Fix XSS on error messages in flash messages from external providers.

src/api-umbrella/web-app/app/controllers/admin/admins/omniauth_callbacks_controller.rb

@@ -98,6 +98,7 @@ def login
         ActionController::Base.helpers.content_tag(:a, "contact us", :href => ApiUmbrellaConfig[:contact_url]),
         " for further assistance.",
       ])
+      flash[:html_safe] = true
 
       redirect_to new_admin_session_path
     end
@@ -111,6 +112,7 @@ def email_unverified_error
       ActionController::Base.helpers.content_tag(:a, "contact us", :href => ApiUmbrellaConfig[:contact_url]),
       " for further assistance.",
     ])
+    flash[:html_safe] = true
 
     redirect_to new_admin_session_path
   end
@@ -121,6 +123,7 @@ def mfa_required_error
       ActionController::Base.helpers.content_tag(:a, "contact us", :href => ApiUmbrellaConfig[:contact_url]),
       " for further assistance.",
     ])
+    flash[:html_safe] = true
 
     redirect_to new_admin_session_path
   end

src/api-umbrella/web-app/app/views/layouts/application.html.erb

@@ -12,7 +12,7 @@
       <% flash.each do |flash_type, message| %>
         <% next unless(message.kind_of?(String)) %>
         <div class="alert <%= bootstrap_class_for(flash_type) %>">
-          <%= message.html_safe %>
+          <%= if(flash[:html_safe]) then message.html_safe else message end %>
         </div>
       <% end %>
 

test/admin_ui/test_flash_messages_html_safety.rb

@@ -0,0 +1,135 @@
+require_relative "../test_helper"
+
+class Test::AdminUi::TestFlashMessagesHtmlSafety < Minitest::Capybara::Test
+  include Capybara::Screenshot::MiniTestPlugin
+  include ApiUmbrellaTestHelpers::Setup
+  include ApiUmbrellaTestHelpers::AdminAuth
+  include ApiUmbrellaTestHelpers::AdminUiLogin
+  include Minitest::Hooks
+
+  def setup
+    super
+    setup_server
+    once_per_class_setup do
+      override_config_set({
+        # While the contact URL should be trusted, since it's configured by an
+        # admin, still test with special character to ensure it's escaped
+        # properly.
+        "contact_url" => "https://example.com/contact/?q='\"><script>alert('hello')</script>",
+        "web" => {
+          "admin" => {
+            "auth_strategies" => {
+              "enabled" => [
+                "google",
+                "max.gov",
+              ],
+              "max.gov" => {
+                "require_mfa" => true,
+              },
+            },
+          },
+        },
+      }, ["--router", "--web"])
+    end
+  end
+
+  def after_all
+    super
+    override_config_reset(["--router", "--web"])
+  end
+
+  def test_unverified_html_message
+    omniauth_data = {
+      "provider" => "google_oauth2",
+      "info" => {
+        "email" => "[email protected]",
+      },
+      "extra" => {
+        "raw_info" => {
+          "email_verified" => false,
+        },
+      },
+    }
+
+    mock_omniauth(omniauth_data) do
+      assert_login_forbidden("Sign in with Google", "not verified")
+      assert_match("The email address '[email protected]' is not verified. Please <a href=\"https://example.com/contact/?q='&quot;&gt;&lt;script&gt;alert('hello')&lt;/script&gt;\">contact us</a> for further assistance.", page.body)
+    end
+  end
+
+  def test_unverified_html_message_with_xss_email
+    omniauth_data = {
+      "provider" => "google_oauth2",
+      "info" => {
+        "email" => "'\"><script>alert('hello')</script>",
+      },
+      "extra" => {
+        "raw_info" => {
+          "email_verified" => false,
+        },
+      },
+    }
+
+    mock_omniauth(omniauth_data) do
+      assert_login_forbidden("Sign in with Google", "not verified")
+      assert_match("The email address ''\"&gt;&lt;script&gt;alert('hello')&lt;/script&gt;' is not verified. Please <a href=\"https://example.com/contact/?q='&quot;&gt;&lt;script&gt;alert('hello')&lt;/script&gt;\">contact us</a> for further assistance.", page.body)
+    end
+  end
+
+  def test_nonexistent_html_message
+    omniauth_data = {
+      "provider" => "google_oauth2",
+      "info" => {
+        "email" => "[email protected]",
+      },
+      "extra" => {
+        "raw_info" => {
+          "email_verified" => true,
+        },
+      },
+    }
+
+    mock_omniauth(omniauth_data) do
+      assert_login_forbidden("Sign in with Google", "not authorized")
+      assert_match("The account for '[email protected]' is not authorized to access the admin. Please <a href=\"https://example.com/contact/?q='&quot;&gt;&lt;script&gt;alert('hello')&lt;/script&gt;\">contact us</a> for further assistance.", page.body)
+    end
+  end
+
+  def test_nonexistent_html_message_with_xss_email
+    omniauth_data = {
+      "provider" => "google_oauth2",
+      "info" => {
+        "email" => "'\"><script>alert('hello')</script>",
+      },
+      "extra" => {
+        "raw_info" => {
+          "email_verified" => true,
+        },
+      },
+    }
+
+    mock_omniauth(omniauth_data) do
+      assert_login_forbidden("Sign in with Google", "not authorized")
+      assert_match("The account for ''\"&gt;&lt;script&gt;alert('hello')&lt;/script&gt;' is not authorized to access the admin. Please <a href=\"https://example.com/contact/?q='&quot;&gt;&lt;script&gt;alert('hello')&lt;/script&gt;\">contact us</a> for further assistance.", page.body)
+    end
+  end
+
+  def test_mfa_required_html_message
+    omniauth_data = {
+      "provider" => "cas",
+      "info" => {
+        "email" => "[email protected]",
+      },
+    }
+
+    mock_omniauth(omniauth_data) do
+      assert_login_forbidden("Sign in with MAX.gov", "must use multi-factor")
+      assert_match("You must use multi-factor authentication to sign in. Please try again, or <a href=\"https://example.com/contact/?q='&quot;&gt;&lt;script&gt;alert('hello')&lt;/script&gt;\">contact us</a> for further assistance.", page.body)
+    end
+  end
+
+  def test_error_message_from_external_provider
+    visit "/admins/auth/google_oauth2/callback?error='\"><script>confirm(document.domain)</script>"
+    assert_match("Could not authenticate you from GoogleOauth2 because \"'\"&gt;&lt;script&gt;confirm(document.domain)&lt;/script&gt;\".", page.body)
+  end
+end