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All webhook event deliveries are signed to ensure authenticity and integrity. Your endpoint must validate the signature before processing any event. Verification requests (webhook.verification) are not signed.

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Transport Requirements

Webhook endpoints must:
  • Use HTTPS
  • Support TLS 1.2 or higher
  • Present a valid certificate
Requests are delivered only over secure connections.

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Signature Header

Each event delivery includes the header:
Format:
During secret regeneration, the header may include two signatures:
Where:
  • t is the Unix timestamp (seconds)
  • v1 is generated using the current secret
  • v0 is generated using the previous secret during the transition window

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Signed Payload Format

The signature is generated from:
Important:
  • Use the exact raw request body.
  • Do not reformat or reserialize JSON before verification.
  • Any change to whitespace or formatting will invalidate the signature.

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Verification Process

To validate a delivery:
  1. Extract the timestamp from the X-Alvys-Signature header.
  2. Extract the signature value.
  3. Read the raw request body exactly as received.
  4. Construct the signed payload string.
  5. Compute an HMAC-SHA256 hash using your webhook secret.
  6. Compare the computed value to the signature(s) provided.
  7. Process the event only if a match is found.
Signature comparison should use constant-time comparison to prevent timing attacks.

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Replay Protection

It is recommended to reject requests where:
This helps reduce replay risk.

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Secret Management

Each webhook has a unique signing secret. The secret:
  • Is generated when the webhook is created.
  • Can be regenerated using the Regenerate Secret Key option in the UI.
  • Should be stored securely.
  • Must never be exposed in client-side code or logs.

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If Signature Validation Fails

If the signature cannot be verified:
  • Return HTTP 401 Unauthorized.
  • Do not process the event.
Signature validation must occur before executing any business logic.