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

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

import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;

/**
 * Java Server side class for Google Authenticator's TOTP generator Thanks to
 * Enrico's blog for the sample code:
 * 
 * @see http 
 *      ://thegreyblog.blogspot.com/2011/12/google-authenticator-using-it-in-
 *      your.htmll
 * 
 * 
 * @see http://code.google.com/p/google-authenticator
 * @see http://tools.ietf.org/id/draft-mraihi-totp-timebased-06.txt
 */
public class GoogleAuthenticator {

// taken from Google pam docs - we probably don't need to mess with these
public static final int SECRET_SIZE = 10;
public static final String SEED = "g8GjEvTbW5oVSV7avLBdwIHqGlUYNzKFI7izOF8GwLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";
public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";

int window_size = 3; // default 3 - max 17 (from google docs)

/**
* set the windows size. This is an integer value representing the number of
* 30 second windows we allow The bigger the window, the more tolerant of
* clock skew we are.
* 
* @param s
*            window size - must be >=1 and <=17. Other values are ignored
*/
public void setWindowSize(int s) {
if (s >= 1 && s <= 17)
window_size = s;
}

/**
* Generate a random secret key. This must be saved by the server and
* associated with the users account to verify the code displayed by Google
* Authenticator. The user must register this secret on their device.
* 
* @return secret key
*/
public static String generateSecretKey() {

SecureRandom sr = null;
try {
sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
sr.setSeed(Base64.decodeBase64(SEED.getBytes()));
byte[] buffer = sr.generateSeed(SECRET_SIZE);
Base32 codec = new Base32();
byte[] bEncodedKey = codec.encode(buffer);
String encodedKey = new String(bEncodedKey);
return encodedKey;

} catch (NoSuchAlgorithmException e) {
// should never occur... configuration error
}
return null;
}

/**
* Return a URL that generates and displays a QR barcode. The user scans
* this bar code with the Google Authenticator application on their
* smartphone to register the auth code. They can also manually enter the
* secret if desired
* 
* @param user
*            user id (e.g. fflinstone)
* @param host
*            host or system that the code is for (e.g. myapp.com)
* @param secret
*            the secret that was previously generated for this user
* @return the URL for the QR code to scan
*/
public static String getQRBarcodeURL(String user, String host, String secret) {
// String format =
// "https://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s%%3Fsecret%%3D%s";
String format = "otpauth://totp/%s--%s?secret=%s";
return String.format(format, user, host, secret);
}// otpauth://totp/OKCoin:sbicrgw@vip.qq.com?secret=LQQZJ6ITK5CKS6YA

/**
* Check the code entered by the user to see if it is valid
* 
* @param secret
*            The users secret.
* @param code
*            The code displayed on the users device
* @param t
*            The time in msec (System.currentTimeMillis() for example)
* @return
*/
public boolean check_code(String secret, long code, long timeMsec) {
Base32 codec = new Base32();
byte[] decodedKey = codec.decode(secret);

// convert unix msec time into a 30 second "window"
// this is per the TOTP spec (see the RFC for details)
long t = (timeMsec / 1000L) / 30L;
// Window is used to check codes generated in the near past.
// You can use this value to tune how far you're willing to go.

for (int i = -window_size; i <= window_size; ++i) {
long hash;
try {
hash = verify_code(decodedKey, t + i);
} catch (Exception e) {
// Yes, this is bad form - but
// the exceptions thrown would be rare and a static
// configuration problem
e.printStackTrace();
throw new RuntimeException(e.getMessage());
// return false;
}
if (hash == code) {
return true;
}
}
// The validation code is invalid.
return false;
}

private static int verify_code(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {
byte[] data = new byte[8];
long value = t;
for (int i = 8; i-- > 0; value >>>= 8) {
data[i] = (byte) value;
}

SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");
Mac mac = Mac.getInstance("HmacSHA1");
mac.init(signKey);
byte[] hash = mac.doFinal(data);

int offset = hash[20 - 1] & 0xF;

// We're using a long because Java hasn't got unsigned int.
long truncatedHash = 0;
for (int i = 0; i < 4; ++i) {
truncatedHash <<= 8;
// We are dealing with signed bytes:
// we just keep the first byte.
truncatedHash |= (hash[offset + i] & 0xFF);
}

truncatedHash &= 0x7FFFFFFF;
truncatedHash %= 1000000;

return (int) truncatedHash;
}
}

/**
* 前缀
*/
private static String webName = Constant.GoogleAuthName;

/**
* 注册GOOGLE认证，先传入用户登录名，返回一个MAP，里面有两个KEY，一个是url(value为二维码地址),一个是secret(
* 为此用户的地址，此地址用于校验)
*/
public static Map<String, String> genSecret(String userName) {
Map<String, String> map = new HashMap<String, String>();
String secret = GoogleAuthenticator.generateSecretKey();
String url = GoogleAuthenticator.getQRBarcodeURL(webName, userName, secret);
// System.out.println("Please register " + url);
// System.out.println("Secret key is " + secret);
map.put("secret", secret);
map.put("url", url);
return map;
}

/**
* 校验GOOGLE认证是否成功
*/
public static boolean auth(long code, String secret) {
long t = System.currentTimeMillis();
GoogleAuthenticator ga = new GoogleAuthenticator();
ga.setWindowSize(5); // should give 5 * 30 seconds of grace...
boolean r = ga.check_code(secret, code, t);
return true;
}

/**
* 我的
*
* @param args
*/
public static void main(String args[]){
//2JCC26754QEFIPUV
boolean res = auth(850161,"2JCC26754QEFIPUV");
System.out.println(res);

}