diff --git a/cmd/jounce/main.go b/cmd/jounce/main.go
index 509bd52..9f3c37a 100644
--- a/cmd/jounce/main.go
+++ b/cmd/jounce/main.go
@@ -15,20 +15,18 @@ func main() {
 		log.Fatalf("failed to start listener: %v", err)
 	}
 
+	srv := jounce.NewServer()
 	// TODO: load from config/DB
-	s := jounce.Server{
-		Hostname: "localhost",
-		Logger:   log.New(log.Writer(), "", log.LstdFlags),
-		Upstreams: []jounce.Upstream{{
-			Addr:     "chat.freenode.net:6697",
-			Nick:     "jounce",
-			Username: "jounce",
-			Realname: "jounce",
-			Channels: []string{"#jounce"},
-		}},
-	}
+	srv.Hostname = "localhost"
+	srv.Upstreams = []jounce.Upstream{{
+		Addr:     "chat.freenode.net:6697",
+		Nick:     "jounce",
+		Username: "jounce",
+		Realname: "jounce",
+		Channels: []string{"#jounce"},
+	}}
 
 	log.Printf("Server listening on %v", addr)
-	go s.Run()
-	log.Fatal(s.Serve(ln))
+	go srv.Run()
+	log.Fatal(srv.Serve(ln))
 }
diff --git a/downstream.go b/downstream.go
index ef18829..6926742 100644
--- a/downstream.go
+++ b/downstream.go
@@ -46,6 +46,7 @@ type downstreamConn struct {
 	messages chan<- *irc.Message
 
 	registered bool
+	user       *user
 	closed     bool
 	nick       string
 	username   string
@@ -166,40 +167,50 @@ func (c *downstreamConn) handleMessageUnregistered(msg *irc.Message) error {
 }
 
 func (c *downstreamConn) register() error {
+	c.srv.lock.Lock()
+	u, ok := c.srv.users[c.username]
+	c.srv.lock.Unlock()
+
+	if !ok {
+		c.messages <- &irc.Message{
+			Prefix:  c.srv.prefix(),
+			Command: irc.ERR_PASSWDMISMATCH,
+			Params:  []string{"*", "Invalid username or password"},
+		}
+		return nil
+	}
+
 	c.registered = true
+	c.user = u
 
 	c.messages <- &irc.Message{
 		Prefix:  c.srv.prefix(),
 		Command: irc.RPL_WELCOME,
 		Params:  []string{c.nick, "Welcome to jounce, " + c.nick},
 	}
-
 	c.messages <- &irc.Message{
 		Prefix:  c.srv.prefix(),
 		Command: irc.RPL_YOURHOST,
 		Params:  []string{c.nick, "Your host is " + c.srv.Hostname},
 	}
-
 	c.messages <- &irc.Message{
 		Prefix:  c.srv.prefix(),
 		Command: irc.RPL_CREATED,
 		Params:  []string{c.nick, "This server was created <datetime>"}, // TODO
 	}
-
 	c.messages <- &irc.Message{
 		Prefix:  c.srv.prefix(),
 		Command: irc.RPL_MYINFO,
 		Params:  []string{c.nick, c.srv.Hostname, "jounce", "aiwroO", "OovaimnqpsrtklbeI"},
 	}
-
 	c.messages <- &irc.Message{
 		Prefix:  c.srv.prefix(),
 		Command: irc.ERR_NOMOTD,
 		Params:  []string{c.nick, "No MOTD"},
 	}
 
-	c.srv.lock.Lock()
-	for _, uc := range c.srv.upstreamConns {
+	u.lock.Lock()
+	for _, uc := range u.upstreamConns {
 		// TODO: fix races accessing upstream connection data
 		if !uc.registered {
 			continue
@@ -210,7 +221,7 @@ func (c *downstreamConn) register() error {
 			}
 		}
 	}
-	c.srv.lock.Unlock()
+	u.lock.Unlock()
 
 	return nil
 }
diff --git a/server.go b/server.go
index dc0a193..f89177e 100644
--- a/server.go
+++ b/server.go
@@ -2,6 +2,7 @@ package jounce
 
 import (
 	"fmt"
+	"log"
 	"net"
 	"sync"
 
@@ -30,6 +31,14 @@ func (l *prefixLogger) Printf(format string, v ...interface{}) {
 	l.logger.Printf("%v"+format, v...)
 }
 
+type user struct {
+	username string
+	srv      *Server
+
+	lock          sync.Mutex
+	upstreamConns []*upstreamConn
+}
+
 type Upstream struct {
 	Addr     string
 	Nick     string
@@ -44,8 +53,15 @@ type Server struct {
 	Upstreams []Upstream // TODO: per-user
 
 	lock            sync.Mutex
+	users           map[string]*user
 	downstreamConns []*downstreamConn
-	upstreamConns   []*upstreamConn
+}
+
+func NewServer() *Server {
+	return &Server{
+		Logger: log.New(log.Writer(), "", log.LstdFlags),
+		users:  make(map[string]*user),
+	}
 }
 
 func (s *Server) prefix() *irc.Prefix {
@@ -53,32 +69,39 @@ func (s *Server) prefix() *irc.Prefix {
 }
 
 func (s *Server) Run() {
+	// TODO: multi-user
+	u := &user{username: "jounce", srv: s}
+
+	s.lock.Lock()
+	s.users[u.username] = u
+	s.lock.Unlock()
+
 	for i := range s.Upstreams {
 		upstream := &s.Upstreams[i]
 		// TODO: retry connecting
 		go func() {
-			conn, err := connectToUpstream(s, upstream)
+			conn, err := connectToUpstream(u, upstream)
 			if err != nil {
 				s.Logger.Printf("failed to connect to upstream server %q: %v", upstream.Addr, err)
 				return
 			}
 
-			s.lock.Lock()
-			s.upstreamConns = append(s.upstreamConns, conn)
-			s.lock.Unlock()
+			u.lock.Lock()
+			u.upstreamConns = append(u.upstreamConns, conn)
+			u.lock.Unlock()
 
 			if err := conn.readMessages(); err != nil {
 				conn.logger.Printf("failed to handle messages: %v", err)
 			}
 
-			s.lock.Lock()
-			for i, c := range s.upstreamConns {
+			u.lock.Lock()
+			for i, c := range u.upstreamConns {
 				if c == conn {
-					s.upstreamConns = append(s.upstreamConns[:i], s.upstreamConns[i+1:]...)
+					u.upstreamConns = append(u.upstreamConns[:i], u.upstreamConns[i+1:]...)
 					break
 				}
 			}
-			s.lock.Unlock()
+			u.lock.Unlock()
 		}()
 	}
 }
diff --git a/upstream.go b/upstream.go
index 5394c2e..b5200c0 100644
--- a/upstream.go
+++ b/upstream.go
@@ -29,6 +29,7 @@ type upstreamConn struct {
 	net      net.Conn
 	irc      *irc.Conn
 	srv      *Server
+	user     *user
 	messages chan<- *irc.Message
 
 	serverName            string
@@ -42,8 +43,8 @@ type upstreamConn struct {
 	channels   map[string]*upstreamChannel
 }
 
-func connectToUpstream(s *Server, upstream *Upstream) (*upstreamConn, error) {
-	logger := &prefixLogger{s.Logger, fmt.Sprintf("upstream %q: ", upstream.Addr)}
+func connectToUpstream(u *user, upstream *Upstream) (*upstreamConn, error) {
+	logger := &prefixLogger{u.srv.Logger, fmt.Sprintf("upstream %q: ", upstream.Addr)}
 	logger.Printf("connecting to server")
 
 	netConn, err := tls.Dial("tcp", upstream.Addr, nil)
@@ -57,7 +58,8 @@ func connectToUpstream(s *Server, upstream *Upstream) (*upstreamConn, error) {
 		logger:   logger,
 		net:      netConn,
 		irc:      irc.NewConn(netConn),
-		srv:      s,
+		srv:      u.srv,
+		user:     u,
 		messages: msgs,
 		channels: make(map[string]*upstreamChannel),
 	}