Allow multiple callback_urls for all backends

[dubit0]

In principle one vouch proxy instance can be used to authenticate users on different vhosts. Putting the nginx config for vouch in a separate file and including it for different vhosts adds a lot of convenience. Such setup currently almost works and only fails at the callback since only a single callback url can be specified in the vouch config. Only the google backend already allows for multiple callback_urls. As can be seen below, it chooses the callback url that matches the identified domain.

vouch-proxy/handlers/handlers.go

Lines 60 to 70 in db84bc6

	if cfg.GenOAuth.Provider == cfg.Providers.Google {
	// If the provider is Google, find a matching redirect URL to use for the client
	domain := domains.Matches(r.Host)
	log.Debugf("looking for redirect URL matching %v", domain)
	for i, v := range cfg.GenOAuth.RedirectURLs {
	if strings.Contains(v, domain) {
	log.Debugf("redirect value matched at [%d]=%v", i, v)
	cfg.OAuthClient.RedirectURL = v
	break
	}
	}

To enable using one vouch proxy on different vhosts, it would be great to move the code out of the if-statement and apply this logic to all backends.

[bnfinet]

Yeah that seems like it'd be good.

domains.Matches in that block is specific to the vouch.domains config element.

vouch-proxy/pkg/domains/domains.go

Line 20 in a832330

func Matches(s string) string {

The test might be better against the originally provided URL stored in the session variable.

[bnfinet]

As per #133 @libussa do you have working code? Care to submit a PR?

If not @jayb1122 perhaps you'd care to work on this?

[libussa]

@bnfinet I do, I just moved the if logic. I didn't however do what you suggested (against the originally provided URL stored in the session variable)

I can submit a PR if you still want it