def route_login_access_token(form_data: OAuth2PasswordRequestForm = Depends()):
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username}, expires_delta=access_token_expires
    )
    return {"access_token": access_token, "token_type": "bearer"}


@app.get("/logout")
async def route_logout_and_remove_cookie():
    response = RedirectResponse(url="/")
    response.delete_cookie("Authorization", domain="localtest.me")
    return response


@app.get("/login_basic")
async def login_basic(auth: BasicAuth = Depends(basic_auth)):
    if not auth:
        response = Response(headers={"WWW-Authenticate": "Basic"}, status_code=401)
        return response

    try:
        decoded = base64.b64decode(auth).decode("ascii")
        username, _, password = decoded.partition(":")
        user = authenticate_user(fake_users_db, username, password)
        if not user:
            raise HTTPException(status_code=400, detail="Incorrect email or password")

        access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
        access_token = create_access_token(
            data={"sub": username}, expires_delta=access_token_expires
        )

        token = jsonable_encoder(access_token)

        response = RedirectResponse(url="/docs")
        response.set_cookie(
            "Authorization",
            value=f"Bearer {token}",
            domain="localtest.me",
            httponly=True,
            max_age=1800,
            expires=1800,
        )
        return response

    except:
        response = Response(headers={"WWW-Authenticate": "Basic"}, status_code=401)
        return response


@app.get("/openapi.json")
async def get_open_api_endpoint(current_user: User = Depends(get_current_active_user)):
    return JSONResponse(get_openapi(title="FastAPI", version=1, routes=app.routes))


@app.get("/docs")
async def get_documentation(current_user: User = Depends(get_current_active_user)):
    return get_swagger_ui_html(openapi_url="/openapi.json", title="docs")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(current_user: User = Depends(get_current_active_user)):
    return [{"item_id": "Foo", "owner": current_user.username}]