使用google身份驗證器實現動態口令驗證

最近有用戶反應我們現有的短信+郵件驗證，不安全及短信條數限制和郵件收驗證碼比較慢的問題，希望我們

也能做一個類似銀行動態口令的驗證方式。經過對可行性的分析及慎重考慮，可以實現一個這樣的功能。

怎么實現呢，是自己開發一個這樣的app?這樣成本太高了，為了節約成本，我們使用互聯網使用比較多的google

身份驗證器。使用它，我們只需要開發服務端就可以了。

google身份驗證器的原理是什么呢？客戶端和服務器事先協商好一個密鑰K，用於一次性密碼的生成過程，此

密鑰不被任何第三方所知道。此外，客戶端和服務器各有一個計數器C，並且事先將計數值同步。進行驗證時，客戶端對

密鑰和計數器的組合(K,C)使用HMAC（Hash-based Message Authentication Code）算法計算一次性密碼，公式如下：

 

HOTP(K,C) = Truncate(HMAC-SHA-1(K,C))

 

上面采用了HMAC-SHA-1，當然也可以使用HMAC-MD5等。HMAC算法得出的值位數比較多，不方便用戶輸入，因

此需要截斷（Truncate）成為一組不太長十進制數（例如6位）。計算完成之后客戶端計數器C計數值加1。用戶將這一組十

進制數輸入並且提交之后，服務器端同樣的計算，並且與用戶提交的數值比較，如果相同，則驗證通過，服務器端將計數值

C增加1。如果不相同，則驗證失敗。

Java服務端實現代碼：板面的做法和配料

 

package com.auth.google;

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;

/**
 *
 *
 * google身份驗證器，java服務端實現
 *
 * @author yangbo
 *
 * @version 創建時間：2017年8月14日 上午10:10:02
 *
 *
 */
public class GoogleAuthenticator {

    // 生成的key長度( Generate secret key length)
    public static final int SECRET_SIZE = 10;

    public static final String SEED = "g8GjEvTbW5oVSV7avL47357438reyhreyuryetredLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";
    // Java實現隨機數算法
    public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";
    // 最多可偏移的時間
    int window_size = 3; // default 3 - max 17

    /**
     * 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.
     * 生成一個隨機秘鑰
     *
     * @return secret key
     */
    public static String generateSecretKey() {
        SecureRandom sr = null;
        try {
            sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
            sr.setSeed(Base64.decodeBase64(SEED));
            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 = "http://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s?secret=%s";
        return String.format(format, user, host, secret);
    }

    /**
     * 生成一個google身份驗證器，識別的字符串，只需要把該方法返回值生成二維碼掃描就可以了。
     *
     * @param user
     *            賬號
     * @param secret
     *            密鑰
     * @return
     */
    public static String getQRBarcode(String user, String secret) {
        String format = "otpauth://totp/%s?secret=%s";
        return String.format(format, user, secret);
    }

    /**
     * Check the code entered by the user to see if it is valid 驗證code是否合法
     *
     * @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;
    }
}

 

 

測試代碼：

 

package com.auth.google;

import org.junit.Test;

/**
 *
 *
 * 身份認證測試
 *
 * @author yangbo
 *
 * @version 創建時間：2017年8月14日 上午11:09:23
 *
 *
 */
public class AuthTest {
    //當測試authTest時候，把genSecretTest生成的secret值賦值給它
    private static String secret="R2Q3S52RNXBTFTOM";

    //@Test
    public void genSecretTest() {// 生成密鑰
         secret = GoogleAuthenticator.generateSecretKey();
        // 把這個qrcode生成二維碼，用google身份驗證器掃描二維碼就能添加成功
        String qrcode = GoogleAuthenticator.getQRBarcode("[e-mail]", secret);
        System.out.println("qrcode:" + qrcode + ",key:" + secret);
    }
    /**
     * 對app的隨機生成的code,輸入並驗證
     */
     @Test
    public void verifyTest() {
        long code = 807337;
        long t = System.currentTimeMillis();
        GoogleAuthenticator ga = new GoogleAuthenticator();
        ga.setWindowSize(5);
        boolean r = ga.check_code(secret, code, t);
        System.out.println("檢查code是否正確？" + r);
    }
}

 

 

具體使用方式(iOS演示)：

第一步：進入iphone的appstore,在搜索框中輸入google身份驗證器，如下圖：

 

選擇上圖中的google authenticator 並安裝。

第二步：運行下面鏈接中下載的demo中的AuthTest的genSecretTest方法，控制台打印的結果如下圖：

key：為app與服務端約定的秘鑰，用於雙方的認證。