Using Discourse as an identity provider (SSO, DiscourseConnect)

Hi :wave:, I wrote this SimpleSAMLphp authentication module to be able to use Discourse as an SSO provider within a SimpleSAMLphp installation. I.e. you can use Discourse as an SSO provider for any services that supports SAML or Shibboleth authentication, which is really nice.

https://github.com/swcc/simplesamlphp-module-authdiscourse

Let me know what you think (if interested to comment on the code you can use Github Issues).

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That’s great! If you’d like to make the module more visible, you could create a topic about it in our #plugin:extras category. That category is a directory of all extensions & integrations for Discourse which are not Discourse plugins,

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EDIT: Mockup image added


I’m implementing this SSO on an existing web site and I just want to check how people are “presenting” their login method to users.

For example, let’s say my web site at www.example.com has a Login button in the top nav.

Should that login button instantly take people to my discourse login auth page? Or is it preferable to display a page / modal of information first, something like:

I’m just wondering if people will get confused if they’re not told what’s about to happen? :thinking:

Does anyone have any user experiences or best practices to share?

And thanks too by the way to @techAPJ for the very detailed first post in this thread, I was able to successfully build this in to my ASP.NET web site from scratch following your steps :+1:t2:

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Is it possible to include a state parameter that gets returned unchanged, like as is done in OAuth? Asp.net core authentication middleware depends on generating a correlation id to prevent CSRF attacks, and I don’t currently have an easy way to include this.

Could you not add one to the querystring of your callback URL before you wrap it up?

Eg:

nonce=NONCE&return_sso_url=https://www.example.com/my/callback_url.aspx?myparam=here

@jessicah I tried this today and yes, it works fine.

        ' Create a Return URL
        Dim strReturnURL As String = "https://www.example.com/authtestRETURNURL.aspx?myownparametershere=surewhynot"

        ' Generate a random nonce. Save it temporarily so that you can verify it with returned nonce value
        Dim strNonce As String = Guid.NewGuid().ToString("N")

        ' Create a new payload with nonce and return url (where the Discourse will redirect user after verification)
        '       Payload should look like: nonce=NONCE&return_sso_url=RETURN_URL
        Dim strPayload As String = "nonce=" & strNonce & "&return_sso_url=" & strReturnURL

Then on the page which is called back you’ll find this inside your decoded SSO query string:

&return_sso_url=http%3A%2F%2Fwww.example.com%2FauthtestRETURNURL.aspx%3Fmyownparametershere%3Dsurewhynot&username=Rich

Hopefully this is what you meant?

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Multi-site approaches to using discourse-auth-proxy?

Are there any examples or recommendations for using Discourse as SSO provider for multi-site authentication?

It seems like the there are two basic multisite approaches:

  1. Use multiple instances of discourse-auth-proxy, one per site protected.
  2. Use a single instance of discourse-auth-proxy so the payload containing return_sso_url changes based upon the source of the login request.

I think either of these could work, but the issue with these two approaches, is
that you still require logging into each different site.
There is also the risk that something is stored in Postgres that will get overwritten by each login from the different sites. ie: site1.com. site2.com
(I don’t know the details of Discourse auth/PG schema, so I don’t know)

What would be ideal is a way to have login performed once, which gets you logged into all the sites in the multi-site group. ie, site1.com, site2.com, site3.com

Apparently Stackoverflow does this using a combination of localSession storage and Iframes as the main enabler. tech description

But I’d really love to know if someone has implemented any approach to
multisite login using Discourse as the SSO provider.
approach 1: multiple instances of discourse-auth-proxy
approach 2: hacked discourse-auth-proxy affecting return_sso_url in payload.
approach 3: #1 or #2 implemented such that logging in once, means you do not have to login again when moving from site1.com to site2.com

I am tagging you @sam, since you originally authored the Go discourse-auth-proxy program.

Hi.

I am stucking at how the provider handle the + sign in return sso url.

In my case, my DiscourseConnect consumer will create a return_sso_url like

  1. raw http://example.com/foo/bar?wpLoginToken=123+\
  2. PHP urlencoded http%3A%2F%2Fexample.com%2Ffoo%2Fbar%3FwpLoginToken%3D123%2B%5C

then DiscourseConnect will return to

  1. http://example.com/foo/bar?wpLoginToken=123%20\&sso=foo&sig=bar
  2. http://example.com/foo/bar?wpLoginToken=123+\&sso=foo&sig=bar

The problem is that the return to url will be handle by the urldecode function in PHP(it’s the core workflow in MediaWiki Authentication), and the wpLoginToken value will be unexpected change from 123+\ to 123 \.

Look like i has found the cause:
https://ruby-doc.org/stdlib-2.7.1/libdoc/uri/rdoc/URI.html#method-c-decode_www_form
https://www.php.net/manual/en/function.urlencode.php

Well, the client and server implement encode/decode but follow different specification.

I’m not asking Discourse to change but looking for advice to resolve this.

Thanks.

Edit:
I resolve it just urlencode the + sign twice.

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Thanks!

I’m trying this presently. I sent you two PRs on GitHub, one for refreshing the docs and one for fixing a bug I hit.

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In Settings > Login, the two DiscourseConnect provider settings are not consecutive, and appear interspersed with the DiscourseConnect settings:

Since the provider and the non-provider settings are for opposite use cases—using Discourse to manage users for something else versus using something else to manage users for Discourse—displaying these settings mixed together invites misconfiguration. It would be less confusing if the two provider settings were consecutive and either entirely before or entirely after the non-provider settings.

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@techAPJ Can this be used with AWS Cognito? I want to create an app in AWS Amplify for my discourse community and want my app to be authenticated through discourse.