Add a stand-alone replayer

The replayer can be used to reproduce crashes for fuzz targets using the
FuzzedDataProvider only given the raw crashing input. This will help
maintainers of OSS-Fuzz projects to reproduce issues even though they
have no access to the Java reproducers, which ClusterFuzz does not
store.

Compared to the full Jazzer driver, it has the advantage that it is a
Java library (with a native library dependency) and can thus be
published to Maven.

Since we currently do not have multi-platform RBE or cross toolchains
set up on GitHub, the packages jars for the individual architectures are
merged in a GitHub Actions pipeline.

1 files changed, 159 insertions, 0 deletions

diff --git a/agent/src/main/java/com/code_intelligence/jazzer/replay/Replayer.java b/agent/src/main/java/com/code_intelligence/jazzer/replay/Replayer.java
new file mode 100644
index 00000000..fc6bfc4f
--- /dev/null
+++ b/agent/src/main/java/com/code_intelligence/jazzer/replay/Replayer.java
@@ -0,0 +1,159 @@
+// Copyright 2021 Code Intelligence GmbH
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.code_intelligence.jazzer.replay;
+
+import com.code_intelligence.jazzer.api.FuzzedDataProvider;
+import com.code_intelligence.jazzer.runtime.FuzzedDataProviderImpl;
+import com.github.fmeum.rules_jni.RulesJni;
+import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.Arrays;
+
+public class Replayer {
+  public static final int STATUS_FINDING = 77;
+  public static final int STATUS_OTHER_ERROR = 1;
+
+  static {
+    try {
+      RulesJni.loadLibrary("replay", Replayer.class);
+    } catch (Throwable t) {
+      t.printStackTrace();
+      System.exit(STATUS_OTHER_ERROR);
+    }
+  }
+
+  public static void main(String[] args) {
+    if (args.length < 2) {
+      System.err.println("Usage: <fuzz target class> <input file path> <fuzzerInitialize args>...");
+      System.exit(STATUS_OTHER_ERROR);
+    }
+    ClassLoader.getSystemClassLoader().setDefaultAssertionStatus(true);
+
+    Class<?> fuzzTargetClass;
+    try {
+      fuzzTargetClass = Class.forName(args[0]);
+    } catch (ClassNotFoundException e) {
+      e.printStackTrace();
+      System.exit(STATUS_OTHER_ERROR);
+      // Without this return the compiler sees fuzzTargetClass as possibly uninitialized.
+      return;
+    }
+
+    String inputFilePath = args[1];
+    byte[] input = loadInput(inputFilePath);
+
+    String[] fuzzTargetArgs = Arrays.copyOfRange(args, 2, args.length);
+    executeFuzzerInitialize(fuzzTargetClass, fuzzTargetArgs);
+    executeFuzzTarget(fuzzTargetClass, input);
+  }
+
+  private static byte[] loadInput(String inputFilePath) {
+    try {
+      return Files.readAllBytes(Paths.get(inputFilePath));
+    } catch (IOException e) {
+      e.printStackTrace();
+      System.exit(STATUS_OTHER_ERROR);
+      // Without this return the compiler sees loadInput as possibly not returning a value.
+      return null;
+    }
+  }
+
+  private static void executeFuzzerInitialize(Class<?> fuzzTarget, String[] args) {
+    // public static void fuzzerInitialize()
+    try {
+      Method fuzzerInitialize = fuzzTarget.getMethod("fuzzerInitialize");
+      fuzzerInitialize.invoke(null);
+      return;
+    } catch (Exception e) {
+      handleInvokeException(e, fuzzTarget);
+    }
+    // public static void fuzzerInitialize(String[] args)
+    try {
+      Method fuzzerInitialize = fuzzTarget.getMethod("fuzzerInitialize", String[].class);
+      fuzzerInitialize.invoke(null, (Object) args);
+    } catch (Exception e) {
+      handleInvokeException(e, fuzzTarget);
+    }
+  }
+
+  public static void executeFuzzTarget(Class<?> fuzzTarget, byte[] input) {
+    // public static void fuzzerTestOneInput(byte[] input)
+    try {
+      Method fuzzerTestOneInput = fuzzTarget.getMethod("fuzzerTestOneInput", byte[].class);
+      fuzzerTestOneInput.invoke(null, (Object) input);
+      return;
+    } catch (Exception e) {
+      handleInvokeException(e, fuzzTarget);
+    }
+    // public static void fuzzerTestOneInput(FuzzedDataProvider data)
+    try {
+      Method fuzzerTestOneInput =
+          fuzzTarget.getMethod("fuzzerTestOneInput", FuzzedDataProvider.class);
+      fuzzerTestOneInput.invoke(null, makeFuzzedDataProvider(input));
+      return;
+    } catch (Exception e) {
+      handleInvokeException(e, fuzzTarget);
+    }
+    System.err.printf("%s must define exactly one of the following two functions:%n"
+            + "    public static void fuzzerTestOneInput(byte[] ...)%n"
+            + "    public static void fuzzerTestOneInput(FuzzedDataProvider ...)%n"
+            + "Note: Fuzz targets returning boolean are no longer supported; exceptions should%n"
+            + "be thrown instead of returning true.%n",
+        fuzzTarget.getName());
+    System.exit(STATUS_OTHER_ERROR);
+  }
+
+  private static void handleInvokeException(Exception e, Class<?> fuzzTarget) {
+    if (e instanceof NoSuchMethodException)
+      return;
+    if (e instanceof InvocationTargetException) {
+      filterOutOwnStackTraceElements(e.getCause(), fuzzTarget);
+      e.getCause().printStackTrace();
+      System.exit(STATUS_FINDING);
+    } else {
+      e.printStackTrace();
+      System.exit(STATUS_OTHER_ERROR);
+    }
+  }
+
+  private static void filterOutOwnStackTraceElements(Throwable t, Class<?> fuzzTarget) {
+    if (t.getCause() != null)
+      filterOutOwnStackTraceElements(t.getCause(), fuzzTarget);
+    if (t.getStackTrace() == null || t.getStackTrace().length == 0)
+      return;
+    StackTraceElement lowestFrame = t.getStackTrace()[t.getStackTrace().length - 1];
+    if (!lowestFrame.getClassName().equals(Replayer.class.getName())
+        || !lowestFrame.getMethodName().equals("main"))
+      return;
+    for (int i = t.getStackTrace().length - 1; i >= 0; i--) {
+      StackTraceElement frame = t.getStackTrace()[i];
+      if (frame.getClassName().equals(fuzzTarget.getName())
+          && frame.getMethodName().equals("fuzzerTestOneInput")) {
+        t.setStackTrace(Arrays.copyOfRange(t.getStackTrace(), 0, i + 1));
+        break;
+      }
+    }
+  }
+
+  private static FuzzedDataProvider makeFuzzedDataProvider(byte[] input) {
+    feedFuzzedDataProvider(input);
+    return new FuzzedDataProviderImpl();
+  }
+
+  private static native void feedFuzzedDataProvider(byte[] input);
+}