Check permission overwrites before bridging channels

.gitignore

@@ -1,5 +1,5 @@
 config.yaml
 discord
 logs/
-mautrix-discord.db
 registration.yaml
+*.db*

discord.go

@@ -1,16 +1,75 @@
 package main
 
 import (
+	"encoding/json"
+	"errors"
+
 	"github.com/bwmarrin/discordgo"
 )
 
-func channelIsBridgeable(channel *discordgo.Channel) bool {
-	switch channel.Type {
-	case discordgo.ChannelTypeGuildText:
-		fallthrough
-	case discordgo.ChannelTypeGuildNews:
-		return true
+func ptrBool(val bool) *bool {
+	return &val
 }
 
+func (user *User) channelIsBridgeable(channel *discordgo.Channel) bool {
+	switch channel.Type {
+	case discordgo.ChannelTypeGuildText, discordgo.ChannelTypeGuildNews:
+		// allowed
+	default:
+		// everything else is not allowed
 		return false
 	}
+
+	hasRole := map[string]bool{
+		channel.GuildID: true,
+	}
+	var roles []string
+	member, err := user.Session.State.Member(channel.GuildID, user.DiscordID)
+	if errors.Is(err, discordgo.ErrStateNotFound) {
+		user.log.Debugfln("Fetching own membership in %s to check own roles", channel.GuildID)
+		member, err = user.Session.GuildMember(channel.GuildID, user.DiscordID)
+		if err != nil {
+			user.log.Warnfln("Failed to get own membership in %s from server to determine own roles for bridging %s: %v", channel.GuildID, channel.ID, err)
+		} else {
+			err = user.Session.State.MemberAdd(member)
+			if err != nil {
+				user.log.Warnfln("Failed to add own membership in %s to cache: %v", channel.GuildID, err)
+			}
+		}
+	} else if err != nil {
+		user.log.Warnfln("Failed to get own membership in %s from cache to determine own roles for bridging %s: %v", channel.GuildID, channel.ID, err)
+	}
+	if member != nil {
+		roles = member.Roles
+		for _, role := range member.Roles {
+			hasRole[role] = true
+		}
+	}
+	var userAllowed, roleAllowed *bool
+	for _, override := range channel.PermissionOverwrites {
+		if override.Type == discordgo.PermissionOverwriteTypeMember && override.ID == user.DiscordID {
+			if override.Allow&discordgo.PermissionViewChannel > 0 {
+				userAllowed = ptrBool(true)
+			} else if override.Deny&discordgo.PermissionViewChannel > 0 {
+				userAllowed = ptrBool(false)
+			}
+		} else if override.Type == discordgo.PermissionOverwriteTypeRole && hasRole[override.ID] {
+			if override.Allow&discordgo.PermissionViewChannel > 0 {
+				roleAllowed = ptrBool(true)
+			} else if override.Deny&discordgo.PermissionViewChannel > 0 {
+				roleAllowed = ptrBool(false)
+			}
+		}
+	}
+	allowed := true
+	if userAllowed != nil {
+		allowed = *userAllowed
+	} else if roleAllowed != nil {
+		allowed = *roleAllowed
+	}
+	if !allowed {
+		dat, _ := json.Marshal(channel.PermissionOverwrites)
+		user.log.Debugfln("Permission overwrites (%s) resulted in %s/%s not being allowed to bridge with roles %+v", dat, channel.GuildID, channel.ID, roles)
+	}
+	return allowed
+}

user.go

@@ -686,7 +686,7 @@ func (user *User) handleGuild(meta *discordgo.Guild, timestamp time.Time, isInSp
 	if len(meta.Channels) > 0 {
 		for _, ch := range meta.Channels {
 			portal := user.GetPortalByMeta(ch)
-			if (guild.AutoBridgeChannels && channelIsBridgeable(ch)) && portal.MXID == "" {
+			if guild.AutoBridgeChannels && portal.MXID == "" && user.channelIsBridgeable(ch) {
 				err := portal.CreateMatrixRoom(user, ch)
 				if err != nil {
 					user.log.Errorfln("Failed to create portal for guild channel %s/%s in initial sync: %v", guild.ID, ch.ID, err)
@@ -744,11 +744,13 @@ func (user *User) channelCreateHandler(_ *discordgo.Session, c *discordgo.Channe
 	}
 	if c.GuildID == "" {
 		user.handlePrivateChannel(portal, c.Channel, time.Now(), true, user.IsInSpace(portal.Key.String()))
-	} else {
+	} else if user.channelIsBridgeable(c.Channel) {
 		err := portal.CreateMatrixRoom(user, c.Channel)
 		if err != nil {
 			user.log.Errorfln("Error creating Matrix room for %s on channel create event: %v", c.ID, err)
 		}
+	} else {
+		user.log.Debugfln("Got channel create event for %s, but it's not bridgeable, ignoring", c.ID)
 	}
 }
 
@@ -1019,7 +1021,7 @@ func (user *User) bridgeGuild(guildID string, everything bool) error {
 	user.addGuildToSpace(guild, false, time.Now())
 	for _, ch := range meta.Channels {
 		portal := user.GetPortalByMeta(ch)
-		if (everything && channelIsBridgeable(ch)) || ch.Type == discordgo.ChannelTypeGuildCategory {
+		if (everything && user.channelIsBridgeable(ch)) || ch.Type == discordgo.ChannelTypeGuildCategory {
 			err = portal.CreateMatrixRoom(user, ch)
 			if err != nil {
 				user.log.Warnfln("Error creating room for guild channel %s: %v", ch.ID, err)