streams/Zotlabs/Module/Jwks.php

<?php

namespace Zotlabs\Module;

use Zotlabs\Lib\Keyutils;
use Zotlabs\Web\Controller;

class Jwks extends Controller {

	function init() {
		
		Keyutils::pemtome(get_config('system','pubkey'),$m,$e);

		/**
		 * RFC7518
		 *
			6.3.1.1.  "n" (Modulus) Parameter

		   The "n" (modulus) parameter contains the modulus value for the RSA
		   public key.  It is represented as a Base64urlUInt-encoded value.

		   Note that implementers have found that some cryptographic libraries
		   prefix an extra zero-valued octet to the modulus representations they
		   return, for instance, returning 257 octets for a 2048-bit key, rather
		   than 256.  Implementations using such libraries will need to take
		   care to omit the extra octet from the base64url-encoded
		   representation.
		*
		*/

		$l = strlen((string) $m);
		if ($l & 1) {
			$m = substr((string) $m,1);
		}

		$keys = [
			[
				'e'   => base64url_encode($e),
				'n'   => base64url_encode($m),
				'kty' => 'RSA',
				'kid' => '0',
			]
		];


		$ret = [
			'keys' => $keys
		];

		if (argc() > 1) {
			$entry = intval(argv(1));
			if ($keys[$entry]) {
				unset($keys[$entry]['kid']);
				json_return_and_die($keys[$entry],'application/jwk+json');
			}
		}

		json_return_and_die($ret,'application/jwk-set+json');
		
	}
}