commit 83da281cbe67cad5e8e225b41156eb15f87992fa
Author: kosipov <mail@kosipov.ru>
Date:   Thu Apr 9 18:17:42 2026 +0200

    Добавить Program.cs

diff --git a/Program.cs b/Program.cs
new file mode 100644
index 0000000..e2c3d74
--- /dev/null
+++ b/Program.cs
@@ -0,0 +1,261 @@
+using System;
+using System.Buffers;
+using System.IO;
+using System.Net;
+using System.Net.Http;
+using System.Net.Sockets;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+class Program
+{
+    static string USER = "user";
+    static string PASS = "pass";
+
+    static async Task Main()
+    {
+        int port = 8888;
+
+        Console.WriteLine($"Local proxy:");
+        Console.WriteLine($"  http://127.0.0.1:{port}");
+        Console.WriteLine($"  login: {USER}");
+        Console.WriteLine($"  pass : {PASS}");
+
+        var listener = new TcpListener(IPAddress.Any, port);
+        listener.Start();
+
+        while (true)
+        {
+            var client = await listener.AcceptTcpClientAsync();
+            _ = Task.Run(() => HandleClient(client));
+        }
+    }
+
+    static async Task HandleClient(TcpClient client)
+    {
+        using (client)
+        {
+            var stream = client.GetStream();
+
+            var request = await ReadHeaders(stream);
+            if (request == null) return;
+
+            if (!CheckAuth(request.HeadersRaw))
+            {
+                await Write407(stream);
+                return;
+            }
+
+            if (request.Method == "CONNECT")
+            {
+                await HandleConnect(stream, request.Target);
+            }
+            else
+            {
+                await HandleHttp(stream, request);
+            }
+        }
+    }
+
+    // ================= HTTP =================
+
+    static async Task HandleHttp(NetworkStream clientStream, HttpRequestData req)
+    {
+        var handler = new SocketsHttpHandler
+        {
+            UseProxy = true,
+            Proxy = new WinHttpProxy(),
+            DefaultProxyCredentials = CredentialCache.DefaultCredentials,
+            AllowAutoRedirect = false
+        };
+
+        using var http = new HttpClient(handler);
+
+        var message = new HttpRequestMessage(new HttpMethod(req.Method), req.Url);
+
+        foreach (var h in req.Headers)
+        {
+            if (!h.Key.Equals("Proxy-Authorization", StringComparison.OrdinalIgnoreCase))
+                message.Headers.TryAddWithoutValidation(h.Key, h.Value);
+        }
+
+        if (req.Body != null)
+            message.Content = new StreamContent(req.Body);
+
+        var resp = await http.SendAsync(message, HttpCompletionOption.ResponseHeadersRead);
+
+        // статус
+        var statusLine = $"HTTP/1.1 {(int)resp.StatusCode} {resp.ReasonPhrase}\r\n";
+        await clientStream.WriteAsync(Encoding.ASCII.GetBytes(statusLine));
+
+        // заголовки
+        foreach (var h in resp.Headers)
+        {
+            foreach (var v in h.Value)
+                await WriteHeader(clientStream, h.Key, v);
+        }
+
+        foreach (var h in resp.Content.Headers)
+        {
+            foreach (var v in h.Value)
+                await WriteHeader(clientStream, h.Key, v);
+        }
+
+        await clientStream.WriteAsync(Encoding.ASCII.GetBytes("\r\n"));
+
+        // тело (стриминг)
+        await resp.Content.CopyToAsync(clientStream);
+    }
+
+    // ================= CONNECT =================
+
+    static async Task HandleConnect(NetworkStream clientStream, string target)
+    {
+        var parts = target.Split(':');
+        string host = parts[0];
+        int port = int.Parse(parts[1]);
+
+        var proxy = new WinHttpProxy();
+        var proxyUri = proxy.GetProxy(new Uri($"https://{host}:{port}"));
+
+        using var upstream = new TcpClient();
+        await upstream.ConnectAsync(proxyUri.Host, proxyUri.Port);
+
+        var upstreamStream = upstream.GetStream();
+
+        // CONNECT к upstream
+        string connectReq =
+            $"CONNECT {host}:{port} HTTP/1.1\r\nHost: {host}:{port}\r\n\r\n";
+
+        await upstreamStream.WriteAsync(Encoding.ASCII.GetBytes(connectReq));
+
+        // читаем ответ от upstream
+        var buffer = new byte[8192];
+        int read = await upstreamStream.ReadAsync(buffer);
+
+        // отвечаем клиенту что туннель открыт
+        await clientStream.WriteAsync(Encoding.ASCII.GetBytes("HTTP/1.1 200 Connection Established\r\n\r\n"));
+
+        // двунаправленный туннель
+        var t1 = upstreamStream.CopyToAsync(clientStream);
+        var t2 = clientStream.CopyToAsync(upstreamStream);
+
+        await Task.WhenAny(t1, t2);
+    }
+
+    // ================= AUTH =================
+
+    static bool CheckAuth(string headers)
+    {
+        string expected = Convert.ToBase64String(Encoding.ASCII.GetBytes($"{USER}:{PASS}"));
+        return headers.Contains($"Proxy-Authorization: Basic {expected}");
+    }
+
+    static async Task Write407(NetworkStream stream)
+    {
+        string resp =
+            "HTTP/1.1 407 Proxy Authentication Required\r\n" +
+            "Proxy-Authenticate: Basic realm=\"proxy\"\r\n\r\n";
+
+        await stream.WriteAsync(Encoding.ASCII.GetBytes(resp));
+    }
+
+    // ================= REQUEST PARSER =================
+
+    class HttpRequestData
+    {
+        public string Method;
+        public string Url;
+        public string Target;
+        public string HeadersRaw;
+        public Dictionary<string, string> Headers = new();
+        public Stream Body;
+    }
+
+    static async Task<HttpRequestData> ReadHeaders(NetworkStream stream)
+    {
+        var buffer = new byte[8192];
+        int read = await stream.ReadAsync(buffer);
+
+        if (read <= 0) return null;
+
+        string text = Encoding.ASCII.GetString(buffer, 0, read);
+
+        var lines = text.Split("\r\n");
+        var first = lines[0].Split(' ');
+
+        var data = new HttpRequestData
+        {
+            Method = first[0],
+            Target = first[1],
+            HeadersRaw = text
+        };
+
+        foreach (var line in lines.Skip(1))
+        {
+            if (string.IsNullOrWhiteSpace(line)) break;
+
+            int idx = line.IndexOf(':');
+            if (idx > 0)
+                data.Headers[line[..idx]] = line[(idx + 1)..].Trim();
+        }
+
+        if (data.Method != "CONNECT")
+        {
+            data.Url = data.Target.StartsWith("http")
+                ? data.Target
+                : $"http://{data.Headers["Host"]}{data.Target}";
+        }
+
+        return data;
+    }
+
+    static async Task WriteHeader(NetworkStream stream, string key, string value)
+    {
+        string line = $"{key}: {value}\r\n";
+        await stream.WriteAsync(Encoding.ASCII.GetBytes(line));
+    }
+}
+
+// ================= WINHTTP PROXY =================
+
+class WinHttpProxy : IWebProxy
+{
+    public ICredentials Credentials { get; set; }
+
+    public Uri GetProxy(Uri destination)
+    {
+        return WinHttpHelper.GetProxyForUrl(destination);
+    }
+
+    public bool IsBypassed(Uri host) => false;
+}
+
+static class WinHttpHelper
+{
+    [DllImport("winhttp.dll", SetLastError = true)]
+    static extern bool WinHttpGetIEProxyConfigForCurrentUser(out WINHTTP_CURRENT_USER_IE_PROXY_CONFIG config);
+
+    public static Uri GetProxyForUrl(Uri url)
+    {
+        WinHttpGetIEProxyConfigForCurrentUser(out var cfg);
+
+        if (!string.IsNullOrEmpty(cfg.lpszProxy))
+        {
+            var parts = cfg.lpszProxy.Split(':');
+            return new Uri($"http://{parts[0]}:{parts[1]}");
+        }
+
+        return url; // direct
+    }
+
+    struct WINHTTP_CURRENT_USER_IE_PROXY_CONFIG
+    {
+        public bool fAutoDetect;
+        public IntPtr lpszAutoConfigUrl;
+        public IntPtr lpszProxy;
+        public IntPtr lpszProxyBypass;
+    }
+}
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