Validating the Webhook Camayak-Signature header – Sample PHP Code

<?php
        private function get_header_signature() {
            $key = 'Camayak-Signature';
            foreach (getallheaders() as $name => $value) {
                if($name == $key) {
                    return $value;
                }
            }
            return NULL;
        }

        private function calculate_signature($epoch) {
            return hash_hmac('sha1', $epoch . $this->api_key, $this->shared_secret);
        }

        public function verify() {
            // Verify that the incoming request is from Camayak.
            $camayak_signature = $this->get_header_signature();
            if(is_null($camayak_signature)) {
                return true;
            }

            // Work out the drift permutations.
            $time = time();
            $epochs = array($time);
            // signed_url_drift is how many seconds into the future and past to generate
            //    test signatures.  3 seconds should be sufficient.
            foreach(range(1, $this->signed_url_drift) as $sec) {
                $epochs[] = $time + $sec;
                $epochs[] = $time - $sec;
            }

            foreach($epochs as $epoch) {
                $signature = $this->calculate_signature($epoch);
                if($signature == $camayak_signature) {
                    return true;
                }
            }
            return false;
        }
?>