Protect Your Data with Twilio SendGrid’s Event Webhook Security

July 13, 2020
Written by
Madison Springgate
Opinions expressed by Twilio contributors are their own

Protect Your Data with Twilio SendGrid’s Event Webhook Security

Corporate data breaches have increased by 67% over the past 5 years. And malicious attacks on your company do not come cheap. According to a study by IBM Security, data breaches can cost an average of $8.19M, as well as lead to multiple long term consequences. To guard against these expensive and long-lasting impacts, security against bad actors is more important than ever before.

Data breaches can be especially costly when it comes to email. Because email provides extensive engagement information, you can develop strategic programs around it. When email data is compromised, marketing and product roadmaps can be dramatically impacted.

IT and security teams highly prioritize the protection of this valuable information. They define and enforce risk mitigation processes, which are put in place to prevent data manipulation and security breaches on your servers. In order to be compliant, you are required to verify that your data is originating from an approved and verified source.

Establishing a secure connection between you and Twilio SendGrid is critical - enter Twilio SendGrid Event Webhook Security!

Secure Event Webhook

The Secure Event Webhook guarantees that your email event data is coming directly from your Twilio SendGrid account. Protect your data and follow security protocol by implementing these two layers of security: Signed Event Webhook Requests and OAuth 2.0.

These two security methods are separate, but can also be implemented simultaneously. While both are highly secure, these features serve different, but valuable security functions. Signed Event Webhook Requests is an authentication method of security, which verifies your identity. OAuth 2.0 is an authorization process that grants permission to access the URL.

With Signed Event Webhook Requests, you are able to verify that the email event data is being posted by a trusted source.

Once enabled, Twilio SendGrid will digitally sign all inbound requests before posting to your HTTP POST URL.

To create the digital signature, we use an asymmetric method of cryptography. This tool is highly secure and easy to implement, as we have developed SDKs for all major languages.

Twilio SendGrid also supports OAuth 2.0. This feature verifies and authorizes Twilio SendGrid, ensuring requests are originating from a trusted source. Through OAuth 2.0, you use the Client Credentials grant type, which requires Twilio SendGrid to post a token with each Event Webhook request. This process provides enhanced security, as well as control over which events you would like to be posted to the URL. However, it also needs advanced configuration, requiring you to provide information for the authorization process.

How Signed Event Webhook Requests works

When you enable Signed Event Webhook Requests, Twilio SendGrid will generate a public/private key pair. The private key is only visible to Twilio SendGrid and accessed when creating the digital signature. The public key (which you can view at any time) is used to verify that the signatures match. Once enabled, each Event Webhook request will have its payload and timestamp hashed using SHA-256.

Using Elliptic Curve Digital Signature Algorithm (ECDSA), Twilio SendGrid will use this hash and the private key to create a digital signature. The signature is then base64 encoded and added to the request as an HTTP header (X-Twilio-Email-Event-Webhook-Signature). The timestamp is also added as an HTTP header (X-Twilio-Email-Event-Webhook-Timestamp) as a measure against replay attacks.

You can verify that an Event Webhook request is from Twilio SendGrid by generating a SHA-256 hash of the payload and the timestamp (from the HTTP header). Then use that hash and the public key to create an ECDSA signature. You will compare this signature with the base64 decoded X-Twilio-Email-Event-Webhook-Signature from the request header to verify that they match. We highly recommend using a package or library from any of our supported languages to automate the signature verification process and make things easier.

How OAuth 2.0 works

You’ll need to provide a Client ID, a Client Secret, and a URL to the authorization service (the token URL), and save this information when creating or editing your Twilio SendGrid Event Webhook.

Once saved, Twilio SendGrid will pass the Client ID and the Client Secret to the token URL and request an access token. The token will then be added to the request as an HTTP Authorization header before posting to your HTTP POST URL. You can trust that the Event Webhook is the verified sender because the token is only shared among your authorization server, Twilio SendGrid, and your application.

Now that you understand how to secure your event webhook, you can implement these new features in your Twilio SendGrid console today! To get set up, follow the instructions provided in Getting Started with the Event Webhook Security Features.

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