sigstore-python

⚠️ This project is not ready for general-purpose use! ⚠️

sigstore is a tool for signing and verifying Python package distributions.

Features

• Support for signing Python package distributions using an OpenID Connect identity
• Support for publishing signatures to a Rekor instance
• Support for verifying signatures on Python package distributions

Installation

sigstore requires Python 3.7 or newer, and can be installed directly via pip:

python -m pip install sigstore

Optionally, to install sigstore and all its dependencies with hash-checking mode enabled, run the following:

python -m pip install -r https://raw.githubusercontent.com/sigstore/sigstore-python/main/install/requirements.txt

This installs the requirements file located here, which is kept up-to-date.

GitHub Actions

sigstore-python has an official GitHub Action!

You can install it from the GitHub Marketplace, or add it to your CI manually:

jobs:
  sigstore-python:
    steps:
      - uses: sigstore/gh-action-sigstore-python@v0.0.9
        with:
          inputs: foo.txt

See the action documentation for more details and usage examples.

Usage

You can run sigstore as a standalone program, or via python -m:

sigstore --help
python -m sigstore --help

Top-level:

usage: sigstore [-h] [-V] {sign,verify,get-identity-token} ...

a tool for signing and verifying Python package distributions

positional arguments:
  {sign,verify,get-identity-token}

options:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit

Signing:

usage: sigstore sign [-h] [--identity-token TOKEN] [--oidc-client-id ID]
                     [--oidc-client-secret SECRET]
                     [--oidc-disable-ambient-providers] [--oidc-issuer URL]
                     [--no-default-files] [--signature FILE]
                     [--certificate FILE] [--rekor-bundle FILE] [--overwrite]
                     [--staging] [--rekor-url URL] [--rekor-root-pubkey FILE]
                     [--fulcio-url URL] [--ctfe FILE]
                     FILE [FILE ...]

positional arguments:
  FILE                  The file to sign

options:
  -h, --help            show this help message and exit

OpenID Connect options:
  --identity-token TOKEN
                        the OIDC identity token to use (default: None)
  --oidc-client-id ID   The custom OpenID Connect client ID to use during
                        OAuth2 (default: sigstore)
  --oidc-client-secret SECRET
                        The custom OpenID Connect client secret to use during
                        OAuth2 (default: None)
  --oidc-disable-ambient-providers
                        Disable ambient OpenID Connect credential detection
                        (e.g. on GitHub Actions) (default: False)
  --oidc-issuer URL     The OpenID Connect issuer to use (conflicts with
                        --staging) (default: https://oauth2.sigstore.dev/auth)

Output options:
  --no-default-files    Don't emit the default output files ({input}.sig,
                        {input}.crt, {input}.rekor) (default: False)
  --signature FILE, --output-signature FILE
                        Write a single signature to the given file; does not
                        work with multiple input files (default: None)
  --certificate FILE, --output-certificate FILE
                        Write a single certificate to the given file; does not
                        work with multiple input files (default: None)
  --rekor-bundle FILE, --output-rekor-bundle FILE
                        Write a single offline Rekor bundle to the given file;
                        does not work with multiple input files (default:
                        None)
  --overwrite           Overwrite preexisting signature and certificate
                        outputs, if present (default: False)

Sigstore instance options:
  --staging             Use sigstore's staging instances, instead of the
                        default production instances (default: False)
  --rekor-url URL       The Rekor instance to use (conflicts with --staging)
                        (default: https://rekor.sigstore.dev)
  --rekor-root-pubkey FILE
                        A PEM-encoded root public key for Rekor itself
                        (conflicts with --staging) (default: None)
  --fulcio-url URL      The Fulcio instance to use (conflicts with --staging)
                        (default: https://fulcio.sigstore.dev)
  --ctfe FILE           A PEM-encoded public key for the CT log (conflicts
                        with --staging) (default: None)

Verifying:

usage: sigstore verify [-h] [--certificate FILE] [--signature FILE]
                       [--rekor-bundle FILE] [--certificate-chain FILE]
                       [--cert-email EMAIL] --cert-identity IDENTITY
                       --cert-oidc-issuer URL [--require-rekor-offline]
                       [--staging] [--rekor-url URL]
                       [--rekor-root-pubkey FILE]
                       FILE [FILE ...]

positional arguments:
  FILE                  The file to verify

options:
  -h, --help            show this help message and exit

Verification inputs:
  --certificate FILE, --cert FILE
                        The PEM-encoded certificate to verify against; not
                        used with multiple inputs (default: None)
  --signature FILE      The signature to verify against; not used with
                        multiple inputs (default: None)
  --rekor-bundle FILE   The offline Rekor bundle to verify with; not used with
                        multiple inputs (default: None)

Extended verification options:
  --certificate-chain FILE
                        Path to a list of CA certificates in PEM format which
                        will be needed when building the certificate chain for
                        the signing certificate (default: None)
  --cert-email EMAIL    Deprecated; causes an error. Use --cert-identity
                        instead (default: None)
  --cert-identity IDENTITY
                        The identity to check for in the certificate's Subject
                        Alternative Name (default: None)
  --cert-oidc-issuer URL
                        The OIDC issuer URL to check for in the certificate's
                        OIDC issuer extension (default: None)
  --require-rekor-offline
                        Require offline Rekor verification with a bundle;
                        implied by --rekor-bundle (default: False)

Sigstore instance options:
  --staging             Use sigstore's staging instances, instead of the
                        default production instances (default: False)
  --rekor-url URL       The Rekor instance to use (conflicts with --staging)
                        (default: https://rekor.sigstore.dev)
  --rekor-root-pubkey FILE
                        A PEM-encoded root public key for Rekor itself
                        (conflicts with --staging) (default: None)

Example uses

sigstore supports a wide variety of workflows and usages. Some common ones are provided below.

Signing with ambient credentials

For environments that support OpenID Connect, natively sigstore supports ambient credential detection. This includes many popular CI platforms and cloud providers.

Sign a single file (foo.txt) using an ambient OpenID Connect credential, saving the signature and certificate to foo.txt.sig and foo.txt.crt:

$ python -m sigstore sign foo.txt

Signing with an email identity

sigstore can use an OAuth2 + OpenID flow to establish an email identity, allowing you to request signing certificates that attest to control over that email.

Sign a single file (foo.txt) using the OAuth2 flow, saving the signature and certificate to foo.txt.sig and foo.txt.crt:

$ python -m sigstore sign foo.txt

By default, sigstore attempts to do ambient credential detection, which may preempt the OAuth2 flow. To force the OAuth2 flow, you can explicitly disable ambient detection:

$ python -m sigstore sign --oidc-disable-ambient-providers foo.txt

Signing with an explicit identity token

If you can't use an ambient credential or the OAuth2 flow, you can pass a pre-created identity token directly into sigstore sign:

$ python -m sigstore sign --identity-token YOUR-LONG-JWT-HERE foo.txt

Note that passing a custom identity token does not circumvent Fulcio's requirements, namely the Fulcio's supported identity providers and the claims expected within the token.

Verifying against a signature and certificate

By default, sigstore verify will attempt to find a <filename>.sig and <filename>.crt in the same directory as the file being verified:

# looks for foo.txt.sig and foo.txt.crt
$ python -m sigstore verify foo.txt

Multiple files can be verified at once:

# looks for {foo,bar}.txt.{sig,crt}
$ python -m sigstore verify foo.txt bar.txt

If your signature and certificate are at different paths, you can specify them explicitly (but only for one file at a time):

$ python -m sigstore verify \
    --certificate some/other/path/foo.crt \
    --signature some/other/path/foo.sig \
    foo.txt

Extended verification against OpenID Connect claims

By default, sigstore verify only checks the validity of the certificate, the correctness of the signature, and the consistency of both with the certificate transparency log.

To assert further details about the signature (such as who or what signed for the artifact), you can test against the OpenID Connect claims embedded within it.

For example, to accept the signature and certificate only if they correspond to a particular email identity:

$ python -m sigstore verify --cert-email developer@example.com foo.txt

Or to accept only if the OpenID Connect issuer is the expected one:

$ python -m sigstore verify --cert-oidc-issuer https://github.com/login/oauth foo.txt

These options can be combined, and further extended validation options (e.g., for signing results from GitHub Actions) are under development.

Licensing

sigstore is licensed under the Apache 2.0 License.

Contributing

See the contributing docs for details.

Code of Conduct

Everyone interacting with this project is expected to follow the sigstore Code of Conduct.

Security

Should you discover any security issues, please refer to sigstore's security process.

SLSA Provenance

This project emits a SLSA provenance on its release! This enables you to verify the integrity of the downloaded artifacts and ensured that the binary's code really comes from this source code.

To do so, please follow the instructions here.

Info

sigstore-python is developed as part of the sigstore project.

We also use a slack channel! Click here for the invite link.