go-gemini/cert.go
2020-10-31 21:33:59 -04:00

180 lines
4.9 KiB
Go

package gemini
import (
"crypto"
"crypto/ed25519"
"crypto/rand"
"crypto/tls"
"crypto/x509"
"encoding/pem"
"log"
"math/big"
"net"
"os"
"path/filepath"
"strings"
"time"
)
// CertificateStore maps hostnames to certificates.
// The zero value of CertificateStore is an empty store ready to use.
type CertificateStore struct {
store map[string]tls.Certificate
dir bool
path string
}
// Add adds a certificate for the given scope to the store.
// It tries to parse the certificate if it is not already parsed.
func (c *CertificateStore) Add(scope string, cert tls.Certificate) {
if c.store == nil {
c.store = map[string]tls.Certificate{}
}
// Parse certificate if not already parsed
if cert.Leaf == nil {
parsed, err := x509.ParseCertificate(cert.Certificate[0])
if err == nil {
cert.Leaf = parsed
}
}
if c.dir {
// Write certificates
log.Printf("gemini: Writing certificate for %s to %s", scope, c.path)
certPath := filepath.Join(c.path, scope+".crt")
keyPath := filepath.Join(c.path, scope+".key")
if err := WriteCertificate(cert, certPath, keyPath); err != nil {
log.Printf("gemini: Failed to write certificate for %s: %s", scope, err)
}
}
c.store[scope] = cert
}
// Lookup returns the certificate for the given scope.
func (c *CertificateStore) Lookup(scope string) (*tls.Certificate, error) {
cert, ok := c.store[scope]
if !ok {
return nil, ErrCertificateNotFound
}
// Ensure that the certificate is not expired
if cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) {
return &cert, ErrCertificateExpired
}
return &cert, nil
}
// Load loads certificates from the given path.
// The path should lead to a directory containing certificates and private keys
// in the form scope.crt and scope.key.
// For example, the hostname "localhost" would have the corresponding files
// localhost.crt (certificate) and localhost.key (private key).
// New certificates will be written to this directory.
func (c *CertificateStore) Load(path string) error {
matches, err := filepath.Glob(filepath.Join(path, "*.crt"))
if err != nil {
return err
}
for _, crtPath := range matches {
keyPath := strings.TrimSuffix(crtPath, ".crt") + ".key"
cert, err := tls.LoadX509KeyPair(crtPath, keyPath)
if err != nil {
continue
}
scope := strings.TrimSuffix(filepath.Base(crtPath), ".crt")
c.Add(scope, cert)
}
c.dir = true
c.path = path
return nil
}
// CertificateOptions configures how a certificate is created.
type CertificateOptions struct {
IPAddresses []net.IP
DNSNames []string
Duration time.Duration
}
// CreateCertificate creates a new TLS certificate.
func CreateCertificate(options CertificateOptions) (tls.Certificate, error) {
crt, priv, err := newX509KeyPair(options)
if err != nil {
return tls.Certificate{}, err
}
var cert tls.Certificate
cert.Leaf = crt
cert.Certificate = append(cert.Certificate, crt.Raw)
cert.PrivateKey = priv
return cert, nil
}
// newX509KeyPair creates and returns a new certificate and private key.
func newX509KeyPair(options CertificateOptions) (*x509.Certificate, crypto.PrivateKey, error) {
// Generate an ED25519 private key
_, priv, err := ed25519.GenerateKey(rand.Reader)
if err != nil {
return nil, nil, err
}
public := priv.Public()
// ED25519 keys should have the DigitalSignature KeyUsage bits set
// in the x509.Certificate template
keyUsage := x509.KeyUsageDigitalSignature
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, nil, err
}
notBefore := time.Now()
notAfter := notBefore.Add(options.Duration)
template := x509.Certificate{
SerialNumber: serialNumber,
NotBefore: notBefore,
NotAfter: notAfter,
KeyUsage: keyUsage,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
IPAddresses: options.IPAddresses,
DNSNames: options.DNSNames,
}
crt, err := x509.CreateCertificate(rand.Reader, &template, &template, public, priv)
if err != nil {
return nil, nil, err
}
cert, err := x509.ParseCertificate(crt)
if err != nil {
return nil, nil, err
}
return cert, priv, nil
}
// WriteCertificate writes the provided certificate and private key
// to certPath and keyPath respectively.
func WriteCertificate(cert tls.Certificate, certPath, keyPath string) error {
certOut, err := os.OpenFile(certPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
defer certOut.Close()
if err := pem.Encode(certOut, &pem.Block{
Type: "CERTIFICATE",
Bytes: cert.Leaf.Raw,
}); err != nil {
return err
}
keyOut, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
defer keyOut.Close()
privBytes, err := x509.MarshalPKCS8PrivateKey(cert.PrivateKey)
if err != nil {
return err
}
return pem.Encode(keyOut, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes})
}