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Use JWK from JSON with the lcobucci/jwt library through phpseclib. Credit to @whatTool for helping with the implementation
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<?php | |
//REQUIREMENTS! | |
//"phpseclib/phpseclib": "^3.0" | |
//"lcobucci/jwt": "^5.0" | |
require_once __DIR__ . '/vendor/autoload.php'; | |
$json = '{ | |
"keys": [ | |
{ | |
"kid":"my key id", | |
"nbf":1493763266, | |
"use":"sig", | |
"kty":"RSA", | |
"e":"something something JWK stuff", | |
"n":"something something JWK stuff" | |
} | |
] | |
}'; | |
function getKeyFromJwkJson(string $kid, string $jwkKeySet): ?\Lcobucci\JWT\Signer\Key | |
{ | |
$data = json_decode($jwkKeySet, true, 512, JSON_THROW_ON_ERROR); | |
if ( | |
!is_array($data) || | |
!array_key_exists('keys', $data) || | |
!is_array($data['keys']) || | |
empty($data['keys']) | |
) { | |
return null; | |
} | |
foreach ($data['keys'] as $key) { | |
//TODO: handle nbf on keys | |
if (($key['kid'] ?? '') == $kid) { | |
$publicKey = \phpseclib3\Crypt\PublicKeyLoader::load( | |
\phpseclib3\Crypt\RSA\Formats\Keys\JWK::load( | |
json_encode($key, JSON_THROW_ON_ERROR) | |
) | |
); | |
return \Lcobucci\JWT\Signer\Key\InMemory::plainText( | |
$publicKey->toString('pkcs8') | |
); | |
} | |
} | |
return null; | |
} | |
$key = getKeyFromJwkJson('my key id', $json); | |
if ($key === null) { | |
//no key found | |
exit(1); | |
} | |
$constraints = [ | |
new \Lcobucci\JWT\Validation\Constraint\SignedWith( | |
new \Lcobucci\JWT\Signer\Rsa\Sha256(), | |
$key | |
), | |
]; |
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Made with Azure B2C in mind, where there can be multiple keys and the JWT has the
kid
in the header.