# The Flask HTTP Digest Authentication Project.
# Author: imacat@mail.imacat.idv.tw (imacat), 2022/10/22
# Copyright (c) 2022 imacat.
#
# 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.
"""The HTTP Digest Authentication.
See RFC 2617 HTTP Authentication: Basic and Digest Access Authentication
"""
from __future__ import annotations
import sys
import typing as t
from functools import wraps
from random import random
from secrets import token_urlsafe
from flask import g, request, Response, session, abort, Flask, Request, \
current_app
from itsdangerous import URLSafeTimedSerializer, BadData
from werkzeug.datastructures import Authorization
from flask_digest_auth.algo import calc_response
from flask_digest_auth.exception import UnauthorizedException
class DigestAuth:
"""The HTTP digest authentication."""
def __init__(self, realm: t.Optional[str] = None):
"""Constructs the HTTP digest authentication.
:param realm: The realm.
"""
self.secret_key: str = token_urlsafe(32)
self.serializer: URLSafeTimedSerializer \
= URLSafeTimedSerializer(self.secret_key)
self.realm: str = "" if realm is None else realm
self.algorithm: t.Optional[str] = None
self.use_opaque: bool = True
self.domain: t.List[str] = []
self.qop: t.List[str] = ["auth", "auth-int"]
self.__get_password_hash: t.Callable[[str], t.Optional[str]] \
= lambda x: None
self.__get_user: t.Callable[[str], t.Optional] = lambda x: None
def login_required(self, view) -> t.Callable:
"""The view decorator for HTTP digest authentication.
:param view:
:return: The login-protected view.
"""
class NoLogInException(Exception):
"""The exception thrown when the user is not authorized."""
@wraps(view)
def login_required_view(*args, **kwargs) -> t.Any:
"""The login-protected view.
:param args: The positional arguments of the view.
:param kwargs: The keyword arguments of the view.
:return: The response.
"""
try:
if "user" not in session:
raise NoLogInException
user: t.Optional[t.Any] = self.__get_user(session["user"])
if user is None:
raise NoLogInException
g.user = user
return view(*args, **kwargs)
except NoLogInException:
state: AuthState = AuthState()
authorization: Authorization = request.authorization
try:
if authorization is None:
raise UnauthorizedException
if authorization.type != "digest":
raise UnauthorizedException(
"Not an HTTP digest authorization")
self.authenticate(state)
session["user"] = authorization.username
g.user = self.__get_user(authorization.username)
return view(*args, **kwargs)
except UnauthorizedException as e:
if len(e.args) > 0:
sys.stderr.write(e.args[0] + "\n")
response: Response = Response()
response.status = 401
response.headers["WWW-Authenticate"] \
= self.make_response_header(state)
abort(response)
return login_required_view
def authenticate(self, state: AuthState) -> None:
"""Authenticate a user.
:param state: The authorization state.
:return: None.
:raise UnauthorizedException: When the authentication failed.
"""
if "digest_auth_logout" in session:
del session["digest_auth_logout"]
raise UnauthorizedException("Logging out")
authorization: Authorization = request.authorization
if self.use_opaque:
if authorization.opaque is None:
raise UnauthorizedException(
"Missing \"opaque\" in the Authorization header")
try:
self.serializer.loads(
authorization.opaque, salt="opaque", max_age=1800)
except BadData:
raise UnauthorizedException("Invalid opaque")
state.opaque = authorization.opaque
password_hash: t.Optional[str] = self.__get_password_hash(
authorization.username)
if password_hash is None:
raise UnauthorizedException(
f"No such user \"{authorization.username}\"")
expected: str = calc_response(
method=request.method, uri=authorization.uri,
password_hash=password_hash, nonce=authorization.nonce,
qop=authorization.qop,
algorithm=authorization.get("algorithm"),
cnonce=authorization.cnonce, nc=authorization.nc,
body=request.data)
if authorization.response != expected:
state.stale = False
raise UnauthorizedException("Incorrect response value")
try:
self.serializer.loads(
authorization.nonce,
salt="nonce" if authorization.opaque is None
else f"nonce-{authorization.opaque}")
except BadData:
state.stale = True
raise UnauthorizedException("Invalid nonce")
def make_response_header(self, state: AuthState) -> str:
"""Composes and returns the WWW-Authenticate response header.
:param state: The authorization state.
:return: The WWW-Authenticate response header.
"""
opaque: t.Optional[str] = None if not self.use_opaque else \
(state.opaque if state.opaque is not None
else self.serializer.dumps(random(), salt="opaque"))
nonce: str = self.serializer.dumps(
random(), salt="nonce" if opaque is None else f"nonce-{opaque}")
header: str = f"Digest realm=\"{self.realm}\""
if len(self.domain) > 0:
domain_list: str = ",".join(self.domain)
header += f", domain=\"{domain_list}\""
header += f", nonce=\"{nonce}\""
if opaque is not None:
header += f", opaque=\"{opaque}\""
if state.stale is not None:
header += f", stale=TRUE" if state.stale else f", stale=FALSE"
if self.algorithm is not None:
header += f", algorithm=\"{self.algorithm}\""
if len(self.qop) > 0:
qop_list: str = ",".join(self.qop)
header += f", qop=\"{qop_list}\""
return header
def register_get_password(self, func: t.Callable[[str], t.Optional[str]])\
-> None:
"""Registers the callback to obtain the password hash.
:param func: The callback that given the username, returns the password
hash, or None if the user does not exist.
:return: None.
"""
self.__get_password_hash = func
def register_get_user(self, func: t.Callable[[str], t.Optional[t.Any]])\
-> None:
"""Registers the callback to obtain the user.
:param func: The callback that given the username, returns the user,
or None if the user does not exist.
:return: None.
"""
self.__get_user = func
def init_app(self, app: Flask) -> None:
"""Initializes the Flask application.
:param app: The Flask application.
:return: None.
"""
try:
from flask_login import LoginManager, login_user
if not hasattr(app, "login_manager"):
raise AttributeError(
"Please run the Flask-Login init-app() first")
login_manager: LoginManager = getattr(app, "login_manager")
@login_manager.unauthorized_handler
def unauthorized() -> None:
"""Handles when the user is unauthorized.
:return: None.
"""
response: Response = Response()
response.status = 401
response.headers["WWW-Authenticate"] \
= self.make_response_header(g.digest_auth_state)
abort(response)
@login_manager.request_loader
def load_user_from_request(req: Request) -> t.Optional[t.Any]:
"""Loads the user from the request header.
:param req: The request.
:return: The authenticated user, or None if the
authentication fails
"""
g.digest_auth_state = AuthState()
authorization: Authorization = req.authorization
try:
if authorization is None:
raise UnauthorizedException
if authorization.type != "digest":
raise UnauthorizedException(
"Not an HTTP digest authorization")
self.authenticate(g.digest_auth_state)
user = login_manager.user_callback(
authorization.username)
login_user(user)
return user
except UnauthorizedException as e:
if str(e) != "":
app.logger.warning(str(e))
return None
except ModuleNotFoundError:
raise ModuleNotFoundError(
"init_app() is only for Flask-Login integration")
@staticmethod
def logout() -> None:
"""Logs out the user.
This actually causes the next authentication to fail, which forces
the browser to ask the user for the username and password again.
:return: None.
"""
if "user" in session:
del session["user"]
try:
if hasattr(current_app, "login_manager"):
from flask_login import logout_user
logout_user()
except ModuleNotFoundError:
pass
session["digest_auth_logout"] = True
class AuthState:
"""The authorization state."""
def __init__(self):
"""Constructs the authorization state."""
self.opaque: t.Optional[str] = None
self.stale: t.Optional[bool] = None