The Great Rewrite (fixes #36, #61, #94, #101)

Rewrite of the file model and pulling mechanism. Needs lots of cleanup
and bugfixes, now...

cmd/stcli/tls.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/base32"
+	"encoding/pem"
+	"math/big"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+const (
+	tlsRSABits = 3072
+	tlsName    = "syncthing"
+)
+
+func loadCert(dir string) (tls.Certificate, error) {
+	return tls.LoadX509KeyPair(filepath.Join(dir, "cert.pem"), filepath.Join(dir, "key.pem"))
+}
+
+func certID(bs []byte) string {
+	hf := sha256.New()
+	hf.Write(bs)
+	id := hf.Sum(nil)
+	return strings.Trim(base32.StdEncoding.EncodeToString(id), "=")
+}
+
+func newCertificate(dir string) {
+	infoln("Generating RSA certificate and key...")
+
+	priv, err := rsa.GenerateKey(rand.Reader, tlsRSABits)
+	fatalErr(err)
+
+	notBefore := time.Now()
+	notAfter := time.Date(2049, 12, 31, 23, 59, 59, 0, time.UTC)
+
+	template := x509.Certificate{
+		SerialNumber: new(big.Int).SetInt64(0),
+		Subject: pkix.Name{
+			CommonName: tlsName,
+		},
+		NotBefore: notBefore,
+		NotAfter:  notAfter,
+
+		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
+		BasicConstraintsValid: true,
+	}
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
+	fatalErr(err)
+
+	certOut, err := os.Create(filepath.Join(dir, "cert.pem"))
+	fatalErr(err)
+	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})
+	certOut.Close()
+	okln("Created RSA certificate file")
+
+	keyOut, err := os.OpenFile(filepath.Join(dir, "key.pem"), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	fatalErr(err)
+	pem.Encode(keyOut, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)})
+	keyOut.Close()
+	okln("Created RSA key file")
+}