Create signed URL for Google Cloud Storage using NodeJS
Stuck Kennedy
I'm trying to create a signature for a privately stored file in Google Cloud Storage; so I can distribute a limited time link.
Currently doing this and the signature is too short...where am I going wrong?
var crypto = require("crypto");
var ttl = new Date().getTime() + 3600;
var id = 'the_target_file.txt';
var bucketName = 'bucket_name';
var POLICY_JSON = "GET\n" + "\n" + "\n" + ttl + "\n" + '/' + bucketName + '/' + id;
// stringify and encode the policy
var stringPolicy = JSON.stringify(POLICY_JSON);
var base64Policy = Buffer(stringPolicy, "utf-8").toString("base64");
// sign the base64 encoded policy
var privateKey = "MY_PRIVATE_KEY";
var sha256 = crypto.createHmac("sha256", privateKey);
var signature = sha256.update(new Buffer(base64Policy, "utf-8")).digest("base64");
console.log ( signature );
Stuck Kennedy
Realised I was doing something wrong...I was hashing the policy string, not signing it. Now the following code gives me the correct output.
var crypto = require("crypto");
var fs = require("fs");
var expiry = new Date().getTime() + 3600;
var key = 'the_target_file';
var bucketName = 'bucket_name';
var accessId = 'my_access_id';
var stringPolicy = "GET\n" + "\n" + "\n" + expiry + "\n" + '/' + bucketName + '/' + key;
var privateKey = fs.readFileSync("gcs.pem","utf8");
var signature = encodeURIComponent(crypto.createSign('sha256').update(stringPolicy).sign(privateKey,"base64"));
var signedUrl = "https://" + bucketName + ".commondatastorage.googleapis.com/" + key +"?GoogleAccessId=" + accessId + "&Expires=" + expiry + "&Signature=" + signature;
console.log(signedUrl);
For completeness... here's a PHP version that does the same thing I use to check the results
$expiry = time() + 3600;
$key = 'the_target_file';
$bucketName = 'bucket_name';
$accessId = 'my_access_id';
$stringPolicy = "GET\n\n\n".$expiry."\n/".$bucketName."/".$key;
$fp = fopen('gcs.pem', 'r');
$priv_key = fread($fp, 8192);
fclose($fp);
$pkeyid = openssl_get_privatekey($priv_key,"password");
if (openssl_sign( $stringPolicy, $signature, $pkeyid, 'sha256' )) {
$signature = urlencode( base64_encode( $signature ) );
echo 'https://'.$bucketName.'.commondatastorage.googleapis.com/'.
$key.'?GoogleAccessId='.$accessId.'&Expires='.$expiry.'&Signature='.$signature;
}