/*
Copyright 2020 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 v1

import (
	"fmt"

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

// +genclient
// +genclient:nonNamespaced
// +genclient:method=UpdateApproval,verb=update,subresource=approval,input=k8s.io/api/certificates/v1.CertificateSigningRequest,result=k8s.io/api/certificates/v1.CertificateSigningRequest
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// CertificateSigningRequest objects provide a mechanism to obtain x509 certificates
// by submitting a certificate signing request, and having it asynchronously approved and issued.
//
// Kubelets use this API to obtain:
//  1. client certificates to authenticate to kube-apiserver (with the "kubernetes.io/kube-apiserver-client-kubelet" signerName).
//  2. serving certificates for TLS endpoints kube-apiserver can connect to securely (with the "kubernetes.io/kubelet-serving" signerName).
//
// This API can be used to request client certificates to authenticate to kube-apiserver
// (with the "kubernetes.io/kube-apiserver-client" signerName),
// or to obtain certificates from custom non-Kubernetes signers.
type CertificateSigningRequest struct {
	metav1.TypeMeta `json:",inline"`
	// +optional
	metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`

	// spec contains the certificate request, and is immutable after creation.
	// Only the request, signerName, expirationSeconds, and usages fields can be set on creation.
	// Other fields are derived by Kubernetes and cannot be modified by users.
	Spec CertificateSigningRequestSpec `json:"spec" protobuf:"bytes,2,opt,name=spec"`

	// status contains information about whether the request is approved or denied,
	// and the certificate issued by the signer, or the failure condition indicating signer failure.
	// +optional
	Status CertificateSigningRequestStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"`
}

// CertificateSigningRequestSpec contains the certificate request.
type CertificateSigningRequestSpec struct {
	// request contains an x509 certificate signing request encoded in a "CERTIFICATE REQUEST" PEM block.
	// When serialized as JSON or YAML, the data is additionally base64-encoded.
	// +listType=atomic
	Request []byte `json:"request" protobuf:"bytes,1,opt,name=request"`

	// 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 `json:"signerName" protobuf:"bytes,7,opt,name=signerName"`

	// 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 `json:"expirationSeconds,omitempty" protobuf:"varint,8,opt,name=expirationSeconds"`

	// usages specifies a set of key usages requested in the issued certificate.
	//
	// Requests for TLS client certificates typically request: "digital signature", "key encipherment", "client auth".
	//
	// Requests for TLS serving certificates typically request: "key encipherment", "digital signature", "server auth".
	//
	// Valid values are:
	//  "signing", "digital signature", "content commitment",
	//  "key encipherment", "key agreement", "data encipherment",
	//  "cert sign", "crl sign", "encipher only", "decipher only", "any",
	//  "server auth", "client auth",
	//  "code signing", "email protection", "s/mime",
	//  "ipsec end system", "ipsec tunnel", "ipsec user",
	//  "timestamping", "ocsp signing", "microsoft sgc", "netscape sgc"
	// +listType=atomic
	Usages []KeyUsage `json:"usages,omitempty" protobuf:"bytes,5,opt,name=usages"`

	// username contains the name of the user that created the CertificateSigningRequest.
	// Populated by the API server on creation and immutable.
	// +optional
	Username string `json:"username,omitempty" protobuf:"bytes,2,opt,name=username"`
	// uid contains the uid of the user that created the CertificateSigningRequest.
	// Populated by the API server on creation and immutable.
	// +optional
	UID string `json:"uid,omitempty" protobuf:"bytes,3,opt,name=uid"`
	// groups contains group membership of the user that created the CertificateSigningRequest.
	// Populated by the API server on creation and immutable.
	// +listType=atomic
	// +optional
	Groups []string `json:"groups,omitempty" protobuf:"bytes,4,rep,name=groups"`
	// extra contains extra attributes of the user that created the CertificateSigningRequest.
	// Populated by the API server on creation and immutable.
	// +optional
	Extra map[string]ExtraValue `json:"extra,omitempty" protobuf:"bytes,6,rep,name=extra"`
}

// Built in signerName values that are honored by kube-controller-manager.
const (
	// "kubernetes.io/kube-apiserver-client" signer issues client certificates that can be used to authenticate to kube-apiserver.
	// Never auto-approved by kube-controller-manager.
	// Can be issued by the "csrsigning" controller in kube-controller-manager.
	KubeAPIServerClientSignerName = "kubernetes.io/kube-apiserver-client"

	// "kubernetes.io/kube-apiserver-client-kubelet" issues client certificates that kubelets use to authenticate to kube-apiserver.
	// Can be auto-approved by the "csrapproving" controller in kube-controller-manager.
	// Can be issued by the "csrsigning" controller in kube-controller-manager.
	KubeAPIServerClientKubeletSignerName = "kubernetes.io/kube-apiserver-client-kubelet"

	// "kubernetes.io/kubelet-serving" issues serving certificates that kubelets use to serve TLS endpoints,
	// which kube-apiserver can connect to securely.
	// Never auto-approved by kube-controller-manager.
	// Can be issued by the "csrsigning" controller in kube-controller-manager.
	KubeletServingSignerName = "kubernetes.io/kubelet-serving"
)

// ExtraValue masks the value so protobuf can generate
// +protobuf.nullable=true
// +protobuf.options.(gogoproto.goproto_stringer)=false
type ExtraValue []string

func (t ExtraValue) String() string {
	return fmt.Sprintf("%v", []string(t))
}

// CertificateSigningRequestStatus contains conditions used to indicate
// approved/denied/failed status of the request, and the issued certificate.
type CertificateSigningRequestStatus struct {
	// conditions applied to the request. Known conditions are "Approved", "Denied", and "Failed".
	// +listType=map
	// +listMapKey=type
	// +optional
	Conditions []CertificateSigningRequestCondition `json:"conditions,omitempty" protobuf:"bytes,1,rep,name=conditions"`

	// certificate is populated with an issued certificate by the signer after an Approved condition is present.
	// This field is set via the /status subresource. Once populated, this field is immutable.
	//
	// If the certificate signing request is denied, a condition of type "Denied" is added and this field remains empty.
	// If the signer cannot issue the certificate, a condition of type "Failed" is added and this field remains empty.
	//
	// Validation requirements:
	//  1. certificate must contain one or more PEM blocks.
	//  2. All PEM blocks must have the "CERTIFICATE" label, contain no headers, and the encoded data
	//   must be a BER-encoded ASN.1 Certificate structure as described in section 4 of RFC5280.
	//  3. Non-PEM content may appear before or after the "CERTIFICATE" PEM blocks and is unvalidated,
	//   to allow for explanatory text as described in section 5.2 of RFC7468.
	//
	// If more than one PEM block is present, and the definition of the requested spec.signerName
	// does not indicate otherwise, the first block is the issued certificate,
	// and subsequent blocks should be treated as intermediate certificates and presented in TLS handshakes.
	//
	// The certificate is encoded in PEM format.
	//
	// When serialized as JSON or YAML, the data is additionally base64-encoded, so it consists of:
	//
	//     base64(
	//     -----BEGIN CERTIFICATE-----
	//     ...
	//     -----END CERTIFICATE-----
	//     )
	//
	// +listType=atomic
	// +optional
	Certificate []byte `json:"certificate,omitempty" protobuf:"bytes,2,opt,name=certificate"`
}

// RequestConditionType is the type of a CertificateSigningRequestCondition
type RequestConditionType string

// Well-known condition types for certificate requests.
const (
	// Approved indicates the request was approved and should be issued by the signer.
	CertificateApproved RequestConditionType = "Approved"
	// Denied indicates the request was denied and should not be issued by the signer.
	CertificateDenied RequestConditionType = "Denied"
	// Failed indicates the signer failed to issue the certificate.
	CertificateFailed RequestConditionType = "Failed"
)

// CertificateSigningRequestCondition describes a condition of a CertificateSigningRequest object
type CertificateSigningRequestCondition struct {
	// type of the condition. Known conditions are "Approved", "Denied", and "Failed".
	//
	// An "Approved" condition is added via the /approval subresource,
	// indicating the request was approved and should be issued by the signer.
	//
	// A "Denied" condition is added via the /approval subresource,
	// indicating the request was denied and should not be issued by the signer.
	//
	// A "Failed" condition is added via the /status subresource,
	// indicating the signer failed to issue the certificate.
	//
	// Approved and Denied conditions are mutually exclusive.
	// Approved, Denied, and Failed conditions cannot be removed once added.
	//
	// Only one condition of a given type is allowed.
	Type RequestConditionType `json:"type" protobuf:"bytes,1,opt,name=type,casttype=RequestConditionType"`
	// status of the condition, one of True, False, Unknown.
	// Approved, Denied, and Failed conditions may not be "False" or "Unknown".
	Status v1.ConditionStatus `json:"status" protobuf:"bytes,6,opt,name=status,casttype=k8s.io/api/core/v1.ConditionStatus"`
	// reason indicates a brief reason for the request state
	// +optional
	Reason string `json:"reason,omitempty" protobuf:"bytes,2,opt,name=reason"`
	// message contains a human readable message with details about the request state
	// +optional
	Message string `json:"message,omitempty" protobuf:"bytes,3,opt,name=message"`
	// lastUpdateTime is the time of the last update to this condition
	// +optional
	LastUpdateTime metav1.Time `json:"lastUpdateTime,omitempty" protobuf:"bytes,4,opt,name=lastUpdateTime"`
	// lastTransitionTime is the time the condition last transitioned from one status to another.
	// If unset, when a new condition type is added or an existing condition's status is changed,
	// the server defaults this to the current time.
	// +optional
	LastTransitionTime metav1.Time `json:"lastTransitionTime,omitempty" protobuf:"bytes,5,opt,name=lastTransitionTime"`
}

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

// CertificateSigningRequestList is a collection of CertificateSigningRequest objects
type CertificateSigningRequestList struct {
	metav1.TypeMeta `json:",inline"`
	// +optional
	metav1.ListMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`

	// items is a collection of CertificateSigningRequest objects
	Items []CertificateSigningRequest `json:"items" protobuf:"bytes,2,rep,name=items"`
}

// KeyUsage 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

// Valid key usages
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"
)
