Copyright 2015 OpenStack Foundation

This work is licensed under a Creative Commons Attribution 3.0
Unported License.

Artifact Signing Toolchain!/story/2000336

The OpenStack Community will publish cryptographic signatures accompanying release artifacts (tarballs, packages, et cetera) to provide a verification of provenance. The Release Team has also expressed interest in automated tagging of Git repositories.

Problem Description

Unlike our Git repositories, where releases are represented by cryptographic signatures of release managers embedded in tags, the artifacts built in our infrastructure from those tagged repository states come with no proof of their origin. Files uploaded to our tarballs site or external services lack any attestation that they’re unmodified since the time of their original creation and publication. This allows, among other risks, the possibility that a published release can be altered either accidentally or by a malicious actor.

Proposed Change

Add a dedicated job node responsible for performing artifact signing between the generation and publication steps.


  • As always, we could do nothing, though the problem remains.
  • We could engineer a system whereby individuals vet release artifacts and upload their own individual attestations, though that’s not necessary precluded by the proposed solution anyway and could operate in parallel if desired.



Primary assignee:

Gerrit Topic

Use Gerrit topic “artifact-signing” for all patches related to this spec.

git-review -t artifact-signing

Work Items

  1. Generate OpenPGP keypair with signing subkey, both set to expire at the beginning of the next development cycle; store the master private key and a revocation certificate with our other service credentials; add the subkey in hiera
  2. Get all infra root admins to sign the artifact signing key and publish those signatures to the keyserver network
  3. openstack-infra/system-config:
    1. Create a puppet class and node definition for
    2. Add basic documentation of the infra root process for handling of the artifact signing key (infra root keysigning, publishing, extending the expiration date, and emergency revocation)
  4. Launch the new server
  5. openstack-infra/system-config: Add to cacti and to the zuul_nodes list in public hiera
  6. openstack-infra/project-config:
    1. Develop a slave script for signing automation and integrate it into the openstack-infra/project-config repo (this could be an extension of or abstraction from some of the existing * scripts)
    2. Add a job to identify the artifact name (based on the tag and details within the repo, or just the tag and have multiple similar jobs), retrieve it, create a detached signature and then upload it back to an adjacent path
    3. Extend the release upload jobs/job-templates to retrieve, validate and incorporate detached signatures, at least for reuploads to external services which currently support it
  7. openstack/governance and/or openstack/ossa: Add documentation of the existence of artifact signatures and instructions on validating them
  8. Send an announcement to the mailing list informing the community of the availability of signatures accompanying all upcoming releases


No new git repositories need to be created.


A new server needs to be created. No existing servers will be affected.

DNS Entries

DNS entries (A/AAAA/PTR) for need to be created.


We will need documentation for key handling/signing/rotation in the openstack/system-config repo, outlining the process followed by infra root admins. Documentation in either the openstack/governance or openstack/ossa repos should probably also be created explaining the existence of our artifact signatures and how they can be validated. There is no anticipated impact to our current developer workflow. An announcement is warranted once the implementation is in place and confirmed working as intended.


There are associated security risks, but they are not regressions from the current situation. Specifically, the artifact master and signing subkeys (and revocation certificate too) need to be safeguarded closely as they provide guarantees against post-release tampering. Our existing secret management solutions should be sufficient for this purpose. The signing subkey is the only one exposed to a separate server (, though our Zuul launchers do also have credentials to log into it as well.

Key sizes/algorithms will be informed by GnuPG default values. We’ll start with 2048-bit RSA but will likely transition to Ed25519 in a later cycle as it becomes more prevalent in the OpenPGP ecosystem.

Note that this spec does not attempt to address trust challenges earlier in the development, test and build toolchain. There are strengthening opportunities throughout our infrastructure, but they are out of scope and should be handled as separate specifications.


One or more artifact signing jobs will need to be created to generate and upload detached signatures to There are also opportunities here to add some additional validation in our jobs which upload to external repositories, as they can potentially validate the detached signatures and refuse to upload if something looks wrong.


There are no dependencies for this specification.