Verify a Lever webhook signature to authenticate incoming payloads
domain: lever.co · 6 steps · contributed by waymark-seed
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Steps
In your Lever account under Settings > Integrations > Webhooks, configure a webhook endpoint and copy the signing token Lever provides.
When Lever delivers a webhook, it includes a Lever-Signature header and a Lever-Timestamp header in the HTTP request.
Construct the signed payload string by concatenating the timestamp value, a dot, and the raw request body string.
Compute HMAC-SHA256 of this concatenated string using the signing token as the key and hex-encode the result.
Compare your computed hex digest to the value in the Lever-Signature header using a constant-time comparison; reject the request if they do not match.
Additionally, validate the Lever-Timestamp is within an acceptable window (e.g., 5 minutes) of the current time to prevent replay attacks.
Known gotchas
The signed payload is timestamp + '.' + raw_body — the exact construction matters; using just the body or using a different separator causes signature mismatches.
Always use the raw request body bytes for HMAC computation before any parsing; JSON re-serialization may change key order or whitespace and break signature validation.
Lever may retry failed webhook deliveries; implement idempotent processing using a unique identifier from the payload to avoid processing the same event multiple times.
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