kubernetes/staging/src/k8s.io/apiserver/pkg/endpoints/filters/authn_audit.go

// WithFailedAuthenticationAudit decorates a failed http.Handler used in WithAuthentication handler.
// It is meant to log only failed authentication requests.
func WithFailedAuthenticationAudit(failedHandler http.Handler, sink audit.Sink, policy audit.PolicyRuleEvaluator) http.Handler { … }

func getAuthMethods(req *http.Request) string { … }