(PHP Extension) Verify a JWT Created by the Amazon Cognito Service

Demonstrates how to verify a JWT created by the Amazon Cognito Service.

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
// Let's get them:

$http = new CkHttp();
$sbJsonKeys = new CkStringBuilder();
$success = $http->QuickGetSb('https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json',$sbJsonKeys);
if ($success == false) {
    print $http->lastErrorText() . "\n";
    exit;
}

$jsonKeys = new CkJsonObject();
$jsonKeys->LoadSb($sbJsonKeys);
$jsonKeys->put_EmitCompact(false);
print $jsonKeys->emit() . "\n";

// Here are the keys:

// {
//   "keys": [
//     {
//       "alg": "RS256",
//       "e": "AQAB",
//       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
//       "kty": "RSA",
//       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
//       "use": "sig"
//     },
//     {
//       "alg": "RS256",
//       "e": "AQAB",
//       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
//       "kty": "RSA",
//       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
//       "use": "sig"
//     }
//   ]
// }

// Try the 1st key.
// jsonKey1 is a CkJsonObject
$jsonKey1 = $jsonKeys->ObjectOf('keys[0]');
if ($jsonKeys->get_LastMethodSuccess() == false) {
    print 'Did not get the 1st JSON public key.' . "\n";
    exit;
}

$pubKey1 = new CkPublicKey();
$success = $pubKey1->LoadFromString($jsonKey1->emit());
if ($success == false) {
    print $pubKey1->lastErrorText() . "\n";
    exit;
}

print 'Success' . "\n";

$jwt = new CkJwt();

// I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
$token = 'eyJ..asXg';

// First verify the signature.
$sigVerified = $jwt->VerifyJwtPk($token,$pubKey1);
print 'verified: ' . $sigVerified . "\n";

// Let's see if the time constraints, if any, are valid.
// The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
// If the current system time is before the "nbf" time, or after the "exp" time,
// then IsTimeValid will return false/0.
// Also, we'll allow a leeway of 60 seconds to account for any clock skew.
// Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
$leeway = 60;
$bTimeValid = $jwt->IsTimeValid($token,$leeway);
print 'time constraints valid: ' . $bTimeValid . "\n";

// Now let's recover the original claims JSON (the payload).
$payload = $jwt->getPayload($token);
// The payload will likely be in compact form:
print $payload . "\n";

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
$json = new CkJsonObject();
$success = $json->Load($payload);
$json->put_EmitCompact(false);
print $json->emit() . "\n";

// We can recover the original JOSE header in the same way:
$joseHeader = $jwt->getHeader($token);
// The payload will likely be in compact form:
print $joseHeader . "\n";

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
$success = $json->Load($joseHeader);
$json->put_EmitCompact(false);
print $json->emit() . "\n";

?>