如何验证 C# 中的 PayPal webhook 签名？

Question

我有一个 C# 应用程序，它接收来自 PayPal 的 Webhook 通知，我想验证 Webhook 签名。

我已经找到了 2 个与同一问题相关的问题，但没有明确的工作解决方案

C# 中的 PayPal webhook 签名验证
如何验证 PayPal Webhook 签名？

public static bool Validate(X509Certificate2 x509Certificate, WebhookSignature webhookSignature)
    {
        bool isValid = false;

        try
        {
            byte[] webhookBodyByte = Encoding.UTF8.GetBytes(webhookSignature.webhook_event);

            uint crc32 = Crc32CAlgorithm.Compute(webhookBodyByte);

            var expectedSignature = string.Format("{0}|{1}|{2}|{3}", webhookSignature.transmission_id, webhookSignature.transmission_time, webhookSignature.webhook_id, crc32);
            byte[] expectedSignatureBytes = Encoding.UTF8.GetBytes(expectedSignature);

            byte[] signatureBytes = Convert.FromBase64String(webhookSignature.transmission_sig);

            using (RSA rsa = x509Certificate.GetRSAPublicKey())
            {
                isValid = rsa.VerifyData(expectedSignatureBytes, signatureBytes, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }

        return isValid;
    }

rsa.VerifyDat 总是返回 false，我认为问题在于计算 CRC32 值。 “如 2 个重复的问题中所述”
有人可以解释一下这个问题吗？

请求正文：

{"id":"WH-9UD89617J3011950R-48P38622S7224850U","event_version":"1.0","create_time":"2021-04-12T13:48:33.815Z","resource_type":"checkout-order","resource_version":"2.0","event_type":"CHECKOUT.ORDER.APPROVED","summary":"An order has been approved by buyer","resource":{"create_time":"2021-04-12T13:47:55Z","purchase_units":[{"reference_id":"default","amount":{"currency_code":"EUR","value":"300.00"},"payee":{"email_address":"sb-6g4h15347490@business.example.com","merchant_id":"6WHMHKSMV4T4E","display_data":{"brand_name":"ieQ Shop"}},"shipping":{"name":{"full_name":"test buyer"},"address":{"address_line_1":"ESpachstr. 1","admin_area_2":"Freiburg","admin_area_1":"Empty","postal_code":"79111","country_code":"DE"}}}],"links":[{"href":"https://api.sandbox.paypal.com/v2/checkout/orders/2PY82104UY468500C","rel":"self","method":"GET"},{"href":"https://api.sandbox.paypal.com/v2/checkout/orders/2PY82104UY468500C","rel":"update","method":"PATCH"},{"href":"https://api.sandbox.paypal.com/v2/checkout/orders/2PY82104UY468500C/capture","rel":"capture","method":"POST"}],"id":"2PY82104UY468500C","intent":"CAPTURE","payer":{"name":{"given_name":"test","surname":"buyer"},"email_address":"rasheed.alsamawi-buyer@gmail.com","payer_id":"WQRMLHUWJA7H4","address":{"address_line_1":"Strasse Nummer X","address_line_2":"Strasse Nummer X","admin_area_2":"admin 2","admin_area_1":"admin 1","postal_code":"12345","country_code":"DE"}},"status":"APPROVED"},"links":[{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-9UD89617J3011950R-48P38622S7224850U","rel":"self","method":"GET"},{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-9UD89617J3011950R-48P38622S7224850U/resend","rel":"resend","method":"POST"}]}    

请求标头：

谢谢