Earlier this year, Buildkite announced support for OpenID Connect tokens. Briefly, a Buildkite agent can request a signed JWT (JSON Web Token) from Buildkite representing details (claims) about its current job. This JWT can then be used to authenticate with systems that accept it.
For Hashicorp Vault, services typically authenticate using the AppRole method with a senstive set of credentials. It’s fine to use this flow on a Buildkite agent to access Vault secrets, but the credentials for this are long-lived.
The new OIDC flow removes to need to manage these long-lived credentials, and also makes it possible to craft fine-grained policies for a Buildkite agent without requiring multiple sets of login credentials!