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.

11 files changed, 401 insertions, 12 deletions

diff --git a/.github/workflows/build-replayer.yml b/.github/workflows/build-replayer.yml
new file mode 100644
index 00000000..aa617416
--- /dev/null
+++ b/.github/workflows/build-replayer.yml
@@ -0,0 +1,76 @@
+name: Release replayer
+
+on:
+  workflow_dispatch:
+
+jobs:
+
+  build_replayer:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-10.15]
+        include:
+          - os: ubuntu-latest
+            arch: "linux"
+            cache: "/home/runner/.cache/bazel-disk"
+          - os: macos-10.15
+            arch: "darwin"
+            cache: "/private/var/tmp/bazel-disk"
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Set up JDK
+        uses: actions/setup-java@v1
+        with:
+          java-version: 8
+
+      - name: Mount Bazel disk cache
+        uses: actions/cache@v2
+        with:
+          path: ${{ matrix.cache }}
+          key: bazel-disk-cache-${{ matrix.arch }}-8
+
+      - name: Build
+        run: |
+          bazelisk build --config=ci --remote_header=x-buildbuddy-api-key=${{ secrets.BUILDBUDDY_API_KEY }} --disk_cache=${{ matrix.cache }} --java_runtime_version=localjdk_${{ matrix.jdk }} //agent/src/main/java/com/code_intelligence/jazzer/replay:Replayer_deploy.jar
+          cp -L bazel-bin/agent/src/main/java/com/code_intelligence/jazzer/replay/Replayer_deploy.jar replayer.jar
+
+      - name: Upload test logs
+        if: always()
+        uses: actions/upload-artifact@v2
+        with:
+          name: replayer_${{ matrix.arch }}.jar
+          path: replayer.jar
+
+  merge_jars:
+    runs-on: ubuntu-latest
+    needs: build_replayer
+
+    steps:
+      - name: Download macOS jar
+        uses: actions/download-artifact@v2
+        with:
+          name: replayer_darwin.jar
+          path: replayer_darwin
+
+      - name: Download Linux jar
+        uses: actions/download-artifact@v2
+        with:
+          name: replayer_linux.jar
+          path: replayer_linux
+
+      - name: Merge jars
+        run: |
+          mkdir merged
+          unzip -o replayer_darwin/replayer.jar -d merged
+          unzip -o replayer_linux/replayer.jar -d merged
+          jar cvmf merged/META-INF/MANIFEST.MF replayer.jar -C merged .
+
+      - name: Upload merged jar
+        uses: actions/upload-artifact@v2
+        with:
+          name: replayer.jar
+          path: replayer.jar
+
diff --git a/agent/src/main/java/com/code_intelligence/jazzer/replay/BUILD.bazel b/agent/src/main/java/com/code_intelligence/jazzer/replay/BUILD.bazel
new file mode 100644
index 00000000..37365d8c
--- /dev/null
+++ b/agent/src/main/java/com/code_intelligence/jazzer/replay/BUILD.bazel
@@ -0,0 +1,18 @@
+load("@fmeum_rules_jni//jni:defs.bzl", "java_library_with_native")
+
+java_library_with_native(
+    name = "replay",
+    srcs = ["Replayer.java"],
+    native_libs = ["//agent/src/main/native/com/code_intelligence/jazzer/replay"],
+    visibility = ["//agent/src/main/native/com/code_intelligence/jazzer/replay:__pkg__"],
+    deps = [
+        "//agent/src/main/java/com/code_intelligence/jazzer/api",
+        "//agent/src/main/java/com/code_intelligence/jazzer/runtime:fuzzed_data_provider",
+    ],
+)
+
+java_binary(
+    name = "Replayer",
+    visibility = ["//visibility:public"],
+    runtime_deps = [":replay"],
+)
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);
+}
diff --git a/agent/src/main/java/com/code_intelligence/jazzer/runtime/BUILD.bazel b/agent/src/main/java/com/code_intelligence/jazzer/runtime/BUILD.bazel
index 764387f0..ff05e026 100644
--- a/agent/src/main/java/com/code_intelligence/jazzer/runtime/BUILD.bazel
+++ b/agent/src/main/java/com/code_intelligence/jazzer/runtime/BUILD.bazel
@@ -1,13 +1,30 @@
 load("@io_bazel_rules_kotlin//kotlin:jvm.bzl", "kt_jvm_library")
 
+java_library(
+    name = "fuzzed_data_provider",
+    srcs = [
+        "FuzzedDataProviderImpl.java",
+    ],
+    visibility = ["//agent/src/main/java/com/code_intelligence/jazzer/replay:__pkg__"],
+    deps = [
+        "//agent/src/main/java/com/code_intelligence/jazzer/api",
+    ],
+)
+
 kt_jvm_library(
     name = "runtime",
-    srcs = glob([
-        "*.java",
-        "*.kt",
-    ]),
+    srcs = glob(
+        [
+            "*.java",
+            "*.kt",
+        ],
+        exclude = [
+            "FuzzedDataProviderImpl.java",
+        ],
+    ),
     visibility = ["//visibility:public"],
     deps = [
+        ":fuzzed_data_provider",
         "//agent/src/main/java/com/code_intelligence/jazzer/api",
         "//agent/src/main/java/com/code_intelligence/jazzer/utils",
     ],
diff --git a/agent/src/main/java/com/code_intelligence/jazzer/runtime/FuzzedDataProviderImpl.java b/agent/src/main/java/com/code_intelligence/jazzer/runtime/FuzzedDataProviderImpl.java
index 0f4708e5..fe4d8ac7 100644
--- a/agent/src/main/java/com/code_intelligence/jazzer/runtime/FuzzedDataProviderImpl.java
+++ b/agent/src/main/java/com/code_intelligence/jazzer/runtime/FuzzedDataProviderImpl.java
@@ -16,8 +16,8 @@ package com.code_intelligence.jazzer.runtime;
 
 import com.code_intelligence.jazzer.api.FuzzedDataProvider;
 
-class FuzzedDataProviderImpl implements FuzzedDataProvider {
-  FuzzedDataProviderImpl() {}
+public class FuzzedDataProviderImpl implements FuzzedDataProvider {
+  public FuzzedDataProviderImpl() {}
 
   @Override public native boolean consumeBoolean();
 
diff --git a/agent/src/main/native/com/code_intelligence/jazzer/replay/BUILD.bazel b/agent/src/main/native/com/code_intelligence/jazzer/replay/BUILD.bazel
new file mode 100644
index 00000000..709156c3
--- /dev/null
+++ b/agent/src/main/native/com/code_intelligence/jazzer/replay/BUILD.bazel
@@ -0,0 +1,13 @@
+load("@fmeum_rules_jni//jni:defs.bzl", "java_native_library")
+
+java_native_library(
+    name = "replay",
+    srcs = [
+        "com_code_intelligence_jazzer_replay_Replayer.cpp",
+    ],
+    java_lib = "//agent/src/main/java/com/code_intelligence/jazzer/replay",
+    visibility = ["//agent/src/main/java/com/code_intelligence/jazzer/replay:__pkg__"],
+    deps = [
+        "//driver:fuzzed_data_provider",
+    ],
+)
diff --git a/agent/src/main/native/com/code_intelligence/jazzer/replay/com_code_intelligence_jazzer_replay_Replayer.cpp b/agent/src/main/native/com/code_intelligence/jazzer/replay/com_code_intelligence_jazzer_replay_Replayer.cpp
new file mode 100644
index 00000000..c4bdfcfb
--- /dev/null
+++ b/agent/src/main/native/com/code_intelligence/jazzer/replay/com_code_intelligence_jazzer_replay_Replayer.cpp
@@ -0,0 +1,48 @@
+// 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.
+
+#include "com_code_intelligence_jazzer_replay_Replayer.h"
+
+#include <jni.h>
+
+#include "driver/fuzzed_data_provider.h"
+
+namespace {
+uint8_t *data = nullptr;
+}
+
+void Java_com_code_1intelligence_jazzer_replay_Replayer_feedFuzzedDataProvider(
+    JNIEnv *env, jclass, jbyteArray input) {
+  if (data == nullptr) {
+    jazzer::SetUpFuzzedDataProvider(*env);
+  } else {
+    delete[] data;
+  }
+
+  std::size_t size = env->GetArrayLength(input);
+  if (env->ExceptionCheck()) {
+    env->ExceptionDescribe();
+    env->FatalError("Failed to get length of input");
+  }
+  data = static_cast<uint8_t *>(operator new(size));
+  if (data == nullptr) {
+    env->FatalError("Failed to allocate memory for a copy of the input");
+  }
+  env->GetByteArrayRegion(input, 0, size, reinterpret_cast<jbyte *>(data));
+  if (env->ExceptionCheck()) {
+    env->ExceptionDescribe();
+    env->FatalError("Failed to copy input");
+  }
+  jazzer::FeedFuzzedDataProvider(data, size);
+}
diff --git a/driver/BUILD.bazel b/driver/BUILD.bazel
index f15a2ddd..d0e0d531 100644
--- a/driver/BUILD.bazel
+++ b/driver/BUILD.bazel
@@ -1,10 +1,5 @@
 load("//bazel:cc.bzl", "cc_17_library")
 
-# None of the targets in this package should be built into shared objects. By
-# disabling the supports_pic feature, we reduce build time otherwise spent on
-# .pic.o files.
-package(features = ["-supports_pic"])
-
 cc_library(
     name = "sanitizer_hooks_with_pc",
     srcs = ["sanitizer_hooks_with_pc.cpp"],
@@ -31,9 +26,12 @@ cc_library(
     hdrs = [
         "fuzzed_data_provider.h",
     ],
+    visibility = [
+        "//agent/src/main/native/com/code_intelligence/jazzer/replay:__pkg__",
+    ],
     deps = [
-        "@bazel_tools//tools/jdk:jni",
         "@com_google_absl//absl/strings:str_format",
+        "@fmeum_rules_jni//jni",
     ],
 )
 
diff --git a/examples/BUILD.bazel b/examples/BUILD.bazel
index ca17ba3f..d721b81d 100644
--- a/examples/BUILD.bazel
+++ b/examples/BUILD.bazel
@@ -150,6 +150,36 @@ java_fuzz_target_test(
     ],
 )
 
+java_binary(
+    name = "JsonSanitizerDenylistCrash",
+    args = [
+        "com.example.JsonSanitizerDenylistFuzzer",
+        "$(location :json_sanitizer_denylist_crash)",
+    ],
+    data = [
+        ":json_sanitizer_denylist_crash",
+    ],
+    main_class = "com.code_intelligence.jazzer.replay.Replayer",
+    runtime_deps = [
+        ":JsonSanitizerDenylistFuzzer_target_deploy.jar",
+        "//agent/src/main/java/com/code_intelligence/jazzer/replay:Replayer_deploy.jar",
+    ],
+)
+
+sh_test(
+    name = "JsonSanitizerDenylistCrashTest",
+    srcs = ["check_for_finding.sh"],
+    args = [
+        "$(location :JsonSanitizerDenylistCrash)",
+        "com.example.JsonSanitizerDenylistFuzzer",
+        "$(location :json_sanitizer_denylist_crash)",
+    ],
+    data = [
+        ":JsonSanitizerDenylistCrash",
+        ":json_sanitizer_denylist_crash",
+    ],
+)
+
 java_fuzz_target_test(
     name = "JsonSanitizerIdempotenceFuzzer",
     srcs = [
diff --git a/examples/check_for_finding.sh b/examples/check_for_finding.sh
new file mode 100755
index 00000000..f60c011c
--- /dev/null
+++ b/examples/check_for_finding.sh
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# Copyright 2021 Code Intelligence GmbH
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+eval "$@"
+# Assert that we either found a crash in java (exit code 77) or an ASan crash
+# (exit code 76).
+declare -i exit_code=$?
+if [ $exit_code -eq 77 ] || [ $exit_code -eq 76 ]
+then
+  if [ "$(ls "$DEFAULT_CRASH_PREFIX/")" ]; then
+    exit 0
+  else
+    exit 1
+  fi
+else
+  echo "Unexpected exit code: $exit_code"
+  exit 1
+fi
diff --git a/examples/json_sanitizer_denylist_crash b/examples/json_sanitizer_denylist_crash
new file mode 100644
index 00000000..7324203a
--- /dev/null
+++ b/examples/json_sanitizer_denylist_crash