feat: implement ISUPPORT and add support for a few easy features

fix: CAP ACK commands with no acknowledged capabilities causing an OOB. Also log unsupported and unknown capabilities and features.
2026-10-24 02:12:33 +00:00 · 2025-08-15 21:10:52 +02:00
parent 4be731c813
commit 41645fb679
4 changed files with 141 additions and 65 deletions
@@ -95,9 +95,13 @@ type Client struct {

 	// The acknowledged capabilities
 	EnabledCapabilities Capabilities
+
+	// The features currently enabled for this client
+	EnabledFeatures Features
 }

 type Capabilities map[string]string
+type Features map[string]string

 type MsgFmtOpts struct {
 	WithTimestamp bool
@@ -58,7 +58,7 @@ const (
 	NOTICE  = "NOTICE"  // Send notices between users and to channels.

 	// Operator Messages
-	KILL = "KILL" // CLose connection between a client and the server. IRC Operators only (do we need this ??)
+	KILL = "KILL" // Close connection between a client and the server. IRC Operators only (do we need this ??)

 	// Optional Messages
 	AWAY     = "AWAY"     // Indicate that the client (user) is away/afk/etc..
@@ -305,64 +305,67 @@ const (

 /* --- RPL_ISUPPORT Parameters --- */
 var Features = map[string]bool{
-	"ACCEPT":      true,
+	"ACCEPT": false,
+	// The AWAYLEN parameter indicates the maximum length for the <reason> of an AWAY command.
+	// If an AWAY <reason> has more characters than this parameter, it may be silently truncated by the server before being passed on to other clients.
+	// Clients MAY receive an AWAY <reason> that has more characters than this parameter
 	"AWAYLEN":     true,
-	"BOT":         true,
-	"CALLERID":    true,
-	"CASEMAPPING": true,
-	"CHANLIMIT":   true,
-	"CHANMODES":   true,
-	"CHANNELLEN":  true,
-	"CHANTYPES":   true, // Channel Types. Default is #. Available are #&
-	"CHARSET":     true, // Deprecated but might still be used
-	"CLIENTVER":   true, // Deprecated but might still be used
-	"CNOTICE":     true,
-	"CPRIVMSG":    true,
-	"DEAF":        true,
-	"ELIST":       true,
-	"ESILENCE":    true,
-	"ETRACE":      true,
-	"EXCEPTS":     true,
-	"EXTBAN":      true,
-	"FNC":         true, // Deprecated but might still be used
-	"INVEX":       true,
-	"KEYLEN":      true,
+	"BOT":         false,
+	"CALLERID":    false,
+	"CASEMAPPING": false,
+	"CHANLIMIT":   false,
+	"CHANMODES":   false,
+	"CHANNELLEN":  false,
+	"CHANTYPES":   false, // Channel Types. Default is #. Available are #&
+	"CHARSET":     false, // Deprecated but might still be used
+	"CLIENTVER":   false, // Deprecated but might still be used
+	"CNOTICE":     false,
+	"CPRIVMSG":    false,
+	"DEAF":        false,
+	"ELIST":       false,
+	"ESILENCE":    false,
+	"ETRACE":      false,
+	"EXCEPTS":     false,
+	"EXTBAN":      false,
+	"FNC":         false, // Deprecated but might still be used
+	"INVEX":       false,
+	"KEYLEN":      false,
 	"KICKLEN":     true,
-	"KNOCK":       true,
-	"LINELEN":     true, // Proposed
-	"MAP":         true, // Deprecated but might still be used
-	"MAXBANS":     true, // Deprecated but might still be used
-	"MAXCHANNELS": true, // Deprecated but might still be used
-	"MAXLIST":     true,
-	"MAXNICKLEN":  true,
-	"MAXPARA":     true, // Deprecated but might still be used
-	"MAXTARGETS":  true,
-	"METADATA":    true,
-	"MODES":       true,
-	"MONITOR":     true,
-	"NAMESX":      true, // Deprecated but might still be used
+	"KNOCK":       false,
+	"LINELEN":     false, // Proposed
+	"MAP":         false, // Deprecated but might still be used
+	"MAXBANS":     false, // Deprecated but might still be used
+	"MAXCHANNELS": false, // Deprecated but might still be used
+	"MAXLIST":     false,
+	"MAXNICKLEN":  false,
+	"MAXPARA":     false, // Deprecated but might still be used
+	"MAXTARGETS":  false,
+	"METADATA":    false,
+	"MODES":       false,
+	"MONITOR":     false,
+	"NAMESX":      false, // Deprecated but might still be used
 	"NETWORK":     true,
 	"NICKLEN":     true,
-	"OVERRIDE":    true,
-	"PREFIX":      true,
-	"SAFELIST":    true,
-	"SECURELIST":  true,
-	"SILENCE":     true,
-	"SSL":         true, // Deprecated but might still be used
-	"STARTTLS":    true, // Deprecated but might still be used
-	"STATUSMSG":   true,
-	"STD":         true, // Deprecated but might still be used
-	"TARGMAX":     true,
+	"OVERRIDE":    false,
+	"PREFIX":      false,
+	"SAFELIST":    false,
+	"SECURELIST":  false,
+	"SILENCE":     false,
+	"SSL":         false, // Deprecated but might still be used
+	"STARTTLS":    false, // Deprecated but might still be used
+	"STATUSMSG":   false,
+	"STD":         false, // Deprecated but might still be used
+	"TARGMAX":     false,
 	"TOPICLEN":    true,
-	"UHNAMES":     true, // Deprecated but might still be used
-	"USERIP":      true,
-	"USERLEN":     true, // Proposed
-	"VBANLIST":    true, // Deprecared but might still be used
-	"VLIST":       true,
-	"WALLCHOPS":   true, // Deprecated but might still be used
-	"WALLVOICES":  true, // Deprecated but might still be used
-	"WATCH":       true,
-	"WHOX":        true,
+	"UHNAMES":     false, // Deprecated but might still be used
+	"USERIP":      false,
+	"USERLEN":     false, // Proposed
+	"VBANLIST":    false, // Deprecared but might still be used
+	"VLIST":       false,
+	"WALLCHOPS":   false, // Deprecated but might still be used
+	"WALLVOICES":  false, // Deprecated but might still be used
+	"WATCH":       false,
+	"WHOX":        false,
 }

 var Capabilities = map[string]bool{
@@ -35,6 +35,7 @@ import (

 func ReadLoop(client *irc.Client) {
 	// 512 bytes as a base + 8192 additional bytes for tags
+	// as specified here: https://modern.ircdocs.horse/#message-format
 	r := bufio.NewReaderSize(client.TCPConn, 8192+512)

 	for {
@@ -235,18 +236,22 @@ func handleCAP(msg irc.Message, client *irc.Client) {
 				value = parts[1]
 			}

-			if commands.Capabilities[key] {
-				// When the final parameter approaches 510 bytes,
-				// we send multiple REQ commands
-				// (https://ircv3.net/specs/extensions/capability-negotiation.html#the-cap-req-subcommand)
-				if length+len(capability) >= 500 {
-					recognizedCaps = append(recognizedCaps, capabilities)
-					capabilities = make(irc.Capabilities, 0)
-					length = 0
-				}
+			if capEnabled, ok := commands.Capabilities[key]; ok {
+				if capEnabled {
+					// When the final parameter approaches 510 bytes,
+					// we send multiple REQ commands
+					// (https://ircv3.net/specs/extensions/capability-negotiation.html#the-cap-req-subcommand)
+					if length+len(capability) >= 500 {
+						recognizedCaps = append(recognizedCaps, capabilities)
+						capabilities = make(irc.Capabilities, 0)
+						length = 0
+					}

-				capabilities[key] = value
-				length += len(capability)
+					capabilities[key] = value
+					length += len(capability)
+				} else {
+					log.Println("Unsupported capability:", capability)
+				}
 			} else {
 				log.Println("Unknown capability:", capability)
 			}
@@ -266,6 +271,9 @@ func handleCAP(msg irc.Message, client *irc.Client) {
 		}
 		client.SendCommand(commands.CAP, "END")
 	case "ACK":
+		if msg.Parameters[2] == "" {
+			return
+		}
 		caps := strings.Split(msg.Parameters[2], " ")
 		for _, capability := range caps {
 			if capability[0] == '-' {
@@ -342,6 +350,34 @@ func handleMYINFO(msg irc.Message, client *irc.Client) {
 	client.Channels[0].AppendMsg(msg.Timestamp, info, msgOpts)
 }

+func handleISUPPORT(msg irc.Message, client *irc.Client) {
+	msgOpts := irc.MsgFmtOpts{
+		WithTimestamp: true,
+		AsServerMsg:   true,
+	}
+
+	for _, token := range msg.Parameters[1 : len(msg.Parameters)-1] {
+		splits := strings.Split(token, "=")
+		key := splits[0]
+		value := ""
+		if len(splits) > 1 {
+			value = splits[1]
+		}
+
+		if supported, known := commands.Features[key]; known {
+			if supported {
+				client.EnabledFeatures[key] = value
+			} else {
+				log.Printf("Unsupported feature: \"%v\" with value: \"%v\"\n", key, value)
+			}
+		} else {
+			log.Printf("Unknown feature: \"%v\" with value: \"%v\"\n", key, value)
+		}
+
+		client.Channels[0].AppendMsg(msg.Timestamp, token, msgOpts)
+	}
+}
+
 func handleLUSERCLIENT(msg irc.Message, client *irc.Client) {
 	message := msg.Parameters[1]

@@ -695,6 +731,8 @@ func HandleCommand(msg irc.Message, client *irc.Client) {
 		handleCREATED(msg, client)
 	case commands.RPL_MYINFO:
 		handleMYINFO(msg, client)
+	case commands.RPL_ISUPPORT:
+		handleISUPPORT(msg, client)
 	case commands.RPL_LUSERCLIENT:
 		handleLUSERCLIENT(msg, client)
 	case commands.RPL_LUSEROP: