Module: NakoPay::Webhook

Defined in:
lib/nakopay/webhook.rb

Overview

Webhook signature verifier.

NakoPay::Webhook.construct_event(raw_body, sig_header, secret)

Header format: t=<unix>,v1=<hex_hmac> Signed payload: <t>.<raw_body>

Constant Summary collapse

DEFAULT_TOLERANCE =

seconds

300

Class Method Summary collapse

Class Method Details

.construct_event(payload, sig_header, secret, tolerance: DEFAULT_TOLERANCE) ⇒ Object

Raises:



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# File 'lib/nakopay/webhook.rb', line 16

def construct_event(payload, sig_header, secret, tolerance: DEFAULT_TOLERANCE)
  raise SignatureVerificationError.new("missing X-NakoPay-Signature header", code: "signature_missing") if sig_header.nil? || sig_header.empty?
  raise SignatureVerificationError.new("webhook secret is required", code: "secret_missing") if secret.nil? || secret.empty?

  parts = sig_header.split(",").each_with_object({}) do |kv, h|
    k, v = kv.split("=", 2)
    h[k.strip] = v.to_s.strip if k && v
  end

  ts = Integer(parts["t"]) rescue nil
  v1 = parts["v1"]
  raise SignatureVerificationError.new("malformed signature header", code: "signature_invalid") if ts.nil? || v1.nil? || v1.empty?

  now = Time.now.to_i
  if (now - ts).abs > tolerance
    raise SignatureVerificationError.new("timestamp outside tolerance window", code: "signature_timestamp_outside_tolerance")
  end

  expected = OpenSSL::HMAC.hexdigest("sha256", secret, "#{ts}.#{payload}")
  unless secure_compare(expected, v1)
    raise SignatureVerificationError.new("signature does not match expected value", code: "signature_mismatch")
  end

  begin
    JSON.parse(payload)
  rescue JSON::ParserError
    raise SignatureVerificationError.new("webhook payload is not valid JSON", code: "payload_invalid_json")
  end
end

.secure_compare(a, b) ⇒ Object 



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# File 'lib/nakopay/webhook.rb', line 46

def secure_compare(a, b)
  return false unless a.bytesize == b.bytesize

  l = a.unpack("C*")
  res = 0
  b.each_byte { |byte| res |= byte ^ l.shift }
  res.zero?
end