go-gemini/cert.go

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2020-09-27 11:50:48 -06:00
package gemini
import (
"bytes"
"crypto/ed25519"
"crypto/rand"
"crypto/x509"
"encoding/pem"
"math/big"
"net"
"os"
"strings"
"time"
)
// CertificateStore maps hostnames to certificates.
type CertificateStore struct {
store map[string]*x509.Certificate // map of hostnames to certificates
}
func NewCertificateStore() *CertificateStore {
return &CertificateStore{
store: map[string]*x509.Certificate{},
}
}
func (c *CertificateStore) Put(hostname string, cert *x509.Certificate) {
c.store[hostname] = cert
}
func (c *CertificateStore) Get(hostname string) *x509.Certificate {
return c.store[hostname]
}
// NewCertificate creates and returns a raw certificate for the given host.
// It generates a self-signed TLS certificate and a ED25519 private key.
func NewCertificate(host string) (crt, key []byte, err error) {
// Generate a ED25519 private key
_, priv, err := ed25519.GenerateKey(rand.Reader)
if err != nil {
return nil, nil, err
}
public := priv.Public().(ed25519.PublicKey)
// ED25519 keys should have the DigitalSignature KeyUsage bits set
// in the x509.Certificate template
keyUsage := x509.KeyUsageDigitalSignature
notBefore := time.Now()
validFor := 365 * 24 * time.Hour
notAfter := notBefore.Add(validFor)
// Generate the serial number
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return nil, nil, err
}
template := x509.Certificate{
SerialNumber: serialNumber,
NotBefore: notBefore,
NotAfter: notAfter,
KeyUsage: keyUsage,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
}
hosts := strings.Split(host, ",")
for _, h := range hosts {
if ip := net.ParseIP(h); ip != nil {
template.IPAddresses = append(template.IPAddresses, ip)
} else {
template.DNSNames = append(template.DNSNames, h)
}
}
// Create the certificate
cert, err := x509.CreateCertificate(rand.Reader, &template, &template, public, priv)
if err != nil {
return nil, nil, err
}
// Encode the certificate
var b bytes.Buffer
if err := pem.Encode(&b, &pem.Block{Type: "CERTIFICATE", Bytes: cert}); err != nil {
return nil, nil, err
}
crt = b.Bytes()
// Encode the key
b = bytes.Buffer{}
if err != nil {
return nil, nil, err
}
privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
if err != nil {
return nil, nil, err
}
if err := pem.Encode(&b, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
return nil, nil, err
}
key = b.Bytes()
return
}
// WriteCertificate writes the provided certificate and private key to name.crt + name.key
func WriteCertificate(name string, crt, key []byte) error {
// Write the certificate
crtPath := name + ".crt"
crtOut, err := os.OpenFile(crtPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
if _, err := crtOut.Write(crt); err != nil {
return err
}
// Write the private key
keyPath := name + ".key"
keyOut, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
if _, err := keyOut.Write(key); err != nil {
return err
}
return nil
}