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Using repoze.who.plugins.ldap in a TurboGears 2.1 app

Jul 19, 2011 | categories: python, turbogears, ldap View Comments

Often, you will need to authenticate against ldap in your webapp. Here's how to make that happen in a freshly quickstarted TurboGears 2.1 app.

Setting up your environment

mkvirtualenv --no-site-packages repoze-ldap-app
pip install tg.devtools
paster quickstart   # call the app repoze-ldap-app, yes to mako and auth
cd repoze-ldap-app
python setup.py develop
pip install genshi  # This is a workaround.
paster setup-app development.ini
paster serve development.ini  # To test if the basic app works.

Point your browser at http://localhost:8080 just to make sure everything is cool.

Setting up repoze.who.plugins.ldap

Add the following line to the install_requires list in setup.py:

    "repoze.who.plugins.ldap",

Run python setup.py develop to install the newly listed repoze plugin.

Add the following four lines to development.ini which reference an as yet unwritten secondary configuration file. Place them just above the sqlalchemy.url=... lines:

# Repoze.who stuff
who.config_file = %(here)s/who.ini
who.log_level = INFO
who.log_stream = stdout

Create a new file who.ini with the following contents:

# This file is adapted from:
# http://threebean.org/blog/2011/07/19/using-repoze-who-plugins-ldap-in-a-turbogears-2-1-app/
# which has been adapted from:
# http://static.repoze.org/whodocs/#middleware-configuration-via-config-file
# which has been adapted from:
# http://code.gustavonarea.net/repoze.who.plugins.ldap/Using.html

[plugin:friendlyform]
use = repoze.who.plugins.friendlyform:FriendlyFormPlugin
login_form_url= /login
login_handler_path = /login_handler
logout_handler_path = /logout_handler
rememberer_name = auth_tkt
post_login_url = /post_login
post_logout_url = /post_logout

[plugin:auth_tkt]
use = repoze.who.plugins.auth_tkt:make_plugin
secret = omg_this_is_so_secret_lololololol_2938485#butts

[plugin:ldap_auth]
# Here I use my own ldap_auth, since by default ldap allows affirmative
# authentication with *no password specified*.  That is lame; I override it.
use = repozeldapapp.lib.auth:ReconnectingAuthenticatorPlugin

# This is the URI of wherever you want to connect to.  I work at RIT.
ldap_connection = ldap://ldap.rit.edu

# This is the base of the 'distinguished names' (DNs) of persons in your
# particular LDAP instance.  It will vary from server to server.
base_dn = ou=People,dc=rit,dc=edu

[plugin:ldap_attributes]
# I also do some overriding for more security in how I get attributes for
# users.
use = repozeldapapp.lib.auth:ReconnectingLDAPAttrsPlugin
ldap_connection = ldap://ldap.rit.edu

[general]
request_classifier = repoze.who.classifiers:default_request_classifier
challenge_decider = repoze.who.classifiers:default_challenge_decider

[mdproviders]
plugins =
    ldap_attributes

[identifiers]
plugins =
    friendlyform;browser
    auth_tkt

[authenticators]
plugins =
    ldap_auth

[challengers]
plugins =
    friendlyform;browser

Create another new file repozeldapapp/lib/auth.py with the following contents:

from repoze.who.plugins.ldap import (
    LDAPAttributesPlugin, LDAPAuthenticatorPlugin
)
import ldap


class URISaver(object):
    """ Saves the ldap_connection str given to repoze authn and authz """
    def __init__(self, *args, **kw):
        self.uri = kw['ldap_connection']
        super(URISaver, self).__init__(*args, **kw)


class ReconnectingLDAPAttrsPlugin(LDAPAttributesPlugin, URISaver):
    """ Gets attributes from LDAP.  Refreshes connection if stale. """

    def add_metadata(self, environ, identity):
        """ Add ldap attributes to the `identity` entry. """

        try:
            return super(ReconnectingLDAPAttrsPlugin, self).add_metadata(
                environ, identity)
        except Exception, e:
            print "FAILED TO CONNECT TO LDAP 1 : " + str(e)
            print "Retrying..."
            self.ldap_connection = ldap.initialize(self.uri)
            return super(ReconnectingLDAPAttrsPlugin, self).add_metadata(
                environ, identity)


class ReconnectingAuthenticatorPlugin(LDAPAuthenticatorPlugin, URISaver):
    """ Authenticates against LDAP.

    - Refreshes connection if stale.
    - Denies anonymously-authenticated users

    """

    def authenticate(self, environ, identity):
        """ Extending the repoze.who.plugins.ldap plugin to make it much
        more secure. """

        res = None

        try:
            # This is unbelievable.  Without this, ldap will
            #   let you bind anonymously
            if not identity.get('password', None):
                return None
            try:
                dn = self._get_dn(environ, identity)
            except (KeyError, TypeError, ValueError):
                return None

            res = super(ReconnectingAuthenticatorPlugin, self).authenticate(
                environ, identity)

            # Sanity check here (for the same reason as the above check)
            if "dn:%s" % dn != self.ldap_connection.whoami_s():
                return None

        except ldap.LDAPError, e:
            print "FAILED TO CONNECT TO LDAP 2 : " + str(e)
            print "Retrying..."
            self.ldap_connection = ldap.initialize(self.uri)

        return res

Finally, do two things to repozeldapapp/config/middleware.py.

Edit it and at the top of the file add:

from repoze.who.config import make_middleware_with_config

Add the following inside the make_app(...) function, just below the comment line about Wrap your base TurboGears 2..., like so:

    # Wrap your base TurboGears 2 application with custom middleware here
    app = make_middleware_with_config(
        app, global_conf,
        app_conf['who.config_file'],
        app_conf['who.log_stream'],
        app_conf['who.log_level'])

Give it a test

Restart the paster server and reload http://localhost:8080. Try logging in as a user in your ldap instance and you should be all gravy.

You should be all gravy.
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