Initial commit

selfcert.go

@@ -0,0 +1,84 @@
+package selfcert
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"net"
+	"time"
+)
+
+func NewTLSConfig(hosts []string) (*tls.Config, error) {
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
+
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		return nil, err
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			Organization: []string{"Acme Co"},
+		},
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().Add(10 * 365 * 24 * time.Hour),
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+
+	for _, h := range hosts {
+		if ip := net.ParseIP(h); ip != nil {
+			template.IPAddresses = append(template.IPAddresses, ip)
+		} else {
+			template.DNSNames = append(template.DNSNames, h)
+		}
+	}
+
+	certBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
+	if err != nil {
+		return nil, err
+	}
+
+	certPem := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certBytes})
+
+	keyBytes, err := x509.MarshalPKCS8PrivateKey(priv)
+	if err != nil {
+		return nil, err
+	}
+
+	keyPem := pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: keyBytes})
+
+	cert, err := tls.X509KeyPair(certPem, keyPem)
+	if err != nil {
+		return nil, err
+	}
+
+	conf := &tls.Config{
+		Certificates: []tls.Certificate{cert},
+		MinVersion:   tls.VersionTLS13,
+		NextProtos:   []string{"h2"},
+	}
+
+	return conf, nil
+}
+
+func NewTLSConfigFromHostPort(hostport string) (*tls.Config, error) {
+	host, _, err := net.SplitHostPort(hostport)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewTLSConfig([]string{host})
+}