问进行Google调用时的无效JWT签名

EN

{"error":"invalid_grant","error_description":"Invalid JWT Signature."}

<?php


$config = json_decode('service_account_key',true);

$jwt_header = '{"alg":"RS256","typ":"JWT"}';
$jwt_header_cryph = urlencode(base64_encode($jwt_header));

$jwt_claim = '{
            "iss": "service_account_id",
            "scope":"https://www.googleapis.com/auth/datastore",
            "aud":"https://oauth2.googleapis.com/token",
            "exp":'.(time()+3600).',
            "sub": "user_email"
            "iat":'.time().'
        }';

$jwt_claim_cryph = urlencode(base64_encode($jwt_claim));

$data = $jwt_header_cryph.".".$jwt_claim_cryph;

$binary_signature = "";

$algo = "SHA256";
openssl_sign($data, $binary_signature, $config['private_key'], $algo);
$jws_signature_cryph = urlencode(base64_encode($binary_signature));


$complete_request = $jwt_header_cryph.".".$jwt_claim_cryph.".".$jws_signature_cryph;

$curl_url = 'https://oauth2.googleapis.com/token';

$fields = array(
    'grant_type' => urlencode('urn:ietf:params:oauth:grant-type:jwt-bearer'),
    'assertion' => $complete_request
);

$fields_string = "";

foreach($fields as $key=>$value) { $fields_string .= $key.'='.$value.'&'; }
rtrim($fields_string, '&');

$ch = curl_init();

curl_setopt($ch,CURLOPT_URL, $curl_url);
curl_setopt($ch,CURLOPT_POST, count($fields));
curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);
curl_setopt($ch,CURLOPT_RETURNTRANSFER, true );


$result = curl_exec($ch);

curl_close($ch);

 $token = json_decode($result, true);
echo($token);