Add verifyRequestSignature helper for webhook validation#227
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mike-engel merged 1 commit intoJul 2, 2026
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Adds a helper to verify that incoming reporting-webhook requests genuinely came from Customer.io, addressing customerio#155. Customer.io signs each request with an HMAC-SHA256 over `v0:<timestamp>:<body>` keyed with your webhook signing secret, sent hex-encoded in the X-CIO-Signature header. The helper recomputes that signature and compares it in constant time (crypto.timingSafeEqual), guarding the length first. It accepts string or Buffer bodies to avoid lossy re-serialization, returns false for a missing/malformed signature, and throws MissingParamError only for an empty signing secret. Includes 11 unit tests (100% coverage), a README section, and the package export.
mike-engel
approved these changes
Jul 2, 2026
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Thanks for this @brian717! This will go out in the next release |
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Summary
Adds a
verifyRequestSignaturehelper so consumers can verify that incoming Customer.io reporting webhooks are authentic, addressing #155.Also, updated the README under a new "Webhooks" section. If this is not important enough to take up space in the main README, it can be removed (or maybe moved elsewhere?)
Testing
11 new unit tests in
test/webhooks.ts, lint and prettier run. All passed locally.Notes
.digest('hex')convention (the docs don't state it explicitly).Note
Medium Risk
Touches webhook authentication logic; incorrect verification could accept forged webhooks, though the change is additive and well-tested.
Overview
Adds
verifyRequestSignatureso apps can confirm Customer.io reporting webhooks are authentic (addresses #155). The helper recomputes HMAC-SHA256 overv0:<timestamp>:<body>with the webhook signing secret, compares the hex digest toX-CIO-SignatureviatimingSafeEqual(with length checks first), and returnsfalsefor bad/missing signatures while throwingMissingParamErrorifsigningSecretis empty. It accepts rawstringorBufferbodies andstringornumbertimestamps.Implementation lives in new
lib/webhooks.ts, re-exported from the package entrypoint. The README gains a Webhooks section with an Express-style example and option docs.test/webhooks.tsadds 11 unit tests covering valid signatures, a golden hash, tampering, wrong secret/timestamp, malformed signatures, and empty secret.Reviewed by Cursor Bugbot for commit 496c2fd. Bugbot is set up for automated code reviews on this repo. Configure here.