在中间件中更改 OWIN Request.Body

Question

我想为 API 调用实施自定义加密中间件。起初，我阅读了请求 body (IOwinContext.Request.Body) 和 headers (Encryption-Key & Signature)。然后，我解密请求 body，这给了我纯 json 字符串。现在是棘手的部分：我想将此 json 写回 IOwinContextRequest.Body，以便可以将其反序列化为 object，然后作为 Controller 方法的参数传递。这是我的做法：

启动：

public partial class Startup
{
    public void Configuration(IAppBuilder app)
    {
        app.Use(typeof(EncryptionMiddleware));

        ...
    }
}

中间件：

public class EncryptionMiddleware : OwinMiddleware
{
    public EncryptionMiddleware(OwinMiddleware next) : base(next)
    {
        //
    }

    public async override Task Invoke(IOwinContext context)
    {
        var request = context.Request;
        string json = GetDecryptedJson(context);
        MemoryStream stream = new MemoryStream();
        stream.Write(json, 0, json.Length);
        request.Headers["Content-Lenght"] = json.Lenght.ToString();
        request.Body = stream;
        await Next.Invoke(context);
    }
}

现在，我得到的是这个错误：

System.Web.Extensions.dll!System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializePrimitiveObject() Exception thrown: 'System.ArgumentException' in System.Web.Extensions.dll
Additional information: Invalid JSON primitive: 8yi9OH2JE0H0cwZ.

原来的IOwinContext.Request.Body是：

8yi9OH2JE0H0cwZ/fyY5Fks4nW(...omitted...)PvL32AVRjLA==

所以我假设您不能以这种方式更改请求 body。为了测试这一点，我重写了这样的中间件：

public async override Task Invoke(IOwinContext context)
{
    var request = context.Request;

    string requestBody = new StreamReader(request.Body).ReadToEnd();
    Debug.WriteLine(requestBody); // Prints "ORIGINAL BODY"
    string newBody = "\"newBody\"";
    MemoryStream memStream = new MemoryStream(Encoding.UTF8.GetBytes(newBody));
    request.Headers["Content-Length"] = newBody.Length.ToString();
    request.Body = memStream;
    await Next.Invoke(context);
}

现在我认为 Controller 方法应该接收 "ORIGINAL BODY" 而不是 "newBody"，但实际上我得到了这个错误：

System.dll!System.Diagnostics.PerformanceCounter.InitializeImpl() Exception thrown: 'System.InvalidOperationException' in System.dll

Additional information: The requested Performance Counter is not a custom counter, it has to be initialized as ReadOnly.

问题是：我的方法有什么问题？重写请求 body 的正确方法是什么？是否有足够的解决方法？ 顺便说一句：数据的解密已经过测试并且是完美无缺的，所以错误不应该起源于那里。

编辑： 在你 answer/comment 之前，已经使用了 TLS。这是另一层安全。我不是在重新发明轮子。我要添加一个新的。

Answer 1

我创建了一些中间件来测试在 OWIN 管道中更改 OWIN Request.Body

public class DecryptionMiddleWare : OwinMiddleware {
    private string expected;
    private string decryptedString;

    public DecryptionMiddleWare(OwinMiddleware next, string expected, string decryptedString)
        : base(next) {
        this.expected = expected;
        this.decryptedString = decryptedString;
    }

    public async override System.Threading.Tasks.Task Invoke(IOwinContext context) {
        await DecryptRequest(context);

        await Next.Invoke(context);
    }

    private async Task DecryptRequest(IOwinContext context) {
        var request = context.Request;
        var requestBody = new StreamReader(request.Body).ReadToEnd();
        Assert.AreEqual(expected, requestBody);
        //Fake decryption code
        if (expected == requestBody) {
            //replace request stream to downstream handlers
            var decryptedContent = new StringContent(decryptedString, Encoding.UTF8, "application/json");
            var requestStream = await decryptedContent.ReadAsStreamAsync();
            request.Body = requestStream;
        }
    }
}

public class AnotherCustomMiddleWare : OwinMiddleware {
    private string expected;
    private string responseContent;

    public AnotherCustomMiddleWare(OwinMiddleware next, string expected, string responseContent)
        : base(next) {
        this.expected = expected;
        this.responseContent = responseContent;
    }

    public async override System.Threading.Tasks.Task Invoke(IOwinContext context) {
        var request = context.Request;
        var requestBody = new StreamReader(request.Body).ReadToEnd();

        Assert.AreEqual(expected, requestBody);

        var owinResponse = context.Response;
        // hold on to original stream
        var owinResponseStream = owinResponse.Body;
        //buffer the response stream in order to intercept downstream writes
        var responseBuffer = new MemoryStream();
        owinResponse.Body = responseBuffer;

        await Next.Invoke(context);

        if (expected == requestBody) {
            owinResponse.ContentType = "text/plain";
            owinResponse.StatusCode = (int)HttpStatusCode.OK;
            owinResponse.ReasonPhrase = HttpStatusCode.OK.ToString();

            var customResponseBody = new StringContent(responseContent);
            var customResponseStream = await customResponseBody.ReadAsStreamAsync();
            await customResponseStream.CopyToAsync(owinResponseStream);

            owinResponse.ContentLength = customResponseStream.Length;
            owinResponse.Body = owinResponseStream;
        }

    }
}

然后在内存中创建 OWIN 集成测试以查看数据如何通过中间件，测试是否接收到正确的数据。

[TestMethod]
public async Task Change_OWIN_Request_Body_Test() {
    var encryptedContent = "Hello World";
    var expectedResponse = "I am working";

    using (var server = TestServer.Create<Startup1>()) {

        var content = new StringContent(encryptedContent);
        var response = await server.HttpClient.PostAsync("/", content);
        var result = await response.Content.ReadAsStringAsync();

        Assert.AreEqual(expectedResponse, result);
    }
}

public class Startup1 {
    public void Configuration(IAppBuilder appBuilder) {
        var encryptedContent = "Hello World";
        var decryptedString = "Hello OWIN";
        var expectedResponse = "I am working";
        appBuilder.Use<DecryptionMiddleWare>(encryptedContent, decryptedString);
        appBuilder.Use<AnotherCustomMiddleWare>(decryptedString, expectedResponse);
    }
}

测试通过，证明数据可以通过OWIN管道传递。

好的，接下来我想看看它是否适用于网络 api。所以创建了一个测试api控制器

public class TestController : ApiController {
    [HttpPost]
    public IHttpActionResult Post([FromBody]string input) {
        if (input == "Hello From OWIN")
            return Ok("I am working");

        return NotFound();
    }
}

并配置了一个新的启动来使用 web api 和自定义解密中间件。

public class Startup2 {
    public void Configuration(IAppBuilder appBuilder) {
        var encryptedContent = "Hello World";
        var decryptedString = "\"Hello From OWIN\"";
        appBuilder.Use<DecryptionMiddleWare>(encryptedContent, decryptedString);

        //Configure Web API middleware
        var config = new HttpConfiguration();
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        appBuilder.UseWebApi(config);
    }
}

这是内存集成测试

[TestMethod]
public async Task Change_OWIN_Request_Body_To_WebApi_Test() {
    var encryptedContent = "Hello World";
    var expectedResponse = "\"I am working\"";

    using (var server = TestServer.Create<Startup2>()) {

        var content = new StringContent(encryptedContent, Encoding.UTF8, "application/json");
        var response = await server.HttpClient.PostAsync("api/Test", content);
        var result = await response.Content.ReadAsStringAsync();

        Assert.AreEqual(expectedResponse, result);
    }
}

也通过了

看看上面的示例代码，看看它是否可以让您深入了解问题中的示例哪里出了问题。

另外请记住确保在网络 api 中间件之前将自定义中间件置于管道的早期。

希望对您有所帮助

Answer 2

我很久以前就解决了这个问题，但是在@Nkosi 的建议下，我发布了解决方案。

我所做的是一种变通方法，或者说 "bridge" 从中间件到动作过滤器。这是代码：

中间件

public class EncryptionMiddleware : OwinMiddleware
{

    public EncryptionMiddleware(OwinMiddleware next) : base(next)
    {
        //
    }

    public async override Task Invoke(IOwinContext context)
    {
        var request = context.Request;

        string requestBody = new StreamReader(request.Body).ReadToEnd();

        var obj = // do your work here
        System.Web.HttpContext.Current.Items[OBJECT_ITEM_KEY] = obj;
        await Next.Invoke(context);
        return;
    }
}

过滤器

public class EncryptedParameter : ActionFilterAttribute, IActionFilter
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var obj = HttpContext.Current.Items[OBJECT_ITEM_KEY];
        HttpContext.Current.Items.Remove(AppConfig.ITEM_DATA_KEY);

        if (filterContext.ActionParameters.ContainsKey("data"))
            filterContext.ActionParameters["data"] = obj;
    }
}

控制器

public class MyController : Controller
{
    [HttpPost]
    [EncryptedParameter]
    public JsonResult MyMethod(MyObject data)
    {
        // your logic here
    }
}

在中间件中更改 OWIN Request.Body

Change OWIN Request.Body in middleware

c#

asp.net-web-api2

owin

owin-middleware