Telegram username Whitelist: only those Users' messages are bridged to IRC

docs/user/config-file-glossary.rst

@@ -171,6 +171,11 @@ Telegram settings
 ``SHOW_DISCONNECT_MESSAGE=true``
     Sends a message to Telegram when the bot disconnects from the IRC side.
 
+``WHITELIST_USERNAMES=""``
+    (Optional) Comma-separated list of Telegram usernames whose messages will be sent to IRC channel.
+    (This always compares the actual @username - not «First name» or alike)
+
+
 **************
 Imgur settings
 **************

env.example

@@ -75,6 +75,8 @@ SHOW_NICK_MESSAGE=false
 SHOW_LEAVE_MESSAGE=false
 LEAVE_MESSAGE_ALLOW_LIST=""
 SHOW_DISCONNECT_MESSAGE=true
+WHITELIST_USERNAMES=""
+
 
 
 ################################################################################

internal/config.go

@@ -65,6 +65,7 @@ type TelegramSettings struct {
 	ShowNickMessage       bool     `env:"SHOW_NICK_MESSAGE" envDefault:"false"`
 	ShowDisconnectMessage bool     `env:"SHOW_DISCONNECT_MESSAGE" envDefault:"false"`
 	MaxMessagePerMinute   int      `env:"MAX_MESSAGE_PER_MINUTE" envDefault:"20"`
+	UsernameWhitelist     []string `env:"WHITELIST_USERNAMES" envSeparator:","`
 }
 
 // ImgurSettings includes settings related to Imgur uploading for Telegram photos

internal/handlers/telegram/handler.go

@@ -17,10 +17,16 @@ type Handler = func(tg *Client, u tgbotapi.Update)
 
 /*
 updateHandler takes in a Telegram Update channel, and determines
-which handler to fire off
+which handler to fire off (optionally only if user is in whitelist)
 */
 func updateHandler(tg *Client, updates tgbotapi.UpdatesChannel) {
 	for u := range updates {
+		if u.Message != nil && u.Message.From != nil && !checkAllowedUsernames(tg.Settings.UsernameWhitelist, u.Message.From.UserName) {
+			tg.logger.LogDebug("Telegram Username is not in whitelist: " + u.Message.From.UserName)
+			tg.logger.LogDebug("Whitelisted Telegram Users: " + strings.Join(tg.Settings.UsernameWhitelist, ", "))
+			continue
+		}
+
 		switch {
 		case u.Message == nil:
 			tg.logger.LogError("Missing message data")

internal/handlers/telegram/helpers.go

@@ -1,6 +1,8 @@
 package telegram
 
 import (
+	"strings"
+
 	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api"
 )
 
@@ -67,3 +69,25 @@ func uploadImage(tg *Client, u tgbotapi.Update) string {
 
 	return getImgurLink(tg, tgLink)
 }
+
+/*
+checkAllowedUsernames checks the Telegram whitelist for a username, and returns whether
+or not the name is in the allow list
+*/
+func checkAllowedUsernames(whitelist []string, username string) bool {
+	// Empty whitelist means no filtering - all users allowed
+	if len(whitelist) == 0 {
+		return true
+	}
+	// Empty username with non-empty whitelist should be rejected
+	if len(username) == 0 {
+		return false
+	}
+	// Filter username against provided whitelist
+	for _, name := range whitelist {
+		if strings.EqualFold(username, name) {
+			return true
+		}
+	}
+	return false
+}