WIP rewrite the daemon

cmd subdir does not build on purpose, it's only left in tree to grab old
code and move it to github.com/zrepl/zrepl/daemon

daemon/serve/serve_tls.go

@@ -0,0 +1,52 @@
+package serve
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"github.com/pkg/errors"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/tlsconf"
+	"net"
+	"time"
+)
+
+type TLSListenerFactory struct {
+	address          string
+	clientCA         *x509.CertPool
+	serverCert       tls.Certificate
+	clientCommonName string
+	handshakeTimeout time.Duration
+}
+
+func TLSListenerFactoryFromConfig(c config.Global, in *config.TLSServe) (lf *TLSListenerFactory, err error) {
+	lf = &TLSListenerFactory{
+		address: in.Listen,
+	}
+
+	if in.Ca == "" || in.Cert == "" || in.Key == "" || in.ClientCN == "" {
+		return nil, errors.New("fields 'ca', 'cert', 'key' and 'client_cn' must be specified")
+	}
+
+	lf.clientCommonName = in.ClientCN
+
+	lf.clientCA, err = tlsconf.ParseCAFile(in.Ca)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot parse ca file")
+	}
+
+	lf.serverCert, err = tls.LoadX509KeyPair(in.Cert, in.Key)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot parse cer/key pair")
+	}
+
+	return lf, nil
+}
+
+func (f *TLSListenerFactory) Listen() (net.Listener, error) {
+	l, err := net.Listen("tcp", f.address)
+	if err != nil {
+		return nil, err
+	}
+	tl := tlsconf.NewClientAuthListener(l, f.clientCA, f.serverCert, f.clientCommonName, f.handshakeTimeout)
+	return tl, nil
+}