There's some prelimiary work here to pull out the construction of a jinja environment to a separate function.
I wanted to load the template at display time rather than load time, so that it's easy to update on the fly. Honestly, I think we should do this with all our templates: the risk of ending up with malformed templates is far outweighed by the improved turnaround time for an admin trying to update them.
We've decided to add a 'brand' field to help clients decide how to style the
buttons.
Also, fix up the allowed characters for idp_id, while I'm in the area.
This is the final step for supporting multiple OIDC providers concurrently.
First of all, we reorganise the config so that you can specify a list of OIDC providers, instead of a single one. Before:
oidc_config:
enabled: true
issuer: "https://oidc_provider"
# etc
After:
oidc_providers:
- idp_id: prov1
issuer: "https://oidc_provider"
- idp_id: prov2
issuer: "https://another_oidc_provider"
The old format is still grandfathered in.
With that done, it's then simply a matter of having OidcHandler instantiate a new OidcProvider for each configured provider.
`distutils` is pretty much deprecated these days, and replaced with
`setuptools`. It's also annoying because it's you can't `pip install` it, and
it's hard to figure out which debian package we should depend on to make sure
it's there.
Since we only use it for a tiny function anyway, let's just vendor said
function into our codebase.
Again in preparation for handling more than one OIDC provider, add a new caveat to the macaroon used as an OIDC session cookie, which remembers which OIDC provider we are talking to. In future, when we get a callback, we'll need it to make sure we talk to the right IdP.
As part of this, I'm adding an idp_id and idp_name field to the OIDC configuration object. They aren't yet documented, and we'll just use the old values by default.
If a user tries to do UI Auth via SSO, but uses the wrong account on the SSO
IdP, try to give them a better error.
Previously, the UIA would claim to be successful, but then the operation in
question would simply fail with "auth fail". Instead, serve up an error page
which explains the failure.
The final part (for now) of my work to implement a username picker in synapse itself. The idea is that we allow
`UsernameMappingProvider`s to return `localpart=None`, in which case, rather than redirecting the browser
back to the client, we redirect to a username-picker resource, which allows the user to enter a username.
We *then* complete the SSO flow (including doing the client permission checks).
The static resources for the username picker itself (in
https://github.com/matrix-org/synapse/tree/rav/username_picker/synapse/res/username_picker)
are essentially lifted wholesale from
https://github.com/matrix-org/matrix-synapse-saml-mozilla/tree/master/matrix_synapse_saml_mozilla/res.
As the comment says, we might want to think about making them customisable, but that can be a follow-up.
Fixes#8876.
