Add support for Resource Owner Password Credentials Grant

[snowzach]

This PR adds support for Resource Owner Password Credentials Grant.
https://www.oauth.com/oauth2-servers/access-tokens/password-grant/

You enable it in the config by setting:

oauth2:
   passwordConnector: local

or replace local with whatever connector you wish to use for password grants.

You then request a token via a

POST /dex/token
grant_type=password&client_id=example-app&client_secret=ZXhhbXBsZS1hcHAtc2VjcmV0&[email protected]&password=password&scope=openid profile email&nonce=2OSwiYXRfaGFzaCI6Il9rMVBZT0ppcGFQc0pHSmlZV

[ericchiang]

Thanks, this look pretty good.

I'm really surprised that handlePasswordGrant is just a huge method with seemingly no shared code with the other token handlers. Can you comment on that before proceeding?

[ericchiang]

nit, this should be a connector.PasswordConnector

[ericchiang]

Same here, the connector should be initialized in cmd so this would be of type connector.PasswordConnector

[jwntrs]

@snowzach are you still looking at this? Really excited for password grant

[snowzach]

@pivotal-jwinters I wanted to finish this quick but the requested changes are a bigger refactor for the code than I have time at the moment. I will get to it eventually but $dayjob has taken over for the time being. Sorry. :(

[jwntrs]

@snowzach no worries. If there's anything I can do to help let me know.

[yadzhang]

@snowzach @ericchiang Any progress on this? I am really need on password grant.

[xtremerui]

Hi, @bonifaido. I went through recent PRs and found you are assigned most of them so I figured you might be the right one to talk with. Sorry in advance.

@pivotal-jwinters and I work for ConcourseCI who uses Dex as its auth backend. We are currently using our own fork of Dex and password grant in this PR has been merged into our fork for almost one year without any issue.

We would love to help here. Could you review the current status of the PR and provide some guidance? @snowzach if you dont mind could we pick up your work? If necessary we could move on to a new PR of password grant, which will be based on @snowzach 's first commit.

Thx!

[snowzach]

@xtremerui by all means you may do anything you like this with merge. I kept meaning to come back to it but just never had time.

[bonifaido]

Hi @xtremerui ! I think this PR looks quite good, we just need to rebase it on current master and resolve the conflicts. Would you guys do that?

[xtremerui]

@bonifaido perfecto! We will update the PR and submit it again from our fork.

[xtremerui]

#1621 is submitted. This PR might be closed. Thx!

[snowzach]

Close in favor of #1621