259 lines
11 KiB
Markdown
259 lines
11 KiB
Markdown
# DeepState
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[](https://empireslacking.herokuapp.com/)
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[](https://travis-ci.org/trailofbits/deepstate)
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DeepState is a framework that provides C and C++ developers with a common interface to various symbolic execution and fuzzing engines. Users can write one test harness using a Google Test-like API, then execute it using multiple backends without having to learn the complexities of the underlying engines. It supports writing unit tests and API sequence tests, as well as automatic test generation. Read more about the goals and design of DeepState in our [paper](https://agroce.github.io/bar18.pdf).
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The [2018 IEEE Cybersecurity Development Conference](https://secdev.ieee.org/2018/home) will include a full tutorial on effective use of DeepState.
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## Overview of Features
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* Tests look like Google Test, but can use symbolic execution/fuzzing to generate data (parameterized unit testing)
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* Easier to learn than binary analysis tools/fuzzers, but provides similar functionality
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* Already supports Manticore, Angr, libFuzzer, file-based fuzzing with e.g., AFL; more back-ends likely in future
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* Switch test generation tool without re-writing test harness
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* Work around show-stopper bugs
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* Find out which tool works best for your code under test
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* Different tools find different bugs/vulnerabilities
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* Fair way to benchmark/bakeoff tools
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* Provides test replay for regression plus effective automatic test case reduction to aid debugging
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* Supports API-sequence generation with extensions to Google Test interface
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* Concise readable way (OneOf) to say "run one of these blocks of code"
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* Same construct supports fixed value set non-determinism
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* E.g., writing a POSIX file system tester is pleasant, not painful as in pure Google Test idioms
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* Provides high-level strategies for improving symbolic execution/fuzzing effectiveness
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* Pumping (novel to DeepState) to pick concrete values when symbolic execution is too expensive
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* Automatic decomposition of integer compares to guide coverage-driven fuzzers
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## Supported Platforms
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DeepState currently targets Linux, with macOS support in progress.
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## Dependencies
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Build:
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- CMake
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- GCC and G++ with multilib support
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- Python 2.7
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- Setuptools
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Runtime:
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- Python 2.7
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- Z3 (for the Manticore backend)
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## Building on Ubuntu 16.04 (Xenial)
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```shell
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sudo apt update && sudo apt-get install build-essential gcc-multilib g++-multilib cmake python python-setuptools libffi-dev z3
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git clone https://github.com/trailofbits/deepstate deepstate
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mkdir deepstate/build && cd deepstate/build
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cmake ../
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make
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```
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## Installing
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Assuming the DeepState build resides in `$DEEPSTATE`, run the following commands to install the DeepState python package:
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```shell
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virtualenv venv
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. venv/bin/activate
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python $DEEPSTATE/build/setup.py install
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```
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The `virtualenv`-enabled `$PATH` should now include two executables: `deepstate` and `deepstate-angr`. These are _executors_, which are used to run DeepState test binaries with specific backends (automatically installed as Python dependencies). The `deepstate` executor uses the Manticore backend while `deepstate-angr` uses angr. They share a common interface where you may specify a number of workers and an output directory for saving backend-generated test cases.
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You can check your build using the test binaries that were (by default) built and emitted to `deepstate/build/examples`. For example, to use angr to symbolically execute the `IntegerOverflow` test harness with 4 workers, saving generated test cases in a directory called `out`, you would invoke:
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```shell
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deepstate-angr --num_workers 4 --output_test_dir out $DEEPSTATE/build/examples/IntegerOverflow
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```
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The resulting `out` directory should look something like:
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```
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out
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└── IntegerOverflow.cpp
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├── SignedInteger_AdditionOverflow
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│ ├── a512f8ffb2c1bb775a9779ec60b699cb.fail
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│ └── f1d3ff8443297732862df21dc4e57262.pass
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└── SignedInteger_MultiplicationOverflow
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├── 6a1a90442b4d898cb3fac2800fef5baf.fail
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└── f1d3ff8443297732862df21dc4e57262.pass
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```
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To run these tests, you can just use the native executable, e.g.:
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```shell
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$DEEPSTATE/build/examples/IntegerOverflow --input_test_dir out
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```
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to run all the generated tests, or
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```shell
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$DEEPSTATE/build/examples/IntegerOverflow --input_test_files_dir out/IntegerOverflow.cpp/SignedInteger_AdditionOverflow --input_which_test SignedInteger_AdditionOverflow
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```
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to run the tests in one directory (in this case, you want to specify
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which test to run, also). You can also run a single test, e.g.:
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```shell
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$DEEPSTATE/build/examples/IntegerOverflow --input_test_file out/IntegerOverflow.cpp/SignedInteger_AdditionOverflow/a512f8ffb2c1bb775a9779ec60b699cb.fail--input_which_test SignedInteger_AdditionOverflow
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```
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In the absence of an `--input_which_test` argument, DeepState defaults
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to the last-defined test. Run the native executable with the `--help`
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argument to see all DeepState options.
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## Usage
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DeepState consists of a static library, used to write test harnesses, and command-line _executors_ written in Python. At this time, the best documentation is in the [examples](/examples) and in our [paper](https://agroce.github.io/bar18.pdf).
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## Fuzzing with libFuzzer
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If you install clang 6.0 or later, and run `cmake` when you install
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with the `BUILD_LIBFUZZER` environment variable defined, you can
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generate tests using LlibFuzzer. Because both DeepState and libFuzzer
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want to be `main`, this requires building a different executable for
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libFuzzer. The `examples` directory shows how this can be done. The
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libFuzzer executable works like any other libFuzzer executable, and
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the tests produced can be run using the normal DeepState executable.
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For example, generating some tests of the `OneOf` example (up to 5,000
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runs), then running those tests to examine the results, would look
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like:
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```shell
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mkdir OneOf_libFuzzer_corpus
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./OneOf_LF -runs=5000 OneOf_libFuzzer_corpus
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./OneOf --input_test_files_dir OneOf_libFuzzer_corpus
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```
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Use the `LIBFUZZER_WHICH_TEST`
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environment variable to control which test libFuzzer runs, using a
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fully qualified name (e.g.,
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`Arithmetic_InvertibleMultiplication_CanFail`). By default, you get
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the last test defined (which works fine if there is only one test).
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Obviously, libFuzzer may work better if you provide a non-empty
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corpus, but fuzzing will work even without an initial corpus, unlike AFL.
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One hint when using libFuzzer is to avoid dynamically allocating
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memory during a test, if that memory would not be freed on a test
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failure. This will leak memory and libFuzzer will run out of memory
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very quickly in each fuzzing session.
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## Test case reduction
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While tests generated by symbolic execution are likely to be highly
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concise already, fuzzer-generated tests may be much larger than they
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need to be.
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DeepState provides a test case reducer to shrink tests intelligently,
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aware of the structure of a DeepState test. For example, if your
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executable is named `TestFileSystem` and the test you want to reduce
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is named `rmdirfail.test` you would use it like this:
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```shell
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deepstate-reduce ./TestFileSystem rmdirfail.test minrmdirfail.test
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```
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In many cases, this will result in finding a different failure or
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crash that allow smaller test cases, so you can also provide a string
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that controls the criteria for which test outputs are considered valid
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reductions (by default, the reducer looks for any test that fails or
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crashes). Only outputs containing the `--criteria` are considered to
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be valid reductions:
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```shell
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deepstate-reduce ./TestFileSystem rmdirfail.test minrmdirfail.test --criteria "FATAL: /root/testfs/super.c(252)"
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```
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The output will look something like:
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```
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ORIGINAL TEST HAS 119 BYTES
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ONEOF REMOVAL REDUCED TEST TO 103 BYTES
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ONEOF REMOVAL REDUCED TEST TO 87 BYTES
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ONEOF REMOVAL REDUCED TEST TO 67 BYTES
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ONEOF REMOVAL REDUCED TEST TO 51 BYTES
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BYTE RANGE REMOVAL REDUCED TEST TO 50 BYTES
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BYTE RANGE REMOVAL REDUCED TEST TO 49 BYTES
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BYTE REDUCTION: BYTE 3 FROM 4 TO 0
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BYTE REDUCTION: BYTE 43 FROM 4 TO 0
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ONEOF REMOVAL REDUCED TEST TO 33 BYTES
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ONEOF REMOVAL REDUCED TEST TO 17 BYTES
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BYTE REDUCTION: BYTE 7 FROM 2 TO 1
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BYTE REDUCTION: BYTE 15 FROM 2 TO 1
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NO REDUCTIONS FOUND
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PADDING TEST WITH 3 ZEROS
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WRITING REDUCED TEST WITH 20 BYTES TO minrmdirfail.test
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```
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You can use `--which_test <testname>` to specify which test to
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run, as with the `--input_which_test` options to test replay.
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## Fuzzing with AFL
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DeepState can also be used with a file-based fuzzer (e.g. AFL). There
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are a few steps to this. First, compile DeepState itself with any
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needed instrumentation. E.g., to use it with AFL, you might want to add
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something like:
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```
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SET(CMAKE_C_COMPILER /usr/local/bin/afl-gcc)
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SET(CMAKE_CXX_COMPILER /usr/local/bin/afl-g++)
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```
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to `deepstate/CMakeLists.txt`. Second, do the same for your DeepState
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test harness and any code it links to you want instrumented. Finally, run the fuzzing via the
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interface to replay test files. For example, to fuzz the `OneOf`
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example, if we were in the `deepstate/build/examples` directory, you
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would do something like:
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```shell
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afl-fuzz -d -i corpus -o afl_OneOf -- ./OneOf --input_test_file @@ --abort_on_fail
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```
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where `corpus` contains at least one file to start fuzzing from. The
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file needs to be smaller than the DeepState input size limit, but has
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few other limitations (for AFL it should also not cause test
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failure). The `abort_on_fail` flag makes DeepState crashes and failed
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tests appear as crashes to the fuzzer.
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To replay the tests from AFL:
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```shell
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./OneOf --input_test_files_dir afl_OneOf/crashes
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./OneOf --input_test_files_dir afl_OneOf/queue
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```
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Finally, if an example has more than one test, you need to specify,
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with a fully qualified name (e.g.,
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`Arithmetic_InvertibleMultiplication_CanFail`), which test to run,
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using the `--input_which_test` flag to the binary. By
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default, DeepState will run the last test defined.
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You can compile with `afl-clang-fast` and `afl-clang-fast++` for
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deferred instrumentation. You'll need code like:
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```
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#ifdef __AFL_HAVE_MANUAL_CONTROL
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__AFL_INIT();
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#endif
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```
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just before the call to `DeepState_Run()` (which reads the entire
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input file) in your `main`.
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## Contributing
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All accepted PRs are awarded bounties by Trail of Bits. Join the #deepstate channel on the [Empire Hacking Slack](https://empireslacking.herokuapp.com/) to discuss ongoing development and claim bounties. Check the [good first issue](https://github.com/trailofbits/deepstate/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22) label for suggested contributions.
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## License
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DeepState is released under [The Apache License 2.0](LICENSE).
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