S3 Server singing Code

sign.js

router.get('/sign_s3', function * () {
    var object_name = this.request.query.s3_object_name;
    var mime_type = this.request.query.s3_object_type;
    
    var now = new Date();
    var expires = Math.ceil((now.getTime() + 1000000) / 1000); // 1000 seconds from now
    var amz_headers = "x-amz-acl:public-read";

    var put_request = "PUT\n\n" + mime_type + "\n" + expires + "\n" + amz_headers + "\n/" + S3_BUCKET + "/" + object_name;

    var signature = crypto.createHmac('sha1', AWS_SECRET_KEY).update(put_request).digest('base64');
    signature = signature.replace('+','%2B').replace('/','%2F').replace('=','%3D');
    signature = encodeURIComponent(signature.trim());
    var url = 'https://' + S3_BUCKET + '.s3.amazonaws.com/' + object_name;

    var credentials = {
        signed_request: url + "?AWSAccessKeyId=" + AWS_ACCESS_KEY + "&Expires=" + expires + "&Signature=" + signature,
        url: url
    };
    this.body = JSON.stringify(credentials);
});