hid: add WebIRC support

Such clients can only be identified through STATS L.

It's a bit weird to abuse the "port" field this way,
but right now, it serves its purpose.

hid/main.go

@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2014 - 2018, Přemysl Eric Janouch <p@janouch.name>
+// Copyright (c) 2014 - 2022, Přemysl Eric Janouch <p@janouch.name>
 //
 // Permission to use, copy, modify, and/or distribute this software for any
 // purpose with or without fee is hereby granted.
@@ -414,6 +414,7 @@ var configTable = []simpleConfigItem{
 	{"bind", ":6667", "Bind addresses of the IRC server"},
 	{"tls_cert", "", "Server TLS certificate (PEM)"},
 	{"tls_key", "", "Server TLS private key (PEM)"},
+	{"webirc_password", "", "Password for WebIRC"},
 
 	{"operators", "", "IRCop TLS certificate SHA-256 fingerprints"},
 
@@ -1437,6 +1438,44 @@ var ircCapHandlers = map[string]func(*client, *ircCapArgs){
 // XXX: Maybe these also deserve to be methods for client?  They operate on
 // global state, though.
 
+func ircParseWEBIRCOptions(options string, out map[string]string) {
+	for _, option := range strings.Split(options, " ") {
+		if equal := strings.IndexByte(option, '='); equal < 0 {
+			out[option] = ""
+		} else {
+			out[option[:equal]] = ircUnescapeMessageTag(option[equal+1:])
+		}
+	}
+}
+
+func ircHandleWEBIRC(msg *message, c *client) {
+	if len(msg.params) < 4 {
+		c.sendReply(ERR_NEEDMOREPARAMS, msg.command)
+		return
+	}
+
+	password, gateway, hostname := msg.params[0], msg.params[1], msg.params[2]
+	if config["webirc_password"] != password {
+		c.closeLink("Invalid WebIRC password")
+		return
+	}
+
+	options := make(map[string]string)
+	if len(msg.params) >= 5 {
+		ircParseWEBIRCOptions(msg.params[4], options)
+	}
+
+	c.hostname = hostname
+	c.port = "WebIRC-" + gateway
+	c.address = net.JoinHostPort(hostname, c.port)
+
+	// Note that this overrides the gateway's certificate, conditionally.
+	fp, _ := options["certfp-sha-256"]
+	if _, secure := options["secure"]; secure && ircIsValidFingerprint(fp) {
+		c.tlsCertFingerprint = strings.ToLower(fp)
+	}
+}
+
 func ircHandleCAP(msg *message, c *client) {
 	if len(msg.params) < 1 {
 		c.sendReply(ERR_NEEDMOREPARAMS, msg.command)
@@ -2908,6 +2947,7 @@ func ircHandleDIE(msg *message, c *client) {
 // TODO: Add a minimal parameter count?
 // TODO: Add a field for oper-only commands? Use flags?
 var ircHandlers = map[string]*ircCommand{
+	"WEBIRC": {false, ircHandleWEBIRC, 0, 0},
 	"CAP":    {false, ircHandleCAP, 0, 0},
 	"PASS":   {false, ircHandlePASS, 0, 0},
 	"NICK":   {false, ircHandleNICK, 0, 0},