TTLabs/EvaporateJS

package example;

import java.io.IOException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang3.StringUtils;

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

/**
 * Servlet implementation class SignerV4Example
 */
public class SignerV4Example extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final String  SECRET_KYE = "your-secret-key";
    private static final String  REGION = "your-region";
    private static final String  SERVICE_NAME = "s3";
    
    
       
    public SignerV4Example() {
        super();
    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String data = request.getParameter("to_sign");
        String dateStamp = request.getParameter("datetime").
                substring(0, 8);
        
         if(StringUtils.isEmpty(data)) {
                response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid data: 'to_sign' parameter not informed");
            } else {
                try {
                    response.getWriter().write(
                            getSignatureKey(getSignatureKey(SECRET_KYE, dateStamp, REGION, SERVICE_NAME,data))
                            );
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
    
    static byte[] HmacSHA256(String data, byte[] key) throws Exception {
        String algorithm="HmacSHA256";
        Mac mac = Mac.getInstance(algorithm);
        mac.init(new SecretKeySpec(key, algorithm));
        return mac.doFinal(data.getBytes("UTF-8"));
    }
    
    public static String getSignatureKey(byte[] signer) {
        return  Hex.encodeHexString(signer);
    }

    static byte[] getSignatureKey(String secretKey, String dateStamp, String regionName, String serviceName, String toSign) throws Exception {
        byte[] kSecret = ("AWS4" + secretKey).getBytes("UTF-8");
        byte[] kDate = HmacSHA256(dateStamp, kSecret);
        byte[] kRegion = HmacSHA256(regionName, kDate);
        byte[] kService = HmacSHA256(serviceName, kRegion);
        byte[] kSigning = HmacSHA256("aws4_request", kService);
        byte[] dataSigning = HmacSHA256(toSign, kSigning);
        return dataSigning;
    }

}