LarpixServer/LarpixVoice/Utils.cs

namespace LarpixVoice;

public class Utils
{
    public static int PORT = 8091;
    public static int MAIN_PORT = 8090;
    public static string SERVER_KEY = "SecretThingOMGSoHardToGuess";
    public static string MAIN_URL = "";

    // Rate limits, requests per minute (fixed 60s window).
    public static int ROOM_USERS_RATE_LIMIT = 120;

    // Shared with the main server: authenticates internal validation requests.
    public static string VOICE_KEY = "";

    private static readonly System.Net.Http.HttpClient AuthHttp = new()
    {
        Timeout = TimeSpan.FromSeconds(3)
    };

    public static void LoadEnv()
    {
        if (File.Exists(".env"))
        {

            foreach (var line in File.ReadAllLines(".env"))
            {
                var trimmed = line.Trim();
                if (string.IsNullOrWhiteSpace(trimmed) || trimmed.StartsWith("#")) continue;

                var parts = trimmed.Split('=', 2, StringSplitOptions.None);
                if (parts.Length == 2)
                {
                    var key = parts[0].Trim();
                    var val = parts[1];
                    int commentIndex = val.IndexOf('#');
                    if (commentIndex >= 0)
                    {
                        val = val.Substring(0, commentIndex);
                    }
                    val = val.Trim();

                    Environment.SetEnvironmentVariable(key, val);
                }
            }
        }

        string? port = Environment.GetEnvironmentVariable("PORT_VOICE");
        if (port != null)
        {
            PORT = int.Parse(port);
        }
        port = Environment.GetEnvironmentVariable("PORT");
        if (port != null)
        {
            MAIN_PORT = int.Parse(port);
        }
        SERVER_KEY = Environment.GetEnvironmentVariable("SERVER_KEY") ?? SERVER_KEY;
        VOICE_KEY = Environment.GetEnvironmentVariable("VOICE_KEY") ?? VOICE_KEY;
        MAIN_URL = Environment.GetEnvironmentVariable("MAIN_URL") ?? $"http://127.0.0.1:{MAIN_PORT}";

        string? roomUsersRateLimitStr = Environment.GetEnvironmentVariable("ROOM_USERS_RATE_LIMIT");
        if (roomUsersRateLimitStr != null && int.TryParse(roomUsersRateLimitStr, out int parsedRoomUsersLimit))
        {
            ROOM_USERS_RATE_LIMIT = parsedRoomUsersLimit;
        }
    }

    // Asks the main server to validate (and atomically consume) the ticket
    // blob presented on a connection's first frame. Fail-closed: any network
    // problem, bad HMAC, timeout or "deny" response rejects the connection.
    public static async Task<bool> AuthorizeConnection(string publicId, string iv, string ct, string roomId, ulong userId)
    {
        if (string.IsNullOrEmpty(VOICE_KEY) || string.IsNullOrEmpty(MAIN_URL)) return false;

        try
        {
            long ts = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
            string body = System.Text.Json.JsonSerializer.Serialize(
                new VoiceAuthBody(roomId, userId.ToString(), publicId, iv, ct),
                JsonAppSerializerContext.Default.VoiceAuthBody
            );

            byte[] keyBytes = System.Security.Cryptography.SHA256.HashData(System.Text.Encoding.UTF8.GetBytes(VOICE_KEY));
            using var hmac = new System.Security.Cryptography.HMACSHA256(keyBytes);
            string mac = System.Buffers.Text.Base64Url.EncodeToString(
                hmac.ComputeHash(System.Text.Encoding.UTF8.GetBytes($"{ts}.{body}"))
            );

            using var request = new System.Net.Http.HttpRequestMessage(System.Net.Http.HttpMethod.Post, $"{MAIN_URL}/_larpix/voice/auth");
            request.Headers.Add("X-Voice-Ts", ts.ToString());
            request.Headers.Add("X-Voice-Mac", mac);
            request.Content = new System.Net.Http.StringContent(body, System.Text.Encoding.UTF8, "application/json");

            using System.Net.Http.HttpResponseMessage response = await AuthHttp.SendAsync(request);
            if (!response.IsSuccessStatusCode)
            {
                Console.WriteLine($"Voice auth: main HTTP {(int)response.StatusCode}");
                return false;
            }
            string content = await response.Content.ReadAsStringAsync();
            if (content.Trim() != "ok")
            {
                Console.WriteLine($"Voice auth: main denied ({content.Trim()})");
                return false;
            }
            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Voice auth: validation request failed ({ex.Message})");
            return false;
        }
    }
}