Skip processing HEAD requests for action tokens

Closes #41834

Signed-off-by: Pedro Igor <pigor.craveiro@gmail.com>

services/src/main/java/org/keycloak/headers/DefaultSecurityHeadersProvider.java

@@ -30,6 +30,8 @@ import jakarta.ws.rs.core.MultivaluedMap;
 import java.util.Collections;
 import java.util.Map;
 
+import static jakarta.ws.rs.HttpMethod.HEAD;
+import static jakarta.ws.rs.HttpMethod.OPTIONS;
 import static org.keycloak.models.BrowserSecurityHeaders.CONTENT_SECURITY_POLICY;
 
 public class DefaultSecurityHeadersProvider implements SecurityHeadersProvider {
@@ -147,10 +149,17 @@ public class DefaultSecurityHeadersProvider implements SecurityHeadersProvider {
                 status == 400 || status == 401 || status == 403 || status == 404) {
                 return true;
             }
-            if (requestContext.getMethod().equalsIgnoreCase("OPTIONS")) {
-                return true;
+
+            String method = requestContext.getMethod().toUpperCase();
+
+            switch (method) {
+                case OPTIONS:
+                    return true;
+                case HEAD:
+                    return status == 200;
             }
         }
+
         return false;
     }
 

services/src/main/java/org/keycloak/services/resources/LoginActionsService.java

@@ -16,6 +16,7 @@
  */
 package org.keycloak.services.resources;
 
+import jakarta.ws.rs.HEAD;
 import org.jboss.logging.Logger;
 import org.keycloak.common.Profile;
 import org.keycloak.common.Profile.Feature;
@@ -548,6 +549,19 @@ public class LoginActionsService {
         return handleActionToken(key, execution, clientId, tabId, clientData, null);
     }
 
+    /**
+     * Skip processing {@link jakarta.ws.rs.HttpMethod#HEAD} requests for action tokens
+     * as they are usually used by mail servers to validate links. The actual request will eventually be
+     * processed by the {@link #executeActionToken} method.
+     *
+     * @return a {@link Response.Status#OK} response with no message body
+     */
+    @Path("action-token")
+    @HEAD
+    public Response executeActionTokenHead() {
+        return Response.ok().build();
+    }
+
     protected <T extends JsonWebToken & SingleUseObjectKeyModel> Response handleActionToken(String tokenString, String execution, String clientId, String tabId, String clientData, 
             TriFunction<ActionTokenHandler<T>, T, ActionTokenContext<T>, Response> preHandleToken) {
         T token;

testsuite/integration-arquillian/tests/base/src/test/java/org/keycloak/testsuite/actions/RequiredActionUpdateEmailTestWithVerificationTest.java

@@ -30,8 +30,10 @@ import java.io.IOException;
 import java.util.List;
 import java.util.UUID;
 
+import jakarta.ws.rs.core.Response.Status;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClientBuilder;
 import org.jboss.arquillian.graphene.page.Page;
-import org.jetbrains.annotations.NotNull;
 import org.junit.Assert;
 import org.junit.Rule;
 import org.junit.Test;
@@ -39,6 +41,7 @@ import org.keycloak.admin.client.resource.AuthenticationManagementResource;
 import org.keycloak.admin.client.resource.UserResource;
 import org.keycloak.authentication.actiontoken.updateemail.UpdateEmailActionToken;
 import org.keycloak.authentication.requiredactions.UpdateEmail;
+import org.keycloak.broker.provider.util.SimpleHttp.Response;
 import org.keycloak.events.Details;
 import org.keycloak.events.EventType;
 import org.keycloak.models.UserModel;
@@ -48,6 +51,7 @@ import org.keycloak.representations.idm.RealmRepresentation;
 import org.keycloak.representations.idm.RequiredActionProviderRepresentation;
 import org.keycloak.representations.idm.UserRepresentation;
 import org.keycloak.representations.idm.UserSessionRepresentation;
+import org.keycloak.testsuite.broker.util.SimpleHttpDefault;
 import org.keycloak.testsuite.pages.ErrorPage;
 import org.keycloak.testsuite.pages.InfoPage;
 import org.keycloak.testsuite.util.GreenMailRule;
@@ -174,6 +178,26 @@ public class RequiredActionUpdateEmailTestWithVerificationTest extends AbstractR
 		assertTrue(ActionUtil.findUserWithAdminClient(adminClient, "test-user@localhost").getRequiredActions().contains(UserModel.RequiredAction.UPDATE_EMAIL.name()));
 	}
 
+    @Test
+    public void testSkipHeadRequestWhenFollowingVerificationLink() throws MessagingException, IOException {
+        oauth.openLoginForm();
+        loginPage.login("test-user@localhost", "password");
+
+        updateEmailPage.assertCurrent();
+        updateEmailPage.changeEmail("new@localhost");
+
+        String confirmationLink = fetchEmailConfirmationLink("new@localhost");
+
+        try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {
+            try (Response response = SimpleHttpDefault.doHead(confirmationLink, httpClient).asResponse()) {
+                assertEquals(Status.OK.getStatusCode(), response.getStatus());
+            }
+        }
+
+        driver.navigate().to(confirmationLink);
+        infoPage.assertCurrent();
+    }
+
     @Test
     public void testForceEmailVerification() throws MessagingException, IOException {
         // disables verify email at the realm level