forked from TrueCloudLab/certificates
329 lines
9.1 KiB
Go
329 lines
9.1 KiB
Go
package vaultcas
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import (
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"bytes"
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"context"
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"crypto/sha256"
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"crypto/x509"
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"encoding/hex"
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"encoding/json"
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"encoding/pem"
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"errors"
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"fmt"
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"math/big"
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"strings"
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"time"
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"github.com/smallstep/certificates/cas/apiv1"
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"github.com/smallstep/certificates/cas/vaultcas/auth/approle"
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"github.com/smallstep/certificates/cas/vaultcas/auth/kubernetes"
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vault "github.com/hashicorp/vault/api"
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)
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func init() {
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apiv1.Register(apiv1.VaultCAS, func(ctx context.Context, opts apiv1.Options) (apiv1.CertificateAuthorityService, error) {
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return New(ctx, opts)
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})
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}
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// VaultOptions defines the configuration options added using the
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// apiv1.Options.Config field.
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type VaultOptions struct {
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PKIMountPath string `json:"pkiMountPath,omitempty"`
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PKIRoleDefault string `json:"pkiRoleDefault,omitempty"`
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PKIRoleRSA string `json:"pkiRoleRSA,omitempty"`
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PKIRoleEC string `json:"pkiRoleEC,omitempty"`
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PKIRoleEd25519 string `json:"pkiRoleEd25519,omitempty"`
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AuthType string `json:"authType,omitempty"`
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AuthMountPath string `json:"authMountPath,omitempty"`
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AuthOptions json.RawMessage `json:"authOptions,omitempty"`
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}
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// VaultCAS implements a Certificate Authority Service using Hashicorp Vault.
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type VaultCAS struct {
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client *vault.Client
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config VaultOptions
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fingerprint string
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}
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type certBundle struct {
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leaf *x509.Certificate
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intermediates []*x509.Certificate
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root *x509.Certificate
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}
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// New creates a new CertificateAuthorityService implementation
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// using Hashicorp Vault
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func New(ctx context.Context, opts apiv1.Options) (*VaultCAS, error) {
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if opts.CertificateAuthority == "" {
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return nil, errors.New("vaultCAS 'certificateAuthority' cannot be empty")
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}
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if opts.CertificateAuthorityFingerprint == "" {
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return nil, errors.New("vaultCAS 'certificateAuthorityFingerprint' cannot be empty")
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}
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vc, err := loadOptions(opts.Config)
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if err != nil {
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return nil, err
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}
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config := vault.DefaultConfig()
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config.Address = opts.CertificateAuthority
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client, err := vault.NewClient(config)
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if err != nil {
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return nil, fmt.Errorf("unable to initialize vault client: %w", err)
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}
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var method vault.AuthMethod
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switch vc.AuthType {
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case "kubernetes":
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method, err = kubernetes.NewKubernetesAuthMethod(vc.AuthMountPath, vc.AuthOptions)
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case "approle":
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method, err = approle.NewApproleAuthMethod(vc.AuthMountPath, vc.AuthOptions)
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default:
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return nil, fmt.Errorf("unknown auth type: %v", vc.AuthType)
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}
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if err != nil {
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return nil, fmt.Errorf("unable to configure auth method: %w", err)
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}
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authInfo, err := client.Auth().Login(ctx, method)
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if err != nil {
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return nil, fmt.Errorf("unable to login to Kubernetes auth method: %w", err)
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}
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if authInfo == nil {
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return nil, errors.New("no auth info was returned after login")
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}
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return &VaultCAS{
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client: client,
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config: *vc,
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fingerprint: opts.CertificateAuthorityFingerprint,
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}, nil
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}
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// CreateCertificate signs a new certificate using Hashicorp Vault.
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func (v *VaultCAS) CreateCertificate(req *apiv1.CreateCertificateRequest) (*apiv1.CreateCertificateResponse, error) {
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switch {
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case req.CSR == nil:
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return nil, errors.New("createCertificate `csr` cannot be nil")
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case req.Lifetime == 0:
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return nil, errors.New("createCertificate `lifetime` cannot be 0")
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}
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cert, chain, err := v.createCertificate(req.CSR, req.Lifetime)
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if err != nil {
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return nil, err
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}
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return &apiv1.CreateCertificateResponse{
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Certificate: cert,
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CertificateChain: chain,
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}, nil
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}
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// GetCertificateAuthority returns the root certificate of the certificate
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// authority using the configured fingerprint.
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func (v *VaultCAS) GetCertificateAuthority(req *apiv1.GetCertificateAuthorityRequest) (*apiv1.GetCertificateAuthorityResponse, error) {
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secret, err := v.client.Logical().Read(v.config.PKIMountPath + "/cert/ca_chain")
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if err != nil {
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return nil, fmt.Errorf("error reading ca chain: %w", err)
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}
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if secret == nil {
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return nil, errors.New("error reading ca chain: response is empty")
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}
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chain, ok := secret.Data["certificate"].(string)
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if !ok {
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return nil, errors.New("error unmarshaling vault response: certificate not found")
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}
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cert, err := getCertificateBundle(chain)
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if err != nil {
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return nil, err
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}
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if cert.root == nil {
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return nil, errors.New("error unmarshaling vault response: root certificate not found")
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}
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sum := sha256.Sum256(cert.root.Raw)
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if !strings.EqualFold(v.fingerprint, strings.ToLower(hex.EncodeToString(sum[:]))) {
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return nil, errors.New("error verifying vault root: fingerprint does not match")
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}
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return &apiv1.GetCertificateAuthorityResponse{
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RootCertificate: cert.root,
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}, nil
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}
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// RenewCertificate will always return a non-implemented error as renewals
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// are not supported yet.
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func (v *VaultCAS) RenewCertificate(req *apiv1.RenewCertificateRequest) (*apiv1.RenewCertificateResponse, error) {
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return nil, apiv1.ErrNotImplemented{Message: "vaultCAS does not support renewals"}
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}
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// RevokeCertificate revokes a certificate by serial number.
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func (v *VaultCAS) RevokeCertificate(req *apiv1.RevokeCertificateRequest) (*apiv1.RevokeCertificateResponse, error) {
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if req.SerialNumber == "" && req.Certificate == nil {
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return nil, errors.New("revokeCertificate `serialNumber` or `certificate` are required")
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}
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var sn *big.Int
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if req.SerialNumber != "" {
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var ok bool
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if sn, ok = new(big.Int).SetString(req.SerialNumber, 10); !ok {
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return nil, fmt.Errorf("error parsing serialNumber: %v cannot be converted to big.Int", req.SerialNumber)
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}
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} else {
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sn = req.Certificate.SerialNumber
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}
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vaultReq := map[string]interface{}{
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"serial_number": formatSerialNumber(sn),
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}
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_, err := v.client.Logical().Write(v.config.PKIMountPath+"/revoke/", vaultReq)
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if err != nil {
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return nil, fmt.Errorf("error revoking certificate: %w", err)
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}
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return &apiv1.RevokeCertificateResponse{
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Certificate: req.Certificate,
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CertificateChain: nil,
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}, nil
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}
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func (v *VaultCAS) createCertificate(cr *x509.CertificateRequest, lifetime time.Duration) (*x509.Certificate, []*x509.Certificate, error) {
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var vaultPKIRole string
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switch {
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case cr.PublicKeyAlgorithm == x509.RSA:
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vaultPKIRole = v.config.PKIRoleRSA
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case cr.PublicKeyAlgorithm == x509.ECDSA:
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vaultPKIRole = v.config.PKIRoleEC
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case cr.PublicKeyAlgorithm == x509.Ed25519:
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vaultPKIRole = v.config.PKIRoleEd25519
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default:
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return nil, nil, fmt.Errorf("unsupported public key algorithm %v", cr.PublicKeyAlgorithm)
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}
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vaultReq := map[string]interface{}{
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"csr": string(pem.EncodeToMemory(&pem.Block{
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Type: "CERTIFICATE REQUEST",
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Bytes: cr.Raw,
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})),
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"format": "pem_bundle",
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"ttl": lifetime.Seconds(),
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}
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secret, err := v.client.Logical().Write(v.config.PKIMountPath+"/sign/"+vaultPKIRole, vaultReq)
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if err != nil {
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return nil, nil, fmt.Errorf("error signing certificate: %w", err)
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}
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if secret == nil {
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return nil, nil, errors.New("error signing certificate: response is empty")
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}
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chain, ok := secret.Data["certificate"].(string)
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if !ok {
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return nil, nil, errors.New("error unmarshaling vault response: certificate not found")
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}
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cert, err := getCertificateBundle(chain)
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if err != nil {
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return nil, nil, err
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}
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// Return certificate and certificate chain
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return cert.leaf, cert.intermediates, nil
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}
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func loadOptions(config json.RawMessage) (*VaultOptions, error) {
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// setup default values
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vc := VaultOptions{
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PKIMountPath: "pki",
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PKIRoleDefault: "default",
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}
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err := json.Unmarshal(config, &vc)
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if err != nil {
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return nil, fmt.Errorf("error decoding vaultCAS config: %w", err)
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}
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if vc.PKIRoleRSA == "" {
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vc.PKIRoleRSA = vc.PKIRoleDefault
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}
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if vc.PKIRoleEC == "" {
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vc.PKIRoleEC = vc.PKIRoleDefault
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}
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if vc.PKIRoleEd25519 == "" {
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vc.PKIRoleEd25519 = vc.PKIRoleDefault
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}
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return &vc, nil
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}
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func parseCertificates(pemCert string) []*x509.Certificate {
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var certs []*x509.Certificate
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rest := []byte(pemCert)
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var block *pem.Block
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for {
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block, rest = pem.Decode(rest)
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if block == nil {
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break
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}
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cert, err := x509.ParseCertificate(block.Bytes)
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if err != nil {
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break
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}
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certs = append(certs, cert)
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}
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return certs
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}
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func getCertificateBundle(chain string) (*certBundle, error) {
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var root *x509.Certificate
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var leaf *x509.Certificate
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var intermediates []*x509.Certificate
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for _, cert := range parseCertificates(chain) {
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switch {
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case isRoot(cert):
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root = cert
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case cert.BasicConstraintsValid && cert.IsCA:
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intermediates = append(intermediates, cert)
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default:
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leaf = cert
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}
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}
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certificate := &certBundle{
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root: root,
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leaf: leaf,
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intermediates: intermediates,
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}
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return certificate, nil
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}
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// isRoot returns true if the given certificate is a root certificate.
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func isRoot(cert *x509.Certificate) bool {
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if cert.BasicConstraintsValid && cert.IsCA {
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return cert.CheckSignatureFrom(cert) == nil
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}
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return false
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}
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// formatSerialNumber formats a serial number to a dash-separated hexadecimal
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// string.
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func formatSerialNumber(sn *big.Int) string {
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var ret bytes.Buffer
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for _, b := range sn.Bytes() {
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if ret.Len() > 0 {
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ret.WriteString("-")
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}
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ret.WriteString(hex.EncodeToString([]byte{b}))
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}
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return ret.String()
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}
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