Add support for post-connection-registration upstream SASL auth

Once the downstream connection has logged in with their bouncer
credentials, allow them to issue more SASL auths which will be
redirected to the upstream network. This allows downstream clients
to provide UIs to login to transparently login to upstream networks.

downstream.go

@@ -244,6 +244,11 @@ var passthroughIsupport = map[string]bool{
 	"WHOX":          true,
 }
 
+type downstreamSASL struct {
+	server                       sasl.Server
+	plainUsername, plainPassword string
+}
+
 type downstreamConn struct {
 	conn
 
@@ -267,12 +272,11 @@ type downstreamConn struct {
 	capVersion      int
 	supportedCaps   map[string]string
 	caps            map[string]bool
+	sasl            *downstreamSASL
 
 	lastBatchRef uint64
 
 	monitored casemapMap
-
-	saslServer sasl.Server
 }
 
 func newDownstreamConn(srv *Server, ic ircConn, id uint64) *downstreamConn {
@@ -686,102 +690,28 @@ func (dc *downstreamConn) handleMessageUnregistered(ctx context.Context, msg *ir
 			return err
 		}
 	case "AUTHENTICATE":
-		if !dc.caps["sasl"] {
+		credentials, err := dc.handleAuthenticateCommand(msg)
-			return ircError{&irc.Message{
-				Prefix:  dc.srv.prefix(),
-				Command: irc.ERR_SASLFAIL,
-				Params:  []string{"*", "AUTHENTICATE requires the \"sasl\" capability to be enabled"},
-			}}
-		}
-		if len(msg.Params) == 0 {
-			return ircError{&irc.Message{
-				Prefix:  dc.srv.prefix(),
-				Command: irc.ERR_SASLFAIL,
-				Params:  []string{"*", "Missing AUTHENTICATE argument"},
-			}}
-		}
-
-		var resp []byte
-		if msg.Params[0] == "*" {
-			dc.saslServer = nil
-			return ircError{&irc.Message{
-				Prefix:  dc.srv.prefix(),
-				Command: irc.ERR_SASLABORTED,
-				Params:  []string{"*", "SASL authentication aborted"},
-			}}
-		} else if dc.saslServer == nil {
-			mech := strings.ToUpper(msg.Params[0])
-			switch mech {
-			case "PLAIN":
-				dc.saslServer = sasl.NewPlainServer(sasl.PlainAuthenticator(func(identity, username, password string) error {
-					// TODO: we can't use the command context here, because it
-					// gets cancelled once the command handler returns. SASL
-					// might take multiple AUTHENTICATE commands to complete.
-					return dc.authenticate(context.TODO(), username, password)
-				}))
-			default:
-				return ircError{&irc.Message{
-					Prefix:  dc.srv.prefix(),
-					Command: irc.ERR_SASLFAIL,
-					Params:  []string{"*", fmt.Sprintf("Unsupported SASL mechanism %q", mech)},
-				}}
-			}
-		} else if msg.Params[0] == "+" {
-			resp = nil
-		} else {
-			// TODO: multi-line messages
-			var err error
-			resp, err = base64.StdEncoding.DecodeString(msg.Params[0])
-			if err != nil {
-				dc.saslServer = nil
-				return ircError{&irc.Message{
-					Prefix:  dc.srv.prefix(),
-					Command: irc.ERR_SASLFAIL,
-					Params:  []string{"*", "Invalid base64-encoded response"},
-				}}
-			}
-		}
-
-		challenge, done, err := dc.saslServer.Next(resp)
 		if err != nil {
-			dc.saslServer = nil
+			return err
-			if ircErr, ok := err.(ircError); ok && ircErr.Message.Command == irc.ERR_PASSWDMISMATCH {
+		} else if credentials == nil {
-				return ircError{&irc.Message{
+			break
-					Prefix:  dc.srv.prefix(),
+		}
-					Command: irc.ERR_SASLFAIL,
+
-					Params:  []string{"*", ircErr.Message.Params[1]},
+		if err := dc.authenticate(ctx, credentials.plainUsername, credentials.plainPassword); err != nil {
-				}}
+			dc.logger.Printf("SASL authentication error: %v", err)
-			}
+			dc.endSASL(&irc.Message{
-			dc.SendMessage(&irc.Message{
 				Prefix:  dc.srv.prefix(),
 				Command: irc.ERR_SASLFAIL,
-				Params:  []string{"*", "SASL error"},
+				Params:  []string{"Authentication failed"},
-			})
-			return fmt.Errorf("SASL authentication failed: %v", err)
-		} else if done {
-			dc.saslServer = nil
-			// Technically we should send RPL_LOGGEDIN here. However we use
-			// RPL_LOGGEDIN to mirror the upstream connection status. Let's see
-			// how many clients that breaks. See:
-			// https://github.com/ircv3/ircv3-specifications/pull/476
-			dc.SendMessage(&irc.Message{
-				Prefix:  dc.srv.prefix(),
-				Command: irc.RPL_SASLSUCCESS,
-				Params:  []string{dc.nick, "SASL authentication successful"},
-			})
-		} else {
-			challengeStr := "+"
-			if len(challenge) > 0 {
-				challengeStr = base64.StdEncoding.EncodeToString(challenge)
-			}
-
-			// TODO: multi-line messages
-			dc.SendMessage(&irc.Message{
-				Prefix:  dc.srv.prefix(),
-				Command: "AUTHENTICATE",
-				Params:  []string{challengeStr},
 			})
+			break
 		}
+
+		// Technically we should send RPL_LOGGEDIN here. However we use
+		// RPL_LOGGEDIN to mirror the upstream connection status. Let's
+		// see how many clients that breaks. See:
+		// https://github.com/ircv3/ircv3-specifications/pull/476
+		dc.endSASL(nil)
 	case "BOUNCER":
 		var subcommand string
 		if err := parseMessageParams(msg, &subcommand); err != nil {
@@ -951,6 +881,107 @@ func (dc *downstreamConn) handleCapCommand(cmd string, args []string) error {
 	return nil
 }
 
+func (dc *downstreamConn) handleAuthenticateCommand(msg *irc.Message) (result *downstreamSASL, err error) {
+	defer func() {
+		if err != nil {
+			dc.sasl = nil
+		}
+	}()
+
+	if !dc.caps["sasl"] {
+		return nil, ircError{&irc.Message{
+			Prefix:  dc.srv.prefix(),
+			Command: irc.ERR_SASLFAIL,
+			Params:  []string{"*", "AUTHENTICATE requires the \"sasl\" capability to be enabled"},
+		}}
+	}
+	if len(msg.Params) == 0 {
+		return nil, ircError{&irc.Message{
+			Prefix:  dc.srv.prefix(),
+			Command: irc.ERR_SASLFAIL,
+			Params:  []string{"*", "Missing AUTHENTICATE argument"},
+		}}
+	}
+	if msg.Params[0] == "*" {
+		return nil, ircError{&irc.Message{
+			Prefix:  dc.srv.prefix(),
+			Command: irc.ERR_SASLABORTED,
+			Params:  []string{"*", "SASL authentication aborted"},
+		}}
+	}
+
+	var resp []byte
+	if dc.sasl == nil {
+		mech := strings.ToUpper(msg.Params[0])
+		var server sasl.Server
+		switch mech {
+		case "PLAIN":
+			server = sasl.NewPlainServer(sasl.PlainAuthenticator(func(identity, username, password string) error {
+				dc.sasl.plainUsername = username
+				dc.sasl.plainPassword = password
+				return nil
+			}))
+		default:
+			return nil, ircError{&irc.Message{
+				Prefix:  dc.srv.prefix(),
+				Command: irc.ERR_SASLFAIL,
+				Params:  []string{"*", fmt.Sprintf("Unsupported SASL mechanism %q", mech)},
+			}}
+		}
+
+		dc.sasl = &downstreamSASL{server: server}
+	} else {
+		// TODO: multi-line messages
+		if msg.Params[0] == "+" {
+			resp = nil
+		} else if resp, err = base64.StdEncoding.DecodeString(msg.Params[0]); err != nil {
+			return nil, ircError{&irc.Message{
+				Prefix:  dc.srv.prefix(),
+				Command: irc.ERR_SASLFAIL,
+				Params:  []string{"*", "Invalid base64-encoded response"},
+			}}
+		}
+	}
+
+	challenge, done, err := dc.sasl.server.Next(resp)
+	if err != nil {
+		return nil, err
+	} else if done {
+		return dc.sasl, nil
+	} else {
+		challengeStr := "+"
+		if len(challenge) > 0 {
+			challengeStr = base64.StdEncoding.EncodeToString(challenge)
+		}
+
+		// TODO: multi-line messages
+		dc.SendMessage(&irc.Message{
+			Prefix:  dc.srv.prefix(),
+			Command: "AUTHENTICATE",
+			Params:  []string{challengeStr},
+		})
+		return nil, nil
+	}
+}
+
+func (dc *downstreamConn) endSASL(msg *irc.Message) {
+	if dc.sasl == nil {
+		return
+	}
+
+	dc.sasl = nil
+
+	if msg != nil {
+		dc.SendMessage(msg)
+	} else {
+		dc.SendMessage(&irc.Message{
+			Prefix:  dc.srv.prefix(),
+			Command: irc.RPL_SASLSUCCESS,
+			Params:  []string{dc.nick, "SASL authentication successful"},
+		})
+	}
+}
+
 func (dc *downstreamConn) setSupportedCap(name, value string) {
 	prevValue, hasPrev := dc.supportedCaps[name]
 	changed := !hasPrev || prevValue != value
@@ -1141,9 +1172,8 @@ func (dc *downstreamConn) register(ctx context.Context) error {
 		return fmt.Errorf("tried to register twice")
 	}
 
-	if dc.saslServer != nil {
+	if dc.sasl != nil {
-		dc.saslServer = nil
+		dc.endSASL(&irc.Message{
-		dc.SendMessage(&irc.Message{
 			Prefix:  dc.srv.prefix(),
 			Command: irc.ERR_SASLABORTED,
 			Params:  []string{"*", "SASL authentication aborted"},
@@ -2330,6 +2360,40 @@ func (dc *downstreamConn) handleMessageRegistered(ctx context.Context, msg *irc.
 			Command: "INVITE",
 			Params:  []string{upstreamUser, upstreamChannel},
 		})
+	case "AUTHENTICATE":
+		// Post-connection-registration AUTHENTICATE is unsupported in
+		// multi-upstream mode, or if the upstream doesn't support SASL
+		uc := dc.upstream()
+		if uc == nil || !uc.caps["sasl"] {
+			return ircError{&irc.Message{
+				Prefix:  dc.srv.prefix(),
+				Command: irc.ERR_SASLFAIL,
+				Params:  []string{dc.nick, "Upstream network authentication not supported"},
+			}}
+		}
+
+		credentials, err := dc.handleAuthenticateCommand(msg)
+		if err != nil {
+			return err
+		}
+
+		if credentials != nil {
+			if uc.saslClient != nil {
+				dc.endSASL(&irc.Message{
+					Prefix:  dc.srv.prefix(),
+					Command: irc.ERR_SASLFAIL,
+					Params:  []string{dc.nick, "Another authentication attempt is already in progress"},
+				})
+				return nil
+			}
+
+			uc.logger.Printf("starting post-registration SASL PLAIN authentication with username %q", credentials.plainUsername)
+			uc.saslClient = sasl.NewPlainClient("", credentials.plainUsername, credentials.plainPassword)
+			uc.enqueueCommand(dc, &irc.Message{
+				Command: "AUTHENTICATE",
+				Params:  []string{"PLAIN"},
+			})
+		}
 	case "MONITOR":
 		// MONITOR is unsupported in multi-upstream mode
 		uc := dc.upstream()
@@ -2700,23 +2764,8 @@ func (dc *downstreamConn) handleMessageRegistered(ctx context.Context, msg *irc.
 
 func (dc *downstreamConn) handleNickServPRIVMSG(ctx context.Context, uc *upstreamConn, text string) {
 	username, password, ok := parseNickServCredentials(text, uc.nick)
-	if !ok {
+	if ok {
-		return
+		uc.network.autoSaveSASLPlain(ctx, username, password)
-	}
-
-	// User may have e.g. EXTERNAL mechanism configured. We do not want to
-	// automatically erase the key pair or any other credentials.
-	if uc.network.SASL.Mechanism != "" && uc.network.SASL.Mechanism != "PLAIN" {
-		return
-	}
-
-	dc.logger.Printf("auto-saving NickServ credentials with username %q", username)
-	n := uc.network
-	n.SASL.Mechanism = "PLAIN"
-	n.SASL.Plain.Username = username
-	n.SASL.Plain.Password = password
-	if err := dc.srv.db.StoreNetwork(ctx, dc.user.ID, &n.Network); err != nil {
-		dc.logger.Printf("failed to save NickServ credentials: %v", err)
 	}
 }
 

upstream.go

@@ -31,6 +31,7 @@ var permanentUpstreamCaps = map[string]bool{
 	"labeled-response": true,
 	"message-tags":     true,
 	"multi-prefix":     true,
+	"sasl":             true,
 	"server-time":      true,
 	"setname":          true,
 
@@ -293,6 +294,12 @@ func (uc *upstreamConn) endPendingCommands() {
 					Command: irc.RPL_ENDOFWHO,
 					Params:  []string{dc.nick, mask, "End of /WHO"},
 				})
+			case "AUTHENTICATE":
+				dc.endSASL(&irc.Message{
+					Prefix:  dc.srv.prefix(),
+					Command: irc.ERR_SASLABORTED,
+					Params:  []string{dc.nick, "SASL authentication aborted"},
+				})
 			default:
 				panic(fmt.Errorf("Unsupported pending command %q", pendingCmd.msg.Command))
 			}
@@ -311,7 +318,7 @@ func (uc *upstreamConn) sendNextPendingCommand(cmd string) {
 
 func (uc *upstreamConn) enqueueCommand(dc *downstreamConn, msg *irc.Message) {
 	switch msg.Command {
-	case "LIST", "WHO":
+	case "LIST", "WHO", "AUTHENTICATE":
 		// Supported
 	default:
 		panic(fmt.Errorf("Unsupported pending command %q", msg.Command))
@@ -612,10 +619,20 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 		uc.saslClient = nil
 		uc.saslStarted = false
 
-		uc.SendMessage(&irc.Message{
+		if dc, _ := uc.dequeueCommand("AUTHENTICATE"); dc != nil && dc.sasl != nil {
-			Command: "CAP",
+			if msg.Command == irc.RPL_SASLSUCCESS {
-			Params:  []string{"END"},
+				uc.network.autoSaveSASLPlain(context.TODO(), dc.sasl.plainUsername, dc.sasl.plainPassword)
-		})
+			}
+
+			dc.endSASL(msg)
+		}
+
+		if !uc.registered {
+			uc.SendMessage(&irc.Message{
+				Command: "CAP",
+				Params:  []string{"END"},
+			})
+		}
 	case irc.RPL_WELCOME:
 		uc.registered = true
 		uc.logger.Printf("connection registered")
@@ -1704,10 +1721,6 @@ func (uc *upstreamConn) requestCaps() {
 		}
 	}
 
-	if uc.requestSASL() && !uc.caps["sasl"] {
-		requestCaps = append(requestCaps, "sasl")
-	}
-
 	if len(requestCaps) == 0 {
 		return
 	}
@@ -1749,6 +1762,9 @@ func (uc *upstreamConn) handleCapAck(name string, ok bool) error {
 
 	switch name {
 	case "sasl":
+		if !uc.requestSASL() {
+			return nil
+		}
 		if !ok {
 			uc.logger.Printf("server refused to acknowledge the SASL capability")
 			return nil

user.go

@@ -404,6 +404,22 @@ func (net *network) detachedMessageNeedsRelay(ch *Channel, msg *irc.Message) boo
 	return ch.RelayDetached == FilterMessage || ((ch.RelayDetached == FilterHighlight || ch.RelayDetached == FilterDefault) && highlight)
 }
 
+func (net *network) autoSaveSASLPlain(ctx context.Context, username, password string) {
+	// User may have e.g. EXTERNAL mechanism configured. We do not want to
+	// automatically erase the key pair or any other credentials.
+	if net.SASL.Mechanism != "" && net.SASL.Mechanism != "PLAIN" {
+		return
+	}
+
+	net.logger.Printf("auto-saving SASL PLAIN credentials with username %q", username)
+	net.SASL.Mechanism = "PLAIN"
+	net.SASL.Plain.Username = username
+	net.SASL.Plain.Password = password
+	if err := net.user.srv.db.StoreNetwork(ctx, net.user.ID, &net.Network); err != nil {
+		net.logger.Printf("failed to save SASL PLAIN credentials: %v", err)
+	}
+}
+
 type user struct {
 	User
 	srv    *Server