/*
Copyright 2016 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package certificates

import (
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	api "k8s.io/kubernetes/pkg/apis/core"
)

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// Describes a certificate signing request
type CertificateSigningRequest struct {
	metav1.TypeMeta
	// +optional
	metav1.ObjectMeta

	// The certificate request itself and any additional information.
	// +optional
	Spec CertificateSigningRequestSpec

	// Derived information about the request.
	// +optional
	Status CertificateSigningRequestStatus
}

// This information is immutable after the request is created. Only the Request
// and Usages fields can be set on creation, other fields are derived by
// Kubernetes and cannot be modified by users.
type CertificateSigningRequestSpec struct {
	// Base64-encoded PKCS#10 CSR data
	Request []byte

	// 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.
	SignerName string

	// expirationSeconds is the requested duration of validity of the issued
	// certificate. The certificate signer may issue a certificate with a different
	// validity duration so a client must check the delta between the notBefore and
	// and notAfter fields in the issued certificate to determine the actual duration.
	//
	// The v1.22+ in-tree implementations of the well-known Kubernetes signers will
	// honor this field as long as the requested duration is not greater than the
	// maximum duration they will honor per the --cluster-signing-duration CLI
	// flag to the Kubernetes controller manager.
	//
	// Certificate signers may not honor this field for various reasons:
	//
	//   1. Old signer that is unaware of the field (such as the in-tree
	//      implementations prior to v1.22)
	//   2. Signer whose configured maximum is shorter than the requested duration
	//   3. Signer whose configured minimum is longer than the requested duration
	//
	// The minimum valid value for expirationSeconds is 600, i.e. 10 minutes.
	//
	// As of v1.22, this field is beta and is controlled via the CSRDuration feature gate.
	//
	// +optional
	ExpirationSeconds *int32

	// usages specifies a set of usage contexts the key will be
	// valid for.
	// See: https://tools.ietf.org/html/rfc5280#section-4.2.1.3
	//      https://tools.ietf.org/html/rfc5280#section-4.2.1.12
	Usages []KeyUsage

	// Information about the requesting user.
	// See user.Info interface for details.
	// +optional
	Username string
	// UID information about the requesting user.
	// See user.Info interface for details.
	// +optional
	UID string
	// Group information about the requesting user.
	// See user.Info interface for details.
	// +optional
	Groups []string
	// Extra information about the requesting user.
	// See user.Info interface for details.
	// +optional
	Extra map[string]ExtraValue
}

// Built in signerName values that are honoured by kube-controller-manager.
// None of these usages are related to ServiceAccount token secrets
// `.data[ca.crt]` in any way.
const (
	// Signs certificates that will be honored as client-certs by the
	// kube-apiserver. Never auto-approved by kube-controller-manager.
	KubeAPIServerClientSignerName = "kubernetes.io/kube-apiserver-client"

	// Signs client certificates that will be honored as client-certs by the
	// kube-apiserver for a kubelet.
	// May be auto-approved by kube-controller-manager.
	KubeAPIServerClientKubeletSignerName = "kubernetes.io/kube-apiserver-client-kubelet"

	// Signs serving certificates that are honored as a valid kubelet serving
	// certificate by the kube-apiserver, but has no other guarantees.
	KubeletServingSignerName = "kubernetes.io/kubelet-serving"

	// Has no guarantees for trust at all. Some distributions may honor these
	// as client certs, but that behavior is not standard kubernetes behavior.
	LegacyUnknownSignerName = "kubernetes.io/legacy-unknown"
)

// ExtraValue masks the value so protobuf can generate
type ExtraValue []string

type CertificateSigningRequestStatus struct {
	// Conditions applied to the request, such as approval or denial.
	// +optional
	Conditions []CertificateSigningRequestCondition

	// If request was approved, the controller will place the issued certificate here.
	// +optional
	Certificate []byte
}

type RequestConditionType string

// These are the possible conditions for a certificate request.
const (
	CertificateApproved RequestConditionType = "Approved"
	CertificateDenied   RequestConditionType = "Denied"
	CertificateFailed   RequestConditionType = "Failed"
)

type CertificateSigningRequestCondition struct {
	// type of the condition. Known conditions include "Approved", "Denied", and "Failed".
	Type RequestConditionType
	// Status of the condition, one of True, False, Unknown.
	// Approved, Denied, and Failed conditions may not be "False" or "Unknown".
	// If unset, should be treated as "True".
	// +optional
	Status api.ConditionStatus
	// brief reason for the request state
	// +optional
	Reason string
	// human readable message with details about the request state
	// +optional
	Message string
	// timestamp for the last update to this condition
	// +optional
	LastUpdateTime metav1.Time
	// lastTransitionTime is the time the condition last transitioned from one status to another.
	// +optional
	LastTransitionTime metav1.Time
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

type CertificateSigningRequestList struct {
	metav1.TypeMeta
	// +optional
	metav1.ListMeta

	// +optional
	Items []CertificateSigningRequest
}

// KeyUsages specifies valid usage contexts for keys.
// See: https://tools.ietf.org/html/rfc5280#section-4.2.1.3
//      https://tools.ietf.org/html/rfc5280#section-4.2.1.12
type KeyUsage string

const (
	UsageSigning           KeyUsage = "signing"
	UsageDigitalSignature  KeyUsage = "digital signature"
	UsageContentCommitment KeyUsage = "content commitment"
	UsageKeyEncipherment   KeyUsage = "key encipherment"
	UsageKeyAgreement      KeyUsage = "key agreement"
	UsageDataEncipherment  KeyUsage = "data encipherment"
	UsageCertSign          KeyUsage = "cert sign"
	UsageCRLSign           KeyUsage = "crl sign"
	UsageEncipherOnly      KeyUsage = "encipher only"
	UsageDecipherOnly      KeyUsage = "decipher only"
	UsageAny               KeyUsage = "any"
	UsageServerAuth        KeyUsage = "server auth"
	UsageClientAuth        KeyUsage = "client auth"
	UsageCodeSigning       KeyUsage = "code signing"
	UsageEmailProtection   KeyUsage = "email protection"
	UsageSMIME             KeyUsage = "s/mime"
	UsageIPsecEndSystem    KeyUsage = "ipsec end system"
	UsageIPsecTunnel       KeyUsage = "ipsec tunnel"
	UsageIPsecUser         KeyUsage = "ipsec user"
	UsageTimestamping      KeyUsage = "timestamping"
	UsageOCSPSigning       KeyUsage = "ocsp signing"
	UsageMicrosoftSGC      KeyUsage = "microsoft sgc"
	UsageNetscapeSGC       KeyUsage = "netscape sgc"
)
