mkcerts: Split into separate file

mkcerts/certs.go

@@ -0,0 +1,79 @@
+// Copyright (c) 2016- Daniel Oaks <daniel@danieloaks.net>
+// released under the MIT license
+
+package mkcerts
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"net"
+	"os"
+	"time"
+)
+
+// CreateCert creates a testing ECDSA certificate, outputting the cert and key at the given filenames.
+func CreateCert(orgName string, host string, certFilename string, keyFilename string) error {
+	validFrom := time.Now()
+	validFor := 365 * 24 * time.Hour
+	notAfter := validFrom.Add(validFor)
+
+	priv, err := ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
+
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		return fmt.Errorf("failed to generate serial number: %s", err)
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			Organization: []string{orgName},
+		},
+		NotBefore: validFrom,
+		NotAfter:  notAfter,
+
+		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+
+	// TODO: allow explicitly listing allowed addresses/names
+	template.IPAddresses = append(template.IPAddresses, net.ParseIP("127.0.0.1"))
+	template.IPAddresses = append(template.IPAddresses, net.ParseIP("::1"))
+	if host != "" {
+		template.DNSNames = append(template.DNSNames, host)
+	}
+	template.DNSNames = append(template.DNSNames, "localhost")
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
+	if err != nil {
+		return fmt.Errorf("Failed to create certificate: %s", err.Error())
+	}
+
+	certOut, err := os.Create(certFilename)
+	if err != nil {
+		return fmt.Errorf("failed to open %s for writing: %s", certFilename, err.Error())
+	}
+	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
+	certOut.Close()
+
+	keyOut, err := os.OpenFile(keyFilename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return fmt.Errorf("failed to open %s for writing: %s", keyFilename, err.Error())
+	}
+	b, err := x509.MarshalECPrivateKey(priv)
+	if err != nil {
+		return fmt.Errorf("Unable to marshal ECDSA private key: %v", err.Error())
+	}
+	pemBlock := pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
+	pem.Encode(keyOut, &pemBlock)
+	keyOut.Close()
+	return nil
+}