验证 SendGrid 的签名事件 Webhook？答案

【问题标题】：Verifying SendGrid's Signed Event Webhook?验证 SendGrid 的签名事件 Webhook？
【发布时间】：2020-06-17 15:29:47
【问题描述】：

我正在尝试通过此链接实施验证。

https://sendgrid.com/docs/for-developers/tracking-events/getting-started-event-webhook-security-features/#the-signed-event-webhook

我不想要其中的 OAuth 部分，而是使用公钥和标头来验证数据。我看过很多与 SendGrid 的 Event Webhook 相关的帖子，但没有什么可以验证的。

这是我尝试过的，但显然有问题。我真的不确定如何将文档中的代码翻译成 C#。我不确定请求中的每条数据应该去哪里。有人对此有任何见解吗？

public async Task<IHttpActionResult> EventsHook()
{
    IEnumerable<string> signatureFromHeader = Request.Headers.GetValues("X-Twilio-Email-Event-Webhook-Signature");
    byte[] timeStampBytes = Encoding.ASCII.GetBytes(Request.Headers.GetValues("X-Twilio-Email-Event-Webhook-Timestamp").First());
    byte[] body = await Request.Content.ReadAsByteArrayAsync();
    byte[] payloadHash = timeStampBytes.Concat(body).ToArray();
    byte[] signatureByteArray = Convert.FromBase64String(signatureFromHeader.First());
    var publicKey = "{myPublicKey}";
    byte[] publicKeyBytes = Convert.FromBase64String(publicKey);

    var ecdsaParams = new ECParameters
    {
        D = publicKeyBytes
    };

    using (var ecdsa = ECDsa.Create(ecdsaParams))
    {
        if (ecdsa.VerifyData(payloadHash, signatureByteArray, HashAlgorithmName.SHA256))
        {
            return Ok();
        }
        return StatusCode(System.Net.HttpStatusCode.Forbidden);
    }
}

【问题讨论】：

标签： c# sendgrid ecdsa webapi

【解决方案1】：

我刚刚实现了这个，我可以帮你解决这个问题：

1- 我使用库starkbank-ecdsa 来验证签名。 2- 我声明了这个接口

public interface IEmailWebHookRequestValidator
{
    bool IsValidRequest(HttpRequest request);
}

3-这个接口的实现是这样的：

public class SendGridWebHookRequestValidator : IEmailWebHookRequestValidator
{
   private const string SIGNATURE_HEADER = "X-Twilio-Email-Event-Webhook-Signature";
   private const string TIMESTAMP_HEADER = "X-Twilio-Email-Event-Webhook-Timestamp";
    
   private readonly string _sendGridWebHookPublicKey;
    
   public SendGridWebHookRequestValidator(ISettingsProvider settingsProvider)
   {
      _sendGridWebHookPublicKey = settingsProvider.SendGridWebHookPublicKey //"public key that you can get from SendGrid website when you enable Event Webhook's signature";
   }
    
   public bool IsValidRequest(HttpRequest request)
   {
      request.Headers.TryGetValue(SIGNATURE_HEADER, out var signatureHeaderValues);
      request.Headers.TryGetValue(TIMESTAMP_HEADER, out var timestampHeaderValues);
    
      var signature = signatureHeaderValues.FirstOrDefault();
      var timestamp = timestampHeaderValues.FirstOrDefault();
    
      if (string.IsNullOrWhiteSpace(signature) || string.IsNullOrWhiteSpace(timestamp))
      {
         return false;
      }
    
      var body = ReadStream(request.Body);
    
      return VerifySignature(_sendGridWebHookPublicKey, body, signature, timestamp);
   }
    

   public bool VerifySignature(string verificationKey, string payload, string signature, string timestamp)
   {
      var publicKey = PublicKey.fromPem(verificationKey);
    
      var timestampedPayload = timestamp + payload;
      var decodedSignature = Signature.fromBase64(signature);
    
      return Ecdsa.verify(timestampedPayload, decodedSignature, publicKey);
   }
    
   public static string ReadStream(Stream stream)
   {
       using var ms = new MemoryStream();
    
       stream.CopyTo(ms);
       return Encoding.UTF8.GetString(ms.GetBuffer(), 0, (int)ms.Length);
   }
}

ISettingsProvider 只是一个帮助您从设置中检索公钥的接口。
当您的 webhook 接收到 httprequest 时，只需将其传递给 IsValidRequest 方法即可轻松使用上述代码。

【讨论】：