PHP Requires Chilkat v11.0.0+

Validate a Google ID Token

See more OAuth2 Examples

Demonstrates how to verify the signature of a Google id token. Chilkat2 PHP

<?php

use Chilkat2\Http;
use Chilkat2\JsonObject;
use Chilkat2\PublicKey;
use Chilkat2\Rsa;
use Chilkat2\StringBuilder;

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

$http = new Http();

// First get the public key we'll be needing..
try {
    $jwkStr = $http->QuickGetStr('https://www.googleapis.com/oauth2/v3/certs');
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// We have the following:

//     {
//       "keys": [
//     {
//       "kid": "e8732db06287515556213b80acbcfd08cfb302a9",
//       "n": "4RIrO30287Wsq3gqXCMkUYMVAeI3H8...w2mbMNEBQ",
//       "kty": "RSA",
//       "e": "AQAB",
//       "alg": "RS256",
//       "use": "sig"
//     },
//     {
//       "kid": "8462a71da4f6d611fc0fecf0fc4ba9c37d65e6cd",
//       "e": "AQAB",
//       "n": "xT_ngLZNmT5GBtJZeTB...Ft4gK0eoFi0d3l8bcw",
//       "alg": "RS256",
//       "use": "sig",
//       "kty": "RSA"
//     }
//       ]
//     }

$json = new JsonObject();
$json->Load($jwkStr);

// -------------------------------------------------

// Load the following..

//  {
//   "access_token": "ya29.a0...0f",
//   "expires_in": 3599,
//   "scope": "openid https://www.googleapis.com/auth/userinfo.email",
//   "token_type": "Bearer",
//   "id_token": "eyJhb...o5nQ"
// }

$jsonToken = new JsonObject();
try {
    $jsonToken->LoadFile('qa_data/tokens/google_sample_id_token.json');
} catch (\Chilkat2\Exception $e) {
    echo "Failed to load the JSON file...\n";
    exit;
}

// Get the id_token;
$sbIdToken = new StringBuilder();
$sbIdToken->Append($jsonToken->StringOf('id_token'));

// Get the signature in base64url format.
// The header + payload remains in sbIdToken.
$sig_b64Url = $sbIdToken->GetAfterFinal('.', true);
$headerPlusPayload = $sbIdToken->GetAsString();

echo $sig_b64Url, "\n";
echo $headerPlusPayload, "\n";

// ---------------------------------------------

// Try validating with each cert's public key.
// Hopefully one will be the key that verifies.

$rsa = new Rsa();
$rsa->EncodingMode = 'base64url';

$jsonKey = new JsonObject();
$pubKey = new PublicKey();

$numKeys = $json->SizeOfArray('keys');
$i = 0;
while ($i < $numKeys) {
    $json->I = $i;

    $json->ObjectOf2('keys[i]', $jsonKey);

    try {
        $pubKey->LoadFromString($jsonKey->Emit());
    } catch (\Chilkat2\Exception $e) {
        echo $e->getMessage(), "\n";
        exit;
    }

    echo $i, "\n";
    echo $pubKey->GetPem(true), "\n";

    $rsa->UsePublicKey($pubKey);

    try {
        $rsa->VerifyStringENC($headerPlusPayload, 'sha256', $sig_b64Url);
        $bVerified = true;
    } catch (\Chilkat2\Exception $e) {
        $bVerified = false;
    }
    echo 'bVerified = ', ($bVerified ? 'true' : 'false'), "\n";

    $i = $i + 1;
}

// The output is:

// 0
// -----BEGIN RSA PUBLIC KEY-----
// MIIBCgKCAQEA4RIrO30287Wsq3gqXCMkUYMVAeI3H8LVE6IXR1krdFeGnZLiGUPw
// cbkeVpXf3lmJdsStOg+jijces2DZCfPyIBiQuLYfxxmAZE6ErJ0QJFg1stwli2Pz
// 9ncYhFoqi8pXr7kEzEJBTzX4thuw56ydbGsshSEznPXoerCJOc7UI2+n0wFCWQ4Y
// LHbh/PrWt4vdadyUUUW/QpQHXQLdD8q/Qwqdj0O9zlJE7R6Elw2E9EqnHyIGu1hm
// LxhqrTru1M18SUhONYbVskV/BCEdVKs//X96849HorWQDCAgVMWfGsdMVq55FAdJ
// 680N5UmQDRynIZ4+PeNGN4S9iw2mbMNEBQIDAQAB
// -----END RSA PUBLIC KEY-----
//
// bVerified = True
// 1
// -----BEGIN RSA PUBLIC KEY-----
// MIIBCgKCAQEAxT/ngLZNmT5GBdkLtJZjNeTB+8B5yWgrq/e5eMZ1hrZhcmLK+dSn
// IkpOPV8/OekV67EnQ7I4II2rcNJnHGrGKZziXO3XN2gtUHE+mBJC99oULSbX/QwB
// Kz7gC/IBPq9EuxTt6Oq6fPkVQ9DbRIgWJSEGBF/KRaNl3kyAlIZfpY7XgHyJTTv8
// E7yAcYKPR+36gzdl+ps0sDLKzUuAtZNq8llK0u80z6AtAUIYwWdkEhM9upy6keKI
// TasIxcsO7M6kZPINUSbh6t5VAm8FuqRmxpgg+9c9/GQSGd89InVypoVzWLQ+wOGg
// 5G4H6JqIgtj0TRFt4gK0eoFi2U0d3l8bcwIDAQAB
// -----END RSA PUBLIC KEY-----
//
// bVerified = False