Creating a signed S3 URL with Javascript

I would try using Knox along with Node.Js . Its known to be a great combination and also itself utilizes the Node.JS Crypto library which is kind of what you're trying to do - saving you time:)

More info here : https://github.com/LearnBoost/knox

Than, you could just do something like:

var knox = require('knox');
var s3Client = knox.createClient({
    key: 'XXX',
    secret: 'XXX',
    bucket: 'XXX'
});

var expires = new Date();
expires.setMinutes(expires.getMinutes() + 30);
var url =  s3Client.signedUrl(filename, expires);

Edit: You could also look into Knox and just check what the signedUrl function does and implement that yourself.Than you could add to the auth.signQuery call an extra option called amazonHeaders:

Client.prototype.signedUrl = function(filename, expiration){
  var epoch = Math.floor(expiration.getTime()/1000);
  var signature = auth.signQuery({
    amazonHeaders: 'response-content-disposition:attachment',
    secret: this.secret,
    date: epoch,
    resource: '/' + this.bucket + url.parse(filename).pathname
  });

  return this.url(filename) +
    '?Expires=' + epoch +
    '&AWSAccessKeyId=' + this.key +
    '&Signature=' + encodeURIComponent(signature);
};

Shai.

maybe one too many newlines?

var stringToSign ='GET\n\n\n' + date + '\n\n' + resource;

If its any help here is a rubbish PHP implementation which definitely works:

class myS3Helper{
public function getSignedImageLink($timeout = 1800)
    {

        $now = new Zend_Date(); //Gives us a time object that is set to NOW
        $now->setTimezone('UTC'); //Set to UTC a-la AWS requirements
        $now->addSecond($timeout);
        $expirationTime = $now->getTimestamp(); //returns unix timestamp representation of the time.

        $signature = urlencode(
                base64_encode(
                        hash_hmac(
                                'sha1', $this->_generateStringToSign($expirationTime),
                                $my_aws_secretkey, 
                                true
                                )
                        )
                );

        //FIXME make this less ugly when I know it works
        $url = 'https://';
        $url .= Zend_Service_Amazon_S3::S3_ENDPOINT; //e.g s3.amazonaws.com
        $url .= $this->_getImagePath(); //e.g /mybucket/myFirstCar.jpg
        $url .='?AWSAccessKeyId=' . $my_aws_key;
        $url .='&Signature=' . $signature; //signature as returned by below function
        $url .='&Expires=' . $expirationTime;

        return $url;


    }

    protected function _generateStringToSign($expires)
    {   

        $string = "GET\n"; //Methods
        $string .= "\n";
        $string .= "\n";
        $string .= "$expires\n"; //Expires
        $string .= $this->_getImagePath();

        return $string;
    }

}

EDIT--

Have a look at this node.js s3 upload code, (it's not mine but found it lying around on my mac - so if anyone can attribute it to someone let me know and i'll do the props). Hopefully this might help (3rd time lucky)

https://gist.github.com/1370593

My implementation using AWS-SDK and Rx.

import AWS from "aws-sdk"
import Rx from 'rx'

/*
* Credentials could be loaded from env variables
* http://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/loading-node-credentials-environment.html
* */

const s3 = new AWS.S3({apiVersion: '2006-03-01'});

export function getS3SignedImage(objectKey) {
    return Rx.Observable.create(function (observer) {
        s3.getSignedUrl('getObject',{
            Bucket: process.env.AWS_BUCKET,
            Key: objectKey
        }, (err, data) => {
            if (err) {
                return observer.onError(err);
            }
            observer.onNext(data);
            observer.onCompleted();
        });
    });
}