backend.services.ads.SignedRequestsHelper Maven / Gradle / Ivy

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Flex App backend.
There is a newer version: 1.2.3
package backend.services.ads;

import db.books.AmazonProperties;
import java.io.UnsupportedEncodingException;

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.Iterator;
import java.util.Map;
import java.util.SortedMap;
import java.util.TimeZone;
import java.util.TreeMap;
import java.util.logging.Level;
import java.util.logging.Logger;

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

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

public class SignedRequestsHelper {

    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 = "webservices.amazon.com"; // must be lowercase
    private String awsAccessKeyId;
    private String awsSecretKey;

    private SecretKeySpec secretKeySpec = null;
    private Mac mac = null;

    public SignedRequestsHelper(AmazonProperties properties) {
        try {
            awsAccessKeyId = properties.getAccessKey();
            awsSecretKey = properties.getSecretKey();
            byte[] secretyKeyBytes = awsSecretKey.getBytes(UTF8_CHARSET);
            secretKeySpec = new SecretKeySpec(secretyKeyBytes, HMAC_SHA256_ALGORITHM);
            mac = Mac.getInstance(HMAC_SHA256_ALGORITHM);
            mac.init(secretKeySpec);
        } catch (UnsupportedEncodingException | InvalidKeyException | NoSuchAlgorithmException ex) {
            Logger.getLogger(SignedRequestsHelper.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

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

        SortedMap sortedParamMap
                = new TreeMap(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(UTF8_CHARSET);
            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;
    }

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

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

        StringBuffer buffer = new StringBuffer();
        Iterator> iter
                = sortedParamMap.entrySet().iterator();

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

    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;
    }
}