Metadata-Version: 1.1
Name: talons
Version: 0.2
Summary: Hooks for Falcon
Home-page: http://github.com/talons/talons
Author: Jay Pipes
Author-email: jaypipes@gmail.com
License: UNKNOWN
Description: # Talons == Falcon Hooks [![Build Status](https://travis-ci.org/talons/talons.png)](https://travis-ci.org/talons/talons)
        
        Talons is a library of WSGI middleware that is designed to work with
        the [Falcon](http://github.com/racker/falcon) lightweight Python framework
        for building RESTful APIs. Like Falcon, Talons aims to be fast, light, and
        flexible.
        
        The first middleware in Talons is authentication middleware, enabling one
        or more backend identity plugins to handle authentication.
        
        # What is `talons.auth`?
        
        `talons.auth` is a namespace package that contains utilies for
        constructing identifying and authenticating middleware and plugins
        designed for applications running the Falcon WSGI micro-framework
        for building REST APIs.
        
        ## A simple usage example
        
        A simple Falcon API application is constructed like so:
        
        ```python
        import falcon
        
        # falcon.API instances are callable WSGI apps
        app = falcon.API()
        ```
        
        To add middleware to a Falcon API application, we simply instantiate the
        desired `talons.auth` middleware and supply it to the `falcon.API()` call:
        
        ```python
        import falcon
        from talons.auth import middleware
        from talons.auth import basicauth, httpheader, htpasswd
        
        # Assume getappconfig() returns a dictionary of application configuration
        # options that may have been read from some INI file...
        config = getappconfig()
        
        auth_middleware = middleware.create_middleware(identify_with=[
                                                         basicauth.Identifier,
                                                         httpheader.Identifier],
                                                       authenticate_with=htpasswd.Authenticator,
                                                       **config)
        
        app = falcon.API(before=[auth_middleware])
        ```
        
        # Details
        
        There are a variety of basic plugins that handle identification of the user making
        an API request and authenticating credentials with a number of common backends,
        including LDAP and SQL data stores.
        
        Authentication involves two main tasks:
        
         * Identifying the user who wishes to be authenticated
         * Validating credentials for the identified user
        
        Classes that derive from `talons.auth.interfaces.Identifies` implement an `identify`
        method that takes the `falcon.request.Request` object from the WSGI pipeline and
        looks at elements of the request to determine who the requesting user is.
        
        The class that stores credential information -- including a login, password/key,
        a set of roles or groups, as well as other metadata about the requesting user --
        is the `talons.auth.interfaces.Identity` class. `talons.auth.interfaces.Identifies`
        subclasses store this `Identity` object in the WSGI environs' "wsgi.identity" bucket.
        
        Classes that derive from `talons.auth.interfaces.Authenticates` implement an
        `authenticate` method that takes a single argument -- a `talons.auth.interfaces.Identity`
        object -- and attempts to validate that the identity is authentic.
        
        To give your Falcon-based WSGI application authentication capabilities, you
        simply create middleware that has one or more `talons.auth.identify` modules
        and one or more `talons.auth.authenticate` modules. We even give you a helper
        method -- `talons.auth.middleware.create_middleware` -- to create such middleware
        in a single call.
        
        ## Identifiers
        
        Each class that derives from `talons.auth.interfaces.Identifies` is called an "Identifier". Each
        class implements a single method, `identify()`, that takes the incoming `falcon.request.Request`
        object as its sole parameter. If the identity of the authenticating user can be determined,
        then the Identifier object stores a `talons.auth.interfaces.Identity` object in the WSGI environ's
        `wsgi.identity` key and returns True.
        
        Multiple Identifier classes can be supplied to the
        `talons.auth.middleware.create_middleware` method to support a variety of ways of
        gleaning identity information from the WSGI request. Each Identifier's
        `identify()` method checks to see if the `wsgi.identity` key is already
        set in the WSGI environs. If it is, the method simply returns True and does
        not attempt to process anything further.
        
        ### `talons.auth.basicauth.Identifier`
        
        The most basic identifier, `talons.auth.basicauth.Identifier` has no
        configuration options and simply looks in the
        [`Authenticate`](http://en.wikipedia.org/wiki/Basic_access_authentication) HTTP
        header for credential information. If the `Authenticate` HTTP header is found
        and contains valid credential information, then that identity information is
        stored in the `wsgi.identity` WSGI environs key.
        
        ### `talons.auth.httpheader.Identifier`
        
        Another simple identifier, `talons.auth.httpheader.Identifier` looks
        for configurable HTTP headers in the incoming WSGI request, and uses the values
        of the HTTP headers to construct a `talons.auth.Identity` object.
        
        A set of configuration options control how this Identifier class behaves:
        
         * `httpheader_user`: HTTP header to look for user/login
           name (required)
         * `httpheader_key`: HTTP header to look for password/key
           (required)
         * `httpheader_$ATTRIBUTE`: HTTP header that, if found, will
           be used to add $ATTRIBUTE to the Identity object stored in the WSGI
           pipeline. (optional)
        
        The above configuration options are supplied to the constructor as keyword
        arguments.
        
        #### Example
        
        Suppose we wanted to extract identity information from the following HTTP
        Headers:
        
         * `X-Auth-User` -- The value of this header will be the authenticating user's
           user name
         * `X-Auth-Password` -- The value of this header will be the authenticating
           user's password
         * `X-Auth-Domain` -- The value of this header should be considered the
           authentication domain that will be considered when authenticating the
           identity. We want to store this value on the `talons.auth.Identity` object's
           `domain` attribute.
        
        Our configuration options would look like this:
        
        ```
        httpheader_user=x-auth-user
        httpheader_key=x-auth-password
        httpheader_domain=x-auth-domain
        ```
        
        ## Authenticators
        
        Each class that derives from `talons.auth.interfaces.Authenticates` is
        called an "Authenticator". Each Authenticator implements a single method,
        `authenticate()`, that takes a `talons.auth.interfaces.Identity` object
        as its sole parameter.
        
        The `authenticate` method verifies that the supplied identity can be
        verified (authenticated). Different implementations will rely on various
        backend storage systems to validate the incoming identity/credentials.
        If authentication was successful, the method returns True, False otherwise.
        
        Talons comes with a few simple examples of Authenticator plugins.
        
        ### `talons.auth.external.Authenticator`
        
        A generic Authenticator plugin that has one main configuration option,
        `external_authn_callable` which should be the "module.function" or
        "module.class.method" dotted-import notation for a function or class
        method that accepts a single parameter. This function will be called by
        the instance of `talons.auth.authenticate.external.Authenticator` to
        validate the credentials of a request.
        
        In addition, there are two other configuration options that indicate
        whether the `external_authfn` function may set the roles or groups
        attributes on the supplied identity:
        
         * `external_sets_roles`: Boolean (defaults to False). A True value
           indicates the plugin may set the roles attribute on the identity
           object.
        
         * `external_sets_groups`: Boolean (defaults to False). A True value
           indicates the plugin may set the groups attribute on the identity
           object.
        
        #### Example
        
        Suppose we have some application code that looks up a stored password
        for a user in a [`Redis`](http://redis.io) Key-Value Store. Salted, encrypted
        passwords for each user are stored in the Redis KVS, along with a
        comma-separated list of roles the user belongs to.
        
        Our application has a Python file called `/application/auth.py` that looks
        like this:
        
        ```python
        import hashlib
        
        import redis
        
        _AUTH_DB = redis.StrictRedis(host='localhost', port=6379, db=0)
        
        
        def _pass_matches_stored_pass(pass, stored_pass):
            # Assume that passwords are stored in Redis in the following format:
            # salt:hashedpass
            # and that the passwords have been hashed with SHA-256
            salt, stored_hashed_pass = stored_pass.split(':')
            hashed_pass = hashlib.sha256(salt.encode() + pass.encode()).hexdigest()
            return hashed_pass == stored_hashed_pass
        
        
        def authenticate(identity):
            user = identity.login
            pass = identity.key
        
            # Assume that user "records" are stored in Redid in the following format:
            # salt:hashedpass#roles
            # Where roles is a comma-separated list of roles
            user_record = _AUTH_DB.get(user)
            if user_record:
                stored_pass, role_list = user_record.split('#')
                auth_success = _pass_matches_stored_pass(pass, stored_pass)
                if auth_success:
                    identity.roles = role_list.split(',')
            return auth_success
        ```
        
        To use the above `application.auth.authenticate` method for authenticating
        identities, we'd supply the following configuration options to the
        `talons.auth.external.Authenticator` constructor:
        
         * `external_authn_callable=application.auth.authenticate`
         * `external_sets_roles=True`
        
        ### `talons.auth.htpasswd.Authenticator`
        
        An Authenticator plugin that queries an Apache htpasswd file to check
        the credentials of a request. The plugin has a single configuration option:
        
         * `htpasswd_path`: The filepath to the Apache htpasswd file to
           use for authentication checks.
        
        ## Authorizers
        
        Each class that derives from `talons.auth.interfaces.Authorizes` is
        called an "Authorizer". Each Authorizer implements a single method,
        `authorize()`, that takes a `talons.auth.interfaces.Identity` object,
        and a `talons.auth.interfaces.ResourceAction` object.
        
        The `ResourceAction` object currently has a single method, `to_string`,
        that returns a "dotted-notation" string describing the requested
        HTTP resource.
        
        For instance, let's say the identity made an HTTP request to:
        
            POST /users/12345/groups
        
        The `ResourceAction.to_string` method that is supplied to the `authorize`
        function would yield the string "users.12345.groups.post". This string is
        useful to plugins that compare the string with the supplied identity object.
        See below for an example that makes this more clear.
        
        At present, there is only a single Authorizer built in to Talons: the
        `talons.auth.external.Authorizer` class. Like its sister, the
        `talons.auth.external.Authenticator`, it accepts an external callable that
        accepts the identity and resource action parameters and returns whether
        the identity is allowed to perform the action on the resource. The single
        configuration parameter is called `external_authz_callable`.
        
        Let's continue the example from above and add an external callable that
        will be used as an authorizer. This callable will compare the result of
        the `ResourceAction`'s `to_string` method against the supplied identity
        object and a hashmap of regular expressions in order to determine if the
        user is permitted to perform an action.
        
        Assuming our application has a Python file called `/application/auth.py` that
        contains the above authenticate code, as well as this:
        like this:
        
        ```python
        import re
        
        
        def self_or_admin(match, identity):
            """
            Returns True if the identity has an admin role or the identity
            matches the requesting user.
            """
            if "admin" in identity.roles:
                return True
            return match.groups(1) == identity.login
        
        
        def anyone(*args):
            return True
        
        
        _POLICY_RULES = [
            (r'^users\.(^\.)+\.get$', self_or_admin),
            (r'^users\.post$', anyone),
        ]
        POLICIES = []
        for regex, fn in _POLICY_RULES:
            POLICIES.append((re.compile(regex), fn))
        
        
        def authorize(identity, resource_action):
            user = identity.login
            res_string = resource_action.to_string()
            for p, fn in _POLICIES:
                m = p.match(res_string)
                if m:
                    return fn(m, identity)
        ```
        
        To use the above `application.auth.authorize` method for authorizing the
        identity that was authenticated, we'd supply the following configuration
        options to the `talons.auth.external.Authorizer` constructor:
        
         * `external_authz_callable=application.auth.authorize`
        
        
        Why `talons.auth`?
        ==================
        
        Why not just use middleware like [repose.who](http://docs.repoze.org/who/2.0/index.html) for
        authentication plugins? Why re-invent the wheel here?
        
        A few reasons, in no particular order:
        
        * Use of the Webob library. I'm not a fan of it, as I've run into numerous issues with
          this library over the years.
        * Use of zope.interfaces. Also not a fan of it. It's a library that seems to be designed
          for traditional C++ programmers instead of feeling like it's designed for Python developers.
          Just use the [abc](http://docs.python.org/2/library/abc.html) module if you absolutely must
          have strict interface enforcement.
        * Trying to override things like logging setup in constructors of middleware.
        * No Paste.
        * Wanted something that fit Falcon's app construction paradigm.
        
        But hey, there's nothing inherently wrong with repoze.who. If you like it, and it works
        for you, use it.
        
        ## Contributing
        
        [Jay Pipes](http://joinfu.com) maintains the Talons library. You can usually find him on the Freenode IRC #openstack-dev
        channel. Interested in improving and enhancing Talons? Pull requests are always welcome.
        
        ## License and Copyright
        
        Copyright 2013, Jay Pipes
        
        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.
        
        
Keywords: falcon
middleware
Platform: UNKNOWN
Classifier: Intended Audience :: Information Technology
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Operating System :: POSIX :: Linux
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 2.6
Classifier: Programming Language :: Python :: 3.3
