Custom callback and user profile URLs for OAuth2

For parsing `oauth2_UsernameField` values like
`profile.preferred_username`, this makes use of `eval()` which is
generally Evil™, but I'm assuming that anyone with permission to edit
config.json likely has permission to make changes to the fedwiki source
code already anyway, so it's fragile rather than increasing a security
attack surface. An alternative would be using  a small function to look
up properties of the `params` / `profile` objects using the same
dotted-path notation.

docs/config-oauth2.md

@@ -1,4 +1,36 @@
+## Generic OAuth 2
 
+### Login provider set-up
+
+Like the other PassportJS login providers, we'll need a separate "OAuth2 Client"
+(others call it an "app", a "product" etc.) for our Federated Wiki instance.
+
+How to do this varies slightly for each provider.
+
+### `config.json`
+
+In general, you will need to specify:
+* `oauth2_clientID` -- some systems generate this for you, others allow you to
+    specify it
+* `oauth2_clientSecret` -- secure key (keep this secret!)
+* `oauth2_AuthorizationURL` and `oauth2_TokenURL` -- from your login provider's documentation
+
+You will also need to specify a callback URL. For some providers, you can add
+this when making a new "OAuth Client" for your wiki, for others you will need to
+specify it with `oauth2_CallbackURL`.
+
+You might also need to tell Federated Wiki how to look up usernames:
+* `oauth2_UserInfoURL` -- from login provider's documentation
+* `oauth2_UsernameField` -- starting with 
+  * `params` for information returned in the original token request, or
+  * `profile` for data returned from `oauth2_UserInfoURL`, if you provided it.
+
+Sometimes, you'll be able to look up the URLs by visiting your provider's
+`/.well-known/openid-configuration` URL in a web browser.
+
+### Examples
+
+#### Nextcloud
 
 ```JSON
 {
@@ -8,8 +40,21 @@
   "oauth2_clientSecret": "CLIENT SECRET",
   "oauth2_AuthorizationURL": "https://auth.example.com/oauth2/authorize",
   "oauth2_TokenURL": "https://auth.example.com/oauth2/token",
-  "wikiDomains": {
-    "example.wiki": {}
-  }
+}
+```
+
+#### Keycloak
+
+```JSON
+{
+  "farm": true,
+  "security_type": "passportjs",
+  "oauth2_clientID": "CLIENT ID",
+  "oauth2_clientSecret": "CLIENT SECRET",
+  "oauth2_AuthorizationURL": "https://auth.example.com/auth/realms/Wiki.Cafe/protocol/openid-connect/auth",
+  "oauth2_TokenURL": "https://auth.example.com/auth/realms/Wiki.Cafe/protocol/openid-connect/token",
+  "oauth2_UserInfoURL": "https://auth.example.com/auth/realms/Wiki.Cafe/protocol/openid-connect/userinfo",
+  "oauth2_CallbackURL": "http://localhost:3000/auth/oauth2/callback",
+  "oauth2_UsernameField": "profile.preferred_username"
 }
 ```

server/social.coffee

@@ -201,23 +201,42 @@ module.exports = exports = (log, loga, argv) ->
 
       oauth2StrategyName = callbackHost + 'OAuth'
 
+      if argv.oauth2_UserInfoURL?
+        OAuth2Strategy::userProfile = (accesstoken, done) -> 
+          console.log "hello"
+          console.log accesstoken
+          @_oauth2._request "GET", argv.oauth2_UserInfoURL, null, null, accesstoken, (err, data) ->
+            if err
+              return done err 
+            try
+              data = JSON.parse data 
+            catch e
+              return done e
+            done(null, data)
+
       passport.use(oauth2StrategyName, new OAuth2Strategy({
         clientID: argv.oauth2_clientID
         clientSecret: argv.oauth2_clientSecret
         authorizationURL: argv.oauth2_AuthorizationURL
-        tokenURL: argv.oauth2_TokenURL
-        # userURL: argv.oauth2_UserURL
-        # scope: 'user:emails'
-        # callbackURL is optional, and if it exists must match that given in
-        # the OAuth application settings - so we don't specify it.
+        tokenURL: argv.oauth2_TokenURL,
+        # not all providers have a way of specifying the callback URL
+        callbackURL: argv.oauth2_CallbackURL,
+        userInfoURL: argv.oauth2_UserInfoURL
         }, (accessToken, refreshToken, params, profile, cb) ->
+          console.log("accessToken", accessToken)
+          console.log("refreshToken", refreshToken)
           console.log("params", params)
           console.log("profile", profile)
+          if argv.oauth2_UsernameField?
+            username_query = argv.oauth2_UsernameField 
+          else 
+            username_query = 'params.user_id'
           user.oauth2 = {
-            id: params.user_id,
-            username: params.user_id,
-            displayName: params.user_id,
+            id: eval username_query,
+            username: eval username_query
+            displayName: eval username_query
           }
+          console.log user.oauth2
           cb(null, user)))
 
     # Github Strategy