SignedRequestHelper.java

package org.ebayopensource.turmeric.demo.consumer;

import java.io.UnsupportedEncodingException;

import java.net.URLDecoder;
import java.net.URLEncoder;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import java.text.DateFormat;
import java.text.SimpleDateFormat;

import java.util.Calendar;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.SortedMap;
import java.util.TimeZone;
import java.util.TreeMap;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

public class SignedRequestHelper {
	private static final String UTF8_CHARSET = "UTF-8";
	private static final String HMAC_SHA256_ALGORITHM = "HmacSHA256";
	private static final String REQUEST_URI = "/onca/xml";
	private static final String REQUEST_METHOD = "GET";

	private String endpoint = "ecs.amazonaws.com"; // must be lowercase
	private String awsAccessKeyId = "AWS access key";
	private String awsSecretKey = "the AWS secret key";

	private SecretKeySpec secretKeySpec = null;
	private Mac mac = null;
	private String currentTimestamp = null;
	private String operation = null;

	public SignedRequestHelper(String operationToSign, String awsAccessKey)
			throws UnsupportedEncodingException, NoSuchAlgorithmException,
			InvalidKeyException {
		this.operation = operationToSign;
		byte[] secretyKeyBytes = awsAccessKey.getBytes();
		secretKeySpec = new SecretKeySpec(secretyKeyBytes,
				HMAC_SHA256_ALGORITHM);
		mac = Mac.getInstance(HMAC_SHA256_ALGORITHM);
		mac.init(secretKeySpec);
	}

	public String sign(Map<String, String> params) {
		params.put("AWSAccessKeyId", awsAccessKeyId);
		params.put("Timestamp", getTimestamp());

		SortedMap<String, String> sortedParamMap = new TreeMap<String, String>(
				params);
		String canonicalQS = canonicalize(sortedParamMap);
		String toSign = REQUEST_METHOD + "\n" + endpoint + "\n" + REQUEST_URI
				+ "\n" + canonicalQS;

		String hmac = hmac(toSign);
		String sig = percentEncodeRfc3986(hmac);
		String url = "http://" + endpoint + REQUEST_URI + "?" + canonicalQS
				+ "&Signature=" + sig;

		return url;
	}

	private String hmac(String stringToSign) {
		String signature = null;
		byte[] data;
		byte[] rawHmac;
/*		try {
*/			data = stringToSign.getBytes();
			rawHmac = mac.doFinal(data);
			Base64 encoder = new Base64();
			signature = new String(encoder.encode(rawHmac));
/*		} catch (UnsupportedEncodingException e) {
			throw new RuntimeException(UTF8_CHARSET + " is unsupported!", e);
		}
*/		return signature;
	}

	public String getTimestamp() {
		if (currentTimestamp == null) {
			Calendar cal = Calendar.getInstance();
			DateFormat dfm = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
			dfm.setTimeZone(TimeZone.getTimeZone("GMT"));
			currentTimestamp = dfm.format(cal.getTime());
		}
		return currentTimestamp;
	}

	private String canonicalize(SortedMap<String, String> sortedParamMap) {
		if (sortedParamMap.isEmpty()) {
			return "";
		}

		StringBuffer buffer = new StringBuffer();
		Iterator<Map.Entry<String, String>> iter = sortedParamMap.entrySet()
				.iterator();

		while (iter.hasNext()) {
			Map.Entry<String, String> kvpair = iter.next();
			buffer.append(percentEncodeRfc3986(kvpair.getKey()));
			buffer.append("=");
			buffer.append(percentEncodeRfc3986(kvpair.getValue()));
			if (iter.hasNext()) {
				buffer.append("&");
			}
		}
		String cannoical = buffer.toString();
		return cannoical;
	}

	private String percentEncodeRfc3986(String s) {
		String out;
		try {
			out = URLEncoder.encode(s, UTF8_CHARSET).replace("+", "%20")
					.replace("*", "%2A").replace("%7E", "~");
		} catch (UnsupportedEncodingException e) {
			out = s;
		}
		return out;
	}

	public String getSignature(String timeStamp) {
		return this.hmac(this.operation + timeStamp);
	}

	public static void main(String[] args) throws InvalidKeyException,
			UnsupportedEncodingException, NoSuchAlgorithmException {
		SignedRequestHelper helper = new SignedRequestHelper("ItemSearch", "AKIAJOK2WVETP65PUAUQ");
		SortedMap<String, String> sortedParamMap = new TreeMap<String, String>();
		sortedParamMap.put("Action", "ItemSearch");
		String timestamp = helper.getTimestamp();
		System.out.println("timestamp = " + timestamp);
		sortedParamMap.put("TimeStamp", timestamp);
		System.out.println(helper.canonicalize(sortedParamMap));
		System.out.println(helper.hmac("ItemSearch" + timestamp));
	}

}