Refactor permission utils to properly account for lack of channel access

PluralKit.Bot/CommandSystem/Context.cs

@@ -9,6 +9,7 @@ using Autofac;
 
 using DSharpPlus;
 using DSharpPlus.Entities;
+using DSharpPlus.Exceptions;
 
 using PluralKit.Bot.Utils;
 using PluralKit.Core;
@@ -281,14 +282,27 @@ namespace PluralKit.Bot
             throw new PKError("You do not have permission to access this information.");
         }
 
-        public DiscordChannel MatchChannel()
+        public async Task<DiscordChannel> MatchChannel()
         {
-            if (!MentionUtils.TryParseChannel(PeekArgument(), out var channel)) return null;
+            if (!MentionUtils.TryParseChannel(PeekArgument(), out var channel)) 
-            var discordChannel = _rest.GetChannelAsync(channel).GetAwaiter().GetResult();
+                return null;
+
+            try
+            {
+                var discordChannel = await _shard.GetChannelAsync(channel);
                 if (discordChannel.Type != ChannelType.Text) return null;
                 
                 PopArgument();
                 return discordChannel;
             }
+            catch (NotFoundException)
+            {
+                return null;
+            }
+            catch (UnauthorizedException)
+            {
+                return null;
+            }
+        }
     }
 }

PluralKit.Bot/Commands/ServerConfig.cs

@@ -25,7 +25,7 @@ namespace PluralKit.Bot
             
             DiscordChannel channel = null;
             if (ctx.HasNext())
-                channel = ctx.MatchChannel() ?? throw new PKSyntaxError("You must pass a #channel to set.");
+                channel = await ctx.MatchChannel() ?? throw new PKSyntaxError("You must pass a #channel to set.");
             if (channel != null && channel.GuildId != ctx.Guild.Id) throw new PKError("That channel is not in this server!");
 
             var cfg = await _data.GetOrCreateGuildConfig(ctx.Guild.Id);
@@ -48,7 +48,7 @@ namespace PluralKit.Bot
             else if (!ctx.HasNext()) throw new PKSyntaxError("You must pass one or more #channels.");
             else while (ctx.HasNext())
             {
-                var channel = ctx.MatchChannel() ?? throw new PKSyntaxError($"Channel \"{ctx.PopArgument().SanitizeMentions()}\" not found.");
+                var channel = await ctx.MatchChannel() ?? throw new PKSyntaxError($"Channel \"{ctx.PopArgument().SanitizeMentions()}\" not found.");
                 if (channel.GuildId != ctx.Guild.Id) throw new PKError($"Channel {ctx.Guild.Id} is not in this server.");
                 affectedChannels.Add(channel);
             }
@@ -73,7 +73,7 @@ namespace PluralKit.Bot
             else if (!ctx.HasNext()) throw new PKSyntaxError("You must pass one or more #channels.");
             else while (ctx.HasNext())
             {
-                var channel = ctx.MatchChannel() ?? throw new PKSyntaxError($"Channel \"{ctx.PopArgument().SanitizeMentions()}\" not found.");
+                var channel = await ctx.MatchChannel() ?? throw new PKSyntaxError($"Channel \"{ctx.PopArgument().SanitizeMentions()}\" not found.");
                 if (channel.GuildId != ctx.Guild.Id) throw new PKError($"Channel {ctx.Guild.Id} is not in this server.");
                 affectedChannels.Add(channel);
             }

PluralKit.Bot/Utils/DiscordUtils.cs

@@ -15,46 +15,53 @@ namespace PluralKit.Bot
         public static DiscordColor Red = new DiscordColor(0xef4b3d);
         public static DiscordColor Gray = new DiscordColor(0x979c9f);
         
+        public static Permissions DM_PERMISSIONS = (Permissions) 0b00000_1000110_1011100110000_000000;
+        
         public static string NameAndMention(this DiscordUser user) {
             return $"{user.Username}#{user.Discriminator} ({user.Mention})";
         }
 
+        // We funnel all "permissions from DiscordMember" calls through here 
+        // This way we can ensure we do the read permission correction everywhere
+        private static Permissions PermissionsInGuild(DiscordChannel channel, DiscordMember member)
+        {
+            var permissions = channel.PermissionsFor(member);
+            
+            // This method doesn't account for channels without read permissions
+            // If we don't have read permissions in the channel, we don't have *any* permissions
+            if ((permissions & Permissions.AccessChannels) != Permissions.AccessChannels)
+                return Permissions.None;
+            
+            return permissions;
+        }
+
         public static async Task<Permissions> PermissionsIn(this DiscordChannel channel, DiscordUser user)
         {
-            if (channel.Guild != null)
+            // Just delegates to PermissionsInSync, but handles the case of a non-member User in a guild properly
-            {
+            // This is a separate method because it requires an async call
-                var member = await channel.Guild.GetMemberAsync(user.Id);
+            if (channel.Guild != null && !(user is DiscordMember))
-                return member.PermissionsIn(channel);
+                return PermissionsInSync(channel, await channel.Guild.GetMemberAsync(user.Id));
-            }
+            return PermissionsInSync(channel, user);
-            
-            if (channel.Type == ChannelType.Private)
-                return (Permissions) 0b00000_1000110_1011100110000_000000;
-
-            return Permissions.None;
         }
         
+        // Same as PermissionsIn, but always synchronous. DiscordUser must be a DiscordMember if channel is in guild.
         public static Permissions PermissionsInSync(this DiscordChannel channel, DiscordUser user)
         {
-            if (user is DiscordMember dm && channel.Guild != null)
+            if (channel.Guild != null && !(user is DiscordMember))
-                return dm.PermissionsIn(channel);
+                throw new ArgumentException("Function was passed a guild channel but a non-member DiscordUser");
-            
-            if (channel.Type == ChannelType.Private)
-                return (Permissions) 0b00000_1000110_1011100110000_000000;
             
+            if (user is DiscordMember m) return PermissionsInGuild(channel, m);
+            if (channel.Type == ChannelType.Private) return DM_PERMISSIONS;
             return Permissions.None;
         }
 
         public static Permissions BotPermissions(this DiscordChannel channel)
         {
+            // TODO: can we get a CurrentMember somehow without a guild context?
+            // at least, without somehow getting a DiscordClient reference as an arg(which I don't want to do)
             if (channel.Guild != null)
-            {
+                return PermissionsInSync(channel, channel.Guild.CurrentMember);
-                var member = channel.Guild.CurrentMember;
+            if (channel.Type == ChannelType.Private) return DM_PERMISSIONS;
-                return channel.PermissionsFor(member);
-            }
-
-            if (channel.Type == ChannelType.Private)
-                return (Permissions) 0b00000_1000110_1011100110000_000000;
-
             return Permissions.None;
         }