more.basicauth: HTTP Basic Authentication integration for Morepath

Overview

This is a Morepath authentication extension for HTTP Basic Authentication. It was originally part of Morepath, but since basic auth is almost always what you don't want we decide to move it to a separate extension.

Some Pros and Cons:

• This argues against basic auth: http://adrianotto.com/2013/02/why-http-basic-auth-is-bad
• But this argues for basic auth: https://www.rdegges.com/2015/why-i-love-basic-auth

Alternative authentication extensions for morepath are:

• more.jwtauth: A token based authentication sytem using JSON Web Token (JWT).
• more.isdangerous: A cookie based identity policy using isdangerous.

Introduction

Basic authentication is special in a number of ways:

• The HTTP response status that triggers basic auth is Unauthorized (401), not the default Forbidden (403). This needs to be sent back to the browser each time login fails, so that the browser asks the user for a username and a password.
• The username and password combination is sent to the server by the browser automatically; there is no need to set some type of cookie on the response. Therefore remember_identity does nothing.
• With basic auth, there is no universal way for a web application to trigger a log out. Therefore forget_identity does nothing either.

To trigger a 401 status when time Morepath raises a 403 status, we can use an exception view, something like this:

from webob.exc import HTTPForbidden

@App.view(model=HTTPForbidden)
def make_unauthorized(self, request):
    @request.after
    def set_status_code(response):
        response.status_code = 401
    return "Unauthorized"

For the login code, as remember_identity is not an option, you can just check the password:

# check whether user has password, using password hash and database
if not user_has_password(username, password):
    return "Sorry, login failed" # or something more fancy

Note that user_has_password stands in for whatever method you use to check a user's password; it's not part of Morepath.

Usage

Here a full example for a basic setup:

import morepath
from more.basicauth import BasicAuthIdentityPolicy
from webob.exc import HTTPForbidden


class App(morepath.App):
    pass


@App.identity_policy()
def get_identity_policy():
    return BasicAuthIdentityPolicy()


@App.verify_identity()
def verify_identity(identity):
    # Do the password validation.
    return user_has_password(identity.username, identity.password)


@App.view(model=HTTPForbidden)
def make_unauthorized(self, request):
    @request.after
    def set_status_code(response):
        response.status_code = 401

    return "Unauthorized"

The login form could look like:

from webob.exc import HTTPProxyAuthenticationRequired


class Login:
    pass


@App.path(model=Login, path='login')
def get_login():
    return Login()


@App.view(model=Login, request_method='POST')
def login(self, request):
    username = request.POST['username']
    password = request.POST['password']

    # Do the password validation.
    if not user_has_password(username, password):
        raise HTTPProxyAuthenticationRequired('Invalid username/password')

    return "You're logged in."  # or something more fancy

Requirements

• Python (3.4, 3.5, 3.7, 3.8, 3.9)
• morepath (>= 0.19)