* fixes#3809 support CSR submission during OIDC authentication
- accepts an optional CSR during OIDC login (all auth methods) and
signs it into a session-bound certificate with a SPIFFE ID derived
from the identity and API session
- returns the signed certificate PEM as a top-level "session_cert"
field in the token endpoint JSON response (CodeExchange, RefreshToken,
TokenExchange)
- adds cert-binding verification on RefreshToken and TokenExchange:
if z_cfs is present the peer cert fingerprint must match (strict),
otherwise falls back to SPIFFE ID verification
- supports cert rotation via csr_pem form parameter on refresh and
token exchange; replaces the session cert fingerprint while
preserving the authenticating cert fingerprint
- adds AuthCertFingerprints (z_acfs) claim to track permanent auth
cert fingerprints separately from rotatable session cert fingerprints
- only the leaf certificate fingerprint is added to z_cfs and z_acfs,
intermediates are never included
- invalid CSR returns 400 Bad Request in OIDC error format
- propagates updated CustomClaims (including CertFingerprints) from
access token to renewed refresh token so rotated fingerprints are
enforced on subsequent refreshes
- adds CertGenerated field to ApiSessionEvent
- advertises OIDC_AUTH_WITH_CSR controller capability when OIDC is
enabled
- adds unit tests for verifyCertBinding (fingerprint, SPIFFE ID,
edge cases) and CsrPem field parsing
- adds integration tests for initial CSR auth (updb, cert, ext-jwt),
cert-binding on refresh/exchange, CSR rotation with cert auth,
SPIFFE fallback and z_cfs transition, and CSR property forging
resistance
* address pr concerns
* add z_cfs len tests on junk chain certs
* strip csr subject info, replace w/ santized values
* fix csr rotation rejection/paths during token exchange/refresh
Andrew Martinez