Shibboleth

Rails
1

Can anyone direct me to a really good tutorial on Shibboleth integration
with Rails, or indeed some sample code? I’ve been tearing my hair out
all day on this one.

Thanks

RobL

2

Rob,

Turns out Shib is really easy to get working once you have shibd up
and kicking.

First, take a look at the restful_authentication plugin to see how
they handle authentication: Relevantly, there’s a @current_user
instance variable with a setter that looks like this:

def current_user
@current_user ||= user_from_database || user_from_session ||
user_from_login
end

As a before_filter, the system makes use of #logged_in? To determine
if a current user could be found. That code is a simple !!
current_user;

Now, shibboleth adds fields to the request headers of all incoming
traffic. Instead of doing the logged_in filter, we just set something
up to create or find a database record that corresponds to the user.
This looks like this (For the shib variable ‘eppn’), assuming that
your User table has a field named eppn.

def current_user
@current_user ||= User.find_or_create_by_eppn(request.env[‘eppn’])
end

That’s it! Of course, you’re going to need a way to ensure that
database record is meaningful in the context of your application - In
our situation, we test for the presence of contact information and
then prompt the user to add it if none exists, but it doesn’t really
matter because the data in our IP to DNA lookup table is sorted by
their eppn anyway.

E-mail back if my sample code doesn’t work!

-Alex

3

Thanks for the response Alex, to be honest I’m getting in a muddle
trying to figure out how this works / fits together, but I’m picking up
bits and pieces here and there. I’ll take a look at RESTful
authentication and have a play.

Can I check I understand this right? From what I understand the user
tries to access and Shibboleth restricted resource, Apache redirects the
user away to the Identity Provider to authenticate themselves and then
when they are redirected back Apache adds this additional header to each
subsequent request to Mongrel? Or is it a header that is added by the
client and sent through with each subsequent request until they are
logged out?

I guess your application deals with the user once they are already
authenticated and that work is done outside of they rails app. Do you
have any sample configuration for the Shibboleth setup? I’ve seen
something called saml2ruby which has been used to interface with the
service provider directly, and I guess setting those headers in another
way its not greatly documented and I guess not required if Apache can do
everything for you.

Is this just for Apache, I think this client uses Nginx and that might
be a problem?

Thanks again

RobL

4

Hi,

I also need to validate users via Shibboleth on a Ruby application using
Nginx and Mongrel.

I’ve searched but not found instructions on how to do this.

Would someone please let me know if they have a resource for
implementation of Shibboleth on a Ruby / Nginx / Mongrel setup?

Thank you!

Joe

5

I still am unsure about Shibboleth with Nginx - if anyone has experience
or suggestions here, please let me know. Thank you!

Joe

6

Rob L. wrote:

Thanks for the response Alex, to be honest I’m getting in a muddle
trying to figure out how this works / fits together, but I’m picking up
bits and pieces here and there. I’ll take a look at RESTful
authentication and have a play.

Some concepts may be useful, but please don’t ever use that piece of
garbage in your application (it relies too much on generated code). You
may find it useful to compare how Authlogic does things.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

7

Hi,

Just pinging the list (again, but a year later!) to see whether anyone
has advice on validating users via Shibboleth on a Ruby application
using Nginx and Mongrel.

I’ve searched but not found instructions on how to do this.

Would someone please let me know if they have a resource for
implementation of Shibboleth on a Ruby / Nginx / Mongrel setup?

Thank you!

Joe

8

I think at this point, the Shibboleth Service Provider itself only
supports Apache and IIS. The integration is straightforward with those
servers. For rails specific authorization, plugging Shibboleth and
Passenger into Apache makes authentication pretty straightforward.

9

On Fri, Mar 4, 2011 at 4:37 PM, Joe U. [email protected] wrote:

Thank you!

Joe

Alex Bartlow’s post in this thread same thread three years ago gives you
the
answer.

http://www.ruby-forum.com/topic/168155

Searching “Shibboleth Rails” in Google produced more information where
other
people have done this using Passenger.

B.

10

If some of you are interested in using Shibboleth with Ruby and without
Apache or IIS, please try rack-saml.

While it supports only a part of Shibboleth SP functions, you can use it
without Apache or IIS frontend.

It was written to be used with omniauth-shibboleth.

FYI

Best Regards,

Toyokazu AKIYAMA

11

The problem with rack-saml https://github.com/toyokazu/rack-saml and
similar is that they don’t support encrypted responses. I ran into this
issue while trying to work with an IdP and encryption enabled (the
encryption was a requirement).

My stack was nginx (1 server frontend) + passengers (multiple servers).
I
tried lots of solutions but I ended up with shibd and Apache web server.

So, shibd + Apache and a little shib.php file that would grab whatever
shibd environment there is after successful authentication, put it in a
memcache and redirect the browser to my original rails app.

Here’s how my shib.php looks like:

<?php $REDIRECT_URL = 'https://rails.app.example.org/_shib'; $MEMCACHE_HOST = 'memcache.host'; $MEMCACHE_PORT = 11211; # connect to memcache server $memcache = new Memcache; $memcache->connect($MEMCACHE_HOST, $MEMCACHE_PORT) or die ("Could not connect"); # create a temp saml session object from shibd environment variables $saml = new stdClass; $saml->provider = $_SERVER['Shib-Identity-Provider']; $saml->common_name = $_SERVER['CommonName']; $saml->given_name = $_SERVER['givenName']; $saml->surname = $_SERVER['surname']; $saml->edu_person_scoped_affiliation = $_SERVER['eduPersonScopedAffiliation']; $saml->uid = $_SERVER['uid']; $saml->email = $_SERVER['mail']; $saml->principal_name = $_SERVER['principalName']; $shib_session_id = $_SERVER['Shib-Session-ID']; # store this object in the memcache with 60 sec expiration $cache_key = 'samlsess:' . $shib_session_id; $memcache->set($cache_key, json_encode($saml), 0, 60) or die ("Failed to store data in memcache"); # send redirect to the rails app that will fetch the above object from the memcache header('Location: ' . $REDIRECT_URL . '?s=' . $shib_session_id); ?>

So, the browser gets redirected to a URL handled by my rails app, a
custom
Devise strategy specifically:

lib/devise/strategies/shibboleth_authenticatable.rb

require ‘json’

module Devise
module Strategies
class ShibAuthError < RuntimeError; end

class ShibbolethAuthenticatable < Devise::Strategies::Base
  # check public/samlsession/index.php for full set of attributes
  SAML_ATTRIBUTES = %w(provider given_name surname uid email idada)

  # The request should go something like

http://HOST/login?s=_23418cd2aadf
# where s parameter is a key of the auth (usually memcached) data
coming from shibd
def valid?
params[:s].present?
end

  # Method that actually decides whether we'll let the user in
  def authenticate!
    # fetch raw data from the cache
    shib_session = Rails.cache.read(params[:s], :raw => true).to_s
    auth_hash = JSON.parse shib_session

    # sometimes IdP wasn't returning all the attributes
    # so just to make sure we have them all
    validate_saml_attributes! auth_hash

    # find existing user or create a new one since we always trust
    # our IdP
    resource =

mapping.to.find_or_initialize_by_ada_id(auth_hash[‘idada’])
if resource.new_record?
# set SAML_ATTRIBUTES in the newly built user
resource.update_from_saml auth_hash

      # store the new user or raise an exception
      raise(ShibAuthError, 'An error occured during new user

creation’)
unless resource.save
end

    # successfully authenticated
    success! resource
  rescue JSON::ParserError, ShibAuthError
    Rails.logger.error("[ShibbolethAuthenticatable] ERROR during

_shib
authentication: #{$!}")
fail(:invalid) unless halted?
end

  private

  # Checks the presence of all the attributes,
  # otherwise raises an exception
  def validate_saml_attributes!(auth_hash)
    raise(ShibAuthError, "No SAML attributes provided") unless

auth_hash
SAML_ATTRIBUTES.each { |a|
raise(ShibAuthError, “#{a} SAML attribute is missing”) if
auth_hash[a].blank?
}
end
end

end
end

I can wrap this in a sample rails app and opensource it if enough people
are interested.