go-cert-gen/internal/cert/client_cert.go

package cert

import (
	"bytes"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"errors"
	"fmt"
	"time"

	"gitlab.com/urkob/go-cert-gen/pkg/client"
)

type clientCert struct {
	certPEM []byte
	keyPEM  []byte
}

func (c *clientCert) Key() []byte {
	return c.keyPEM
}

func (c *clientCert) PEM() []byte {
	return c.certPEM
}

func newClientCert(config *client.ClientCertConfig, rootCA *x509.Certificate, rootKeyPEM []byte) ([]byte, []byte, error) {
	template := &x509.Certificate{
		SerialNumber: config.Serial,
		Subject: pkix.Name{
			Organization:  []string{config.Subject.Organization},
			Country:       []string{config.Subject.Country},
			Province:      []string{config.Subject.Province},
			Locality:      []string{config.Subject.Locality},
			StreetAddress: []string{config.Subject.StreetAddress},
			PostalCode:    []string{config.Subject.PostalCode},
		},
		NotBefore:    time.Now(),
		NotAfter:     time.Now().Add(config.Duration),
		SubjectKeyId: config.SubjectKeyId,
		ExtKeyUsage:  config.ExtKeyUsage,
		KeyUsage:     config.KeyUsage,
	}

	block, _ := pem.Decode(rootKeyPEM)
	if block == nil {
		return nil, nil, errors.New("pem.Decode")
	}

	caPrivKey, err := x509.ParsePKCS8PrivateKey(block.Bytes)
	if err != nil {
		return nil, nil, fmt.Errorf("x509.ParsePKCS8PrivateKey: %s", err)
	}

	priv, err := newPrivateKey()
	if err != nil {
		return nil, nil, fmt.Errorf("newPrivateKey: %s", err)
	}

	der, err := x509.CreateCertificate(rand.Reader, template, rootCA, &priv.PublicKey, caPrivKey)
	if err != nil {
		return nil, nil, fmt.Errorf("x509.CreateCertificate: %s", err)
	}

	out := &bytes.Buffer{}
	err = pem.Encode(out, &pem.Block{Type: CERTIFICATE, Bytes: der})
	if err != nil {
		return nil, nil, fmt.Errorf("pem.Encode: %s", err)
	}

	certPEM := out.Bytes()
	keyPEM, err := encodePrivateKey(priv)
	if err != nil {
		return nil, nil, fmt.Errorf("encodePrivateKey: %s", err)
	}

	return certPEM, keyPEM, nil
}