- Add handlers for service account issuer metadata.
- Add option to manually override JWKS URI.
- Add unit and integration tests.
- Add a separate ServiceAccountIssuerDiscovery feature gate.
Additional notes:
- If not explicitly overridden, the JWKS URI will be based on
the API server's external address and port.
- The metadata server is configured with the validating key set rather
than the signing key set. This allows for key rotation because tokens
can still be validated by the keys exposed in the JWKs URL, even if the
signing key has been rotated (note this may still be a short window if
tokens have short lifetimes).
- The trust model of OIDC discovery requires that the relying party
fetch the issuer metadata via HTTPS; the trust of the issuer metadata
comes from the server presenting a TLS certificate with a trust chain
back to the from the relying party's root(s) of trust. For tests, we use
a local issuer (https://kubernetes.default.svc) for the certificate
so that workloads within the cluster can authenticate it when fetching
OIDC metadata. An API server cannot validly claim https://kubernetes.io,
but within the cluster, it is the authority for kubernetes.default.svc,
according to the in-cluster config.
Co-authored-by: Michael Taufen <mtaufen@google.com>
This commit fills out the JWT "kid" (KeyID) field on most
serviceaccount tokens we create. The KeyID value we use is derived
from the public key of keypair that backs the cluster's OIDC issuer.
OIDC verifiers use the KeyID to smoothly cope with key rotations:
* During a rotation, the verifier will have multiple keys cached
from the issuer, any of which could have signed the token being
verified. KeyIDs let the verifier pick the appropriate key
without having to try each one.
* Seeing a new KeyID is a trigger for the verifier to invalidate its
cached keys and fetch the new set of valid keys from the identity
provider.
The value we use for the KeyID is derived from the identity provider's
public key by serializing it in DER format, taking the SHA256 hash,
and then urlsafe base64-encoding it. This gives a value that is
strongly bound to the key, but can't be reversed to obtain the public
key, which keeps people from being tempted to derive the key from the
key ID and using that for verification.
Tokens based on jose OpaqueSigners are omitted for now --- I don't see
any way to actually run the API server that results in an OpaqueSigner
being used.
Right now if a JWT for an unknown issuer, for any subject hits the
serviceaccount token authenticator, we return a errors as if the token
was meant for us but we couldn't find a key to verify it. We should
instead return nil, false, nil.
This change helps us support multiple service account token
authenticators with different issuers.
- Move public key functions to client-go/util/cert
- Move pki file helper functions to client-go/util/cert
- Standardize on certutil package alias
- Update dependencies to client-go/util/cert
Public utility methods and JWT parsing, and controller specific logic.
Also remove the coupling between ServiceAccountTokenGetter and the
authenticator class.
