CertificateSigningRequestSpec.signerName

signerName indicates the requested signer, and is a qualified name. List/watch requests for CertificateSigningRequests can filter on this field using a "spec.signerName=NAME" fieldSelector. Well-known Kubernetes signers are: 1. "kubernetes.io/kube-apiserver-client": issues client certificates that can be used to authenticate to kube-apiserver. Requests for this signer are never auto-approved by kube-controller-manager, can be issued by the "csrsigning" controller in kube-controller-manager. 2. "kubernetes.io/kube-apiserver-client-kubelet": issues client certificates that kubelets use to authenticate to kube-apiserver. Requests for this signer can be auto-approved by the "csrapproving" controller in kube-controller-manager, and can be issued by the "csrsigning" controller in kube-controller-manager. 3. "kubernetes.io/kubelet-serving" issues serving certificates that kubelets use to serve TLS endpoints, which kube-apiserver can connect to securely. Requests for this signer are never auto-approved by kube-controller-manager, and can be issued by the "csrsigning" controller in kube-controller-manager. More details are available at https://k8s.io/docs/reference/access-authn-authz/certificate-signing-requests/#kubernetes-signers Custom signerNames can also be specified. The signer defines: 1. Trust distribution: how trust (CA bundles) are distributed. 2. Permitted subjects: and behavior when a disallowed subject is requested. 3. Required, permitted, or forbidden x509 extensions in the request (including whether subjectAltNames are allowed, which types, restrictions on allowed values) and behavior when a disallowed extension is requested. 4. Required, permitted, or forbidden key usages / extended key usages. 5. Expiration/certificate lifetime: whether it is fixed by the signer, configurable by the admin. 6. Whether or not requests for CA certificates are allowed.