Signed requests

Sign events and webhooks

Signing requests

Both webhooks and events can be signed for extra security.

Signing webhooks

For webhooks if you'd like the requests to be signed to ensure that they are authentic requests from formsort, you can enable the sign security. Read more about creating a webhook here.

Signing events

All events for variant_revision_published are signed by default. The signature for verfication can be found on the "Events" page.

Note: The signing key is generated by Formsort, and is different across events and webhooks.

How to verify a signature

To generate the signature for verification, use the original HTTP request body (aka JSON payload) and:

  1. Hash the request body with SH256, encrypting it with signing key.

    1. You can obtain the key in the Integrations tab when this option is enabled.

  2. Base64 encode the result in a URL-safe-way, using - and _ instead of the + and / characters. This is necessary as Formsort sends the signature in an HTTP header.

  3. Remove the trailing = signs. Those are often generated by the hashing libraries as padding.

Sample implementations of the signature code follow:

import base64
import hashlib
import hmac


def as_bytes(v):
    return v.encode("utf8")


def hmac_sign(signing_key, original_request_body):  # unmodified, a jsonified string
    key = as_bytes(signing_key)
    message = as_bytes(original_request_body)
    return (
        # Note:
        # 1. for url safety, use - and _ characters instead of + and / respectively
        # 2. remove the padding = signs at the end of the signature
        base64.urlsafe_b64encode(
            hmac.new(key, message, hashlib.sha256).digest())
            .rstrip(b"=")
            .decode("utf8")
    )

Note

When signing is enabled, Formsort will send the following additional HTTP headers on webhook requestsο»ΏIf signature is enabled, then X-Formsort-Secure will have the value of "sign" and X-Formsort-Signature will have the signature itself.

HeaderValue

X-Formsort-Secure

sign

X-Formsort-Signature

{the hash}

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