downstream: ignore nickname during connection registration

Just force-set the nickname and completely disregard what the client
sets during connection registration. Clients must discover their
effective nickname via RPL_WELCOME.

downstream.go

@@ -286,6 +286,12 @@ type downstreamSASL struct {
 	pendingResp                  bytes.Buffer
 }
 
+type downstreamRegistration struct {
+	nick     string
+	username string
+	password string
+}
+
 type downstreamConn struct {
 	conn
 
@@ -295,16 +301,16 @@ type downstreamConn struct {
 	user            *user
 	nick            string
 	nickCM          string
-	rawUsername     string
 	networkName     string
 	clientName      string
 	realname        string
 	hostname        string
 	account         string   // RPL_LOGGEDIN/OUT state
-	password        string   // empty after authentication
 	network         *network // can be nil
 	isMultiUpstream bool
 
+	registration *downstreamRegistration // nil after RPL_WELCOME
+
 	negotiatingCaps bool
 	capVersion      int
 	caps            capRegistry
@@ -326,6 +332,7 @@ func newDownstreamConn(srv *Server, ic ircConn, id uint64) *downstreamConn {
 		nickCM:       "*",
 		caps:         newCapRegistry(),
 		monitored:    newCasemapMap(0),
+		registration: new(downstreamRegistration),
 	}
 	dc.monitored.SetCasemapping(casemapASCII)
 	dc.hostname = remoteAddr
@@ -702,31 +709,15 @@ func (dc *downstreamConn) handleMessage(ctx context.Context, msg *irc.Message) e
 func (dc *downstreamConn) handleMessageUnregistered(ctx context.Context, msg *irc.Message) error {
 	switch msg.Command {
 	case "NICK":
-		var nick string
+		if err := parseMessageParams(msg, &dc.registration.nick); err != nil {
-		if err := parseMessageParams(msg, &nick); err != nil {
 			return err
 		}
-		if nick == "" || strings.ContainsAny(nick, illegalNickChars) {
-			return ircError{&irc.Message{
-				Command: irc.ERR_ERRONEUSNICKNAME,
-				Params:  []string{dc.nick, nick, "Nickname contains illegal characters"},
-			}}
-		}
-		nickCM := casemapASCII(nick)
-		if nickCM == serviceNickCM {
-			return ircError{&irc.Message{
-				Command: irc.ERR_NICKNAMEINUSE,
-				Params:  []string{dc.nick, nick, "Nickname reserved for bouncer service"},
-			}}
-		}
-		dc.nick = nick
-		dc.nickCM = nickCM
 	case "USER":
-		if err := parseMessageParams(msg, &dc.rawUsername, nil, nil, &dc.realname); err != nil {
+		if err := parseMessageParams(msg, &dc.registration.username, nil, nil, nil); err != nil {
 			return err
 		}
 	case "PASS":
-		if err := parseMessageParams(msg, &dc.password); err != nil {
+		if err := parseMessageParams(msg, &dc.registration.password); err != nil {
 			return err
 		}
 	case "CAP":
@@ -805,7 +796,7 @@ func (dc *downstreamConn) handleMessageUnregistered(ctx context.Context, msg *ir
 		dc.logger.Printf("unhandled message: %v", msg)
 		return newUnknownCommandError(msg.Command)
 	}
-	if dc.rawUsername != "" && dc.nick != "*" && !dc.negotiatingCaps {
+	if dc.registration.nick != "" && dc.registration.username != "" && !dc.negotiatingCaps {
 		return dc.register(ctx)
 	}
 	return nil
@@ -1269,8 +1260,8 @@ func (dc *downstreamConn) register(ctx context.Context) error {
 		})
 	}
 
-	password := dc.password
+	password := dc.registration.password
-	dc.password = ""
+	dc.registration.password = ""
 	if dc.user == nil {
 		if password == "" {
 			if dc.caps.IsEnabled("sasl") {
@@ -1286,8 +1277,8 @@ func (dc *downstreamConn) register(ctx context.Context) error {
 			}
 		}
 
-		if err := dc.authenticate(ctx, dc.rawUsername, password); err != nil {
+		if err := dc.authenticate(ctx, dc.registration.username, password); err != nil {
-			dc.logger.Printf("PASS authentication error for user %q: %v", dc.rawUsername, err)
+			dc.logger.Printf("PASS authentication error for user %q: %v", dc.registration.username, err)
 			return ircError{&irc.Message{
 				Command: irc.ERR_PASSWDMISMATCH,
 				Params:  []string{dc.nick, authErrorReason(err)},
@@ -1295,7 +1286,7 @@ func (dc *downstreamConn) register(ctx context.Context) error {
 		}
 	}
 
-	_, fallbackClientName, fallbackNetworkName := unmarshalUsername(dc.rawUsername)
+	_, fallbackClientName, fallbackNetworkName := unmarshalUsername(dc.registration.username)
 	if dc.clientName == "" {
 		dc.clientName = fallbackClientName
 	} else if fallbackClientName != "" && dc.clientName != fallbackClientName {
@@ -1314,6 +1305,7 @@ func (dc *downstreamConn) register(ctx context.Context) error {
 	}
 
 	dc.registered = true
+	dc.registration = nil
 	dc.logger.Printf("registration complete for user %q", dc.user.Username)
 	return nil
 }
@@ -1342,7 +1334,19 @@ func (dc *downstreamConn) loadNetwork(ctx context.Context) error {
 		// Some clients only allow specifying the nickname (and use the
 		// nickname as a username too). Strip the network name from the
 		// nickname when auto-saving networks.
-		nick, _, _ := unmarshalUsername(dc.nick)
+		nick, _, _ := unmarshalUsername(dc.registration.nick)
+		if nick == "" || strings.ContainsAny(nick, illegalNickChars) {
+			return ircError{&irc.Message{
+				Command: irc.ERR_ERRONEUSNICKNAME,
+				Params:  []string{dc.nick, dc.registration.nick, "Nickname contains illegal characters"},
+			}}
+		}
+		if casemapASCII(nick) == serviceNickCM {
+			return ircError{&irc.Message{
+				Command: irc.ERR_NICKNAMEINUSE,
+				Params:  []string{dc.nick, dc.registration.nick, "Nickname reserved for bouncer service"},
+			}}
+		}
 
 		dc.logger.Printf("auto-saving network %q", dc.networkName)
 		var err error
@@ -1388,6 +1392,15 @@ func (dc *downstreamConn) welcome(ctx context.Context) error {
 
 	dc.updateSupportedCaps()
 
+	if uc := dc.upstream(); uc != nil {
+		dc.nick = uc.nick
+	} else if dc.network != nil {
+		dc.nick = GetNick(&dc.user.User, &dc.network.Network)
+	} else {
+		dc.nick = dc.user.Username
+	}
+	dc.nickCM = casemapASCII(dc.nick)
+
 	isupport := []string{
 		fmt.Sprintf("CHATHISTORY=%v", chatHistoryLimit),
 		"CASEMAPPING=ascii",
@@ -1452,7 +1465,6 @@ func (dc *downstreamConn) welcome(ctx context.Context) error {
 		})
 	}
 
-	dc.updateNick()
 	dc.updateRealname()
 	dc.updateAccount()