fix redirectUrl after custom oauth successful login initiated by iframe command, fixes #5042 (#5043)

packages/rocketchat-ui/lib/iframeCommands.js

@@ -19,12 +19,17 @@ const commands = {
 			}, event.origin);
 		};
 
-		if (typeof data.service === 'string') {
+		const siteUrl = Meteor.settings.Site_Url + '/';
+		if (typeof data.redirectUrl !== 'string' || !data.redirectUrl.startsWith(siteUrl)) {
+			data.redirectUrl = null;
+		}
+
+		if (typeof data.service === 'string' && window.ServiceConfiguration) {
 			const customOauth = ServiceConfiguration.configurations.findOne({service: data.service});
 
 			if (customOauth) {
 				const customLoginWith = Meteor['loginWith' + _.capitalize(customOauth.service, true)];
-				const customRedirectUri = window.OAuth._redirectUri(customOauth.service, customOauth);
+				const customRedirectUri = data.redirectUrl || siteUrl;
 				customLoginWith.call(Meteor, {'redirectUrl': customRedirectUri}, customOAuthCallback);
 			}
 		}