more.jwtauth 0.4

Overview

This is a Morepath authentication extension for the JSON Web Token (JWT) Authentication.

For more information about JWT, see:

• JSON Web Token draft - the official JWT draft

• Auth with JSON Web Tokens - an interesting blog post by José Padilla

To access resources using JWT Access Authentication, the client must have obtained a JWT to make signed requests to the server. The Token can be opaque to client, although, unless it is encrypted, the client can read the claims made in the token.

JWT validates the authenticity of the claimset using the signature.

This plugin uses the PyJWT library from José Padilla for verifying JWTs.

Introduction

The general workflow of JWT Access Authentication:

• After the client has sent the login form we check if the user exists and if the password is valid.

• In this case more.jwtauth generates a JWT token including all information in a claim set and send it back to the client inside the HTTP authentication header.

• The client stores it in some local storage and send it back in the authentication header on every request.

• more.jwtauth validates the authenticity of the claim set using the signature included in the token.

• The logout should be handled by the client by removing the token and making some cleanup depending on the implementation.

You can include all necessary information about the identity in the token so JWT Access Authentication can be used by a stateless service e.g. with external password validation.

Usage

For a basic setup just set the necessary settings including a key or key file and pass them to JWTIdentityPolicy:

import morepath
from more.jwtauth import JWTIdentityPolicy


class App(morepath.App):
    pass


@App.setting_section(section="jwtauth")
def get_jwtauth_settings():
    return {
        # Set a key or key file.
        'master_secret': 'secret',

        # Adjust the settings which you need.
        'leeway': 10
    }


@App.identity_policy()
def get_identity_policy(settings):
    # Get the jwtauth settings as a dictionary.
    jwtauth_settings = settings.jwtauth.__dict__.copy()

    # Pass the settings dictionary to the identity policy.
    return JWTIdentityPolicy(**jwtauth_settings)


@App.verify_identity()
def verify_identity(identity):
    # As we use a token based authentication we can trust the claimed identity.
    return True

The login can be done in the standard Morepath way. You can add extra information about the identity, which will be stored in the JWT token and can be accessed through the morepath.Identity object:

class Login(object):
    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']

    # Here you get some extra user information.
    fullname = request.POST['fullname']
    email = request.POST['email']
    role = request.POST['role']

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

    @request.after
    def remember(response):
        # We pass the extra info to the identity object.
        identity = morepath.Identity(username, fullname=fullname, email=email, role=role)
        morepath.remember_identity(response, request, identity)

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

Don’t use reserved claim names as “iss”, “aud”, “exp”, “nbf”, “iat”, “jti” and the user_id_claim (default: “sub”, see settings). They will be silently ignored.

Advanced:

For testing or if we want to use some methods of the JWTIdentityPolicy class directly we can pass the settings as arguments to the class:

identity_policy = JWTIdentityPolicy(
    master_secret='secret',
    leeway=10
)

Requirements

• Python (2.7, 3.3, 3.4, 3.5)

• morepath (>= 0.11.1)

• PyJWT (1.3.0)

• cryptography (0.9.1 - be sure to install all dependencies as referenced in https://cryptography.io/en/latest/installation)

Algorithms

The JWT spec supports several algorithms for cryptographic signing. This library currently supports:

HS256

HMAC using SHA-256 hash algorithm (default)

HS384

HMAC using SHA-384 hash algorithm

HS512

HMAC using SHA-512 hash algorithm

ES256

ECDSA signature algorithm using SHA-256 hash algorithm

ES384

ECDSA signature algorithm using SHA-384 hash algorithm

ES512

ECDSA signature algorithm using SHA-512 hash algorithm

PS256

RSASSA-PSS signature using SHA-256 and MGF1 padding with SHA-256

PS384

RSASSA-PSS signature using SHA-384 and MGF1 padding with SHA-384

PS512

RSASSA-PSS signature using SHA-512 and MGF1 padding with SHA-512

RS256

RSASSA-PKCS1-v1_5 signature algorithm using SHA-256 hash algorithm

RS384

RSASSA-PKCS1-v1_5 signature algorithm using SHA-384 hash algorithm

RS512

RSASSA-PKCS1-v1_5 signature algorithm using SHA-512 hash algorithm

Settings

There are some settings that you can override. Here are all the defaults:

@App.setting_section(section="jwtauth")
def get_jwtauth_settings():
    return {
        'master_secret': None,
        'private_key': None,
        'private_key_file': None,
        'public_key': None,
        'public_key_file': None,
        'algorithm': "HS256",
        'expiration_delta': datetime.timedelta(hours=6),
        'leeway': 0,
        'verify_expiration': True,
        'issuer': None,
        'auth_header_prefix': "JWT",
        'userid_claim': "sub"
    }

The following settings are available:

master_secret

A secret known only by the server, used for the default HMAC (HS*) algorithm. Default is None.

private_key

An Elliptic Curve or an RSA private_key used for the EC (EC*) or RSA (PS*/RS*) algorithms. Default is None.

private_key_file

A file holding an Elliptic Curve or an RSA encoded (PEM/DER) private_key. Default is None.

public_key

An Elliptic Curve or an RSA public_key used for the EC (EC*) or RSA (PS*/RS*) algorithms. Default is None.

public_key_file

A file holding an Elliptic Curve or an RSA encoded (PEM/DER) public_key. Default is None.

algorithm

The algorithm used to sign the key. Defaults is HS256.

expiration_delta

Time delta from now until the token will expire. Set to None to disable. Default is 6 hours.

leeway

The leeway, which allows you to validate an expiration time which is in the past, but not very far. To use as a datetime.timedelta. Defaults is None.

verify_expiration

If you set it to False and expiration_delta is not None, you should verify the “exp” claim by yourself and if it is expired you can either refresh the token or you must reject it. Default is True.

issuer

This is a string that will be checked against the iss claim of the token. You can use this e.g. if you have several related apps with exclusive user audience. Default is None (do not check iss on JWT).

auth_header_prefix

You can modify the Authorization header value prefix that is required to be sent together with the token. The default value is JWT. Another common value used for tokens is Bearer.

userid_claim

The claim, which contains the user id. The default claim is ‘sub’.

The library takes either a master_secret or private_key/public_key pair. In the later case the algorithm must be an EC*, PS* or RS* version.

Inspiration

This module is inspired by:

• The pyramid_jwtauth package from Alex Kavanagh.

• The django-rest-framework-jwt package from José Padilla.