Make plugin loading stricter

Today we load plugins reflectively, looking for constructors that
conform to specific signatures. This commit tightens the reflective
operations here, not allowing plugins to have ambiguous constructors.

Relates #25405

1 files changed, 87 insertions, 0 deletions

diff --git a/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java b/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java
index 7f91d11acd..c3fd0b19f7 100644
--- a/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java
+++ b/core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java
@@ -30,6 +30,7 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.List;
 import java.util.Locale;
 
@@ -151,4 +152,90 @@ public class PluginsServiceTests extends ESTestCase {
         assertThat(e, hasToString(containsString(expected)));
     }
 
+    public void testLoadPluginWithNoPublicConstructor() {
+        class NoPublicConstructorPlugin extends Plugin {
+
+            private NoPublicConstructorPlugin() {
+
+            }
+
+        }
+
+        final Path home = createTempDir();
+        final Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), home).build();
+        final IllegalStateException e =
+                expectThrows(IllegalStateException.class, () -> newPluginsService(settings, NoPublicConstructorPlugin.class));
+        assertThat(e, hasToString(containsString("no public constructor")));
+    }
+
+    public void testLoadPluginWithMultiplePublicConstructors() {
+        class MultiplePublicConstructorsPlugin extends Plugin {
+
+            @SuppressWarnings("unused")
+            public MultiplePublicConstructorsPlugin() {
+
+            }
+
+            @SuppressWarnings("unused")
+            public MultiplePublicConstructorsPlugin(final Settings settings) {
+
+            }
+
+        }
+
+        final Path home = createTempDir();
+        final Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), home).build();
+        final IllegalStateException e =
+                expectThrows(IllegalStateException.class, () -> newPluginsService(settings, MultiplePublicConstructorsPlugin.class));
+        assertThat(e, hasToString(containsString("no unique public constructor")));
+    }
+
+    public void testLoadPluginWithNoPublicConstructorOfCorrectSignature() {
+        class TooManyParametersPlugin extends Plugin {
+
+            @SuppressWarnings("unused")
+            public TooManyParametersPlugin(Settings settings, Path configPath, Object object) {
+
+            }
+
+        }
+
+        class TwoParametersFirstIncorrectType extends Plugin {
+
+            @SuppressWarnings("unused")
+            public TwoParametersFirstIncorrectType(Object object, Path configPath) {
+
+            }
+        }
+
+        class TwoParametersSecondIncorrectType extends Plugin {
+
+            @SuppressWarnings("unused")
+            public TwoParametersSecondIncorrectType(Settings settings, Object object) {
+
+            }
+
+        }
+
+        class OneParameterIncorrectType extends Plugin {
+
+            @SuppressWarnings("unused")
+            public OneParameterIncorrectType(Object object) {
+
+            }
+        }
+
+        final Collection<Class<? extends Plugin>> classes = Arrays.asList(
+                TooManyParametersPlugin.class,
+                TwoParametersFirstIncorrectType.class,
+                TwoParametersSecondIncorrectType.class,
+                OneParameterIncorrectType.class);
+        for (Class<? extends Plugin> pluginClass : classes) {
+            final Path home = createTempDir();
+            final Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), home).build();
+            final IllegalStateException e = expectThrows(IllegalStateException.class, () -> newPluginsService(settings, pluginClass));
+            assertThat(e, hasToString(containsString("no public constructor of correct signature")));
+        }
+    }
+
 }