feat: add feature to detect runtime generated classes (#64)

pom.xml

@@ -87,6 +87,21 @@
         <artifactId>log4j-core</artifactId>
         <version>2.20.0</version>
       </dependency>
+      <dependency>
+        <groupId>org.ow2.asm</groupId>
+        <artifactId>asm</artifactId>
+        <version>9.5</version>
+      </dependency>
+      <dependency>
+        <groupId>org.ow2.asm</groupId>
+        <artifactId>asm-tree</artifactId>
+        <version>9.5</version>
+      </dependency>
+      <dependency>
+        <groupId>org.ow2.asm</groupId>
+        <artifactId>asm-util</artifactId>
+        <version>9.5</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>
 

terminator-commons/pom.xml

@@ -44,6 +44,18 @@
       <groupId>org.apache.logging.log4j</groupId>
       <artifactId>log4j-core</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-tree</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-util</artifactId>
+    </dependency>
   </dependencies>
 
   <build>

terminator-commons/src/main/java/io/github/algomaster99/terminator/commons/fingerprint/classfile/RuntimeClass.java

@@ -0,0 +1,23 @@
+package io.github.algomaster99.terminator.commons.fingerprint.classfile;
+
+import java.util.Objects;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.Opcodes;
+
+public class RuntimeClass {
+
+    private RuntimeClass() {}
+
+    /**
+     * Proxy classes are not synthetic classes, but they are runtime generated.
+     */
+    public static boolean isProxyClass(byte[] classfileBytes) {
+        ClassReader reader = new ClassReader(classfileBytes);
+        return Objects.equals(reader.getSuperName(), "java/lang/reflect/Proxy");
+    }
+
+    public static boolean isSynthetic(byte[] classfileBytes) {
+        ClassReader reader = new ClassReader(classfileBytes);
+        return (reader.getAccess() & Opcodes.ACC_SYNTHETIC) != 0;
+    }
+}

terminator-commons/src/test/java/io/github/algomaster99/terminator/commons/fingerprint/classfile/ClassfileTest.java

@@ -0,0 +1,62 @@
+package io.github.algomaster99.terminator.commons.fingerprint.classfile;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.util.TraceClassVisitor;
+
+public class ClassfileTest {
+
+    private static final Path TEST_RESOURCES = Path.of("src/test/resources");
+
+    @Nested
+    class IsRuntimeGeneratedClass {
+        private static final Path CLASSFILE = TEST_RESOURCES.resolve("classfile");
+
+        @Test
+        void isAProxyClass_true() throws IOException {
+            Path proxy39 = CLASSFILE.resolve("$Proxy39.class");
+            Path proxy40 = CLASSFILE.resolve("$Proxy40.class");
+
+            assertThat(RuntimeClass.isProxyClass(Files.readAllBytes(proxy39))).isTrue();
+            assertThat(RuntimeClass.isProxyClass(Files.readAllBytes(proxy40))).isTrue();
+        }
+
+        @Test
+        void isProxyClass_false() throws IOException {
+            Path maven = CLASSFILE.resolve("Maven.class");
+
+            assertThat(RuntimeClass.isProxyClass(Files.readAllBytes(maven))).isFalse();
+        }
+
+        @Test
+        void isSyntheticClass_true() throws IOException {
+            Path synthetic = CLASSFILE.resolve("$Proxy39.class");
+
+            byte[] unmodifiedBytes = Files.readAllBytes(synthetic);
+            assertThat(RuntimeClass.isSynthetic(unmodifiedBytes)).isFalse();
+
+            byte[] modifiedBytes = makeClassfileSynthetic(Files.readAllBytes(synthetic));
+            assertThat(RuntimeClass.isSynthetic(modifiedBytes)).isTrue();
+        }
+
+        private static byte[] makeClassfileSynthetic(byte[] classfileBytes) {
+            ClassNode classNode = new ClassNode();
+            ClassReader classReader = new ClassReader(classfileBytes);
+            classReader.accept(classNode, 0);
+            classNode.access |= Opcodes.ACC_SYNTHETIC;
+
+            ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
+            classNode.accept(new TraceClassVisitor(writer, null));
+            return writer.toByteArray();
+        }
+    }
+}

watchdog-agent/pom.xml

@@ -30,26 +30,6 @@
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
     </dependency>
-    <dependency>
-      <groupId>net.bytebuddy</groupId>
-      <artifactId>byte-buddy-dep</artifactId>
-      <version>1.14.6</version>
-    </dependency>
-    <dependency>
-      <groupId>org.ow2.asm</groupId>
-      <artifactId>asm</artifactId>
-      <version>9.5</version>
-    </dependency>
-    <dependency>
-      <groupId>org.ow2.asm</groupId>
-      <artifactId>asm-tree</artifactId>
-      <version>9.5</version>
-    </dependency>
-    <dependency>
-      <groupId>org.ow2.asm</groupId>
-      <artifactId>asm-util</artifactId>
-      <version>9.5</version>
-    </dependency>
     <dependency>
       <groupId>org.junit.jupiter</groupId>
       <artifactId>junit-jupiter-api</artifactId>

watchdog-agent/src/main/java/io/github/algomaster99/Terminator.java

@@ -2,6 +2,7 @@
 
 import static io.github.algomaster99.terminator.commons.fingerprint.classfile.HashComputer.computeHash;
 
+import io.github.algomaster99.terminator.commons.fingerprint.classfile.RuntimeClass;
 import io.github.algomaster99.terminator.commons.fingerprint.provenance.Provenance;
 import java.lang.instrument.ClassFileTransformer;
 import java.lang.instrument.Instrumentation;
@@ -33,6 +34,9 @@ public byte[] transform(
 
     private static byte[] isLoadedClassWhitelisted(String className, byte[] classfileBuffer) {
         Map<String, List<Provenance>> fingerprints = options.getFingerprints();
+        if (RuntimeClass.isProxyClass(classfileBuffer) || RuntimeClass.isSynthetic(classfileBuffer)) {
+            return classfileBuffer;
+        }
         if (INTERNAL_PACKAGES.stream().anyMatch(className::startsWith)) {
             return classfileBuffer;
         }

watchdog-agent/src/test/java/AgentTest.java

@@ -92,7 +92,7 @@ void sorald_0_8_5_shouldExitWith_1() throws IOException, InterruptedException {
         Process p = pb.start();
         int exitCode = p.waitFor();
 
-        assertThat(exitCode).isEqualTo(1);
+        assertThat(exitCode).isEqualTo(0);
     }
 
     private static void deleteContentsOfFile(String file) throws InterruptedException, IOException {