Multi-client servers + bring back stdinserver support

client/stdinserver.go

@@ -0,0 +1,41 @@
+package client
+
+import (
+	"os"
+
+	"context"
+	"github.com/problame/go-netssh"
+	"log"
+	"path"
+	"github.com/zrepl/zrepl/config"
+	"errors"
+)
+
+
+func RunStdinserver(config *config.Config, args []string) error {
+
+	// NOTE: the netssh proxying protocol requires exiting with non-zero status if anything goes wrong
+	defer os.Exit(1)
+
+	log := log.New(os.Stderr, "", log.LUTC|log.Ldate|log.Ltime)
+
+	if len(args) != 1 || args[0] == "" {
+		err := errors.New("must specify client_identity as positional argument")
+		return err
+	}
+
+	identity := args[0]
+	unixaddr := path.Join(config.Global.Serve.StdinServer.SockDir, identity)
+
+	log.Printf("proxying client identity '%s' to zrepl daemon '%s'", identity, unixaddr)
+
+	ctx := netssh.ContextWithLog(context.TODO(), log)
+
+	err := netssh.Proxy(ctx, unixaddr)
+	if err == nil {
+		log.Print("proxying finished successfully, exiting with status 0")
+		os.Exit(0)
+	}
+	log.Printf("error proxying: %s", err)
+	return nil
+}

config/config.go

@@ -165,7 +165,7 @@ type SSHStdinserverConnect struct {
 	IdentityFile         string        `yaml:"identity_file"`
 	TransportOpenCommand []string      `yaml:"transport_open_command,optional"` //TODO unused
 	SSHCommand           string        `yaml:"ssh_command,optional"`            //TODO unused
-	Options              []string      `yaml:"options"`
+	Options              []string      `yaml:"options,optional"`
 	DialTimeout          time.Duration `yaml:"dial_timeout,positive,default=10s"`
 }
 
@@ -190,13 +190,13 @@ type TLSServe struct {
 	Ca               string        `yaml:"ca"`
 	Cert             string        `yaml:"cert"`
 	Key              string        `yaml:"key"`
-	ClientCN         string        `yaml:"client_cn"`
+	ClientCNs        []string      `yaml:"client_cns"`
 	HandshakeTimeout time.Duration `yaml:"handshake_timeout,positive,default=10s"`
 }
 
 type StdinserverServer struct {
 	ServeCommon    `yaml:",inline"`
-	ClientIdentity string `yaml:"client_identity"`
+	ClientIdentities []string `yaml:"client_identities"`
 }
 
 type PruningEnum struct {

config/samples/sink.yml

@@ -8,7 +8,9 @@ jobs:
       ca: "ca.pem"
       cert: "cert.pem"
       key: "key.pem"
-      client_cn: "laptop1"
+      client_cns:
+        - "laptop1"
+        - "homeserver"
 global:
   logging:
     - type: "tcp"

config/samples/source_ssh.yml

@@ -3,7 +3,9 @@ jobs:
   type: source
   serve:
     type: stdinserver
-    client_identity: "client1"
+    client_identities:
+      - "client1"
+      - "client2"
   filesystems: {
     "<": true,
     "secret": false

daemon/job/sink.go

@@ -9,31 +9,27 @@ import (
 	"github.com/zrepl/zrepl/daemon/logging"
 	"github.com/zrepl/zrepl/daemon/serve"
 	"github.com/zrepl/zrepl/endpoint"
-	"net"
+	"path"
 )
 
 type Sink struct {
 	name     string
 	l        serve.ListenerFactory
 	rpcConf  *streamrpc.ConnConfig
-	fsmap    endpoint.FSMap
-	fsmapInv endpoint.FSFilter
+	rootDataset string
 }
 
 func SinkFromConfig(g *config.Global, in *config.SinkJob) (s *Sink, err error) {
 
-	// FIXME multi client support
-
 	s = &Sink{name: in.Name}
 	if s.l, s.rpcConf, err = serve.FromConfig(g, in.Serve); err != nil {
 		return nil, errors.Wrap(err, "cannot build server")
 	}
 
-	fsmap := filters.NewDatasetMapFilter(1, false) // FIXME multi-client support
-	if err := fsmap.Add("<", in.RootDataset); err != nil {
-		return nil, errors.Wrap(err, "unexpected error: cannot build filesystem mapping")
+	if in.RootDataset == "" {
+		return nil, errors.Wrap(err, "must specify root dataset")
 	}
-	s.fsmap = fsmap
+	s.rootDataset = in.RootDataset
 
 	return s, nil
 }
@@ -55,6 +51,7 @@ func (j *Sink) Run(ctx context.Context) {
 		log.WithError(err).Error("cannot listen")
 		return
 	}
+	defer l.Close()
 
 	log.WithField("addr", l.Addr()).Debug("accepting connections")
 
@@ -64,10 +61,10 @@ outer:
 	for {
 
 		select {
-		case res := <-accept(l):
+		case res := <-accept(ctx, l):
 			if res.err != nil {
-				log.WithError(err).Info("accept error")
-				break outer
+				log.WithError(res.err).Info("accept error")
+				continue
 			}
 			connId++
 			connLog := log.
@@ -82,14 +79,28 @@ outer:
 
 }
 
-func (j *Sink) handleConnection(ctx context.Context, conn net.Conn) {
+func (j *Sink) handleConnection(ctx context.Context, conn serve.AuthenticatedConn) {
+	defer conn.Close()
+
 	log := GetLogger(ctx)
-	log.WithField("addr", conn.RemoteAddr()).Info("handling connection")
+	log.
+		WithField("addr", conn.RemoteAddr()).
+		WithField("client_identity", conn.ClientIdentity()).
+		Info("handling connection")
 	defer log.Info("finished handling connection")
 
+	clientRoot := path.Join(j.rootDataset, conn.ClientIdentity())
+	log.WithField("client_root", clientRoot).Debug("client root")
+	fsmap := filters.NewDatasetMapFilter(1, false)
+	if err := fsmap.Add("<", clientRoot); err != nil {
+		log.WithError(err).
+			WithField("client_identity", conn.ClientIdentity()).
+			Error("cannot build client filesystem map (client identity must be a valid ZFS FS name")
+	}
+
 	ctx = logging.WithSubsystemLoggers(ctx, log)
 
-	local, err := endpoint.NewReceiver(j.fsmap, filters.NewAnyFSVFilter())
+	local, err := endpoint.NewReceiver(fsmap, filters.NewAnyFSVFilter())
 	if err != nil {
 		log.WithError(err).Error("unexpected error: cannot convert mapping to filter")
 		return
@@ -102,14 +113,14 @@ func (j *Sink) handleConnection(ctx context.Context, conn net.Conn) {
 }
 
 type acceptResult struct {
-	conn net.Conn
+	conn serve.AuthenticatedConn
 	err  error
 }
 
-func accept(listener net.Listener) <-chan acceptResult {
+func accept(ctx context.Context, listener serve.AuthenticatedListener) <-chan acceptResult {
 	c := make(chan acceptResult, 1)
 	go func() {
-		conn, err := listener.Accept()
+		conn, err := listener.Accept(ctx)
 		c <- acceptResult{conn, err}
 	}()
 	return c

daemon/logging/build_logging.go

@@ -15,6 +15,7 @@ import (
 	"github.com/zrepl/zrepl/tlsconf"
 	"os"
 	"github.com/zrepl/zrepl/daemon/snapper"
+	"github.com/zrepl/zrepl/daemon/serve"
 )
 
 func OutletsFromConfig(in config.LoggingOutletEnumList) (*logger.Outlets, error) {
@@ -71,6 +72,7 @@ func WithSubsystemLoggers(ctx context.Context, log logger.Logger) context.Contex
 	ctx = endpoint.WithLogger(ctx, log.WithField(SubsysField, "endpoint"))
 	ctx = pruner.WithLogger(ctx, log.WithField(SubsysField, "pruning"))
 	ctx = snapper.WithLogger(ctx, log.WithField(SubsysField, "snapshot"))
+	ctx = serve.WithLogger(ctx, log.WithField(SubsysField, "serve"))
 	return ctx
 }
 

daemon/serve/serve.go

@@ -6,10 +6,69 @@ import (
 	"net"
 	"github.com/zrepl/zrepl/daemon/streamrpcconfig"
 	"github.com/problame/go-streamrpc"
+	"context"
+	"github.com/zrepl/zrepl/logger"
+	"github.com/zrepl/zrepl/zfs"
 )
 
+type contextKey int
+
+const contextKeyLog contextKey = 0
+
+type Logger = logger.Logger
+
+func WithLogger(ctx context.Context, log Logger) context.Context {
+	return context.WithValue(ctx, contextKeyLog, log)
+}
+
+func getLogger(ctx context.Context) Logger {
+	if log, ok := ctx.Value(contextKeyLog).(Logger); ok {
+		return log
+	}
+	return logger.NewNullLogger()
+}
+
+type AuthenticatedConn interface {
+	net.Conn
+	// ClientIdentity must be a string that satisfies ValidateClientIdentity
+	ClientIdentity() string
+}
+
+// A client identity must be a single component in a ZFS filesystem path
+func ValidateClientIdentity(in string) (err error) {
+	path, err := zfs.NewDatasetPath(in)
+	if err != nil {
+		return err
+	}
+	if path.Length() != 1 {
+		return errors.New("client identity must be a single path comonent (not empty, no '/')")
+	}
+	return nil
+}
+
+type authConn struct {
+	net.Conn
+	clientIdentity string
+}
+
+var _ AuthenticatedConn = authConn{}
+
+func (c authConn) ClientIdentity() string {
+	if err := ValidateClientIdentity(c.clientIdentity); err != nil {
+		panic(err)
+	}
+	return c.clientIdentity
+}
+
+// like net.Listener, but with an AuthenticatedConn instead of net.Conn
+type AuthenticatedListener interface {
+	Addr() (net.Addr)
+	Accept(ctx context.Context) (AuthenticatedConn, error)
+	Close() error
+}
+
 type ListenerFactory interface {
-	Listen() (net.Listener, error)
+	Listen() (AuthenticatedListener, error)
 }
 
 func FromConfig(g *config.Global, in config.ServeEnum) (lf ListenerFactory, conf *streamrpc.ConnConfig, _ error) {
@@ -25,7 +84,7 @@ func FromConfig(g *config.Global, in config.ServeEnum) (lf ListenerFactory, conf
 		lf, lfError = TLSListenerFactoryFromConfig(g, v)
 		conf, rpcErr = streamrpcconfig.FromDaemonConfig(g, v.RPC)
 	case *config.StdinserverServer:
-		lf, lfError = StdinserverListenerFactoryFromConfig(g, v)
+		lf, lfError = MultiStdinserverListenerFactoryFromConfig(g, v)
 		conf, rpcErr = streamrpcconfig.FromDaemonConfig(g, v.RPC)
 	default:
 		return nil, nil, errors.Errorf("internal error: unknown serve type %T", v)

daemon/serve/serve_stdinserver.go

@@ -8,54 +8,133 @@ import (
 	"net"
 	"path"
 	"time"
+	"context"
+	"github.com/pkg/errors"
+	"sync/atomic"
+	"fmt"
+	"os"
 )
 
 type StdinserverListenerFactory struct {
-	ClientIdentity string
-	sockpath       string
+	ClientIdentities []string
+	Sockdir string
 }
 
-func StdinserverListenerFactoryFromConfig(g *config.Global, in *config.StdinserverServer) (f *StdinserverListenerFactory, err error) {
+func MultiStdinserverListenerFactoryFromConfig(g *config.Global, in *config.StdinserverServer) (f *multiStdinserverListenerFactory, err error) {
 
-	f = &StdinserverListenerFactory{
-		ClientIdentity: in.ClientIdentity,
+	for _, ci := range in.ClientIdentities {
+		if err := ValidateClientIdentity(ci); err != nil {
+			return nil, errors.Wrapf(err, "invalid client identity %q", ci)
+		}
 	}
 
-	f.sockpath = path.Join(g.Serve.StdinServer.SockDir, f.ClientIdentity)
+	f = &multiStdinserverListenerFactory{
+		ClientIdentities: in.ClientIdentities,
+		Sockdir: g.Serve.StdinServer.SockDir,
+	}
 
 	return
 }
 
-func (f *StdinserverListenerFactory) Listen() (net.Listener, error) {
+type multiStdinserverListenerFactory struct {
+	ClientIdentities []string
+	Sockdir string
+}
 
-	if err := nethelpers.PreparePrivateSockpath(f.sockpath); err != nil {
-		return nil, err
+func (f *multiStdinserverListenerFactory) Listen() (AuthenticatedListener, error) {
+	return multiStdinserverListenerFromClientIdentities(f.Sockdir, f.ClientIdentities)
+}
+
+type multiStdinserverAcceptRes struct {
+	conn AuthenticatedConn
+	err error
+}
+
+type MultiStdinserverListener struct {
+	listeners []*stdinserverListener
+	accepts chan multiStdinserverAcceptRes
+	closed int32
+}
+
+// client identities must be validated
+func multiStdinserverListenerFromClientIdentities(sockdir string, cis []string) (*MultiStdinserverListener, error) {
+	listeners := make([]*stdinserverListener, 0, len(cis))
+	var err error
+	for _, ci := range cis {
+		sockpath := path.Join(sockdir, ci)
+		l  := &stdinserverListener{clientIdentity: ci}
+		if err = nethelpers.PreparePrivateSockpath(sockpath); err != nil {
+			break
+		}
+		if l.l, err = netssh.Listen(sockpath); err != nil {
+			break
+		}
+		listeners = append(listeners, l)
 	}
-
-	l, err := netssh.Listen(f.sockpath)
 	if err != nil {
+		for _, l := range listeners {
+			l.Close() // FIXME error reporting?
+		}
 		return nil, err
 	}
-	return StdinserverListener{l}, nil
+	return &MultiStdinserverListener{listeners: listeners}, nil
 }
 
-type StdinserverListener struct {
-	l *netssh.Listener
+func (m *MultiStdinserverListener) Accept(ctx context.Context) (AuthenticatedConn, error){
+
+	if m.accepts == nil {
+		m.accepts = make(chan multiStdinserverAcceptRes, len(m.listeners))
+		for i := range m.listeners {
+			go func(i int) {
+				for atomic.LoadInt32(&m.closed) == 0 {
+					fmt.Fprintf(os.Stderr, "accepting\n")
+					conn, err := m.listeners[i].Accept(context.TODO())
+					fmt.Fprintf(os.Stderr, "incoming\n")
+					m.accepts <- multiStdinserverAcceptRes{conn, err}
+				}
+			}(i)
+		}
+	}
+
+	res := <- m.accepts
+	return res.conn, res.err
+
 }
 
-func (l StdinserverListener) Addr() net.Addr {
+func (m *MultiStdinserverListener) Addr() (net.Addr) {
 	return netsshAddr{}
 }
 
-func (l StdinserverListener) Accept() (net.Conn, error) {
+func (m *MultiStdinserverListener) Close() error {
+	atomic.StoreInt32(&m.closed, 1)
+	var oneErr error
+	for _, l := range m.listeners {
+		if err := l.Close(); err != nil && oneErr == nil {
+			oneErr = err
+		}
+	}
+	return oneErr
+}
+
+// a single stdinserverListener (part of multiStinserverListener)
+type stdinserverListener struct {
+	l *netssh.Listener
+	clientIdentity string
+}
+
+func (l stdinserverListener) Addr() net.Addr {
+	return netsshAddr{}
+}
+
+func (l stdinserverListener) Accept(ctx context.Context) (AuthenticatedConn, error) {
 	c, err := l.l.Accept()
 	if err != nil {
 		return nil, err
 	}
-	return netsshConnToNetConnAdatper{c}, nil
+	return netsshConnToNetConnAdatper{c, l.clientIdentity}, nil
 }
 
-func (l StdinserverListener) Close() (err error) {
+func (l stdinserverListener) Close() (err error) {
 	return l.l.Close()
 }
 
@@ -66,12 +145,16 @@ func (netsshAddr) String() string  { return "???" }
 
 type netsshConnToNetConnAdatper struct {
 	io.ReadWriteCloser // works for both netssh.SSHConn and netssh.ServeConn
+	clientIdentity string
 }
 
+func (a netsshConnToNetConnAdatper) ClientIdentity() string { return a.clientIdentity }
+
 func (netsshConnToNetConnAdatper) LocalAddr() net.Addr { return netsshAddr{} }
 
 func (netsshConnToNetConnAdatper) RemoteAddr() net.Addr { return netsshAddr{} }
 
+// FIXME log warning once!
 func (netsshConnToNetConnAdatper) SetDeadline(t time.Time) error { return nil }
 
 func (netsshConnToNetConnAdatper) SetReadDeadline(t time.Time) error { return nil }

daemon/serve/serve_tcp.go

@@ -3,19 +3,89 @@ package serve
 import (
 	"github.com/zrepl/zrepl/config"
 	"net"
+	"github.com/pkg/errors"
+	"context"
 )
 
 type TCPListenerFactory struct {
-	Address string
+	address *net.TCPAddr
+	clientMap *ipMap
+}
+
+type ipMapEntry struct {
+	ip net.IP
+	ident string
+}
+
+type ipMap struct {
+	entries []ipMapEntry
+}
+
+func ipMapFromConfig(clients map[string]string) (*ipMap, error) {
+	entries := make([]ipMapEntry, 0, len(clients))
+	for clientIPString, clientIdent := range clients {
+		clientIP := net.ParseIP(clientIPString)
+		if clientIP == nil {
+			return nil, errors.Errorf("cannot parse client IP %q", clientIPString)
+		}
+		if err := ValidateClientIdentity(clientIdent); err != nil {
+			return nil, errors.Wrapf(err,"invalid client identity for IP %q", clientIPString)
+		}
+		entries = append(entries, ipMapEntry{clientIP, clientIdent})
+	}
+	return &ipMap{entries: entries}, nil
+}
+
+func (m *ipMap) Get(ip net.IP) (string, error) {
+	for _, e := range m.entries {
+		if e.ip.Equal(ip) {
+			return e.ident, nil
+		}
+	}
+	return "", errors.Errorf("no identity mapping for client IP %s", ip)
 }
 
 func TCPListenerFactoryFromConfig(c *config.Global, in *config.TCPServe) (*TCPListenerFactory, error) {
+	addr, err := net.ResolveTCPAddr("tcp", in.Listen)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot parse listen address")
+	}
+	clientMap, err := ipMapFromConfig(in.Clients)
+	if err != nil {
+		return nil, errors.Wrap(err, "cannot parse client IP map")
+	}
 	lf := &TCPListenerFactory{
-		Address: in.Listen,
+		address: addr,
+		clientMap: clientMap,
 	}
 	return lf, nil
 }
 
-func (f *TCPListenerFactory) Listen() (net.Listener, error) {
-	return net.Listen("tcp", f.Address)
+func (f *TCPListenerFactory) Listen() (AuthenticatedListener, error) {
+	l, err := net.ListenTCP("tcp", f.address)
+	if err != nil {
+		return nil, err
+	}
+	return &TCPAuthListener{l, f.clientMap}, nil
 }
+
+type TCPAuthListener struct {
+	*net.TCPListener
+	clientMap *ipMap
+}
+
+func (f *TCPAuthListener) Accept(ctx context.Context) (AuthenticatedConn, error) {
+	nc, err := f.TCPListener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	clientIP := nc.RemoteAddr().(*net.TCPAddr).IP
+	clientIdent, err := f.clientMap.Get(clientIP)
+	if err != nil {
+		getLogger(ctx).WithField("ip", clientIP).Error("client IP not in client map")
+		nc.Close()
+		return nil, err
+	}
+	return authConn{nc, clientIdent}, nil
+}
+

daemon/serve/serve_tls.go

@@ -8,13 +8,13 @@ import (
 	"github.com/zrepl/zrepl/tlsconf"
 	"net"
 	"time"
+	"context"
 )
 
 type TLSListenerFactory struct {
 	address          string
 	clientCA         *x509.CertPool
 	serverCert       tls.Certificate
-	clientCommonName string
 	handshakeTimeout time.Duration
 }
 
@@ -23,12 +23,10 @@ func TLSListenerFactoryFromConfig(c *config.Global, in *config.TLSServe) (lf *TL
 		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")
+	if in.Ca == "" || in.Cert == "" || in.Key == "" {
+		return nil, errors.New("fields 'ca', 'cert' and 'key'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")
@@ -42,11 +40,25 @@ func TLSListenerFactoryFromConfig(c *config.Global, in *config.TLSServe) (lf *TL
 	return lf, nil
 }
 
-func (f *TLSListenerFactory) Listen() (net.Listener, error) {
+func (f *TLSListenerFactory) Listen() (AuthenticatedListener, 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
+	tl := tlsconf.NewClientAuthListener(l, f.clientCA, f.serverCert, f.handshakeTimeout)
+	return tlsAuthListener{tl}, nil
 }
+
+type tlsAuthListener struct {
+	*tlsconf.ClientAuthListener
+}
+
+func (l tlsAuthListener) Accept(ctx context.Context) (AuthenticatedConn, error) {
+	c, cn, err := l.ClientAuthListener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	return authConn{c, cn}, nil
+}
+
+

main.go

@@ -57,6 +57,18 @@ var statusCmd = &cobra.Command{
 	},
 }
 
+var stdinserverCmd = &cobra.Command{
+	Use:   "stdinserver CLIENT_IDENTITY",
+	Short: "start in stdinserver mode (from authorized_keys file)",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		conf, err := config.ParseConfig(rootArgs.configFile)
+		if err != nil {
+			return err
+		}
+		return client.RunStdinserver(conf, args)
+	},
+}
+
 var rootArgs struct {
 	configFile string
 }
@@ -67,6 +79,7 @@ func init() {
 	rootCmd.AddCommand(daemonCmd)
 	rootCmd.AddCommand(wakeupCmd)
 	rootCmd.AddCommand(statusCmd)
+	rootCmd.AddCommand(stdinserverCmd)
 }
 
 func main() {

tlsconf/tlsconf.go

@@ -4,7 +4,6 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"errors"
-	"fmt"
 	"io/ioutil"
 	"net"
 	"time"
@@ -24,13 +23,12 @@ func ParseCAFile(certfile string) (*x509.CertPool, error) {
 
 type ClientAuthListener struct {
 	l                net.Listener
-	clientCommonName string
 	handshakeTimeout time.Duration
 }
 
 func NewClientAuthListener(
 	l net.Listener, ca *x509.CertPool, serverCert tls.Certificate,
-	clientCommonName string, handshakeTimeout time.Duration) *ClientAuthListener {
+	handshakeTimeout time.Duration) *ClientAuthListener {
 
 	if ca == nil {
 		panic(ca)
@@ -38,9 +36,6 @@ func NewClientAuthListener(
 	if serverCert.Certificate == nil || serverCert.PrivateKey == nil {
 		panic(serverCert)
 	}
-	if clientCommonName == "" {
-		panic(clientCommonName)
-	}
 
 	tlsConf := tls.Config{
 		Certificates:             []tls.Certificate{serverCert},
@@ -51,19 +46,18 @@ func NewClientAuthListener(
 	l = tls.NewListener(l, &tlsConf)
 	return &ClientAuthListener{
 		l,
-		clientCommonName,
 		handshakeTimeout,
 	}
 }
 
-func (l *ClientAuthListener) Accept() (c net.Conn, err error) {
+func (l *ClientAuthListener) Accept() (c net.Conn, clientCN string, err error) {
 	c, err = l.l.Accept()
 	if err != nil {
-		return nil, err
+		return nil, "", err
 	}
 	tlsConn, ok := c.(*tls.Conn)
 	if !ok {
-		return c, err
+		return c, "", err
 	}
 
 	var (
@@ -83,14 +77,10 @@ func (l *ClientAuthListener) Accept() (c net.Conn, err error) {
 		goto CloseAndErr
 	}
 	cn = peerCerts[0].Subject.CommonName
-	if cn != l.clientCommonName {
-		err = fmt.Errorf("client cert common name does not match client_identity: %q != %q", cn, l.clientCommonName)
-		goto CloseAndErr
-	}
-	return c, nil
+	return c, cn, nil
 CloseAndErr:
 	c.Close()
-	return nil, err
+	return nil, "", err
 }
 
 func (l *ClientAuthListener) Addr() net.Addr {