Middleware for Verifying Inter-Service API Calls

VerifyHMAC.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Cache;

class VerifyHMAC
{
    public function handle(Request $request, Closure $next)
    {
        $signature = $request->header('X-Signature');
        $timestamp = $request->header('X-Timestamp');
        $nonce = $request->header('X-Nonce');

        if (!$signature || !$timestamp || !$nonce) {
            abort(401, 'Missing HMAC headers');
        }

        $now = time();
        $ttl = config('services.hmac.ttl', 30);

        if (!is_numeric($timestamp) || abs($now - (int) $timestamp) > $ttl) {
            abort(401, 'Expired request');
        }

        $nonce_key = "hmac_nonce:{$nonce}";

        if (! Cache::add($nonce_key, true, $ttl)) {
            abort(401, 'Replay detected');
        }

        $body = $request->getContent() ?? '';
        $body_hash = hash('sha256', $body);

        $canonical = implode("\n", [
            strtoupper($request->method()),
            '/' . ltrim($request->path(), '/'),
            $body_hash,
            $timestamp,
            $nonce,
        ]);

        $expected = hash_hmac(
            'sha256',
            $canonical,
            config("services.hmac.key")
        );

        if (!hash_equals($expected, $signature)) {
            abort(401, 'Invalid signature');
        }

        return $next($request);
    }
}