sharp-chat/SharpChat/C2SPacketHandlers/AuthC2SPacketHandler.cs

using SharpChat.Auth;
using SharpChat.Bans;
using SharpChat.Configuration;
using SharpChat.SockChat.S2CPackets;

namespace SharpChat.C2SPacketHandlers;

public class AuthC2SPacketHandler(
    AuthClient authClient,
    BansClient bansClient,
    Channel defaultChannel,
    CachedValue<int> maxMsgLength,
    CachedValue<int> maxConns
) : C2SPacketHandler {
    private readonly Channel DefaultChannel = defaultChannel ?? throw new ArgumentNullException(nameof(defaultChannel));
    private readonly CachedValue<int> MaxMessageLength = maxMsgLength ?? throw new ArgumentNullException(nameof(maxMsgLength));
    private readonly CachedValue<int> MaxConnections = maxConns ?? throw new ArgumentNullException(nameof(maxConns));

    public bool IsMatch(C2SPacketHandlerContext ctx) {
        return ctx.CheckPacketId("1");
    }

    public async Task Handle(C2SPacketHandlerContext ctx) {
        string[] args = ctx.SplitText(3);

        string? authMethod = args.ElementAtOrDefault(1);
        string? authToken = args.ElementAtOrDefault(2);

        if(string.IsNullOrWhiteSpace(authMethod) || string.IsNullOrWhiteSpace(authToken)) {
            await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.AuthInvalid));
            ctx.Connection.Dispose();
            return;
        }

        if(authMethod.All(c => c is >= '0' and <= '9') && authToken.Contains(':')) {
            string[] tokenParts = authToken.Split(':', 2);
            authMethod = tokenParts[0];
            authToken = tokenParts[1];
        }

        try {
            AuthResult authResult = await authClient.AuthVerifyAsync(
                ctx.Connection.RemoteAddress,
                authMethod,
                authToken
            );

            BanInfo? banInfo = await bansClient.BanGetAsync(authResult.UserId, ctx.Connection.RemoteAddress);
            if(banInfo is not null) {
                Logger.Write($"<{ctx.Connection.Id}> User is banned.");
                await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.Banned, banInfo.IsPermanent ? DateTimeOffset.MaxValue : banInfo.ExpiresAt));
                ctx.Connection.Dispose();
                return;
            }

            await ctx.Chat.ContextAccess.WaitAsync();
            try {
                User? user = ctx.Chat.Users.FirstOrDefault(u => u.UserId == authResult.UserId);

                if(user == null)
                    user = new User(
                        authResult.UserId,
                        authResult.UserName ?? $"({authResult.UserId})",
                        authResult.UserColour,
                        authResult.UserRank,
                        authResult.UserPermissions
                    );
                else
                    await ctx.Chat.UpdateUser(
                        user,
                        userName: authResult.UserName ?? $"({authResult.UserId})",
                        colour: authResult.UserColour,
                        rank: authResult.UserRank,
                        perms: authResult.UserPermissions
                    );

                // Enforce a maximum amount of connections per user
                if(ctx.Chat.Connections.Count(conn => conn.User == user) >= MaxConnections) {
                    await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.MaxSessions));
                    ctx.Connection.Dispose();
                    return;
                }

                ctx.Connection.BumpPing();
                ctx.Connection.User = user;
                await ctx.Connection.Send(new CommandResponseS2CPacket(0, LCR.WELCOME, false, $"Welcome to Flashii Chat, {user.UserName}!"));

                if(File.Exists("welcome.txt")) {
                    IEnumerable<string> lines = File.ReadAllLines("welcome.txt").Where(x => !string.IsNullOrWhiteSpace(x));
                    string? line = lines.ElementAtOrDefault(RNG.Next(lines.Count()));

                    if(!string.IsNullOrWhiteSpace(line))
                        await ctx.Connection.Send(new CommandResponseS2CPacket(0, LCR.WELCOME, false, line));
                }

                await ctx.Chat.HandleJoin(user, DefaultChannel, ctx.Connection, MaxMessageLength);
            } finally {
                ctx.Chat.ContextAccess.Release();
            }
        } catch(AuthFailedException ex) {
            Logger.Write($"<{ctx.Connection.Id}> Failed to authenticate: {ex}");
            await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.AuthInvalid));
            ctx.Connection.Dispose();
            throw;
        } catch(Exception ex) {
            Logger.Write($"<{ctx.Connection.Id}> Failed to authenticate: {ex}");
            await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.Exception));
            ctx.Connection.Dispose();
            throw;
        }
    }
}