PEP 740 blog post

docs/blog/posts/2024-11-14-pypi-now-supports-digital-attestations.md

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+---
+title: PyPI now supports digital attestations
+description: Announcing support for PEP 740 on the Python Package Index
+authors:
+  - di
+date: 2024-11-14
+tags:
+  - publishing
+  - security
+  - oidc
+---
+
+PyPI package maintainers can now publish signed digital attestations when
+publishing, in order to further increase trust in the supply-chain security of
+their projects. Additionally, a new API is available for consumers and
+installers to verify published attestations.
+
+Many projects have already begun publishing attestations, with more than 20,000
+attestations already published.
+
+This finalizes PyPI's support for [PEP 740], and follows directly from previous
+work to add support for [Trusted Publishing], as well as the [deprecation and
+removal of PGP signatures].
+
+<!-- more -->
+
+### Why not plain signatures?
+
+PyPI's support for digital attestations has three key advantages over regular
+cryptographic signatures, such as those provided by PGP:
+
+* **Attestations are signed by an identity, not a key pair:**
+  Similar to our recent support for Trusted Publishing, PyPI's support for
+  digital attestations relies upon Open ID Connect (OIDC) identities. By signing
+  attestations with identities, and not a public/private key pair, we mitigate the
+  potential for an individual's key loss or compromise, one of the most common failure cases for
+  PGP signing.
+* **Attestations provide a verifiable link to an upstream source repository:**
+  By signing with the identity of the upstream source repository, such as in the
+  case of an upload of a project built with GitHub Actions, PyPI's support for
+  digital attestations defines a strong and verifiable association between a file
+  on PyPI and the source repository, workflow, and even the commit hash that
+  produced and uploaded the file. Additionally, publishing attestations to a
+  transparency log helps mitigate against both compromise of PyPI and compromise
+  of the projects themselves.
+* **Attestations are verified when uploaded, and must be verifiable to be uploaded:**
+  Upon review of the state of historical PGP signatures published to PyPI, [we
+  found that many signatures were not verifiable], either by PyPI or by end
+  users. With support for PEP 740, PyPI only permits attestations with a
+  verifiable signature to be uploaded and redistributed by the index. This
+  ensures that all attestations are verifiable and useful for all PyPI users.
+
+Much more detail is provided in a corresponding blog post by Trail of Bits:
+[Attestations: a new generation of signatures on PyPI].
+
+### How to view a file's attestations
+For consumers and package installers wanting to perform verification, PyPI
+currently provides two ways to access digital attestations associated with a
+given file on PyPI:
+
+* **A new Integrity API for PyPI**
+  The [Integrity API](https://docs.pypi.org/api/integrity/) provides programmatic
+  access to PyPI's implementation of PEP 740. Operating on individual files, it
+  collects all published attestations for a given file and returns them as a
+  single response.
+
+* **A new web UI for viewing per-file attributes**
+  Similarly, we have introduced a new page on PyPI's web UI, displaying details
+  for individual files, including the presence of any attestations about the
+  file. You can see an example here:
+  <https://pypi.org/project/sampleproject/#sampleproject-4.0.0.tar.gz>
+
+### Get started today
+
+The generation and publication of attestations happens by default, and no
+changes are necessary for projects that meet all of these conditions:
+
+1. publish from GitHub Actions;
+2. via [Trusted Publishing]; and
+3. use the [pypa/gh-action-pypi-publish] action to publish.
+
+Support for automatic attestation generation and publication from other Trusted
+Publisher environments [is planned]. While not recommended, maintainers can also
+[manually generate and publish attestations].
+
+### Acknowledgements
+
+Support for work on PEP 740's authoring and design was provided by the
+[Sovereign Tech Agency] and the Google Open Source Security Team.
+
+Funding for the implementation of PEP 740 was provided by the Google Open
+Source Security Team, and much of the development work on PyPI and related
+tools was performed by [Trail of Bits], with special thanks to contributors
+[William Woodruff] and [Facundo Tuesca].
+
+Thanks to the the [Sigstore project] for their work popularizing identity-based signing, hosting a public-good transparency log, and continued support of the [Python client for Sigstore].
+
+Many thanks to [Sviatoslav Sydorenko] as well for his support and ongoing
+maintenence of the [pypa/gh-action-pypi-publish] action, as well his support
+for implementing PEP 740 in the action.
+
+---
+
+_Dustin Ingram is a maintainer of the Python Package Index._
+
+[PEP 740]: https://peps.python.org/pep-0740/
+[Trusted Publishing]: https://docs.pypi.org/trusted-publishers/
+[deprecation and removal of PGP signatures]: https://blog.pypi.org/posts/2023-05-23-removing-pgp/
+[pypa/gh-action-pypi-publish]: https://github.com/pypa/gh-action-pypi-publish
+[Attestations: a new generation of signatures on PyPI]: https://blog.trailofbits.com/2024/11/14/attestations-a-new-generation-of-signatures-on-pypi/
+[Integrity API]: https://docs.pypi.org/api/integrity/
+[we announced last year]: 2023-04-20-introducing-trusted-publishers.md
+[we found that many signatures were not verifiable]: https://blog.yossarian.net/2023/05/21/PGP-signatures-on-PyPI-worse-than-useless
+[manually generate and publish attestations]: https://docs.pypi.org/attestations/producing-attestations/#the-manual-way
+[Sovereign Tech Agency]: https://www.sovereign.tech/tech/python-package-index
+[is planned]: https://github.com/pypi/warehouse/issues/17001
+[Trail of Bits]: https://www.trailofbits.com/
+[William Woodruff]: https://github.com/woodruffw
+[Facundo Tuesca]: https://github.com/facutuesca
+[Sigstore project]: https://www.sigstore.dev/
+[Python client for Sigstore]: https://pypi.org/project/sigstore/
+[Sviatoslav Sydorenko]: https://github.com/webknjaz