有盆友好奇所谓的网络穿透是怎么做的
然后talk is cheap，please show code
所以只好写个简单且常见的websocket例子，
这里的例子大致是这个原理
浏览器插件(或者其他)首先将正常访问请求 --> 转换为socks5访问 --> 假代理服务器建立websocket链接，然后传输socks5协议数据 --> 允许websocket的网关由于不解析websocket数据而不知道是socks5所以未做拦截 --> 真代理服务器从websocket中解析socks5进行转发处理
代码如下
Socks5 --> websocket 端
csharp
internal class Socks5ToWSMiddleware : ITcpProxyMiddleware
{
private readonly IForwarderHttpClientFactory httpClientFactory;
private readonly ILoadBalancingPolicyFactory loadBalancing;
private readonly ProxyLogger logger;
private readonly TimeProvider timeProvider;
public Socks5ToWSMiddleware(IForwarderHttpClientFactory httpClientFactory, ILoadBalancingPolicyFactory loadBalancing, ProxyLogger logger, TimeProvider timeProvider)
{
this.httpClientFactory = httpClientFactory;
this.loadBalancing = loadBalancing;
this.logger = logger;
this.timeProvider = timeProvider;
}
public Task InitAsync(ConnectionContext context, CancellationToken token, TcpDelegate next)
{
// 过滤符合的路由配置
var feature = context.Features.Get<IL4ReverseProxyFeature>();
if (feature is not null)
{
var route = feature.Route;
if (route is not null && route.Metadata is not null
&& route.Metadata.TryGetValue("socks5ToWS", out var b) && bool.TryParse(b, out var isSocks5) && isSocks5)
{
feature.IsDone = true;
route.ClusterConfig?.InitHttp(httpClientFactory);
return Proxy(context, feature, token);
}
}
return next(context, token);
}
private async Task Proxy(ConnectionContext context, IL4ReverseProxyFeature feature, CancellationToken token)
{ // loadBalancing 选取有效 ip
var route = feature.Route;
var cluster = route.ClusterConfig;
DestinationState selectedDestination;
if (cluster is null)
{
selectedDestination = null;
}
else
{
selectedDestination = feature.SelectedDestination;
selectedDestination ??= loadBalancing.PickDestination(feature);
}
if (selectedDestination is null)
{
logger.NotFoundAvailableUpstream(route.ClusterId);
Abort(context);
return;
}
selectedDestination.ConcurrencyCounter.Increment();
try
{
await SendAsync(context, feature, selectedDestination, cluster, route.Transformer, token);
selectedDestination.ReportSuccessed();
}
catch
{
selectedDestination.ReportFailed();
throw;
}
finally
{
selectedDestination.ConcurrencyCounter.Decrement();
}
}
private async Task<ForwarderError> SendAsync(ConnectionContext context, IL4ReverseProxyFeature feature, DestinationState selectedDestination, ClusterConfig? cluster, IHttpTransformer transformer, CancellationToken token)
{
// 创建 websocket 请求， 这里为了简单，只创建简单 http1.1 websocket
var destinationPrefix = selectedDestination.Address;
if (destinationPrefix is null || destinationPrefix.Length < 8)
{
throw new ArgumentException("Invalid destination prefix.", nameof(destinationPrefix));
}
var route = feature.Route;
var requestConfig = cluster.HttpRequest ?? ForwarderRequestConfig.Empty;
var httpClient = cluster.HttpMessageHandler ?? throw new ArgumentNullException("httpClient");
var destinationRequest = new HttpRequestMessage();
destinationRequest.Version = HttpVersion.Version11;
destinationRequest.VersionPolicy = HttpVersionPolicy.RequestVersionOrLower;
destinationRequest.Method = HttpMethod.Get;
destinationRequest.RequestUri ??= new Uri(destinationPrefix, UriKind.Absolute);
destinationRequest.Headers.TryAddWithoutValidation(HeaderNames.Connection, HeaderNames.Upgrade);
destinationRequest.Headers.TryAddWithoutValidation(HeaderNames.Upgrade, HttpForwarder.WebSocketName);
destinationRequest.Headers.TryAddWithoutValidation(HeaderNames.SecWebSocketVersion, "13");
destinationRequest.Headers.TryAddWithoutValidation(HeaderNames.SecWebSocketKey, ProtocolHelper.CreateSecWebSocketKey());
destinationRequest.Content = new EmptyHttpContent();
if (!string.IsNullOrWhiteSpace(selectedDestination.Host))
{
destinationRequest.Headers.TryAddWithoutValidation(HeaderNames.Host, selectedDestination.Host);
}
// 建立websocket 链接，成功则直接 复制原始 req/resp 数据，不做任何而外处理
var destinationResponse = await httpClient.SendAsync(destinationRequest, token);
if (destinationResponse.StatusCode == HttpStatusCode.SwitchingProtocols)
{
using var destinationStream = await destinationResponse.Content.ReadAsStreamAsync(token);
var clientStream = new DuplexPipeStreamAdapter<Stream>(null, context.Transport, static i => i);
var activityCancellationSource = ActivityCancellationTokenSource.Rent(route.Timeout);
var requestTask = StreamCopier.CopyAsync(isRequest: true, clientStream, destinationStream, StreamCopier.UnknownLength, timeProvider, activityCancellationSource,
autoFlush: destinationResponse.Version == HttpVersion.Version20, token).AsTask();
var responseTask = StreamCopier.CopyAsync(isRequest: false, destinationStream, clientStream, StreamCopier.UnknownLength, timeProvider, activityCancellationSource, token).AsTask();
var task = await Task.WhenAny(requestTask, responseTask);
await clientStream.DisposeAsync();
if (task.IsCanceled)
{
Abort(context);
activityCancellationSource.Cancel();
if (task.Exception is not null)
{
throw task.Exception;
}
}
}
else
{
Abort(context);
return ForwarderError.UpgradeRequestDestination;
}
return ForwarderError.None;
}
public Task<ReadOnlyMemory<byte>> OnRequestAsync(ConnectionContext context, ReadOnlyMemory<byte> source, CancellationToken token, TcpProxyDelegate next)
{
return next(context, source, token);
}
public Task<ReadOnlyMemory<byte>> OnResponseAsync(ConnectionContext context, ReadOnlyMemory<byte> source, CancellationToken token, TcpProxyDelegate next)
{
return next(context, source, token);
}
private static void Abort(ConnectionContext upstream)
{
upstream.Transport.Input.CancelPendingRead();
upstream.Transport.Output.CancelPendingFlush();
upstream.Abort();
}
}websocket --> Socks5 端
csharp
internal class WSToSocks5HttpMiddleware : IMiddleware
{
private static ReadOnlySpan<byte> EncodedWebSocketKey => "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"u8;
private WebSocketMiddleware middleware;
private readonly Socks5Middleware socks5Middleware;
public WSToSocks5HttpMiddleware(IOptions<WebSocketOptions> options, ILoggerFactory loggerFactory, Socks5Middleware socks5Middleware)
{
middleware = new WebSocketMiddleware(Scoks5, options, loggerFactory);
this.socks5Middleware = socks5Middleware;
}
private async Task Scoks5(HttpContext context)
{
var upgradeFeature = context.Features.Get<IHttpUpgradeFeature>();
// 检查是否未正确 websocket 请求
var f = context.Features.Get<IHttpWebSocketFeature>();
if (f.IsWebSocketRequest)
{
// 返回 websocket 接受信息
var responseHeaders = context.Response.Headers;
responseHeaders.Connection = HeaderNames.Upgrade;
responseHeaders.Upgrade = HttpForwarder.WebSocketName;
responseHeaders.SecWebSocketAccept = CreateResponseKey(context.Request.Headers.SecWebSocketKey.ToString());
var stream = await upgradeFeature!.UpgradeAsync(); // Sets status code to 101
// 建原始 websocket stream 包装成 pipe 方便使用原来的 socks5Middleware 实现
var memoryPool = context is IMemoryPoolFeature s ? s.MemoryPool : MemoryPool<byte>.Shared;
StreamPipeReaderOptions readerOptions = new StreamPipeReaderOptions
(
pool: memoryPool,
bufferSize: memoryPool.GetMinimumSegmentSize(),
minimumReadSize: memoryPool.GetMinimumAllocSize(),
leaveOpen: true,
useZeroByteReads: true
);
var writerOptions = new StreamPipeWriterOptions
(
pool: memoryPool,
leaveOpen: true
);
var input = PipeReader.Create(stream, readerOptions);
var output = PipeWriter.Create(stream, writerOptions);
var feature = context.Features.Get<IReverseProxyFeature>();
var route = feature.Route;
using var cts = CancellationTokenSourcePool.Default.Rent(route.Timeout);
var token = cts.Token;
context.Features.Set<IL4ReverseProxyFeature>(new L4ReverseProxyFeature() { IsDone = true, Route = route });
// socks5Middleware 进行转发
await socks5Middleware.Proxy(new WebSocketConnection(context.Features)
{
Transport = new WebSocketDuplexPipe() { Input = input, Output = output },
ConnectionId = context.Connection.Id,
Items = context.Items,
}, null, token);
}
else
{
context.Response.StatusCode = StatusCodes.Status400BadRequest;
}
}
public static string CreateResponseKey(string requestKey)
{
// "The value of this header field is constructed by concatenating /key/, defined above in step 4
// in Section 4.2.2, with the string "258EAFA5-E914-47DA-95CA-C5AB0DC85B11", taking the SHA-1 hash of
// this concatenated value to obtain a 20-byte value and base64-encoding"
// https://tools.ietf.org/html/rfc6455#section-4.2.2
// requestKey is already verified to be small (24 bytes) by 'IsRequestKeyValid()' and everything is 1:1 mapping to UTF8 bytes
// so this can be hardcoded to 60 bytes for the requestKey + static websocket string
Span<byte> mergedBytes = stackalloc byte[60];
Encoding.UTF8.GetBytes(requestKey, mergedBytes);
EncodedWebSocketKey.CopyTo(mergedBytes[24..]);
Span<byte> hashedBytes = stackalloc byte[20];
var written = SHA1.HashData(mergedBytes, hashedBytes);
if (written != 20)
{
throw new InvalidOperationException("Could not compute the hash for the 'Sec-WebSocket-Accept' header.");
}
return Convert.ToBase64String(hashedBytes);
}
public Task InvokeAsync(HttpContext context, RequestDelegate next)
{
// 过滤符合的路由配置
var feature = context.Features.Get<IReverseProxyFeature>();
if (feature is not null)
{
var route = feature.Route;
if (route is not null && route.Metadata is not null
&& route.Metadata.TryGetValue("WSToSocks5", out var b) && bool.TryParse(b, out var isSocks5) && isSocks5)
{
// 这里偷个懒，利用现成的 WebSocketMiddleware 检查 websocket 请求，
return middleware.Invoke(context);
}
}
return next(context);
}
}
internal class WebSocketConnection : ConnectionContext
{
public WebSocketConnection(IFeatureCollection features)
{
this.features = features;
}
public override IDuplexPipe Transport { get; set; }
public override string ConnectionId { get; set; }
private IFeatureCollection features;
public override IFeatureCollection Features => features;
public override IDictionary<object, object?> Items { get; set; }
}
internal class WebSocketDuplexPipe : IDuplexPipe
{
public PipeReader Input { get; set; }
public PipeWriter Output { get; set; }
}所以利用 websocket 伪装的例子大致就是这样就可以完成 tcp的 socks5 处理了 udp我就不来了
最后有兴趣的同学给 L4/L7的代理 VKProxy点个赞呗 (暂时没有使用文档，等啥时候有空把配置ui站点完成了再来吧)