WebSSO initial redirect 404s

[Colleen Murphy]

On current master of horizon, when WebSSO is configured, after selecting the SSO auth method from the "Authenticate Using" dropdown menu, instead of redirecting to the configured identity provider, horizon redirects to /dashboard/auth/login/default/auth/OS-FEDERATION/websso/mapped and then 404s.

git bisect shows that this is the commit that introduced the bug: https://review.openstack.org/593650

stable/rocky works fine.

Steps to reproduce
------------------

Configure horizon with:

 WEBSSO_ENABLED = True
 WEBSSO_CHOICES = (("credentials", _("Keystone Credentials")), ("mapped", _("External Authentication Service")),)
 DEBUG = True

In the dropdown menu on the login screen, select "External Authentication Service"

Expected behavior
-----------------

Horizon should redirect to the configured identity provider for the keystone federation protocol named "mapped". If you have not fully set up federation in keystone, keystone should return a 401.

Actual behavior
---------------

Horizon returns a 404 with this message:

Using the URLconf defined in openstack_dashboard.urls, Django tried these URL patterns, in this order:

^$ [name='splash']
^api/
^header/
^home/$ [name='user_home']
^i18n/js/(?P<packages>\S+?)/$ [name='jsi18n']
^i18n/setlang/$ [name='set_language']
^i18n/
^jasmine-legacy/$ [name='jasmine_tests']
^jasmine/.*?$
^settings/
^identity/
^admin/
^project/
^ngdetails/ [name='ngdetails']
^auth/ ^login/$ [name='login']
^auth/ ^logout/$ [name='logout']
^auth/ ^switch/(?P<tenant_id>[^/]+)/$ [name='switch_tenants']
^auth/ ^switch_services_region/(?P<region_name>[^/]+)/$ [name='switch_services_region']
^auth/ ^switch_keystone_provider/(?P<keystone_provider>[^/]+)/$ [name='switch_keystone_provider']
^auth/ ^websso/$ [name='websso']
^auth/ ^error/$
^dashboard\/static\/(?P<path>.*)$
^dashboard\/media\/(?P<path>.*)$
^500/$
The current path, auth/login/default/auth/OS-FEDERATION/websso/mapped, didn't match any of these.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/611349

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/611387

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/611387
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=1953c689e86ecdf131b4cf176bf4ff47b53493cf
Submitter: Zuul
Branch: master

commit 1953c689e86ecdf131b4cf176bf4ff47b53493cf
Author: Radomir Dopieralski <email address hidden>
Date: Wed Oct 17 18:44:21 2018 +0200

    Properly calculate auth_url for WEBSSO from POST data

    The redirect for WEBSSO takes its data directly from the request's
    POST data, and the format of that data has changed, so now we need
    to convert it for it to work correctly.

    Change-Id: I5b18e555a9bc6b24be1e59465f07e73e99739e22
    closes-bug: #1794710

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/rocky
Review: https://review.openstack.org/617256

[OpenStack Infra (hudson-openstack)]

Change abandoned by Radomir Dopieralski (<email address hidden>) on branch: stable/rocky
Review: https://review.openstack.org/617256

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/horizon 15.0.0.0b2 development milestone.

[OpenStack Infra (hudson-openstack)]

Change abandoned by ayoung (<email address hidden>) on branch: master
Review: https://review.openstack.org/611349