Validating Twilio Authy Callbacks
As of November 2022, Twilio no longer provides support for Authy SMS/Voice-only customers. Customers who were also using Authy TOTP or Push prior to March 1, 2023 are still supported. The Authy API is now closed to new customers and will be fully deprecated in the future.
For new development, we encourage you to use the Verify v2 API.
Existing customers will not be impacted at this time until Authy API has reached End of Life. For more information about migration, see Migrating from Authy to Verify for SMS.
When using Webhooks with push authentications, Twilio will send a callback to your application's exposed URL when a user interacts with your
ApprovalRequest. While testing, you can accept all incoming webhooks, but in production, you'll need to verify the authenticity of incoming requests.
Twilio sends an HTTP Header
X-Authy-Signature with every outgoing request to your application.
X-Authy-Signature is a HMAC signature of the full message body sent from Twilio hashed with your Application API Key (from Authy in the Twilio Console).
You can find complete code snippets here on Github.
Verify a Twilio Authy Callback
Checking the authenticity of the
X-Authy-Signature HTTP Header is a 6 step process.
- Create a string using the
URLwithout any parameters
- Flatten the received JSON body and sort this list in case-sensitive order and convert them to URL format
- Grab the nonce from the
- Join the nonce, HTTP method ('
POST'), and the sorted parameters together with the vertical pipe, ('|') character
- Use HMAC-SHA256 to hash the string using your Application API Key
- Base64 Encode the digest (as described in RFC 4648 - do not include line breaks)
Here is every step summarized so you can get an idea of the whole process.
Once you have encoded the digest, you can compare the resulting string with the
X-Authy-Signature HTTP Header. If they match, the incoming request is from Twilio. If there is a mismatch, you should reject the request as fraudulent.
Need some help?
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