discord: Add AllowMention to restrict allowed mentions (#1462)

* Add DisablePingEveryoneHere/DisablePingRoles/DisablePingUsers keys to config

* Add basic AllowedMentions behavior to discord webhooks

* Initialize b.AllowedMentions on Discord Bridger init

* Call b.getAllowedMentions on each webhook to allow config hot reloading

* Add AllowedMentions on all Discord webhooks/messages

* Add DisablePingEveryoneHere/DisablePingRoles/DisablePingUsers to matterbridge.toml.sample

* Change 'Disable' for 'Allow' and revert logic in Discord AllowedMentions

* Update Discord AllowedMentions in matterbridge.toml.sample

* Fix typo in DisableWebPagePreview

* Replace 'AllowPingEveryoneHere' with 'AllowPingEveryone'

* Replace 3 AllowPingEveryone/Roles/Users bools with an array

* Fix typo

bridge/config/config.go

@@ -85,6 +85,7 @@ type ChannelMember struct {
 type ChannelMembers []ChannelMember
 
 type Protocol struct {
+	AllowMention           []string // discord
 	AuthCode               string   // steam
 	BindAddress            string   // mattermost, slack // DEPRECATED
 	Buffer                 int      // api

bridge/discord/discord.go

@@ -305,6 +305,7 @@ func (b *Bdiscord) handleEventBotUser(msg *config.Message, channelID string) (st
 
 	m := discordgo.MessageSend{
 		Content:         msg.Username + msg.Text,
+		AllowedMentions: b.getAllowedMentions(),
 	}
 
 	if msg.ParentValid() {
@@ -337,6 +338,7 @@ func (b *Bdiscord) handleUploadFile(msg *config.Message, channelID string) (stri
 		m := discordgo.MessageSend{
 			Content:         msg.Username + fi.Comment,
 			Files:           []*discordgo.File{&file},
+			AllowedMentions: b.getAllowedMentions(),
 		}
 		_, err = b.c.ChannelMessageSendComplex(channelID, &m)
 		if err != nil {

bridge/discord/helpers.go

@@ -9,6 +9,30 @@ import (
 	"github.com/matterbridge/discordgo"
 )
 
+func (b *Bdiscord) getAllowedMentions() *discordgo.MessageAllowedMentions {
+	// If AllowMention is not specified, then allow all mentions (default Discord behavior)
+	if !b.IsKeySet("AllowMention") {
+		return nil
+	}
+
+	// Otherwise, allow only the mentions that are specified
+	allowedMentionTypes := make([]discordgo.AllowedMentionType, 0, 3)
+	for _, m := range b.GetStringSlice("AllowMention") {
+		switch m {
+		case "everyone":
+			allowedMentionTypes = append(allowedMentionTypes, discordgo.AllowedMentionTypeEveryone)
+		case "roles":
+			allowedMentionTypes = append(allowedMentionTypes, discordgo.AllowedMentionTypeRoles)
+		case "users":
+			allowedMentionTypes = append(allowedMentionTypes, discordgo.AllowedMentionTypeUsers)
+		}
+	}
+
+	return &discordgo.MessageAllowedMentions{
+		Parse: allowedMentionTypes,
+	}
+}
+
 func (b *Bdiscord) getNick(user *discordgo.User, guildID string) string {
 	b.membersMutex.RLock()
 	defer b.membersMutex.RUnlock()

bridge/discord/webhook.go

@@ -66,6 +66,7 @@ func (b *Bdiscord) webhookSend(msg *config.Message, channelID string) (*discordg
 				Content:         msg.Text,
 				Username:        msg.Username,
 				AvatarURL:       msg.Avatar,
+				AllowedMentions: b.getAllowedMentions(),
 			},
 		)
 		if err != nil {
@@ -92,6 +93,7 @@ func (b *Bdiscord) webhookSend(msg *config.Message, channelID string) (*discordg
 					AvatarURL:       msg.Avatar,
 					File:            &file,
 					Content:         content,
+					AllowedMentions: b.getAllowedMentions(),
 				},
 			)
 			if e2 != nil {
@@ -126,6 +128,7 @@ func (b *Bdiscord) handleEventWebhook(msg *config.Message, channelID string) (st
 		err := b.transmitter.Edit(channelID, msg.ID, &discordgo.WebhookParams{
 			Content:         msg.Text,
 			Username:        msg.Username,
+			AllowedMentions: b.getAllowedMentions(),
 		})
 		if err == nil {
 			return msg.ID, nil

matterbridge.toml.sample

@@ -848,6 +848,14 @@ Server="yourservername"
 ## All settings below can be reloaded by editing the file.
 ## They are also all optional.
 
+# AllowMention controls which mentions are allowed. If not specified, all mentions are allowed.
+# Note that even when a mention is not allowed, it will still be displayed nicely and be clickable. It just prevents the ping/notification.
+#
+# "everyone" allows @everyone and @here mentions
+# "roles" allows @role mentions
+# "users" allows @user mentions
+AllowMention=["everyone", "roles", "users"]
+
 # ShowEmbeds shows the title, description and URL of embedded messages (sent by other bots)
 ShowEmbeds=false