pypi-attestations

A library to generate and convert between Sigstore Bundles and PEP 740 Attestation objects.

[!IMPORTANT] This library is an implementation detail within the reference implementation of PEP 740. Most users should not need to interact with it directly; see the PyPI documentation for full details.

Installation

python -m pip install pypi-attestations

Usage as a library

See the full API documentation here.

Signing and verification

Use these APIs to create a PEP 740-compliant Attestation object by signing a Python artifact (i.e: sdist or wheel files), and to verify an Attestation object against a Python artifact.

from pathlib import Path

from pypi_attestations import Attestation, Distribution
from sigstore.oidc import Issuer
from sigstore.models import ClientTrustConfig
from sigstore.sign import SigningContext
from sigstore.verify import Verifier, policy

dist = Distribution.from_file(Path("test_package-0.0.1-py3-none-any.whl"))

# Sign a Python artifact
trust_config = ClientTrustConfig.production()
issuer: Issuer = Issuer(trust_config.signing_config.get_oidc_url())
signing_ctx = SigningContext.from_trust_config(trust_config)

with signing_ctx.signer(issuer.identity_token(), cache=True) as signer:
    attestation = Attestation.sign(signer, dist)

print(attestation.model_dump_json())

# Verify an attestation against a Python artifact
attestation_path = Path("test_package-0.0.1-py3-none-any.whl.attestation")
attestation = Attestation.model_validate_json(attestation_path.read_bytes())
identity = policy.Identity(identity="example@gmail.com", issuer="https://accounts.google.com")
attestation.verify(identity=identity, dist=dist)

Low-level model conversions

These conversions assume that any Sigstore Bundle used as an input was created by signing a distribution file.

from pathlib import Path
from pypi_attestations import Attestation
from sigstore.models import Bundle

# Sigstore Bundle -> PEP 740 Attestation object
bundle_path = Path("test_package-0.0.1-py3-none-any.whl.sigstore")
with bundle_path.open("rb") as f:
    sigstore_bundle = Bundle.from_json(f.read())
attestation_object = Attestation.from_bundle(sigstore_bundle)
print(attestation_object.model_dump_json())

# PEP 740 Attestation object -> Sigstore Bundle
attestation_path = Path("attestation.json")
with attestation_path.open("rb") as f:
    attestation = Attestation.model_validate_json(f.read())
bundle = attestation.to_bundle()
print(bundle.to_json())

Usage as a command line tool

[!IMPORTANT] The pypi-attestations CLI is intended primarily for experimentation, and is not considered a stable interface for generating or verifying attestations. Users are encouraged to generate attestations using the official PyPA publishing action or via this package's public Python APIs.

pypi-attestations --help
usage: pypi-attestation [-h] [-v] [-V] COMMAND ...

Sign, inspect or verify PEP 740 attestations

positional arguments:
  COMMAND        The operation to perform
    sign         Sign one or more inputs
    verify       Verify one or more inputs
    inspect      Inspect one or more inputs
    convert      Convert a Sigstore bundle into a PEP 740 attestation

options:
  -h, --help     show this help message and exit
  -v, --verbose  run with additional debug logging; supply multiple times to
                 increase verbosity (default: 0)
  -V, --version  show program's version number and exit

Signing a package

[!NOTE] If run locally (i.e. not within GitHub Actions or another source of ambient OIDC credentials), this will open a browser window to perform the Sigstore OAuth flow.

# Generate a whl file
make package
pypi-attestations sign dist/pypi_attestations-*.whl

Inspecting a PEP 740 Attestation

[!WARNING] Inspecting does not mean verifying. It only prints the structure of the attestation.

pypi-attestations inspect dist/pypi_attestations-*.whl.publish.attestation

Verifying a PEP 740 Attestation

pypi-attestations verify attestation  \
  --identity https://github.com/trailofbits/pypi-attestations/.github/workflows/release.yml@refs/tags/v0.0.19 \
  test/assets/pypi_attestations-0.0.19.tar.gz

Verifying a PyPI package

[!NOTE] The package to verify can be passed either as a path to a local file, a pypi: prefixed filename (e.g: 'pypi:sampleproject-1.0.0-py3-none-any.whl'), or as a direct URL to the artifact hosted by PyPI.

# Download the artifact (and its provenance) from PyPI and verify it
pypi-attestations verify pypi --repository https://github.com/sigstore/sigstore-python \
  pypi:sigstore-3.6.1-py3-none-any.whl

# or alternatively, using the direct URL:
pypi-attestations verify pypi --repository https://github.com/sigstore/sigstore-python \
  https://files.pythonhosted.org/packages/70/f5/324edb6a802438e97e289992a41f81bb7a58a1cda2e49439e7e48896649e/sigstore-3.6.1-py3-none-any.whl

# Verify the artifact and its provenance using local files
pypi-attestations verify pypi --repository https://github.com/sigstore/sigstore-python \
  --provenance-file ~/Downloads/sigstore-3.6.1-py3-none-any.whl.provenance \
  ~/Downloads/sigstore-3.6.1-py3-none-any.whl

This command downloads the artifact and its provenance from PyPI. The artifact is then verified against the provenance, while also checking that the provenance's signing identity matches the repository specified by the user.

Converting a Sigstore bundle into a PEP 740 Attestation

pypi-attestations convert --output-file /tmp/rfc8785-0.1.2-py3-none-any.whl.publish.attestation  \
  test/assets/rfc8785-0.1.2-py3-none-any.whl.sigstore

License

Copyright 2024 Trail of Bits

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.