Provide SP metadata from jupyterhub.

[distortedsignal]

Usually, SAML Service Providers supply metadata so that IdPs can easily interoperate with the individual services. After a request from @guillaumeeb, I thought that it would be a good plan for the Authenticator to also supply this metadata.

This is a pretty early cut of this ability, but I think it's a good start. I'll try using this with one of the IdPs that my company has set up and make changes to this branch. I think this completes #5.

Currently, if the jupyterhub is set up on localhost at port 8000, the returned XML looks like this:

<?xml version="1.0"?>
<EntityDescriptor
 entityID="http://localhost:8000"
 xmlns="urn:oasis:names:tc:SAML:2.0:metadata"
 xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
 xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
    <SPSSODescriptor
     AuthnRequestsSigned="false"
     protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
        <NameIDFormat>
            urn:oasis:names:tc:SAML:2.0:nameid-format:transient
        </NameIDFormat>
        <AssertionConsumerService
         Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
         Location="http://localhost:8000/hub/login"/>
    </SPSSODescriptor>
</EntityDescriptor>

Obviously this isn't as useful as it could be. There are currently issues open on the Authenticator to support fields such as SP OrganizationName and OrganizationDisplayName. I want to make this change small enough to be comprehensible.

Developer Certificate of Origin Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors. 660 York Street, Suite 102, San Francisco, CA 94110 USA

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or

(b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or

(c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it.

(d) I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license(s) involved.

Signed-off-by: Tom Kelley distortedsignal@gmail.com

[guillaumeeb]

Thanks again @distortedsignal, just tell me when this is ready to test, but if I understand correctly, in my case this will at least need another PR.

[distortedsignal]

@guillaumeeb you're right - this is step 1. You'll probably want to test version 0.0.4. I'll ping you when that is ready to go.