本文主要讲述一下如何使用aerogear-otp生成otp,以及相关源码分析
全称是one time password,通常用来支持双因素认证。主要可以分两类
这里主要讲TOTP
主要的步骤如下:
绑定secret之后,就可以使用one time password进行验证了。
String secret = Base32.random();
Totp totp = new Totp(secret);
String uri = totp.uri(account);
将这个uri作为二维码的信息,即可。
/**
* Prover - To be used only on the client side
* Retrieves the encoded URI to generated the QRCode required by Google Authenticator
*
* @param name Account name
* @return Encoded URI
*/
public String uri(String name) {
try {
return String.format("otpauth://totp/%s?secret=%s", URLEncoder.encode(name, "UTF-8"), secret);
} catch (UnsupportedEncodingException e) {
throw new IllegalArgumentException(e.getMessage(), e);
}
}
它的格式otpauth://totp/%s?secret=%s,Google Authenticator APP或阿里云的身份宝均支持这种格式的识别。
boolean isValid = totp.verify(code);
其源码如下
/**
* Verifier - To be used only on the server side
* <p/>
* Taken from Google Authenticator with small modifications from
* {@see <a href="http://code.google.com/p/google-authenticator/source/browse/src/com/google/android/apps/authenticator/PasscodeGenerator.java?repo=android#212">PasscodeGenerator.java</a>}
* <p/>
* Verify a timeout code. The timeout code will be valid for a time
* determined by the interval period and the number of adjacent intervals
* checked.
*
* @param otp Timeout code
* @return True if the timeout code is valid
* <p/>
* Author: sweis@google.com (Steve Weis)
*/
public boolean verify(String otp) {
long code = Long.parseLong(otp);
long currentInterval = clock.getCurrentInterval();
int pastResponse = Math.max(DELAY_WINDOW, 0);
for (int i = pastResponse; i >= 0; --i) {
int candidate = generate(this.secret, currentInterval - i);
if (candidate == code) {
return true;
}
}
return false;
}
这里有个DELAY_WINDOW参数,是为了防止手机客户端与服务器端的时差引入的。默认值是1,即允许那个code在手机端过期30秒之内到服务端验证还有效。
aerogear-otp-java-1.0.0-sources.jar!/org/jboss/aerogear/security/otp/Totp.java
private int generate(String secret, long interval) {
return hash(secret, interval);
}
private int hash(String secret, long interval) {
byte[] hash = new byte[0];
try {
//Base32 encoding is just a requirement for google authenticator. We can remove it on the next releases.
hash = new Hmac(Hash.SHA1, Base32.decode(secret), interval).digest();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
} catch (Base32.DecodingException e) {
e.printStackTrace();
}
return bytesToInt(hash);
}
private int bytesToInt(byte[] hash) {
// put selected bytes into result int
int offset = hash[hash.length - 1] & 0xf;
int binary = ((hash[offset] & 0x7f) << 24) |
((hash[offset + 1] & 0xff) << 16) |
((hash[offset + 2] & 0xff) << 8) |
(hash[offset + 3] & 0xff);
return binary % Digits.SIX.getValue();
}
/**
* Retrieves the current OTP
*
* @return OTP
*/
public String now() {
return leftPadding(hash(secret, clock.getCurrentInterval()));
}
private String leftPadding(int otp) {
return String.format("%06d", otp);
}