Hide CSRF configuration UI when only DefaultCrumbIssuer is available (#26057)

* Hide CSRF configuration UI when only DefaultCrumbIssuer is available

* Add test for CSRF section visibility

* Remove unused import in GlobalCrumbIssuerConfigurationTest

* Add @TestExtension DummyCrumbIssuer to provide second CrumbIssuer descriptor in test environment

* Fix CSRF configuration test assertions per review feedback

* Fix unused import in CSRF configuration test

* Fix hidden test assertion to check DummyCrumbIssuer absence

* Fix CSRF test: use TestCrumbIssuer, assert CSRF section hidden correctly

* Merge CSRF tests into single class, remove separate WithDummy file

* Merge CSRF tests into single class, remove separate WithDummy file

* Use non-deprecated DefaultCrumbIssuer constructor in test

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Daniel Beck <1831569+daniel-beck@users.noreply.github.com>
Co-authored-by: Mark Waite <mark.earl.waite@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

core/src/main/resources/hudson/security/csrf/GlobalCrumbIssuerConfiguration/config.groovy

@@ -1,19 +1,31 @@
 package hudson.security.csrf.GlobalCrumbIssuerConfiguration
 
 import hudson.security.csrf.CrumbIssuer
+import hudson.security.csrf.DefaultCrumbIssuer
 
-def f=namespace(lib.FormTagLib)
+def f = namespace(lib.FormTagLib)
 def all = CrumbIssuer.all()
+def disableCsrf =
+    hudson.security.csrf.GlobalCrumbIssuerConfiguration.DISABLE_CSRF_PROTECTION
 
-if (!all.isEmpty()) {
+def onlyDefaultIssuer =
+    all.size() == 1 && all[0].clazz == DefaultCrumbIssuer
+
+def showCsrfConfig = !onlyDefaultIssuer || disableCsrf
+
+if (showCsrfConfig) {
     f.section(title: _("CSRF Protection")) {
-        if (hudson.security.csrf.GlobalCrumbIssuerConfiguration.DISABLE_CSRF_PROTECTION) {
+        if (disableCsrf) {
             f.entry {
                 p(raw(_('disabled')))
                 p(_('unsupported'))
             }
         } else {
-            f.dropdownDescriptorSelector(title: _("Crumb Issuer"), descriptors: all, field: 'crumbIssuer')
+            f.dropdownDescriptorSelector(
+                title: _("Crumb Issuer"),
+                descriptors: all,
+                field: 'crumbIssuer'
+            )
         }
     }
 }

test/src/test/java/hudson/security/csrf/GlobalCrumbIssuerConfigurationTest.java

@@ -0,0 +1,74 @@
+package hudson.security.csrf;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.not;
+
+import hudson.ExtensionList;
+import hudson.model.Descriptor;
+import java.util.ArrayList;
+import java.util.List;
+import org.htmlunit.html.HtmlPage;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.jvnet.hudson.test.JenkinsRule;
+import org.jvnet.hudson.test.junit.jupiter.WithJenkins;
+
+@WithJenkins
+class GlobalCrumbIssuerConfigurationTest {
+
+    private JenkinsRule j;
+
+    @BeforeEach
+    void setUp(JenkinsRule rule) {
+        j = rule;
+    }
+
+    @Test
+    void csrfSectionHiddenWhenOnlyDefaultIssuerAvailable() throws Exception {
+        // Remove all non-default CrumbIssuer descriptors so only DefaultCrumbIssuer remains
+        ExtensionList<Descriptor<CrumbIssuer>> descriptors = j.jenkins.getDescriptorList(CrumbIssuer.class);
+        List<Descriptor<CrumbIssuer>> toRemove = new ArrayList<>();
+        for (Descriptor<CrumbIssuer> d : descriptors) {
+            if (!(d instanceof DefaultCrumbIssuer.DescriptorImpl)) {
+                toRemove.add(d);
+            }
+        }
+        descriptors.removeAll(toRemove);
+
+        j.jenkins.setCrumbIssuer(new DefaultCrumbIssuer());
+
+        JenkinsRule.WebClient wc = j.createWebClient();
+        HtmlPage page = wc.goTo("configureSecurity");
+        String pageContent = page.asNormalizedText();
+
+        assertThat(pageContent, not(containsString("CSRF Protection")));
+    }
+
+    @Test
+    void csrfSectionShownWhenNonDefaultIssuerConfigured() throws Exception {
+        // TestCrumbIssuer is registered by Jenkins test harness automatically,
+        // so CrumbIssuer.all() has more than just DefaultCrumbIssuer and CSRF section is shown.
+        JenkinsRule.WebClient wc = j.createWebClient();
+        HtmlPage page = wc.goTo("configureSecurity");
+        String pageContent = page.asNormalizedText();
+
+        assertThat(pageContent, containsString("CSRF Protection"));
+    }
+
+    @Test
+    void csrfSectionShownWhenCsrfProtectionDisabled() throws Exception {
+        boolean original = GlobalCrumbIssuerConfiguration.DISABLE_CSRF_PROTECTION;
+        try {
+            GlobalCrumbIssuerConfiguration.DISABLE_CSRF_PROTECTION = true;
+
+            JenkinsRule.WebClient wc = j.createWebClient();
+            HtmlPage page = wc.goTo("configureSecurity");
+            String pageContent = page.asNormalizedText();
+
+            assertThat(pageContent, containsString("This configuration is unavailable because"));
+        } finally {
+            GlobalCrumbIssuerConfiguration.DISABLE_CSRF_PROTECTION = original;
+        }
+    }
+}