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certificates.go
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certificates.go
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package buildkitd
import (
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math"
"math/big"
"net"
"os"
"path"
"path/filepath"
"time"
"github.com/pkg/errors"
)
type certificateData struct {
Key *rsa.PrivateKey
CertBytes []byte
Cert *x509.Certificate
}
const (
buildkit = "buildkit"
earthly = "earthly"
)
// GenerateCertificates creates and saves a CA and certificates for both sides of an mTLS TCP connection.
func GenerateCertificates(dir string) error {
ca, err := createAndSaveCA(dir)
if err != nil {
return errors.Wrap(err, "create CA")
}
err = createAndSaveCertificate(ca, buildkit, dir)
if err != nil {
return errors.Wrap(err, "create buildkit certificate")
}
err = createAndSaveCertificate(ca, earthly, dir)
if err != nil {
return errors.Wrap(err, "create earthly certificate")
}
return nil
}
func createAndSaveCertificate(ca *certificateData, role, dir string) error {
certKey, err := rsa.GenerateKey(rand.Reader, 4096)
if err != nil {
return errors.Wrapf(err, "generate %s key", role)
}
serial, err := rand.Int(rand.Reader, big.NewInt(math.MaxInt64))
if err != nil {
return errors.Wrapf(err, "generate %s serial", role)
}
cert := &x509.Certificate{
SerialNumber: serial,
Subject: pkix.Name{
Organization: []string{fmt.Sprintf("Earthly GRPC: %v side", role)},
},
DNSNames: []string{"localhost"},
IPAddresses: []net.IP{net.IPv6loopback, net.ParseIP("127.0.0.1")},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
SubjectKeyId: []byte(role),
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
KeyUsage: x509.KeyUsageDigitalSignature,
}
certBytes, err := x509.CreateCertificate(rand.Reader, cert, ca.Cert, &certKey.PublicKey, ca.Key)
if err != nil {
return errors.Wrapf(err, "generate %s certificate", role)
}
err = saveCertAndKeyAsPEM(role, dir, certBytes, certKey)
if err != nil {
return errors.Wrap(err, "save role")
}
return nil
}
func createAndSaveCA(dir string) (*certificateData, error) {
caKey, err := rsa.GenerateKey(rand.Reader, 4096)
if err != nil {
return nil, err
}
ca := &x509.Certificate{
SerialNumber: big.NewInt(2021),
Subject: pkix.Name{
Organization: []string{"Earthly Buildkit GRPC CA"},
},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
IsCA: true,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
BasicConstraintsValid: true,
}
caBytes, err := x509.CreateCertificate(rand.Reader, ca, ca, &caKey.PublicKey, caKey)
if err != nil {
return nil, err
}
err = saveCertAndKeyAsPEM("ca", dir, caBytes, caKey)
if err != nil {
return nil, errors.Wrap(err, "save CA")
}
return &certificateData{
Key: caKey,
CertBytes: caBytes,
Cert: ca,
}, nil
}
func saveCertAndKeyAsPEM(prefix, dir string, certBytes []byte, key *rsa.PrivateKey) error {
certFile := filepath.Join(dir, fmt.Sprintf("%s_cert.pem", prefix))
err := saveAsPEM(certFile, "CERTIFICATE", certBytes)
if err != nil {
return errors.Wrapf(err, "failed to save certificate %s", certFile)
}
keyFile := filepath.Join(dir, fmt.Sprintf("%s_key.pem", prefix))
err = saveAsPEM(keyFile, "RSA PRIVATE KEY", x509.MarshalPKCS1PrivateKey(key))
if err != nil {
return errors.Wrapf(err, "failed to save key %s", keyFile)
}
return nil
}
func saveAsPEM(fn, typ string, bytes []byte) error {
err := os.MkdirAll(path.Dir(fn), 0755)
if err != nil {
return err
}
f, err := os.Create(fn)
if err != nil {
return err
}
defer f.Close()
err = pem.Encode(f, &pem.Block{
Type: typ,
Bytes: bytes,
})
if err != nil {
return err
}
err = f.Chmod(0444)
if err != nil {
return err
}
return nil
}