3 files changed, 32 insertions, 22 deletions
diff --git a/changelog.d/7152.feature b/changelog.d/7152.feature
new file mode 100644
index 0000000000..fafa79c7e7
--- /dev/null
+++ b/changelog.d/7152.feature
@@ -0,0 +1 @@
+Improve the support for SSO authentication on the login fallback page.
diff --git a/synapse/static/client/login/index.html b/synapse/static/client/login/index.html
index bcb6bc6bb7..712b0e3980 100644
--- a/synapse/static/client/login/index.html
+++ b/synapse/static/client/login/index.html
@@ -9,7 +9,7 @@
 <body onload="matrixLogin.onLoad()">
     <center>
         <br/>
-        <h1>Log in with one of the following methods</h1>
+        <h1 id="title"></h1>
 
         <span id="feedback" style="color: #f00"></span>
 
diff --git a/synapse/static/client/login/js/login.js b/synapse/static/client/login/js/login.js
index 276c271bbe..debe464371 100644
--- a/synapse/static/client/login/js/login.js
+++ b/synapse/static/client/login/js/login.js
@@ -1,37 +1,41 @@
 window.matrixLogin = {
     endpoint: location.origin + "/_matrix/client/r0/login",
     serverAcceptsPassword: false,
-    serverAcceptsCas: false,
     serverAcceptsSso: false,
 };
 
+var title_pre_auth = "Log in with one of the following methods";
+var title_post_auth = "Logging in...";
+
 var submitPassword = function(user, pwd) {
     console.log("Logging in with password...");
+    set_title(title_post_auth);
     var data = {
         type: "m.login.password",
         user: user,
         password: pwd,
     };
     $.post(matrixLogin.endpoint, JSON.stringify(data), function(response) {
-        show_login();
         matrixLogin.onLogin(response);
     }).error(errorFunc);
 };
 
 var submitToken = function(loginToken) {
     console.log("Logging in with login token...");
+    set_title(title_post_auth);
     var data = {
         type: "m.login.token",
         token: loginToken
     };
     $.post(matrixLogin.endpoint, JSON.stringify(data), function(response) {
-        show_login();
         matrixLogin.onLogin(response);
     }).error(errorFunc);
 };
 
 var errorFunc = function(err) {
-    show_login();
+    // We want to show the error to the user rather than redirecting immediately to the
+    // SSO portal (if SSO is the only login option), so we inhibit the redirect.
+    show_login(true);
 
     if (err.responseJSON && err.responseJSON.error) {
         setFeedbackString(err.responseJSON.error + " (" + err.responseJSON.errcode + ")");
@@ -45,26 +49,33 @@ var setFeedbackString = function(text) {
     $("#feedback").text(text);
 };
 
-var show_login = function() {
-    $("#loading").hide();
-
+var show_login = function(inhibit_redirect) {
     var this_page = window.location.origin + window.location.pathname;
     $("#sso_redirect_url").val(this_page);
 
-    if (matrixLogin.serverAcceptsPassword) {
-        $("#password_flow").show();
+    // If inhibit_redirect is false, and SSO is the only supported login method, we can
+    // redirect straight to the SSO page
+    if (matrixLogin.serverAcceptsSso) {
+        if (!inhibit_redirect && !matrixLogin.serverAcceptsPassword) {
+            $("#sso_form").submit();
+            return;
+        }
+
+        // Otherwise, show the SSO form
+        $("#sso_form").show();
     }
 
-    if (matrixLogin.serverAcceptsSso) {
-        $("#sso_flow").show();
-    } else if (matrixLogin.serverAcceptsCas) {
-        $("#sso_form").attr("action", "/_matrix/client/r0/login/cas/redirect");
-        $("#sso_flow").show();
+    if (matrixLogin.serverAcceptsPassword) {
+        $("#password_flow").show();
     }
 
-    if (!matrixLogin.serverAcceptsPassword && !matrixLogin.serverAcceptsCas && !matrixLogin.serverAcceptsSso) {
+    if (!matrixLogin.serverAcceptsPassword && !matrixLogin.serverAcceptsSso) {
         $("#no_login_types").show();
     }
+
+    set_title(title_pre_auth);
+
+    $("#loading").hide();
 };
 
 var show_spinner = function() {
@@ -74,17 +85,15 @@ var show_spinner = function() {
     $("#loading").show();
 };
 
+var set_title = function(title) {
+    $("#title").text(title);
+};
 
 var fetch_info = function(cb) {
     $.get(matrixLogin.endpoint, function(response) {
         var serverAcceptsPassword = false;
-        var serverAcceptsCas = false;
         for (var i=0; i<response.flows.length; i++) {
             var flow = response.flows[i];
-            if ("m.login.cas" === flow.type) {
-                matrixLogin.serverAcceptsCas = true;
-                console.log("Server accepts CAS");
-            }
             if ("m.login.sso" === flow.type) {
                 matrixLogin.serverAcceptsSso = true;
                 console.log("Server accepts SSO");
@@ -102,7 +111,7 @@ var fetch_info = function(cb) {
 matrixLogin.onLoad = function() {
     fetch_info(function() {
         if (!try_token()) {
-            show_login();
+            show_login(false);
         }
     });
 };