Bug: 211030211

Clone this repo:
  1. 73ef01c Add a wrapper for jazzer_setup by Zi Wang · 7 weeks ago master
  2. 4d5be65 Adding JazzerSetup target to build everything needed for Java development. There are Jazzer scripts that need these built by Cory Barker · 8 weeks ago
  3. baa144a Make Jazzer API device supported by Muhammad Haseeb Ahmad · 9 weeks ago
  4. 743c872 Sync AOSP fork to Jazzer upstream by Mark · 3 months ago
  5. 327677a all: Make global state in FuzzedDataProviderImpl local by Fabian Meumertzheim · 3 months ago

Jazzer

Maven Central GitHub Actions Fuzzing Status

Jazzer is a coverage-guided, in-process fuzzer for the JVM platform developed by Code Intelligence. It is based on libFuzzer and brings many of its instrumentation-powered mutation features to the JVM.

The JVM bytecode is executed inside the fuzzer process, which ensures fast execution speeds and allows seamless fuzzing of native libraries.

Jazzer currently supports the following platforms:

  • Linux x86_64
  • macOS 10.15+ x86_64 (experimental support for arm64)
  • Windows x86_64

News: Jazzer available in OSS-Fuzz

Code Intelligence and Google have teamed up to bring support for Java, Kotlin, and other JVM-based languages to OSS-Fuzz, Google's project for large-scale fuzzing of open-souce software. Read the blogpost over at the Google Security Blog.

If you want to learn more about Jazzer and OSS-Fuzz, watch the FuzzCon 2020 talk by Abhishek Arya and Fabian Meumertzheim.

Getting Jazzer

Using Docker

The “distroless” Docker image cifuzz/jazzer includes Jazzer together with OpenJDK 11. Just mount a directory containing your compiled fuzz target into the container under /fuzzing by running:

docker run -v path/containing/the/application:/fuzzing cifuzz/jazzer <arguments>

If Jazzer produces a finding, the input that triggered it will be available in the same directory.

Compiling with Bazel

Dependencies

Jazzer has the following dependencies when being built from source:

  • Bazel 4 or later
  • JDK 8 or later (e.g. OpenJDK)
  • Clang and LLD 9.0 or later (using a recent version is strongly recommended)

It is recommended to use Bazelisk to automatically download and install Bazel. Simply download the release binary for your OS and architecture and ensure that it is available in the PATH. The instructions below will assume that this binary is called bazel - Bazelisk is a thin wrapper around the actual Bazel binary and can be used interchangeably.

Compilation

Assuming the dependencies are installed, build Jazzer from source as follows:

$ git clone https://github.com/CodeIntelligenceTesting/jazzer
$ cd jazzer
# Note the double dash used to pass <arguments> to Jazzer rather than Bazel.
$ bazel run //:jazzer -- <arguments>

If you prefer to build binaries that can be run without Bazel, use the following command to build your own archive with release binaries:

$ bazel build //:jazzer_release
...
INFO: Found 1 target...
Target //:jazzer_release up-to-date:
  bazel-bin/jazzer_release.tar.gz
...

This will print the path of a jazzer_release.tar.gz archive that contains the same binaries that would be part of a release.

macOS

The build may fail with the clang shipped with Xcode. If you encounter issues during the build, add --config=toolchain right after run or build in the bazelisk commands above to use a checked-in toolchain that is known to work. Alternatively, manually install LLVM and set CC to the path of LLVM clang.

rules_fuzzing

Support for Jazzer has recently been added to rules_fuzzing, the official Bazel rules for fuzzing. See their README for instructions on how to use Jazzer in a Java Bazel project.

Using the provided binaries

Binary releases are available under Releases, but do not always include the latest changes.

The binary distributions of Jazzer consist of the following components:

  • jazzer - main binary
  • jazzer_agent_deploy.jar - Java agent that performs bytecode instrumentation and tracks coverage (automatically loaded by jazzer)
  • jazzer_api_deploy.jar - contains convenience methods for creating fuzz targets and defining custom hooks

The additional release artifact examples_deploy.jar contains most of the examples and can be used to run them without having to build them (see Examples below).

After unpacking the archive, run Jazzer via

./jazzer <arguments>

If this leads to an error message saying that libjvm.so has not been found, the path to the local JRE needs to be specified in the JAVA_HOME environment variable.

Examples

Multiple examples for instructive and real-world Jazzer fuzz targets can be found in the examples/ directory. A toy example can be run as follows:

# Using Bazel:
bazel run //examples:ExampleFuzzer
# Using the binary release and examples_deploy.jar:
./jazzer --cp=examples_deploy.jar

This should produce output similar to the following:

INFO: Loaded 1 hooks from com.example.ExampleFuzzerHooks
INFO: Instrumented com.example.ExampleFuzzer (took 81 ms, size +83%)
INFO: libFuzzer ignores flags that start with '--'
INFO: Seed: 2735196724
INFO: Loaded 1 modules   (65536 inline 8-bit counters): 65536 [0xe387b0, 0xe487b0),
INFO: Loaded 1 PC tables (65536 PCs): 65536 [0x7f9353eff010,0x7f9353fff010),
INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes
INFO: A corpus is not provided, starting from an empty corpus
#2      INITED cov: 2 ft: 2 corp: 1/1b exec/s: 0 rss: 94Mb
#1562   NEW    cov: 4 ft: 4 corp: 2/14b lim: 17 exec/s: 0 rss: 98Mb L: 13/13 MS: 5 ShuffleBytes-CrossOver-InsertRepeatedBytes-ShuffleBytes-CMP- DE: "magicstring4"-
#1759   REDUCE cov: 4 ft: 4 corp: 2/13b lim: 17 exec/s: 0 rss: 99Mb L: 12/12 MS: 2 ChangeBit-EraseBytes-
#4048   NEW    cov: 6 ft: 6 corp: 3/51b lim: 38 exec/s: 0 rss: 113Mb L: 38/38 MS: 4 ChangeBit-ChangeByte-CopyPart-CrossOver-
#4055   REDUCE cov: 6 ft: 6 corp: 3/49b lim: 38 exec/s: 0 rss: 113Mb L: 36/36 MS: 2 ShuffleBytes-EraseBytes-
#4266   REDUCE cov: 6 ft: 6 corp: 3/48b lim: 38 exec/s: 0 rss: 113Mb L: 35/35 MS: 1 EraseBytes-
#4498   REDUCE cov: 6 ft: 6 corp: 3/47b lim: 38 exec/s: 0 rss: 114Mb L: 34/34 MS: 2 EraseBytes-CopyPart-
#4764   REDUCE cov: 6 ft: 6 corp: 3/46b lim: 38 exec/s: 0 rss: 115Mb L: 33/33 MS: 1 EraseBytes-
#5481   REDUCE cov: 6 ft: 6 corp: 3/44b lim: 43 exec/s: 0 rss: 116Mb L: 31/31 MS: 2 InsertByte-EraseBytes-
#131072 pulse  cov: 6 ft: 6 corp: 3/44b lim: 1290 exec/s: 65536 rss: 358Mb

== Java Exception: java.lang.IllegalStateException: mustNeverBeCalled has been called
        at com.example.ExampleFuzzer.mustNeverBeCalled(ExampleFuzzer.java:38)
        at com.example.ExampleFuzzer.fuzzerTestOneInput(ExampleFuzzer.java:32)
DEDUP_TOKEN: eb6ee7d9b256590d
== libFuzzer crashing input ==
MS: 1 CMP- DE: "\x00C"-; base unit: 04e0ccacb50424e06e45f6184ad45895b6b8df8f
0x6d,0x61,0x67,0x69,0x63,0x73,0x74,0x72,0x69,0x6e,0x67,0x34,0x74,0x72,0x69,0x6e,0x67,0x34,0x74,0x69,0x67,0x34,0x7b,0x0,0x0,0x43,0x34,0xa,0x0,0x0,0x0,
magicstring4tring4tig4{\x00\x00C4\x0a\x00\x00\x00
artifact_prefix='./'; Test unit written to crash-efea1e8fc83a15217d512e20d964040a68a968c3
Base64: bWFnaWNzdHJpbmc0dHJpbmc0dGlnNHsAAEM0CgAAAA==
reproducer_path='.'; Java reproducer written to Crash_efea1e8fc83a15217d512e20d964040a68a968c3.java

Here you can see the usual libFuzzer output in case of a crash, augmented with JVM-specific information. Instead of a native stack trace, the details of the uncaught Java exception that caused the crash are printed, followed by the fuzzer input that caused the exception to be thrown (if it is not too long). More information on what hooks and Java reproducers are can be found below.

See examples/BUILD.bazel for the list of all possible example targets.

Usage

Creating a fuzz target

Jazzer requires a JVM class containing the entry point for the fuzzer. This is commonly referred to as a “fuzz target” and may be as simple as the following Java example:

package com.example.MyFirstFuzzTarget;

public class MyFirstFuzzTarget {
    public static void fuzzerTestOneInput(byte[] input) {
        ...
        // Call the function under test with arguments derived from input and
        // throw an exception if something unwanted happens.
        ...
    }
}

A Java fuzz target class needs to define exactly one of the following functions:

  • public static void fuzzerTestOneInput(byte[] input): Ideal for fuzz targets that naturally work on raw byte input (e.g. image parsers).
  • public static void fuzzerTestOneInput(com.code_intelligence.api.FuzzedDataProvider data): A variety of types of “fuzzed data” is made available via the FuzzedDataProvider interface (see below for more information on this interface).

The fuzzer will repeatedly call this function with generated inputs. All unhandled exceptions are caught and reported as errors.

The optional functions public static void fuzzerInitialize() or public static void fuzzerInitialize(String[] args) can be defined if initial setup is required. These functions will be called once before the first call to fuzzerTestOneInput.

The optional function public static void fuzzerTearDown() will be run just before the JVM is shut down.

Kotlin

An example of a Kotlin fuzz target can be found in KlaxonFuzzer.kt.

Running the fuzzer

The fuzz target needs to be compiled and packaged into a .jar archive. Assuming that this archive is called fuzz_target.jar and depends on libraries available as lib1.jar and lib2.jar, fuzzing is started by invoking Jazzer with the following arguments:

--cp=fuzz_target.jar:lib1.jar:lib2.jar --target_class=com.example.MyFirstFuzzTarget <optional_corpus_dir>

The fuzz target class can optionally be specified by adding it as the value of the Jazzer-Fuzz-Target-Class attribute in the JAR's manifest. If there is only a single such attribute among all manifests of JARs on the classpath, Jazzer will use its value as the fuzz target class.

Bazel produces the correct type of .jar from a java_binary target with create_executable = False and deploy_manifest_lines = ["Jazzer-Fuzz-Target-Class: com.example.MyFirstFuzzTarget"] by adding the suffix _deploy.jar to the target name.

Fuzzed Data Provider

For most non-trivial fuzz targets it is necessary to further process the byte array passed from the fuzzer, for example to extract multiple values or convert the input into a valid java.lang.String. We provide functionality similar to atheris' FuzzedDataProvider and libFuzzer's FuzzedDataProvider.h to simplify the task of writing JVM fuzz targets.

If the function public static void fuzzerTestOneInput(FuzzedDataProvider data) is defined in the fuzz target, it will be passed an object implementing com.code_intelligence.jazzer.api.FuzzedDataProvider that allows consuming the raw fuzzer input as values of common types. This can look as follows:

package com.example.MySecondFuzzTarget;

import com.code_intelligence.jazzer.api.FuzzedDataProvider;

public class MySecondFuzzTarget {
    public static void callApi(int val, String text) {
        ...
    }

    public static void fuzzerTestOneInput(FuzzedDataProvider data) {
        callApi1(data.consumeInt(), data.consumeRemainingAsString());
    }
}

The FuzzedDataProvider interface definition is contained in jazzer_api_deploy.jar in the binary release and can be built by the Bazel target //agent:jazzer_api_deploy.jar. It is also available from Maven Central. For additional information, see the javadocs.

It is highly recommended to use FuzzedDataProvider for generating java.lang.String objects inside the fuzz target instead of converting the raw byte array to directly via a String constructor as the FuzzedDataProvider implementation is engineered to minimize copying and generate both valid and invalid ASCII-only and Unicode strings.

Autofuzz mode

The Autofuzz mode enables fuzzing arbitrary methods without having to manually create fuzz targets. Instead, Jazzer will attempt to generate suitable and varied inputs to a specified methods using only public API functions available on the classpath.

To use Autofuzz, specify the --autofuzz flag and provide a fully qualified method reference, e.g.:

--autofuzz=org.apache.commons.imaging.Imaging::getBufferedImage

To autofuzz a constructor the ClassType::new format can be used.
If there are multiple overloads, and you want Jazzer to only fuzz one, you can optionally specify the signature of the method to fuzz:

--autofuzz=org.apache.commons.imaging.Imaging::getBufferedImage(java.io.InputStream,java.util.Map)

The format of the signature agrees with that obtained from the part after the # of the link to the Javadocs for the particular method.

Under the hood, Jazzer tries various ways of creating objects from the fuzzer input. For example, if a parameter is an interface or an abstract class, it will look for all concrete implementing classes on the classpath. Jazzer can also create objects from classes that follow the builder design pattern or have a default constructor and use setters to set the fields.

Creating objects from fuzzer input can lead to many reported exceptions. Jazzer addresses this issue by ignoring exceptions that the target method declares to throw. In addition to that, you can provide a list of exceptions to be ignored during fuzzing via the --autofuzz_ignore flag in the form of a comma-separated list. You can specify concrete exceptions (e.g., java.lang.NullPointerException), in which case also subclasses of these exception classes will be ignored, or glob patterns to ignore all exceptions in a specific package (e.g. java.lang.* or com.company.**).

When fuzzing with --autofuzz, Jazzer automatically enables the --keep_going mode to keep fuzzing indefinitely after the first finding. Set --keep_going=N explicitly to stop after the N-th finding.

Docker

To facilitate using the Autofuzz mode, there is a docker image that you can use to fuzz libraries just by providing their Maven coordinates. The dependencies will then be downloaded and autofuzzed:

docker run cifuzz/jazzer-autofuzz <Maven coordinates> --autofuzz=<method reference> <further arguments>

As an example, you can autofuzz the json-sanitizer library as follows:

docker run -it cifuzz/jazzer-autofuzz \
   com.mikesamuel:json-sanitizer:1.2.0 \
   com.google.json.JsonSanitizer::sanitize \
   --autofuzz_ignore=java.lang.ArrayIndexOutOfBoundsException \
   --keep_going=1

Reproducing a bug

When Jazzer manages to find an input that causes an uncaught exception or a failed assertion, it prints a Java stack trace and creates two files that aid in reproducing the crash without Jazzer:

  • crash-<sha1_of_input> contains the raw bytes passed to the fuzz target (just as with libFuzzer C/C++ fuzz targets). The crash can be reproduced with Jazzer by passing the path to the crash file as the only positional argument.
  • Crash-<sha1_of_input>.java contains a class with a main function that invokes the fuzz target with the crashing input. This is especially useful if using FuzzedDataProvider as the raw bytes of the input do not directly correspond to the values consumed by the fuzz target. The .java file can be compiled with just the fuzz target and its dependencies in the classpath (plus jazzer_api_deploy.jar if using `FuzzedDataProvider).

Minimizing a crashing input

Every crash stack trace is accompanied by a DEDUP_TOKEN that uniquely identifies the relevant parts of the stack trace. This value is used by libFuzzer while minimizing a crashing input to ensure that the smaller inputs reproduce the “same” bug. To minimize a crashing input, execute Jazzer with the following arguments in addition to --cp and --target_class:

-minimize_crash=1 <path/to/crashing_input>

Parallel execution

libFuzzer offers the -fork=N and -jobs=N flags for parallel fuzzing, both of which are also supported by Jazzer.

Limitations

Jazzer currently maintains coverage information in a global variable that is shared among threads. This means that while fuzzing multi-threaded fuzz targets is theoretically possible, the reported coverage information may be misleading.

Findings

Jazzer has so far uncovered the following vulnerabilities and bugs:

ProjectBugStatusCVEfound by
OpenJDKOutOfMemoryError via a small BMP imagefixedCVE-2022-21360Code Intelligence
OpenJDKOutOfMemoryError via a small TIFF imagefixedCVE-2022-21366Code Intelligence
protocolbuffers/protobufSmall protobuf messages can consume minutes of CPU timefixedCVE-2021-22569OSS-Fuzz
jhy/jsoupMore than 19 Bugs found in HTML and XML parserfixedCVE-2021-37714Code Intelligence
Apache/commons-compressInfinite loop when loading a crafted 7zfixedCVE-2021-35515Code Intelligence
Apache/commons-compressOutOfMemoryError when loading a crafted 7zfixedCVE-2021-35516Code Intelligence
Apache/commons-compressInfinite loop when loading a crafted TARfixedCVE-2021-35517Code Intelligence
Apache/commons-compressOutOfMemoryError when loading a crafted ZIPfixedCVE-2021-36090Code Intelligence
Apache/PDFBoxInfinite loop when loading a crafted PDFfixedCVE-2021-27807Code Intelligence
Apache/PDFBoxOutOfMemoryError when loading a crafted PDFfixedCVE-2021-27906Code Intelligence
netplex/json-smart-v1
netplex/json-smart-v2
JSONParser#parse throws an undeclared exceptionfixedCVE-2021-27568@GanbaruTobi
OWASP/json-sanitizerOutput can contain</script> and ]]>, which allows XSSfixedCVE-2021-23899Code Intelligence
OWASP/json-sanitizerOutput can be invalid JSON and undeclared exceptions can be thrownfixedCVE-2021-23900Code Intelligence
alibaba/fastjonJSON#parse throws undeclared exceptionsfixedCode Intelligence
Apache/commons-compressInfinite loop and OutOfMemoryError in TarFilefixedCode Intelligence
Apache/commons-compressNullPointerException in ZipFilefixedCode Intelligence
Apache/commons-imagingParsers for multiple image formats throw undeclared exceptionsreportedCode Intelligence
Apache/PDFBoxVarious undeclared exceptionsfixedCode Intelligence
cbeust/klaxonDefault parser throws runtime exceptionsfixedCode Intelligence
FasterXML/jackson-dataformats-binaryCBORParser throws an undeclared exception due to missing bounds checks when parsing UnicodefixedCode Intelligence
FasterXML/jackson-dataformats-binaryCBORParser throws an undeclared exception on dangling arraysfixedCode Intelligence
ngageoint/tiff-javareadTiff Index Out Of Boundsfixed@raminfp
google/re2jNullPointerException in Pattern.compilereported@schirrmacher
google/gsonArrayIndexOutOfBounds in ParseStringfixed@DavidKorczynski

As Jazzer is used to fuzz JVM projects in OSS-Fuzz, an additional list of bugs can be found on the OSS-Fuzz issue tracker.

If you find bugs with Jazzer, we would like to hear from you! Feel free to open an issue or submit a pull request.

Advanced Options

Various command line options are available to control the instrumentation and fuzzer execution. Since Jazzer is a libFuzzer-compiled binary, all positional and single dash command-line options are parsed by libFuzzer. Therefore, all Jazzer options are passed via double dash command-line flags, i.e., as --option=value (note the = instead of a space).

A full list of command-line flags can be printed with the --help flag. For the available libFuzzer options please refer to its documentation for a detailed description.

Passing JVM arguments

When Jazzer is launched, it starts a JVM in which it executes the fuzz target. Arguments for this JVM can be provided via the JAVA_OPTS environment variable.

Alternatively, arguments can also be supplied via the --jvm_args argument. Multiple arguments are delimited by the classpath separator, which is ; on Windows and : else. For example, to enable preview features as well as set a maximum heap size, add the following to the Jazzer invocation:

# Windows
--jvm_args=--enable-preview;-Xmx1000m
# Linux & macOS
--jvm_args=--enable-preview:-Xmx1000m

Arguments specified with --jvm_args take precendence over those in JAVA_OPTS.

Coverage Instrumentation

The Jazzer agent inserts coverage markers into the JVM bytecode during class loading. libFuzzer uses this information to guide its input mutations towards increased coverage.

It is possible to restrict instrumentation to only a subset of classes with the --instrumentation_includes flag. This is especially useful if coverage inside specific packages is of higher interest, e.g., the user library under test rather than an external parsing library in which the fuzzer is likely to get lost. Similarly, there is --instrumentation_excludes to exclude specific classes from instrumentation. Both flags take a list of glob patterns for the java class name separated by colon:

--instrumentation_includes=com.my_com.**:com.other_com.** --instrumentation_excludes=com.my_com.crypto.**

By default, JVM-internal classes and Java as well as Kotlin standard library classes are not instrumented, so these do not need to be excluded manually.

Trace Instrumentation

The agent adds additional hooks for tracing compares, integer divisions, switch statements and array indices. These hooks correspond to clang's data flow hooks. The particular instrumentation types to apply can be specified using the --trace flag, which accepts the following values:

  • cov: AFL-style edge coverage
  • cmp: compares (int, long, String) and switch cases
  • div: divisors in integer divisions
  • gep: constant array indexes
  • indir: call through Method#invoke
  • all: shorthand to apply all available instrumentations (except gep)

Multiple instrumentation types can be combined with a colon (Linux, macOS) or a semicolon (Windows).

Value Profile

The run-time flag -use_value_profile=1 enables libFuzzer's value profiling mode. When running with this flag, the feedback about compares and constants received from Jazzer's trace instrumentation is associated with the particular bytecode location and used to provide additional coverage instrumentation. See ExampleValueProfileFuzzer.java for a fuzz target that would be very hard to fuzz without value profile.

Custom Hooks

In order to obtain information about data passed into functions such as String.equals or String.startsWith, Jazzer hooks invocations to these methods. This functionality is also available to fuzz targets, where it can be used to implement custom sanitizers or stub out methods that block the fuzzer from progressing (e.g. checksum verifications or random number generation). See ExampleFuzzerHooks.java for an example of such a hook. An example for a sanitizer can be found in ExamplePathTraversalFuzzerHooks.java.

Method hooks can be declared using the @MethodHook annotation defined in the com.code_intelligence.jazzer.api package, which is contained in jazzer_api_deploy.jar (binary release) or built by the target //agent:jazzer_api_deploy.jar (Bazel). It is also available from Maven Central. See the javadocs of the @MethodHook API for more details.

To use the compiled method hooks they have to be available on the classpath provided by --cp and can then be loaded by providing the flag --custom_hooks, which takes a colon-separated list of names of classes to load hooks from. If a hook is meant to be applied to a class in the Java standard library, it has to be loaded from a JAR file so that Jazzer can add it to the bootstrap class loader search. This list of custom hooks can alternatively be specified via the Jazzer-Hook-Classes attribute in the fuzz target JAR's manifest.

Suppressing stack traces

With the flag --keep_going=N Jazzer continues fuzzing until N unique stack traces have been encountered.

Particular stack traces can also be ignored based on their DEDUP_TOKEN by passing a comma-separated list of tokens via --ignore=<token_1>,<token2>.

Export coverage information

The internally gathered JaCoCo coverage information can be exported in human-readable and JaCoCo execution data format (.exec). These can help identify code areas that have not been covered by the fuzzer and thus may require more comprehensive fuzz targets or a more extensive initial corpus to reach.

The human-readable report contains coverage information, like branch and line coverage, on file level. It's useful to get a quick overview about the overall coverage. The flag --coverage_report=<file> can be used to generate it.

Similar to the JaCoCo dump command, the flag --coverage_dump=<file> specifies a coverage dump file, often called jacoco.exec, that is generated after the fuzzing run. It contains a binary representation of the gathered coverage data in the JaCoCo format.

The JaCoCo report command can be used to generate reports based on this coverage dump. The JaCoCo CLI tools are available on their GitHub release page as zip file. The report tool is located in the lib folder and can be used as described in the JaCoCo CLI documentation. For example the following command generates an HTML report in the folder report containing all classes available in classes.jar and their coverage as captured in the export coverage.exec. Source code to include in the report is searched for in some/path/to/sources. After execution the index.html file in the output folder can be opened in a browser.

java -jar path/to/jacococli.jar report coverage.exec \
  --classfiles classes.jar \
  --sourcefiles some/path/to/sources \
  --html report \
  --name FuzzCoverageReport

Advanced fuzz targets

Fuzzing with Native Libraries

Jazzer supports fuzzing of native libraries loaded by the JVM, for example via System.load(). For the fuzzer to get coverage feedback, these libraries have to be compiled with -fsanitize=fuzzer-no-link.

Additional sanitizers such as AddressSanitizer or UndefinedBehaviorSanitizer are often desirable to uncover bugs inside the native libraries. The required compilation flags for native libraries are as follows:

  • AddressSanitizer: -fsanitize=fuzzer-no-link,address
  • UndefinedBehaviorSanitizer: -fsanitize=fuzzer-no-link,undefined (add -fno-sanitize-recover=all to crash on UBSan reports)

Then, use the appropriate driver //:jazzer_asan or //:jazzer_ubsan.

Note: Sanitizers other than AddressSanitizer and UndefinedBehaviorSanitizer are not yet supported. Furthermore, due to the nature of the JVM's GC, LeakSanitizer reports too many false positives to be useful and is thus disabled.

The fuzz targets ExampleFuzzerWithNativeASan and ExampleFuzzerWithNativeUBSan in the examples/ directory contain minimal working examples for fuzzing with native libraries. Also see TurboJpegFuzzer for a real-world example.

Fuzzing with Custom Mutators

LibFuzzer API offers two functions to customize the mutation strategy which is especially useful when fuzzing functions that require structured input. Jazzer does not define LLVMFuzzerCustomMutator nor LLVMFuzzerCustomCrossOver and leaves the mutation strategy entirely to libFuzzer. However, custom mutators can easily be integrated by compiling a mutator library which defines LLVMFuzzerCustomMutator (and optionally LLVMFuzzerCustomCrossOver) and pre-loading the mutator library:

# Using Bazel:
LD_PRELOAD=libcustom_mutator.so bazel run //:jazzer -- <arguments>
# Using the binary release:
LD_PRELOAD=libcustom_mutator.so ./jazzer <arguments>

Credit

The following developers have contributed to Jazzer before its public release:

Sergej Dechand, Christian Hartlage, Fabian Meumertzheim, Sebastian Pöplau, Mohammed Qasem, Simon Resch, Henrik Schnor, Khaled Yakdan

The LLVM-style edge coverage instrumentation for JVM bytecode used by Jazzer relies on JaCoCo. Previously, Jazzer used AFL-style coverage instrumentation as pioneered by kelinci.