| | |
| | | *************************************************** |
| | | :mod:`repoze.who` -- WSGI Authentication Middleware |
| | | *************************************************** |
| | | ``repoze.who`` -- WSGI Authentication Middleware / API |
| | | ====================================================== |
| | | |
| | | :Author: Chris McDonough |
| | | :Release: 0.1 |
| | | Overview |
| | | -------- |
| | | |
| | | .. module:: repoze.who |
| | | :synopsis: WSGI authentication middleware |
| | | ``repoze.who`` is an identification and authentication framework |
| | | for arbitrary WSGI applications. ``repoze.who`` can be configured |
| | | either as WSGI middleware or as an API for use by an application. |
| | | |
| | | .. topic:: Overview |
| | | |
| | | ``repoze.who`` is an identification and authentication framework |
| | | for arbitrary WSGI applications. It acts as WSGI middleware. |
| | | |
| | | ``repoze.who`` is inspired by Zope 2's Pluggable Authentication |
| | | Service (PAS) (but ``repoze.who`` is not dependent on Zope in any |
| | | way; it is useful for any WSGI application). It provides no |
| | | facility for authorization (ensuring whether a user can or cannot |
| | | perform the operation implied by the request). This is considered |
| | | to be the domain of the WSGI application. |
| | | ``repoze.who`` is inspired by Zope 2's Pluggable Authentication |
| | | Service (PAS) (but ``repoze.who`` is not dependent on Zope in any |
| | | way; it is useful for any WSGI application). It provides no facility |
| | | for authorization (ensuring whether a user can or cannot perform the |
| | | operation implied by the request). This is considered to be the |
| | | domain of the WSGI application. |
| | | |
| | | It attemtps to reuse implementations from ``paste.auth`` for some |
| | | of its functionality. |
| | | |
| | | Middleware Responsibilities |
| | | =========================== |
| | | |
| | | ``repoze.who`` as middleware has one major function on ingress: it |
| | | conditionally places identification and authentication information |
| | | (including a ``REMOTE_USER`` value) into the WSGI environment and |
| | | allows the request to continue to a downstream WSGI application. |
| | | |
| | | ``repoze.who`` as middleware has one major function on egress: it |
| | | examines the headers set by the downstream application, the WSGI |
| | | environment, or headers supplied by other plugins and conditionally |
| | | challenges for credentials. |
| | | |
| | | Configuration Points |
| | | ==================== |
| | | |
| | | Classifiers |
| | | ----------- |
| | | |
| | | ``repoze.who`` "classifies" the request on middleware ingress. |
| | | Request classification happens before identification and |
| | | authentication. A request from a browser might be classified a |
| | | different way that a request from an XML-RPC client. ``repoze.who`` |
| | | uses request classifiers to decide which other components to consult |
| | | during subsequent identification, authentication, and challenge steps. |
| | | Plugins are free to advertise themselves as willing to participate in |
| | | identification and authorization for a request based on this |
| | | classification. The request classification system is pluggable. |
| | | ``repoze.who`` provides a default classifier that you may use. You |
| | | may extend the classification system by making ``repoze.who`` aware of |
| | | a different request classifier implementation. |
| | | |
| | | Challenge Deciders |
| | | ------------------ |
| | | |
| | | ``repoze.who`` uses a "challenge decider" to decide whether the |
| | | response returned from a downstream application requires a challenge |
| | | plugin to fire. When using the default challenge decider, only the |
| | | status is used (if it starts with ``401``, a challenge is required). |
| | | You may supply a different challenge decider as necessary. |
| | | |
| | | Plugins |
| | | ------- |
| | | |
| | | ``repoze.who`` has core functionality designed around the concept of |
| | | plugins. Plugins are instances that are willing to perform one or |
| | | more identification- and/or authentication-related duties. Each |
| | | plugin can be configured arbitrarily. |
| | | |
| | | ``repoze.who`` consults the set of configured plugins when it |
| | | intercepts a WSGI request, and gives some subset of them a chance to |
| | | influence what ``repoze.who`` does for the current request. |
| | | |
| | | Lifecycle of a Request |
| | | ====================== |
| | | |
| | | ``repoze.who`` performs duties both on middleware "ingress" and on |
| | | middleware "egress". |
| | | |
| | | Request (Ingress) Stages |
| | | ------------------------ |
| | | |
| | | ``repoze.who`` performs the following operations in the following order |
| | | during middleware ingress: |
| | | |
| | | 1. Request Classification |
| | | |
| | | The WSGI environment is examined and the request is classified |
| | | into one "type" of request. The callable named as the |
| | | ``classifer`` argument to the ``repoze.who`` middleware |
| | | constructor is used to perform the classification. It returns a |
| | | value that is considered to be the request classification. |
| | | |
| | | 2. Identification |
| | | |
| | | Identifiers which nominate themselves as willing to extract data |
| | | for a particular class of request (as provided by the request |
| | | classifier) will be consulted to retrieve credentials data from |
| | | the environment. For example, a basic auth identifier might use |
| | | the ``HTTP_AUTHORIZATION`` header to find login and password |
| | | information. Identifiers are also responsible for providing |
| | | header information to set and remove authentication information in |
| | | the response. |
| | | |
| | | 3. Authentication |
| | | |
| | | Authenticators which nominate themselves as willing to |
| | | authenticate for a particular class of request will be consulted |
| | | to compare information provided by the identification plugins |
| | | that returned credentials. For example, an htpasswd |
| | | authenticator might look in a file for a user record matching |
| | | any of the identities. If it finds one, and if the password |
| | | listed in the record matches the password provided by an |
| | | identity, the userid of the user would be returned (which would |
| | | be the same as the login name). |
| | | |
| | | 4. Metadata Provision |
| | | |
| | | The identity of the authenticated user found during the |
| | | authentication step can be augmented with arbitrary metadata. |
| | | For example, a metadata provider plugin might augment the |
| | | identity with first, middle and last names, or a more |
| | | specialized metadata provider might augment the identity with a |
| | | list of role or group names. |
| | | |
| | | Response (Egress) Stages |
| | | ------------------------ |
| | | |
| | | ``repoze.who`` performs the following operations in the following order |
| | | during middleware egress: |
| | | |
| | | 1. Challenge Decision |
| | | |
| | | The WSGI environment and the status and headers returned by the |
| | | downstream application may be examined to determine whether a |
| | | challenge is required. Typically, only the status is used (if it |
| | | starts with ``401``, a challenge is required). This behavior is |
| | | pluggable. It is replaced by changing the ``challenge_decider`` |
| | | argument to the middleware. |
| | | |
| | | 2. Challenge |
| | | |
| | | Challengers which nominate themselves as willing to execute a |
| | | challenge for a particular class of request (as provided by the |
| | | classifier) will be consulted, and one will be chosen to perform |
| | | a challenge. A challenger plugin can use application-returned |
| | | headers, the WSGI environment, and other items to determine what |
| | | sort of operation should be performed to actuate the challenge. |
| | | Note that ``repoze.who`` defers to the identifier plugin which |
| | | provided the identity (if any) to reset credentials at challenge |
| | | time; this is not the responsibility of the challenger. |
| | | |
| | | Plugin Types |
| | | ============ |
| | | |
| | | Identifier Plugins |
| | | ------------------ |
| | | |
| | | You can register a plugin as willing to act as an "identifier". An |
| | | identifier examines the WSGI environment and attempts to extract |
| | | credentials from the environment. These credentials are used by |
| | | authenticator plugins to perform authentication. In some cases, an |
| | | identification plugin can "preauthenticate" an identity (and can thus |
| | | act as an authenticator plugin). |
| | | |
| | | Authenticator Plugins |
| | | --------------------- |
| | | |
| | | You may register a plugin as willing to act as an "authenticator". |
| | | Authenticator plugins are responsible for resolving a set of |
| | | credentials provided by an identifier plugin into a user id. |
| | | Typically, authenticator plugins will perform a lookup into a database |
| | | or some other persistent store, check the provided credentials against |
| | | the stored data, and return a user id if the credentials can be |
| | | validated. |
| | | |
| | | The user id provided by an authenticator is eventually passed to |
| | | downstream WSGI applications in the "REMOTE_USER' environment |
| | | variable. Additionally, the "identity" of the user (as provided by |
| | | the identifier from whence the identity came) is passed along to |
| | | downstream application in the ``repoze.who.identity`` environment |
| | | variable. |
| | | |
| | | Metadata Provider Plugins |
| | | ------------------------- |
| | | |
| | | You may register a plugin as willing to act as a "metadata provider" |
| | | (aka mdprovider). Metadata provider plugins are responsible for |
| | | adding arbitrary information to the identity dictionary for |
| | | consumption by downstream applications. For instance, a metadata |
| | | provider plugin may add "group" information to the the identity. |
| | | |
| | | Challenger Plugins |
| | | ------------------ |
| | | |
| | | You may register a plugin as willing to act as a "challenger". |
| | | Challenger plugins are responsible for initiating a challenge to the |
| | | requesting user. Challenger plugins are invoked by ``repoze.who`` when it |
| | | decides a challenge is necessary. A challenge might consist of |
| | | displaying a form or presenting the user with a basic or digest |
| | | authentication dialog. |
| | | |
| | | Default Plugin Implementations |
| | | ============================== |
| | | |
| | | ``repoze.who`` ships with a variety of default plugins that do |
| | | authentication, identification, challenge and metadata provision. |
| | | |
| | | .. module:: repoze.who.plugins.auth_tkt |
| | | |
| | | .. class:: AuthTktCookiePlugin(secret, cookie_name='auth_tkt', secure=False, include_ip=False) |
| | | |
| | | An :class:`AuthTktCookiePlugin` is an ``IIdentifier`` plugin which |
| | | remembers its identity state in a client-side cookie. This plugin |
| | | uses the ``paste.auth.auth_tkt``"auth ticket" protocol. It should |
| | | be instantiated passing a *secret*, which is used to encrypt the |
| | | cookie on the client side and decrypt the cookie on the server side. |
| | | The cookie name used to store the cookie value can be specified |
| | | using the *cookie_name* parameter. If *secure* is False, the cookie |
| | | will be sent across any HTTP or HTTPS connection; if it is True, the |
| | | cookie will be sent only across an HTTPS connection. If |
| | | *include_ip* is True, the ``REMOTE_ADDR`` of the WSGI environment |
| | | will be placed in the cookie. |
| | | |
| | | .. module:: repoze.who.plugins.basicauth |
| | | |
| | | .. class:: BasicAuthPlugin(realm) |
| | | |
| | | A :class:`BasicAuthPlugin` plugin is both an ``IIdentifier`` and |
| | | ``IChallenger`` plugin that implements the Basic Access |
| | | Authentication scheme described in :rfc:`2617`. It looks for |
| | | credentials within the ``HTTP-Authorization`` header sent by |
| | | browsers. It challenges by sending an ``WWW-Authenticate`` header |
| | | to the browser. The single argument *realm* indicates the basic |
| | | auth realm that should be sent in the ``WWW-Authenticate`` header. |
| | | |
| | | .. module:: repoze.who.plugins.cookie |
| | | |
| | | .. class:: InsecureCookiePlugin(cookie_name) |
| | | |
| | | A :class:`InsecureCookiePlugin` is an ``IIdentifier`` plugin. It |
| | | stores identification information in an insecure form (the base64 |
| | | value of the username and password separated by a colon) in a |
| | | client-side cookie. It accepts a single argument named |
| | | *cookie_name*. This is the cookie name of the cookie used to store |
| | | the identification information. |
| | | |
| | | .. module:: repoze.who.plugins.form |
| | | |
| | | .. class:: FormPlugin(login_form_qs, rememberer_name, formbody=None, formcallable=None) |
| | | |
| | | A :class:`FormPlugin` is both an ``IIdentifier`` and ``IChallenger`` |
| | | plugin. It intercepts form POSTs to gather identification at |
| | | ingress and conditionally displays a login form at egress if |
| | | challenge is required. *login_form_qs* is a query string value used |
| | | to denote that a form POST is destined for the form plugin, |
| | | *rememberer_name* is the configuration name of another |
| | | ``IIdentifier`` plugin that will be used to perform ``remember`` and |
| | | ``forget`` duties for the FormPlugin (it does not do these itself), |
| | | *formbody* is a literal string that should be displayed as the form |
| | | body. *formcallable* is a callable that will return a form body if |
| | | *formbody* is None. |
| | | |
| | | .. class:: RedirectingFormPlugin(login_form_url, login_handler_path, logout_handler_path, rememberer_name) |
| | | |
| | | A :class:`RedirectingFormPlugin` is both an ``IIdentifier`` and |
| | | ``IChallenger`` plugin. It intercepts form POSTs to gather |
| | | identification at ingress and conditionally redirects a login form |
| | | at egress if challenge is required (as opposed to the |
| | | :class:`FormPlugin`, it does not handle its own form generation). |
| | | *login_form_url* is a URL that should be redirected to when a |
| | | challnge is required. *login_handler_path* is the path that the |
| | | form will POST to, signifying that the plugin should gather |
| | | credentials. *logout_handler_path* is a path that can be called to |
| | | log the current user out when visited. *rememberer_name* is the |
| | | configuration name of another ``IIdentifier`` plugin that will be |
| | | used to perform ``remember`` and ``forget`` duties for the |
| | | FormPlugin (it does not do these itself). |
| | | |
| | | .. module:: repoze.who.plugins.htpasswd |
| | | |
| | | .. class:: HTPasswdPlugin(filename, check) |
| | | |
| | | .. module:: repoze.who.plugins.sql |
| | | |
| | | .. class:: SQLAuthenticatorPlugin(query, conn_factory, compare_fn) |
| | | |
| | | .. class:: SQLMetadataProviderPlugin(name, query, conn_factory, filter) |
| | | |
| | | |
| | | Middleware Configuration via Python Code |
| | | ======================================== |
| | | |
| | | .. module:: repoze.who.middleware |
| | | |
| | | .. class:: PluggableAuthenticationMiddleware(app, identifiers, challengers, mdproviders, classifier, challenge_decider, log_stream=None, log_level=logging.INFO, remote_user_key='REMOTE_USER') |
| | | |
| | | The primary method of configuring the ``repoze.who`` middleware is |
| | | to use straight Python code, meant to be consumed by frameworks |
| | | which construct and compose middleware pipelines without using a |
| | | configuration file. |
| | | |
| | | In the middleware constructor: *app* is the "next" application in |
| | | the WSGI pipeline. *identifiers* is a sequence of ``IIdentifier`` |
| | | plugins, *challengers* is a sequence of ``IChallenger`` plugins, |
| | | *mdproviders* is a sequence of ``IMetadataProvider`` plugins. Any |
| | | of these can be specified as the empty sequence. *classifier* is a |
| | | request classifier callable, *challenge_decider* is a challenge |
| | | decision callable. *log_stream* is a stream object (an object with |
| | | a ``write`` method), *log_level* is a numeric value that maps to the |
| | | ``logging`` module's notion of log levels, *remote_user_key* is the |
| | | key in which the ``REMOTE_USER`` (userid) value should be placed in |
| | | the WSGI environment for consumption by downstream applications. |
| | | |
| | | An example configuration which uses the default plugins follows:: |
| | | |
| | | from repoze.who.plugins.basicauth import BasicAuthPlugin |
| | | from repoze.who.plugins.auth_tkt import AuthTktCookiePlugin |
| | | from repoze.who.plugins.cookie import InsecureCookiePlugin |
| | | from repoze.who.plugins.form import FormPlugin |
| | | from repoze.who.plugins.htpasswd import HTPasswdPlugin |
| | | io = StringIO() |
| | | salt = 'aa' |
| | | for name, password in [ ('admin', 'admin'), ('chris', 'chris') ]: |
| | | io.write('%s:%s\n' % (name, password)) |
| | | io.seek(0) |
| | | def cleartext_check(password, hashed): |
| | | return password == hashed |
| | | htpasswd = HTPasswdPlugin(io, cleartext_check) |
| | | basicauth = BasicAuthPlugin('repoze.who') |
| | | auth_tkt = AuthTktCookiePlugin('secret', 'auth_tkt') |
| | | form = FormPlugin('__do_login', rememberer_name='auth_tkt') |
| | | form.classifications = { IIdentifier:['browser'], |
| | | IChallenger:['browser'] } # only for browser |
| | | identifiers = [('form', form),('auth_tkt',auth_tkt),('basicauth',basicauth)] |
| | | authenticators = [('htpasswd', htpasswd)] |
| | | challengers = [('form',form), ('basicauth',basicauth)] |
| | | mdproviders = [] |
| | | from repoze.who.classifiers import default_request_classifier |
| | | from repoze.who.classifiers import default_challenge_decider |
| | | log_stream = None |
| | | import os |
| | | if os.environ.get('WHO_LOG'): |
| | | log_stream = sys.stdout |
| | | middleware = PluggableAuthenticationMiddleware( |
| | | app, |
| | | identifiers, |
| | | authenticators, |
| | | challengers, |
| | | mdproviders, |
| | | default_request_classifier, |
| | | default_challenge_decider, |
| | | log_stream = log_stream, |
| | | log_level = logging.DEBUG |
| | | ) |
| | | return middleware |
| | | |
| | | The above example configures the repoze.who middleware with: |
| | | |
| | | - Three ``IIdentifier`` plugins (form auth, auth_tkt cookie, and a |
| | | basic auth plugin). The form auth plugin is set up to fire only |
| | | when the request is a ``browser`` request (as per the request |
| | | classifier). In this setup, when "identification" needs to be |
| | | performed, the form auth plugin will be checked first, then the |
| | | auth_tkt cookie plugin, then the basic auth plugin. |
| | | |
| | | - One ``IAuthenticator`` plugin: an htpasswd one. This htpasswd |
| | | plugin is configured with two valid username/password combinations: |
| | | chris/chris, and admin/admin. When an username and password is |
| | | found via any identifier, it will be checked against this |
| | | authenticator. |
| | | |
| | | - Two ``IChallenger`` plugins: the form plugin, then the basic auth |
| | | plugin. The form auth will fire if the request is a ``browser`` |
| | | request, otherwise the baisc auth plugin will fire. |
| | | |
| | | The rest of the middleware configuration is for values like logging |
| | | and the classifier and decider implementations. These use the default |
| | | implementations. |
| | | |
| | | Middleware Configuration via Config File |
| | | ======================================== |
| | | |
| | | .. note:: |
| | | |
| | | Configuration via a config file is complete "science fiction" |
| | | currently; it is meant to be implemented in a later revision. See |
| | | "Middleware Configuration via Python Code" for the baseline |
| | | mechanisms. |
| | | |
| | | ``repoze.who`` may be configured using a ConfigParser-style .INI file. |
| | | The configuration file has five main types of sections: plugin |
| | | sections, a general section, an identifiers section, an authenticators |
| | | section, and a challengers section. Each "plugin" section defines a |
| | | configuration for a particular plugin. The identifiers, |
| | | authenticators, and challengers sections refer to these plugins to |
| | | form a site configuration. The general section is general middleware |
| | | configuration. |
| | | |
| | | ``repoze.who``'s configuration file can be pointed to within a PasteDeploy |
| | | configuration file :: |
| | | |
| | | [filter:who] |
| | | use = egg:repoze.who#who |
| | | config_file = %(here)s/who.ini |
| | | |
| | | Below is an example of a configuration file that might be used to |
| | | configure the ``repoze.who`` middleware. A set of plugins are defined, |
| | | and they are referred to by following non-plugin sections. |
| | | |
| | | In the below configuration, five plugins are defined. The form, and |
| | | basicauth plugins are nominated to act as challenger plugins. The |
| | | form, cookie, and basicauth plugins are nominated to act as |
| | | identification plugins. The htpasswd and sqlusers plugins are |
| | | nominated to act as authenticator plugins. :: |
| | | |
| | | [plugin:form] |
| | | # identificaion and challenge |
| | | use = egg:repoze.who#form |
| | | login_form_qs = __do_login |
| | | rememberer_name = cookie |
| | | form = %(here)s/login_form.html |
| | | |
| | | [plugin:cookie] |
| | | # identification |
| | | use = egg:repoze.who#cookie |
| | | cookie_name = repoze.who.auth |
| | | |
| | | [plugin:basicauth] |
| | | # identification and challenge |
| | | use = egg:repoze.who#basicauth |
| | | realm = repoze |
| | | |
| | | [plugin:htpasswd] |
| | | # authentication |
| | | use = egg:repoze.who#htpasswd |
| | | filename = %(here)s/users.htpasswd |
| | | check_fn = egg:repoze.who#crypt_check |
| | | |
| | | [plugin:sqlusers] |
| | | # authentication |
| | | use = egg:repoze.who#squsersource |
| | | db = sqlite://database?user=foo&pass=bar |
| | | get_userinfo = select id, password from users |
| | | check_fn = egg:repoze.who#crypt_check |
| | | |
| | | [plugin:properties] |
| | | use = egg:repoze.who#ini_metadata |
| | | filename = %(here)s/etc/properties.ini |
| | | handler = egg:repoze.who#ini_default |
| | | |
| | | [plugin:roles] |
| | | use = egg:repoze.who#ini_metadata |
| | | filename = %(here)s/etc/roles.ini |
| | | |
| | | [general] |
| | | request_classifier = egg:repoze.who#defaultrequestclassifier |
| | | challenge_decider = egg:repoze.who#defaultchallengedecider |
| | | |
| | | [identifiers] |
| | | # plugin_name:classifier_name:.. or just plugin_name (good for any) |
| | | plugins = |
| | | form:browser |
| | | basicauth |
| | | |
| | | [authenticators] |
| | | # plugin_name:classifier_name.. or just plugin_name (good for any) |
| | | plugins = |
| | | htpasswd |
| | | sqlusers |
| | | |
| | | [challengers] |
| | | # plugin_name:classifier_name:.. or just plugin_name (good for any) |
| | | plugins = |
| | | form:browser |
| | | basicauth |
| | | |
| | | [mdproviders] |
| | | plugins = |
| | | properties |
| | | roles |
| | | |
| | | The basicauth section configures a plugin that does identification and |
| | | challenge for basic auth credentials. The form section configures a |
| | | plugin that does identification and challenge (its implementation |
| | | defers to the cookie plugin for identification "forget" and "remember" |
| | | duties, thus the "identifier_impl_name" key; this is looked up at |
| | | runtime). The cookie section configures a plugin that does |
| | | identification for cookie auth credentials. The htpasswd plugin |
| | | obtains its user info from a file. The sqlusers plugin obtains its |
| | | user info from a sqlite database. |
| | | |
| | | The identifiers section provides an ordered list of plugins that are |
| | | willing to provide identification capability. These will be consulted |
| | | in the defined order. The tokens on each line of the ``plugins=`` key |
| | | are in the form "plugin_name:requestclassifier_name:..." (or just |
| | | "plugin_name" if the plugin can be consulted regardless of the |
| | | classification of the request). The configuration above indicates |
| | | that the system will look for credentials using the form plugin (if |
| | | the request is classified as a browser request), then the cookie |
| | | identifier (unconditionally), then the basic auth plugin |
| | | (unconditionally). |
| | | |
| | | The authenticators section provides an ordered list of plugins that |
| | | provide authenticator capability. These will be consulted in the |
| | | defined order, so the system will look for users in the file, then in |
| | | the sql database when attempting to validate credentials. No |
| | | classification prefixes are given to restrict which of the two plugins |
| | | are used, so both plugins are consulted regardless of the |
| | | classification of the request. Each authenticator is called with each |
| | | set of identities found by the identifier plugins. The first identity |
| | | that can be authenticated is used to set ``REMOTE_USER``. |
| | | |
| | | The mdproviders section provides an ordered list of plugins that |
| | | provide metadata provider capability. These will be consulted in the |
| | | defined order. Each will have a chance (on ingress) to provide add |
| | | metadata to the authenticated identity. Our example mdproviders |
| | | section shows two plugins configured: "properties", and "roles". The |
| | | (fictional) properties plugin will add information related to user |
| | | properties (e.g. first name, last name, phone number, etc) to the |
| | | identity dictionary. The (fictional) roles mdprovider will add |
| | | information representing the user's "roles" in the context of the |
| | | current request to the identity dictionary. |
| | | |
| | | The challengers section provides an ordered list of plugins that |
| | | provide challenger capability. These will be consulted in the defined |
| | | order, so the system will consult the cookie auth plugin first, then |
| | | the basic auth plugin. Each will have a chance to initiate a |
| | | challenge. The above configuration indicates that the form challenger |
| | | will fire if it's a browser request, and the basic auth challenger |
| | | will fire if it's not (fallback). |
| | | |
| | | Writing ``repoze.who`` Plugins |
| | | ============================== |
| | | |
| | | ``repoze.who`` can be extended arbitrarily through the creation of |
| | | plugins. Plugins are of one of four types: identifier plugins, |
| | | authenticator plugins, metadata provider plugins, and challenge |
| | | plugins. |
| | | |
| | | Writing An Identifier Plugin |
| | | ---------------------------- |
| | | |
| | | An identifier plugin (aka an ``IIdentifier`` plugin) must do three |
| | | things: extract credentials from the request and turn them into an |
| | | "identity", "remember" credentials, and "forget" credentials. |
| | | |
| | | Here's a simple cookie identification plugin that does these three |
| | | things :: |
| | | |
| | | class InsecureCookiePlugin(object): |
| | | |
| | | def __init__(self, cookie_name): |
| | | self.cookie_name = cookie_name |
| | | |
| | | def identify(self, environ): |
| | | cookies = get_cookies(environ) |
| | | cookie = cookies.get(self.cookie_name) |
| | | |
| | | if cookie is None: |
| | | return None |
| | | |
| | | import binascii |
| | | try: |
| | | auth = cookie.value.decode('base64') |
| | | except binascii.Error: # can't decode |
| | | return None |
| | | |
| | | try: |
| | | login, password = auth.split(':', 1) |
| | | return {'login':login, 'password':password} |
| | | except ValueError: # not enough values to unpack |
| | | return None |
| | | |
| | | def remember(self, environ, identity): |
| | | cookie_value = '%(login)s:%(password)s' % identity |
| | | cookie_value = cookie_value.encode('base64').rstrip() |
| | | from paste.request import get_cookies |
| | | cookies = get_cookies(environ) |
| | | existing = cookies.get(self.cookie_name) |
| | | value = getattr(existing, 'value', None) |
| | | if value != cookie_value: |
| | | # return a Set-Cookie header |
| | | set_cookie = '%s=%s; Path=/;' % (self.cookie_name, cookie_value) |
| | | return [('Set-Cookie', set_cookie)] |
| | | |
| | | def forget(self, environ, identity): |
| | | # return a expires Set-Cookie header |
| | | expired = ('%s=""; Path=/; Expires=Sun, 10-May-1971 11:59:00 GMT' % |
| | | self.cookie_name) |
| | | return [('Set-Cookie', expired)] |
| | | |
| | | def __repr__(self): |
| | | return '<%s %s>' % (self.__class__.__name__, id(self)) |
| | | |
| | | Note that the plugin implements three "interface" methods: "identify", |
| | | "forget" and "remember". The formal specification for the arguments |
| | | and return values expected from these methods are available in the |
| | | ``interfaces.py`` file in ``repoze.who`` as the ``IIdentifier`` |
| | | interface, but let's examine them less formally one at a time. |
| | | |
| | | .. module:: repoze.who.interfaces |
| | | |
| | | .. class:: IIdentifier |
| | | |
| | | .. method:: IIdentifier.identify(environ) |
| | | |
| | | The ``identify`` method of our InsecureCookiePlugin accepts a |
| | | single argument "environ". This will be the WSGI environment |
| | | dictionary. Our plugin attempts to grub through the cookies sent |
| | | by the client, trying to find one that matches our cookie name. If |
| | | it finds one that matches, it attempts to decode it and turn it |
| | | into a login and a password, which it returns as values in a |
| | | dictionary. This dictionary is thereafter known as an "identity". |
| | | If it finds no credentials in cookies, it returns None (which is |
| | | not considered an identity). |
| | | |
| | | More generally, the ``identify`` method of an ``IIdentifier`` |
| | | plugin is called once on WSGI request "ingress", and it is expected |
| | | to grub arbitrarily through the WSGI environment looking for |
| | | credential information. In our above plugin, the credential |
| | | information is expected to be in a cookie but credential |
| | | information could be in a cookie, a form field, basic/digest auth |
| | | information, a header, a WSGI environment variable set by some |
| | | upstream middleware or whatever else someone might use to stash |
| | | authentication information. If the plugin finds credentials in the |
| | | request, it's expected to return an "identity": this must be a |
| | | dictionary. The dictionary is not required to have any particular |
| | | keys or value composition, although it's wise if the identification |
| | | plugin looks for both a login name and a password information to |
| | | return at least {'login':login_name, 'password':password}, as some |
| | | authenticator plugins may depend on presence of the names "login" |
| | | and "password" (e.g. the htpasswd and sql ``IAuthenticator`` |
| | | plugins). If an ``IIdentifier`` plugin finds no credentials, it is |
| | | expected to return None. |
| | | |
| | | An ``IIdentifier`` plugin is also permitted to "preauthenticate" an |
| | | identity. If the identifier plugin knows that the identity is |
| | | "good" (e.g. in the case of ticket-based authentication where the |
| | | userid is embedded into the ticket), it can insert a special key |
| | | into the identity dictionary: ``repoze.who.userid``. If this key |
| | | is present in the identity dictionary, no authenticators will be |
| | | asked to authenticate the identity. This effectively allows an |
| | | ``IIdentifier`` plugin to become an ``IAuthenticator`` plugin when |
| | | breaking apart the responsibility into two separate plugins is |
| | | "make-work". Preauthenticated identities will be selected first |
| | | when deciding which identity to use for any given request. Our |
| | | cookie plugin doesn't use this feature. |
| | | |
| | | .. method:: IIdentifier.remember(environ, identity) |
| | | |
| | | If we've passed a REMOTE_USER to the WSGI application during |
| | | ingress (as a result of providing an identity that could be |
| | | authenticated), and the downstream application doesn't kick back |
| | | with an unauthorized response, on egress we want the requesting |
| | | client to "remember" the identity we provided if there's some way |
| | | to do that and if he hasn't already, in order to ensure he will |
| | | pass it back to us on subsequent requests without requiring another |
| | | login. The remember method of an ``IIdentifier`` plugin is called for |
| | | each non-unauthenticated response. It is the responsibility of the |
| | | ``IIdentifier`` plugin to conditionally return HTTP headers that will |
| | | cause the client to remember the credentials implied by "identity". |
| | | |
| | | Our InsecureCookiePlugin implements the "remember" method by |
| | | returning headers which set a cookie if and only if one is not |
| | | already set with the same name and value in the WSGI environment. |
| | | These headers will be tacked on to the response headers provided by |
| | | the downstream application during the response. |
| | | |
| | | When you write a remember method, most of the work involved is |
| | | determining *whether or not* you need to return headers. It's |
| | | typical to see remember methods that compute an "old state" and a |
| | | "new state" and compare the two against each other in order to |
| | | determine if headers need to be returned. In our example |
| | | InsecureCookiePlugin, the "old state" is ``cookie_value`` and the |
| | | "new state" is ``value``. |
| | | |
| | | .. method:: IIdentifier.forget(environ, identity) |
| | | |
| | | Eventually the WSGI application we're serving will issue a "401 |
| | | Unauthorized" or another status signifying that the request could |
| | | not be authorized. ``repoze.who`` intercepts this status and calls |
| | | ``IIdentifier`` plugins asking them to "forget" the credentials implied |
| | | by the identity. It is the "forget" method's job at this point to |
| | | return HTTP headers that will effectively clear any credentials on |
| | | the requesting client implied by the "identity" argument. |
| | | |
| | | Our InsecureCookiePlugin implements the "forget" method by |
| | | returning a header which resets the cookie that was set earlier by |
| | | the remember method to one that expires in the past (on my |
| | | birthday, in fact). This header will be tacked onto the response |
| | | headers provided by the downstream application. |
| | | |
| | | Writing an Authenticator Plugin |
| | | ------------------------------- |
| | | |
| | | An authenticator plugin (aka an ``IAuthenticator`` plugin) must do |
| | | only one thing (on "ingress"): accept an identity and check if the |
| | | identity is "good". If the identity is good, it should return a "user |
| | | id". This user id may or may not be the same as the "login" provided |
| | | by the user. An ``IAuthenticator`` plugin will be called for each |
| | | identity found during the identification phase (there may be multiple |
| | | identities for a single request, as there may be multiple |
| | | ``IIdentifier`` plugins active at any given time), so it may be called |
| | | multiple times in the same request. |
| | | |
| | | Here's a simple authenticator plugin that attempts to match an |
| | | identity against ones defined in an "htpasswd" file that does just |
| | | that:: |
| | | |
| | | class SimpleHTPasswdPlugin(object): |
| | | |
| | | def __init__(self, filename): |
| | | self.filename = filename |
| | | |
| | | # IAuthenticatorPlugin |
| | | def authenticate(self, environ, identity): |
| | | try: |
| | | login = identity['login'] |
| | | password = identity['password'] |
| | | except KeyError: |
| | | return None |
| | | |
| | | f = open(self.filename, 'r') |
| | | |
| | | for line in f: |
| | | try: |
| | | username, hashed = line.rstrip().split(':', 1) |
| | | except ValueError: |
| | | continue |
| | | if username == login: |
| | | if crypt_check(password, hashed): |
| | | return username |
| | | return None |
| | | |
| | | def crypt_check(password, hashed): |
| | | from crypt import crypt |
| | | salt = hashed[:2] |
| | | return hashed == crypt(password, salt) |
| | | |
| | | An ``IAuthenticator`` plugin implements one "interface" method: |
| | | "authentictate". The formal specification for the arguments and |
| | | return values expected from these methods are available in the |
| | | ``interfaces.py`` file in ``repoze.who`` as the ``IAuthenticator`` |
| | | interface, but let's examine this method here less formally. |
| | | |
| | | .. class:: IAuthenticator |
| | | |
| | | .. method:: IAuthenticator.authenticate(environ, identity) |
| | | |
| | | The ``authenticate`` method accepts two arguments: the WSGI |
| | | environment and an identity. Our SimpleHTPasswdPlugin |
| | | ``authenticate`` implementation grabs the login and password out of |
| | | the identity and attempts to find the login in the htpasswd file. |
| | | If it finds it, it compares the crypted version of the password |
| | | provided by the user to the crypted version stored in the htpasswd |
| | | file, and finally, if they match, it returns the login. If they do |
| | | not match, it returns None. |
| | | |
| | | Note that our plugin's ``authenticate`` method does not assume that |
| | | the keys ``login`` or ``password`` exist in the identity; although |
| | | it requires them to do "real work" it returns None if they are not |
| | | present instead of raising an exception. This is required by the |
| | | ``IAuthenticator`` interface specification. |
| | | |
| | | Writing a Challenger Plugin |
| | | --------------------------- |
| | | |
| | | A challenger plugin (aka an ``IChallenger`` plugin) must do only one |
| | | thing on "egress": return a WSGI application which performs a |
| | | "challenge". A WSGI application is a callable that accepts an |
| | | "environ" and a "start_response" as its parameters; see "PEP 333" for |
| | | further definition of what a WSGI application is. A challenge asks |
| | | the user for credentials. |
| | | |
| | | Here's an example of a simple challenger plugin:: |
| | | |
| | | from paste.httpheaders import WWW_AUTHENTICATE |
| | | from paste.httpexceptions import HTTPUnauthorized |
| | | |
| | | class BasicAuthChallengerPlugin(object): |
| | | |
| | | def __init__(self, realm): |
| | | self.realm = realm |
| | | |
| | | # IChallenger |
| | | def challenge(self, environ, status, app_headers, forget_headers): |
| | | head = WWW_AUTHENTICATE.tuples('Basic realm="%s"' % self.realm) |
| | | if head[0] not in forget_headers: |
| | | head = head + forget_headers |
| | | return HTTPUnauthorized(headers=head) |
| | | |
| | | Note that the plugin implements a single "interface" method: |
| | | "challenge". The formal specification for the arguments and return |
| | | values expected from this method is available in the "interfaces.py" |
| | | file in ``repoze.who`` as the ``IChallenger`` interface. This method |
| | | is called when ``repoze.who`` determines that the application has |
| | | returned an "unauthorized" response (e.g. a 401). Only one challenger |
| | | will be consulted during "egress" as necessary (the first one to |
| | | return a non-None response). |
| | | |
| | | .. class:: IChallenger |
| | | |
| | | .. method:: IChallenger.challenge(environ, status, app_headers, forget_headers) |
| | | |
| | | The challenge method takes environ (the WSGI environment), 'status' |
| | | (the status as set by the downstream application), the |
| | | "app_headers" (headers returned by the application), and the |
| | | "forget_headers" (headers returned by all participating |
| | | ``IIdentifier`` plugins whom were asked to "forget" this user). |
| | | |
| | | Our BasicAuthChallengerPlugin takes advantage of the fact that the |
| | | HTTPUnauthorized exception imported from paste.httpexceptions can |
| | | be used as a WSGI application. It first makes sure that we don't |
| | | repeat headers if an identification plugin has already set a |
| | | "WWW-Authenticate" header like ours, then it returns an instance of |
| | | HTTPUnauthorized, passing in merged headers. This will cause a |
| | | basic authentication dialog to be presented to the user. |
| | | |
| | | Writing a Metadata Provider Plugin |
| | | ---------------------------------- |
| | | |
| | | A metadata provider plugin (aka an ``IMetadataProvider`` plugin) must |
| | | do only one thing (on "ingress"): "scribble" on the identity |
| | | dictionary provided to it when it is called. An ``IMetadataProvider`` |
| | | plugin will be called with the final "best" identity found during the |
| | | authentication phase, or not at all if no "best" identity could be |
| | | authenticated. Thus, each ``IMetadataProvider`` plugin will be called |
| | | exactly zero or one times during a request. |
| | | |
| | | Here's a simple metadata provider plugin that provides "property" |
| | | information from a dictionary:: |
| | | |
| | | _DATA = { |
| | | 'chris': {'first_name':'Chris', 'last_name':'McDonough'} , |
| | | 'whit': {'first_name':'Whit', 'last_name':'Morriss'} |
| | | } |
| | | |
| | | class SimpleMetadataProvider(object): |
| | | |
| | | def add_metadata(self, environ, identity): |
| | | userid = identity.get('repoze.who.userid') |
| | | info = _DATA.get(userid) |
| | | if info is not None: |
| | | identity.update(info) |
| | | |
| | | .. class:: IMetadataProvider |
| | | |
| | | .. method:: IMetadataProvider.add_metadata(environ, identity) |
| | | |
| | | Arbitrarily add information to the identity dict based in other data |
| | | in the environment or identity. |
| | | |
| | | Further Information about Interfaces |
| | | ==================================== |
| | | |
| | | For further information about interfaces, see the module |
| | | ``repoze.who.interfaces``. |
| | | |
| | | See the ``docs`` subdirectory of this package (also available at least |
| | | provisionally at http://static.repoze.org/whodocs) for more |
| | | information. |