s3 post signature

gistfile1.txt

http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-authentication-HTTPPOST.html
calculating a signature.
it has a few componenets.
a. security policy
b. secret access key
c. YYYMMMDDD
d. region
e. service
--
create a function that accepts 5 parameters
if input is 'alpha', 'beta', 'charlie', 'delta', 'echo'
you will get
step 1: YWxwaGE=
'alpha' in base64
step 2: 41575334627261766f
"AWS4" + 'beta' in hex
step 3: 00ce876cf352b93ed17012f318cf978432b658a3f6462e76bc918be51a8ea4b0
HmacSHA256('charlie', byte content of step 2)
step 4: 13673e0e290302747f9a14e8eee353a21f936965a1871ccd78bf5f206028606a
HmacSHA256('delta', byte content of step 3)
step 5: a773894f2252dd5815e525a83bad7dd5c17df6b7415838f0662948eaccb97f29
HmacSHA256('echo', byte content of step 4)
step 6: 3f9baa134ef279b39da4ab7ff8835662a70b1ac67d88da71540d437cb5488493
HmacSHA256('aws4_request', byte content of step 5)
step 7: 7b9d11447e7bba48ef0d530f49d82de8adfd7b7ae064b144e6ac60d82166e4a6
HmacSHA256(step1, byte content of step 6)
result is 7b9d11447e7bba48ef0d530f49d82de8adfd7b7ae064b144e6ac60d82166e4a6
====
another example
"fish", "green", "20160301", "ap-southeast-2", "s3"
step 1:ZmlzaA==
'fish' in base64

step 2:41575334677265656e
'AWS4' + 'green' in hex

step 3:d0dcd115158409d74ea070f20ad61c4651cb86d1a609f74f4964300c258b6dc6
HmacSHA256('20160301', byte content of step 2)

step 4:5e77c91a5ef8c14d73969c21befdf24c3d6e5ee23d6a2c191500e4ce2321553f
HmacSHA256('ap-southeast-2', byte content of step 3)

step 5:6440c57d0604a90857936d8ab2eea85982060e9a213c86ba1140598e7eb08468
HmacSHA256('s3', byte content of step 4)

step 6:9f9cce4e141ea8ef162fdef0b904e5260ac826036662cba94edc715690e01f8a
HmacSHA256('aws4_request', byte content of step 5)

step 7:8f32d6d8524397196512e02b6ed9a885d821de49f02d9922a1dd0a718c3150b1
HmacSHA256('ZmlzaA==', byte content of step 6)
result is 8f32d6d8524397196512e02b6ed9a885d821de49f02d9922a1dd0a718c3150b1
==
var CryptoJS = require("crypto-js");

var policy = 'fish';
var secretKey = 'green';
var dateStamp = '20160301';
var regionName = 'ap-southeast-2';
var serviceName = 's3';
var policyInBase64 = new Buffer(policy).toString('base64');

function create_signature(policyInBase64, secretKey, dateStamp, regionName, serviceName) {
        var step1 = policyInBase64;
        console.log('step 1: ' + step1);

        var step2 = "AWS4" + secretKey;
        console.log('step 2: ' + new Buffer(step2).toString('hex'));

        var step3 = CryptoJS.HmacSHA256(dateStamp, step2);
        console.log('step 3: ' + step3.toString(CryptoJS.enc.Hex))

        var step4 = CryptoJS.HmacSHA256(regionName, step3);
        console.log('step 4: ' + step4.toString(CryptoJS.enc.Hex))

        var step5 = CryptoJS.HmacSHA256(serviceName, step4);
        console.log('step 5: ' + step5.toString(CryptoJS.enc.Hex))

        var step6 = CryptoJS.HmacSHA256('aws4_request', step5);
        console.log('step 6: ' + step6.toString(CryptoJS.enc.Hex))

        var step7 = CryptoJS.HmacSHA256(step1, step6);
        console.log('result : ' + step7.toString(CryptoJS.enc.Hex))

}
create_signature(policyInBase64, secretKey, dateStamp, regionName, serviceName);

$ node hash.js 
step 1: ZmlzaA==
step 2: 41575334677265656e
step 3: d0dcd115158409d74ea070f20ad61c4651cb86d1a609f74f4964300c258b6dc6
step 4: 5e77c91a5ef8c14d73969c21befdf24c3d6e5ee23d6a2c191500e4ce2321553f
step 5: 6440c57d0604a90857936d8ab2eea85982060e9a213c86ba1140598e7eb08468
step 6: 9f9cce4e141ea8ef162fdef0b904e5260ac826036662cba94edc715690e01f8a
result : 8f32d6d8524397196512e02b6ed9a885d821de49f02d9922a1dd0a718c3150b1
===
minimal policy
{"expiration": "2016-02-19T23:04:44.515Z","conditions": [{"bucket": "titi-wangsa-bucket-1"},{"x-amz-credential": "AKIAI6HWQ3FQQY2DDMPQ/20160219/ap-southeast-2/s3/aws4_request"},{"x-amz-date": "20160219T225944Z"},{"x-amz-algorithm": "AWS4-HMAC-SHA256"},["starts-with", "$key", ""]]}

==
	private void populatePost(final HttpPost httpPost) {
		final MultipartEntityBuilder builder = MultipartEntityBuilder.create();
		builder.addTextBody("key", "${filename}");
		builder.addTextBody("policy", policyBase64);
		builder.addTextBody("x-amz-signature", signature);
		builder.addTextBody("x-amz-credential", credential);
		builder.addTextBody("x-amz-date", date4);

		builder.addTextBody("x-amz-algorithm", "AWS4-HMAC-SHA256");
		final File file = new File("./blank.jpg");
		builder.addBinaryBody("file", file);
		final HttpEntity entity = builder.build();
		httpPost.setEntity(entity);
	}