ASP.NET Core Proxies made easy.
dotnet add package AspNetCore.ProxyDownload the source and run.
dotnet restore
dotnet test src/Test/AspNetCore.Proxy.Tests.csproj.NET Standard 2.0, .NET Core 3.0, .NET Core 5.0 and .NET Core 6.0.
First, you must add the required services.
public void ConfigureServices(IServiceCollection services)
{
...
services.AddProxies();
...
}You can run a proxy over all endpoints by using RunProxy in your Configure method.
app.RunProxy(proxy => proxy.UseHttp("http://google.com"));In addition, you can route this proxy depending on the context. You can return a string or ValueTask<string> from the computer.
app.RunProxy(proxy => proxy
.UseHttp((context, args) =>
{
if(context.Request.Path.StartsWithSegments("/should/forward/to/favorite"))
return "http://myfavoriteserver.com";
return "http://myhttpserver.com";
})
.UseWs((context, args) => "ws://mywsserver.com"));You can define mapped proxy routes in your Configure method at startup.
app.UseRouting();
app.UseEndpoints(endpoints => endpoints.MapControllers());
app.UseProxies(proxies =>
{
// Bare string.
proxies.Map("echo/post", proxy => proxy.UseHttp("https://postman-echo.com/post"));
// Computed to task.
proxies.Map("api/comments/task/{postId}", proxy => proxy.UseHttp((_, args) => new ValueTask<string>($"https://jsonplaceholder.typicode.com/comments/{args["postId"]}")));
// Computed to string.
proxies.Map("api/comments/string/{postId}", proxy => proxy.UseHttp((_, args) => $"https://jsonplaceholder.typicode.com/comments/{args["postId"]}"));
});ASP.NET Core allows you to configure the behavior of its HTTP client objects by registering a named HttpClient with its own HttpClientHandler, which can then be referred to by name elsewhere. This can be used to support features such as server certificate custom validation. The UseProxies setup supports using such a named client:
proxies.Map( "/api/v1/...", proxy => proxy.UseHttp(
(context, args) => ...,
builder => builder.WithHttpClientName("myClientName")));...where "myClientName" was previously registered as:
services
.AddHttpClient("myClientName")
.ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler() {
ServerCertificateCustomValidationCallback = MyValidateCertificateMethod,
UseDefaultCredentials = true
});You can also route all unhandled requests to another server, e.g.
app.UseStatusCodePages(async statusCodeContext =>
{
var context = statusCodeContext.HttpContext;
if (context.Response.StatusCode == StatusCodes.Status404NotFound)
{
var request = context.Features.Get<IHttpRequestFeature>();
if (request != null)
{
await context.HttpProxyAsync($"https://example.com{request.RawTarget}");
}
}
});You can define a proxy over a specific endpoint on an existing Controller by leveraging the ProxyAsync extension methods.
public class MyController : Controller
{
[Route("api/posts/{postId}")]
public Task GetPosts(int postId)
{
return this.HttpProxyAsync($"https://jsonplaceholder.typicode.com/posts/{postId}");
}
}NOTE: The body of the request should not be consumed by the controller (i.e., the controller should not have any
[FromBody]parameters); otherwise, the proxy operation will fail. This is due to the fact that the body is read from aStream, and thatStreamis progressed when the body is read.
You can "catch all" using ASP.NET **rest semantics.
[Route("api/google/{**rest}")]
public Task ProxyCatchAll(string rest)
{
// If you don't need the query string, then you can remove this.
var queryString = this.Request.QueryString.Value;
return this.HttpProxyAsync($"https://google.com/{rest}{queryString}");
}In addition, you can proxy to WebSocket endpoints.
public class MyController : Controller
{
[Route("ws")]
public Task OpenWs()
{
return this.WsProxyAsync($"wss://mywsendpoint.com/ws");
}
}You can also pass special options that apply when the proxy operation occurs.
public class MyController : Controller
{
private HttpProxyOptions _httpOptions = HttpProxyOptionsBuilder.Instance
.WithShouldAddForwardedHeaders(false)
.WithHttpClientName("MyCustomClient")
.WithIntercept(async context =>
{
if(context.Connection.RemotePort == 7777)
{
context.Response.StatusCode = 300;
await context.Response.WriteAsync("I don't like this port, so I am not proxying this request!");
return true;
}
return false;
})
.WithBeforeSend((c, hrm) =>
{
// Set something that is needed for the downstream endpoint.
hrm.Headers.Authorization = new AuthenticationHeaderValue("Basic");
return Task.CompletedTask;
})
.WithAfterReceive((c, hrm) =>
{
// Alter the content in some way before sending back to client.
var newContent = new StringContent("It's all greek...er, Latin...to me!");
hrm.Content = newContent;
return Task.CompletedTask;
})
.WithHandleFailure(async (c, e) =>
{
// Return a custom error response.
c.Response.StatusCode = 403;
await c.Response.WriteAsync("Things borked.");
}).Build();
private WsProxyOptions _wsOptions = WsProxyOptionsBuilder.Instance
.WithBufferSize(8192)
.WithIntercept(context => new ValueTask<bool>(context.WebSockets.WebSocketRequestedProtocols.Contains("interceptedProtocol")))
.WithBeforeConnect((context, wso) =>
{
wso.AddSubProtocol("myRandomProto");
return Task.CompletedTask;
})
.WithHandleFailure(async (context, e) =>
{
context.Response.StatusCode = 599;
await context.Response.WriteAsync("Failure handled.");
}).Build();
[Route("api/posts/{postId}")]
public Task GetPosts(int postId)
{
return this.ProxyAsync("http://myhttpendpoint.com", "ws://mywsendpoint.com", _httpOptions, _wsOptions);
}
}The MIT License (MIT)
Copyright (c) 2017 Aaron Roney
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