SONAR-8351 limit number of webhooks to 10

server/sonar-server/src/main/java/org/sonar/server/computation/task/projectanalysis/webhook/WebhookPostTask.java

 import org.sonar.server.computation.task.projectanalysis.component.TreeRootHolder;
 
 import static java.lang.String.format;
+import static org.sonar.core.config.WebhookProperties.MAX_WEBHOOKS_PER_TYPE;
 
 public class WebhookPostTask implements PostProjectAnalysisTask {
 
     String[] webhookIds = settings.getStringArray(propertyKey);
     return Arrays.stream(webhookIds)
       .map(webhookId -> format("%s.%s", propertyKey, webhookId))
+      .limit(MAX_WEBHOOKS_PER_TYPE)
       .collect(Collectors.toList(webhookIds.length));
   }
 

server/sonar-server/src/test/java/org/sonar/server/computation/task/projectanalysis/webhook/WebhookPostTaskTest.java

 
 import java.io.IOException;
 import java.util.Date;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 import org.junit.Rule;
 import org.junit.Test;
 import org.sonar.api.ce.posttask.CeTask;
     verify(deliveryStorage, times(2)).persist(any(WebhookDelivery.class));
     verify(deliveryStorage).purge(PROJECT_UUID);
   }
+
   @Test
   public void send_project_webhooks() {
     settings.setProperty("sonar.webhooks.project", "1");
     verify(deliveryStorage).purge(PROJECT_UUID);
   }
 
+  @Test
+  public void process_only_the_10_first_global_webhooks() {
+    testMaxWebhooks("sonar.webhooks.global");
+  }
+
+  @Test
+  public void process_only_the_10_first_project_webhooks() {
+    testMaxWebhooks("sonar.webhooks.project");
+  }
+
+  private void testMaxWebhooks(String property) {
+    IntStream.range(1, 15)
+      .forEach(i -> {
+        settings.setProperty(property + "." + i + ".name", "First");
+        settings.setProperty(property + "." + i + ".url", "http://url");
+        caller.enqueueSuccess(NOW, 200, 1_234);
+      });
+    settings.setProperty(property, IntStream.range(1, 15).mapToObj(String::valueOf).collect(Collectors.joining(",")));
+
+    execute();
+
+    assertThat(caller.countSent()).isEqualTo(10);
+    assertThat(logTester.logs(LoggerLevel.DEBUG).stream().filter(log -> log.contains("Sent"))).hasSize(10);
+  }
+
   private void execute() {
     SettingsRepository settingsRepository = new TestSettingsRepository(settings);
     WebhookPostTask task = new WebhookPostTask(rootHolder, settingsRepository, caller, deliveryStorage);

sonar-core/src/main/java/org/sonar/core/config/WebhookProperties.java

   public static final String NAME_FIELD = "name";
   public static final String URL_FIELD = "url";
 
+  /**
+   * Maximum allowed number of webhooks per type (globally or per project).
+   * That is required to not become a DoS attacker, for instance
+   * if thousands of webhooks are configured.
+   */
+  public static final long MAX_WEBHOOKS_PER_TYPE = 10;
+
   /**
    * Prefix of the properties to be automatically exported from scanner to payload
    */
 
   private static final String CATEGORY = "webhooks";
   private static final String DESCRIPTION = "Webhooks are used to notify external services when a project analysis is done. " +
-    "A HTTP POST request including a JSON payload is sent to each of the provided URLs. " +
+    "A HTTP POST request including a JSON payload is sent to each of the provided URLs. <br/>" +
+    "Maximum " + MAX_WEBHOOKS_PER_TYPE + " webhooks are allowed. <br/>" +
     "Learn more in the <a href=\"#\">Webhooks documentation</a>.";
 
   private WebhookProperties() {