lnd.xprv/cert/selfsigned.go
2019-12-18 10:28:22 +01:00

176 lines
4.5 KiB
Go

package cert
import (
"bytes"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"io/ioutil"
"math/big"
"net"
"os"
"time"
)
const (
// DefaultAutogenValidity is the default validity of a self-signed
// certificate. The value corresponds to 14 months
// (14 months * 30 days * 24 hours).
DefaultAutogenValidity = 14 * 30 * 24 * time.Hour
)
var (
// End of ASN.1 time.
endOfTime = time.Date(2049, 12, 31, 23, 59, 59, 0, time.UTC)
// Max serial number.
serialNumberLimit = new(big.Int).Lsh(big.NewInt(1), 128)
)
// GenCertPair generates a key/cert pair to the paths provided. The
// auto-generated certificates should *not* be used in production for public
// access as they're self-signed and don't necessarily contain all of the
// desired hostnames for the service. For production/public use, consider a
// real PKI.
//
// This function is adapted from https://github.com/btcsuite/btcd and
// https://github.com/btcsuite/btcutil
func GenCertPair(org, certFile, keyFile string, tlsExtraIPs,
tlsExtraDomains []string, certValidity time.Duration) error {
now := time.Now()
validUntil := now.Add(certValidity)
// Check that the certificate validity isn't past the ASN.1 end of time.
if validUntil.After(endOfTime) {
validUntil = endOfTime
}
// Generate a serial number that's below the serialNumberLimit.
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
return fmt.Errorf("failed to generate serial number: %s", err)
}
// Collect the host's IP addresses, including loopback, in a slice.
ipAddresses := []net.IP{net.ParseIP("127.0.0.1"), net.ParseIP("::1")}
// addIP appends an IP address only if it isn't already in the slice.
addIP := func(ipAddr net.IP) {
for _, ip := range ipAddresses {
if ip.Equal(ipAddr) {
return
}
}
ipAddresses = append(ipAddresses, ipAddr)
}
// Add all the interface IPs that aren't already in the slice.
addrs, err := net.InterfaceAddrs()
if err != nil {
return err
}
for _, a := range addrs {
ipAddr, _, err := net.ParseCIDR(a.String())
if err == nil {
addIP(ipAddr)
}
}
// Add extra IPs to the slice.
for _, ip := range tlsExtraIPs {
ipAddr := net.ParseIP(ip)
if ipAddr != nil {
addIP(ipAddr)
}
}
// Collect the host's names into a slice.
host, err := os.Hostname()
if err != nil {
// Nothing much we can do here, other than falling back to
// localhost as fallback. A hostname can still be provided with
// the tlsExtraDomain parameter if the problem persists on a
// system.
host = "localhost"
}
dnsNames := []string{host}
if host != "localhost" {
dnsNames = append(dnsNames, "localhost")
}
dnsNames = append(dnsNames, tlsExtraDomains...)
// Also add fake hostnames for unix sockets, otherwise hostname
// verification will fail in the client.
dnsNames = append(dnsNames, "unix", "unixpacket")
// Also add hostnames for 'bufconn' which is the hostname used for the
// in-memory connections used on mobile.
dnsNames = append(dnsNames, "bufconn")
// Generate a private key for the certificate.
priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
return err
}
// Construct the certificate template.
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
Organization: []string{org},
CommonName: host,
},
NotBefore: now.Add(-time.Hour * 24),
NotAfter: validUntil,
KeyUsage: x509.KeyUsageKeyEncipherment |
x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
IsCA: true, // so can sign self.
BasicConstraintsValid: true,
DNSNames: dnsNames,
IPAddresses: ipAddresses,
}
derBytes, err := x509.CreateCertificate(rand.Reader, &template,
&template, &priv.PublicKey, priv)
if err != nil {
return fmt.Errorf("failed to create certificate: %v", err)
}
certBuf := &bytes.Buffer{}
err = pem.Encode(certBuf, &pem.Block{Type: "CERTIFICATE",
Bytes: derBytes})
if err != nil {
return fmt.Errorf("failed to encode certificate: %v", err)
}
keybytes, err := x509.MarshalECPrivateKey(priv)
if err != nil {
return fmt.Errorf("unable to encode privkey: %v", err)
}
keyBuf := &bytes.Buffer{}
err = pem.Encode(keyBuf, &pem.Block{Type: "EC PRIVATE KEY",
Bytes: keybytes})
if err != nil {
return fmt.Errorf("failed to encode private key: %v", err)
}
// Write cert and key files.
if err = ioutil.WriteFile(certFile, certBuf.Bytes(), 0644); err != nil {
return err
}
if err = ioutil.WriteFile(keyFile, keyBuf.Bytes(), 0600); err != nil {
os.Remove(certFile)
return err
}
return nil
}