gistfile1.js

var crypto = require("crypto")
	, util = require("util")
	, express = require("express");

var s3 = {
	access_key_id: "<access_key>"
	, secret_key: "<your_secret_key>"
	, bucket: "<your_bucket>"
	, acl: "public-read"
	, https: "false"
	, error_message: ""
	, pad: function(n) {
		if ((n+"").length == 1) {
			return "0" + n;
		}
		return ""+n;
	}, expiration_date: function() {
		var now = new Date();
		var date = new Date( now.getTime() + (3600 * 1000) );
		var ed = date.getFullYear() + "-" + this.pad(date.getMonth()+1) + "-" + this.pad(date.getDate());
			ed += "T" + this.pad(date.getHours()) + ":" + this.pad(date.getMinutes()) + ":" + this.pad(date.getSeconds()) + ".000Z";
		return ed;
	}
};

var app = express.createServer();
app.get("/crossdomain.xml", function(req,res) {
	res.header("Content-Type", "text/xml");
	res.end("<?xml version=\"1.0\"?><!DOCTYPE cross-domain-policy SYSTEM \"http://www.adobe.com/xml/dtds/cross-domain-policy.dtd\"><cross-domain-policy><allow-access-from domain=\"*\" to-ports=\"*\" secure=\"false\" /></cross-domain-policy>");
});
app.get("/", function(req,res) {
	var expiry_date = s3.expiration_date();
	var signatureString = "{\n		'expiration': '" + expiry_date + "',\n"
			+ "		'conditions': [\n"
			+ "				{'bucket': '" + s3.bucket + "'},"
			+ "				{'key': '" + req.param("key", null) + "'},"
			+ "				{'acl': '" + s3.acl + "'},"
			+ "				{'Content-Type': '" + req.param("content_type", null) + "'},"
			+ "				{'Content-Disposition': 'attachment'},"
			+ "				['starts-with', '$Filename', ''],"
			+ "				['eq', '$success_action_status', '201']\n	]\n}";

	var policy = new Buffer(signatureString).toString('base64').replace(/\n|\r/, '');
	var hmac = crypto.createHmac("sha1", s3.secret_key);
	var hash2 = hmac.update(policy);
	var signature = hmac.digest(encoding="base64");
	var xmlString = "<hash>";
	xmlString += "<policy>" + policy + "</policy>";
	xmlString += "<signature>" + signature + "</signature>";
	xmlString += "<bucket>" + s3.bucket + "</bucket>";
	xmlString += "<accesskeyid>" + s3.access_key_id + "</accesskeyid>";
	xmlString += "<acl>" + s3.acl + "</acl>";
	xmlString += "<expirationdate>" + expiry_date + "</expirationdate>";
	xmlString += "<https>" + s3.https + "</https>";
	xmlString += "<errorMessage>" + s3.error_message + "</errorMessage>";
	xmlString += "</hash>";
	
	res.end(xmlString);
	
});
app.listen(1374);