Sample Cognito webhook receiver

app.rb

require 'sinatra'
require 'json'
require 'openssl'
require 'base64'

ENDPOINT_SECRET = 'fe1eb40c8e8d2164ffff0316a40e5f237f2e2742877e6c47a969643411547f74'

post '/webhook' do
	puts ""
	puts 'Webhook received!'
	puts ""

	json = request.body.read
	puts "JSON Hash From Body:"
	puts JSON.parse(json)
	puts ""

	puts "Cognito-Signature Header:"
	puts header = request.env['HTTP_COGNITO_SIGNATURE']
	puts ""

	# parse down the header
	header_hash = header.split(',').each_with_object({}) do |pair_string, hash|
		arr = pair_string.split('=', 2)
		hash[arr[0]] = arr[1]
	end

	puts "Timestamp in header:"
	puts timestamp = header_hash["t"]
	puts "Header signature string:"
	puts header_signature = header_hash["v1"]

	created_signature = Base64.strict_encode64(
  	OpenSSL::HMAC.digest(
    	OpenSSL::Digest::SHA256.new, ENDPOINT_SECRET, "#{timestamp}.#{json}"
  	)
	)
	puts "Created signature string:"
	puts created_signature
	if created_signature == header_signature
		puts "They match!"
	else
		puts "THEY DO NOT MATCH!!!"
	end
	puts ""
end