Macaron

Macaron is a supply chain security analysis tool from Oracle Labs, which focuses on the build integrity of an artifact and the artifact dependencies. It is based on the Supply chain Levels for Software Artifacts (SLSA) specification, which aims at preventing some of the software supply chain attacks as the systems get more complex, especially with respect to the use of open-source third-party code in applications. Attacks include stealing credentials, injecting malicious code etc., and it is critical to have security assurance on the third-party code to guarantee that the integrity of the code has not been compromised.

Macaron uses SLSA requirements specifications v0.1 to define concrete rules for protecting software integrity that can be checked for compliance requirements automatically. Macaron provides a customizable checker platform that makes it easy to define checks that depend on each other. This is particularly useful for implementing checks for SLSA levels. In addition, Macaron also checks a user-specified policy for the repository to detect unexpected behavior in the build process. Macaron is a work-in-progress project and currently supports Maven and Gradle Java build systems only. We plan to support build systems for other languages, such as Python in future.

Table of Contents

• Getting started
• Running Macaron
• How to Contribute
• Security issue reports
• License

Getting started

Prerequisites

• Python 3.11
• Go 1.18
• JDK 11

Prepare the environment

Clone the project and install Macaron.

make venv
. .venv/bin/activate
make setup

Running Macaron

usage: macaron [-h] [-v] [-o OUTPUT_DIR] -t PERSONAL_ACCESS_TOKEN {analyze,dump_defaults,verify} ...

The main parameters for Macaron are:

• [-v]: Run Macaron with more debug outputs.
• [-o OUTPUT_DIR]: The directory to store the results. The default value will be the Macaron repo path.
• -t PERSONAL_ACCESS_TOKEN: The GitHub access token. It's mandatory to have one for using any feature of Macaron. A valid token will provide increased request rate, request limit and access to resources (e.g. GitHub Actions workflow data). Macaron is tested for valid GitHub access tokens only. The method to obtain a GitHub personal access token is described in the next section.

Apart from the main parameters listed above, you should choose the command to run, which requires other parameters. At the moment, Macaron has three commands.

• analyze: analyze the SLSA level of a single repository.
• dump_defaults: dump the default values in the output directory.
• verify: verify a provenance against a policy.

Obtaining the GitHub personal access token

Create your own Github access token (please refer to the instructions here). When creating this token, make sure to assign at least repo permissions.

The GitHub token should be stored in an environment variable and supplied to Macaron via command line parameters.

Analyzing SLSA levels of a repository

This section describes the analyze command of Macaron.

Run this command to determine the SLSA level of a repository:

python -m macaron [-v] analyze -rp <path_to_target_repo> [-b <branch_name>] [-d <digest>] -c <config_path>

The main input parameters of the analyze command:

• -rp <path_to_target_repo> specifies the path to the repository to analyze. This path can be both a local path (e.g. /path/to/repo) or a remote path (e.g. git@github.com:organization/repo_name.git or https://github.com/organization/repo_name.git).
• [-b <branch_name>]: The name of the branch to analyze. If not specified, Macaron will checkout the default branch (if a remote path is supplied) or use the current branch that HEAD is on (if a local path is supplied).
• [-d <digest>]: The hash of the commit to checkout in the current branch. This hash must be in full form. If not specified, Macaron will checkout the latest commit of the current branch.
• -c <config_path>: The path to the configuration yaml file. This option cannot be used together with the -rp option.

Example I: Analyzing the GitHub repository apache/maven on the latest commit of the default branch without using a config file:

python -m macaron -t $GH_TOKEN -o output analyze -rp https://github.com/apache/maven.git

Example II: Doing the same thing as Example I, but using a config file:

python -m macaron -t $GH_TOKEN -o output analyze -c <path-to-maven_config.yaml>

target:
  id: "apache/maven"
  branch: ""
  digest: ""
  path: "https://github.com/apache/maven.git"

The results of the examples above will be stored in output/reports/github_com/apache/maven/ in HTML and JSON formats.

Notes:

• Macaron automatically detects and analyzes direct dependencies for Java Maven projects. This process might take a while during the first run but will be faster during the subsequent runs. To skip analyzing the dependencies you can pass --skip-deps option.
• If you supply a remote path, the repository is cloned to git_repos/ before the analysis starts. If the repository has already been cloned to git_repos/, Macaron will not clone the repository and proceed to analyze the local repo instead.
• The branch and digest in the config file or -b and -d in the CLI are all optional and can be omitted.

Verifying a policy

Macaron, currently, provides a PoC policy engine that checks a verified SLSA provenance against compliance requirements expressed as a policy. The result is reported in the JSON and HTML reports as a check called mcn_policy_check_1.

python -m macaron -t $GH_TOKEN -po <path-to-policy.yaml> analyze -rp https://github.com/apache/maven.git

The policy is a YAML file that contains expected values of predicates in SLSA provenance v0.2. Here is an example policy file:

metadata:
  id: MACARON_1
  description: "Micronaut policy - SLSA provenance v0.2."

definition:
  _type: https://in-toto.io/Statement/v0.1
  predicateType: https://slsa.dev/provenance/v0.2

  predicate:
    builder:
      id: https://github.com/slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@refs/tags/v1.2.1
    buildType: https://github.com/slsa-framework/slsa-github-generator/generic@v1

    invocation:
      configSource:
        uri: git+https://github.com/micronaut-projects/micronaut-security@refs/tags/v3.8.3
        entryPoint: .github/workflows/release.yml

You can also run the policy verifier directly like below:

python -m macaron -po <path_to_policy.yaml> verify -pr <path_to_prov_file>

Note. The policy engine is under active development and will support more complex policies soon. Stay tuned.

How to Contribute

We welcome contributions! See our general contribution guidelines.

To contribute to Macaron, first create a virtual environment by either using the Makefile:

make venv  # Create a new virtual environment in .venv folder using Python 3.11.

or for a specific version of Python:

PYTHON=python3.11 make venv  # Same virtual environment for a different Python version.

Activate the virtual environment:

. .venv/bin/activate

Finally, set up Macaron with all of its extras and initialize the local git hooks:

make setup

With that in place, you’re ready to build and contribute to Macaron!

Updating dependent packages

It’s likely that during development you’ll add or update dependent packages in the pyproject.toml file, which requires an update to the virtual environment:

make upgrade

Git hooks

Using the pre-commit tool and its .pre-commit-config.yaml configuration, the following git hooks are active in this repository:

• When committing code, a number of pre-commit hooks ensure that your code is formatted according to PEP 8 using the black tool, and they’ll invoke flake8 (and various plugins), pylint and mypy to check for lint and correct types. There are more checks, but those two are the important ones. You can adjust the settings for these tools in the pyproject.toml or .flake8 configuration files.
• The commit message hook enforces conventional commit messages and that, in turn, enables a semantic release of this package on the Github side: upon merging changes into the main branch, the release action uses the Commitizen tool to produce a changelog and it computes the next version of this package and publishes a release — all based on the commit messages of a release.
• Using a pre-push hook this package is also set up to run pytest; in addition, the coverage plugin makes sure that all of your package’s code is covered by tests and Hypothesis is already installed to help with generating test payloads.

You can also run these hooks manually, which comes in very handy during daily development tasks. For example

make check-code

runs all the code checks (i.e. bandit, flake8, pylint and mypy), whereas

make check

runs all installed git hooks over your code. For more control over the code checks, the Makefile also implements the check-bandit, check-flake8, check-lint, check-mypy, and check-go goals.

Testing

As mentioned above, this repository is set up to use pytest either standalone or as a pre-push git hook. Tests are stored in the tests/ folder, and you can run them manually like so:

make test

which runs all tests in both your local Python virtual environment. For more options, see the pytest command-line flags. Also note that pytest includes doctest, which means that module and function docstrings may contain test code that executes as part of the unit tests.

Test code coverage is already tracked using coverage and the pytest-cov plugin for pytest, and it measures how much code in the src/macaron/ folder is covered by tests.

Hypothesis is a package that implements property based testing and that provides payload generation for your tests based on strategy descriptions (more). Using its pytest plugin Hypothesis is ready to be used for this package.

To run integration tests run:

make integration-test

Generating documentation

As mentioned above, all package code should make use of Python docstrings in reStructured text format. Using these docstrings and the documentation template in the docs/source/ folder, you can then generate proper documentation in different formats using the Sphinx tool:

make docs

This example generates documentation in HTML, which can then be found here:

open docs/_build/html/index.html

Security issue reports

Security issue reports should follow our reporting guidelines.

License

Macaron is licensed under the Universal Permissive License (UPL), Version 1.0.