main: fix TLS cert autogen and server configuration

lnd.go

@@ -1,9 +1,16 @@
 package main
 
 import (
+	"bytes"
 	"crypto/rand"
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
 	"fmt"
 	"io/ioutil"
+	"math/big"
 	"net"
 	"net/http"
 	_ "net/http/pprof"
@@ -33,13 +40,20 @@ import (
 )
 
 const (
-	autogenCertValidity = 10 * 365 * 24 * time.Hour
+	// Make certificate valid for 14 months.
+	autogenCertValidity = 14 /*months*/ * 30 /*days*/ * 24 * time.Hour
 )
 
 var (
 	cfg              *config
 	shutdownChannel  = make(chan struct{})
 	registeredChains = newChainRegistry()
+
+	// 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)
 )
 
 // lndMain is the true entry point for lnd. This function is required since
@@ -229,11 +243,38 @@ func lndMain() error {
 	if err := rpcServer.Start(); err != nil {
 		return err
 	}
-	sCreds, err := credentials.NewServerTLSFromFile(cfg.TLSCertPath,
-		cfg.TLSKeyPath)
+	cert, err := tls.LoadX509KeyPair(cfg.TLSCertPath, cfg.TLSKeyPath)
 	if err != nil {
 		return err
 	}
+	tlsConf := &tls.Config{
+		Certificates: []tls.Certificate{cert},
+		/*
+		 * These cipher suites fit the following criteria:
+		 * - Don't use outdated algorithms like SHA-1 and 3DES
+		 * - Don't use ECB mode or other insecure symmetric methods
+		 * - Included in the TLS v1.2 suite
+		 * - Are available in the Go 1.7.6 standard library (more are
+		 *   available in 1.8.3 and will be added after lnd no longer
+		 *   supports 1.7, including suites that support CBC mode)
+		 *
+		 * The cipher suites are ordered from strongest to weakest
+		 * primitives, but the client's preference order has more
+		 * effect during negotiation.
+		**/
+		// TODO(aakselrod): add more cipher suites when 1.7 isn't
+		// supported.
+		CipherSuites: []uint16{
+			tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+			tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+			tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
+			tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+			tls.TLS_RSA_WITH_AES_128_GCM_SHA256,
+		},
+		MinVersion: tls.VersionTLS12,
+	}
+	sCreds := credentials.NewTLS(tlsConf)
 	opts := []grpc.ServerOption{grpc.Creds(sCreds)}
 	grpcServer := grpc.NewServer(opts...)
 	lnrpc.RegisterLightningServer(grpcServer, rpcServer)
@@ -268,9 +309,14 @@ func lndMain() error {
 	}
 	go func() {
 		restEndpoint := fmt.Sprintf(":%d", loadedConfig.RESTPort)
+		listener, err := tls.Listen("tcp", restEndpoint, tlsConf)
+		if err != nil {
+			ltndLog.Errorf("gRPC proxy unable to listen on "+
+				"localhost%s", restEndpoint)
+			return
+		}
 		rpcsLog.Infof("gRPC proxy started at localhost%s", restEndpoint)
-		http.ListenAndServeTLS(restEndpoint, cfg.TLSCertPath,
-			cfg.TLSKeyPath, mux)
+		http.Serve(listener, mux)
 	}()
 
 	// If we're not in simnet mode, We'll wait until we're fully synced to
@@ -379,23 +425,122 @@ func fileExists(name string) bool {
 	return true
 }
 
-// genCertPair generates a key/cert pair to the paths provided.
-// This function is adapted from https://github.com/btcsuite/btcd
+// 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(certFile, keyFile string) error {
 	rpcsLog.Infof("Generating TLS certificates...")
 
 	org := "lnd autogenerated cert"
-	validUntil := time.Now().Add(autogenCertValidity)
-	cert, key, err := btcutil.NewTLSCertPair(org, validUntil, nil)
+	now := time.Now()
+	validUntil := now.Add(autogenCertValidity)
+
+	// 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 bytes.Equal(ip, 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)
+		}
+	}
+
+	// Collect the host's names into a slice.
+	host, err := os.Hostname()
+	if err != nil {
+		return err
+	}
+	dnsNames := []string{host}
+	if host != "localhost" {
+		dnsNames = append(dnsNames, "localhost")
+	}
+
+	// Generate a private key for the certificate.
+	priv, err := rsa.GenerateKey(rand.Reader, 4096)
 	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,
+
+		// This signature algorithm is most likely to be compatible
+		// with clients using less-common TLS libraries like BoringSSL.
+		SignatureAlgorithm: x509.SHA256WithRSA,
+	}
+
+	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 := x509.MarshalPKCS1PrivateKey(priv)
+	keyBuf := &bytes.Buffer{}
+	err = pem.Encode(keyBuf, &pem.Block{Type: "RSA 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, cert, 0644); err != nil {
+	if err = ioutil.WriteFile(certFile, certBuf.Bytes(), 0644); err != nil {
 		return err
 	}
-	if err = ioutil.WriteFile(keyFile, key, 0600); err != nil {
+	if err = ioutil.WriteFile(keyFile, keyBuf.Bytes(), 0600); err != nil {
 		os.Remove(certFile)
 		return err
 	}