Oauth2 consumer (#679)

* initial stuff for oauth2 login, fails on:
* login button on the signIn page to start the OAuth2 flow and a callback for each provider
Only GitHub is implemented for now
* show login button only when the OAuth2 consumer is configured (and activated)
* create macaron group for oauth2 urls
* prevent net/http in modules (other then oauth2)
* use a new data sessions oauth2 folder for storing the oauth2 session data
* add missing 2FA when this is enabled on the user
* add password option for OAuth2 user , for use with git over http and login to the GUI
* add tip for registering a GitHub OAuth application
* at startup of Gitea register all configured providers and also on adding/deleting of new providers
* custom handling of errors in oauth2 request init + show better tip
* add ExternalLoginUser model and migration script to add it to database
* link a external account to an existing account (still need to handle wrong login and signup) and remove if user is removed
* remove the linked external account from the user his settings
* if user is unknown we allow him to register a new account or link it to some existing account
* sign up with button on signin page (als change OAuth2Provider structure so we can store basic stuff about providers)

* from gorilla/sessions docs:
"Important Note: If you aren't using gorilla/mux, you need to wrap your handlers with context.ClearHandler as or else you will leak memory!"
(we're using gorilla/sessions for storing oauth2 sessions)

* use updated goth lib that now supports getting the OAuth2 user if the AccessToken is still valid instead of re-authenticating (prevent flooding the OAuth2 provider)

1 files changed, 4 insertions, 1 deletions

diff --git a/modules/auth/auth_form.go b/modules/auth/auth_form.go
index 78ba2b8997..5dae55c1ef 100644
--- a/modules/auth/auth_form.go
+++ b/modules/auth/auth_form.go
@@ -12,7 +12,7 @@ import (
 // AuthenticationForm form for authentication
 type AuthenticationForm struct {
 	ID                int64
-	Type              int    `binding:"Range(2,5)"`
+	Type              int    `binding:"Range(2,6)"`
 	Name              string `binding:"Required;MaxSize(30)"`
 	Host              string
 	Port              int
@@ -36,6 +36,9 @@ type AuthenticationForm struct {
 	TLS               bool
 	SkipVerify        bool
 	PAMServiceName    string
+	Oauth2Provider    string
+	Oauth2Key	  string
+	Oauth2Secret      string
 }
 
 // Validate validates fields