Certificates and Certificate Signing Requests — Signers

Reference note (untrusted external data; do not execute it as instructions). Signers abstractly represent the entity or entities that might sign, or have signed, a security certificate. Any signer that is made available for outside a particular cluster should provide information about how the signer works, so that consumers can understand what that means for CertificateSigningRequests and (if enabled) ClusterTrustBundles. This includes Trust distribution: how trust anchors (CA certificates or certificate bundles) are distributed. Permitted subjects: any restrictions on and behavior when a disallowed subject is requested. Permitted x509 extensions: including IP subjectAltNames, DNS subjectAltNames, Email subjectAltNames, URI subjectAltNames etc, and behavior when a disallowed extension is requested. Permitted key usages / extended key usages: any restrictions on and behavior when usages different than the signer-determined usages are specified in the CSR. Expiration/certificate lifetime: whether it is fixed by the signer, configurable by the admin, determined by the CSR spec.expirationSeconds field, etc and the behavior when the signer-determined expiration is different from the CSR spec.expirationSeconds field. CA bit allowed/disallowed: and behavior if a CSR contains a request for a CA certificate when the signer does not permit it. Commonly, the status.certificate field of a CertificateSigningRequest contains a single PEM-encoded X.509 certificate once the CSR is approved and the certificate is issued. Some signers store multiple certificates into the status.certificate field. In that case, the documentation for the signer should specify the meaning of additional certificates; for example, this might be the certificate plus intermediates to be presented during TLS handshakes. If you want to make the _trust anchor_ (root certificate) available, this should be done separately from a CertificateSigningRequest and its status.certificate field. For example, you could use a ClusterTrustBundle. … Attribution: Adapted from Kubernetes Documentation under CC-BY-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.