GHSA-j7c9-79x7-8hpr

## Summary An authorized attacker can bypass authorization checks and revoke any SSH certificate issued by Step CA by using a valid revocation token. ## Details Step CA users can obtain SSH certificates from a few provisioners. The SSHPOP provisioner allows revocation of the SSH certificate (preventing future certificate renewals) using a token. Due to a missing validity check, this token could be used to revoke any SSH certificate issued by the CA. To create a token, an attacker must have access to the CA endpoint and a valid SSH certificate, meaning they were already authorized to obtain an SSH certificate. The attacker must also know the serial number of the certificate they want to revoke. ## Impact There is no way to mitigate this attack. It is recommended to update to v0.29.0 or newer. ## Fix In v0.29.0, the token validation logic was strengthened to bind each token to a specific SSH certificate serial number. ## Acknowledgements This issue was identified and reported by Gabriel Departout and Andy Russon, from [AMOSSYS](http://amossys.fr/). This audit was sponsored by [ANSSI](https://cyber.gouv.fr/) (French Cybersecurity Agency) based on [their Open-Source security audit program](https://cyber.gouv.fr/open-source-lanssi#:~:text=Financement%20d%27%C3%A9valuations%20de%20s%C3%A9curit%C3%A9%20de%20logiciels%20libres). ## Embargo List If your organization runs Step CA in production and would like advance, embargoed notification of future security updates, visit https://u.step.sm/disclosure to request inclusion on our embargo list. Stay safe, and thank you for helping us keep the ecosystem secure.