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| package com.demo.sign.otp;
import java.nio.ByteBuffer;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.util.List;
import java.util.Locale;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
public class HOTP {
private static final int DEFAULT_PASSWORD_LENGTH = 6;
private static final String HOTP_HMAC_ALGORITHM = "HmacSHA1";
private final Mac prototypeMac;
private final int passwordLength;
private final int modDivisor;
private final String formatString;
public HOTP() throws NoSuchAlgorithmException {
this(DEFAULT_PASSWORD_LENGTH, HOTP_HMAC_ALGORITHM);
}
public HOTP(final String algorithm) throws NoSuchAlgorithmException {
this(DEFAULT_PASSWORD_LENGTH, algorithm);
}
public HOTP(final int passwordLength, final String algorithm) throws NoSuchAlgorithmException {
if (!PasswordLength.getValidPasswordLength().contains(passwordLength)) {
throw new IllegalArgumentException("Password length must be between 6 and 8 digits.");
}
this.prototypeMac = Mac.getInstance(algorithm);
PasswordLength pl = PasswordLength.getByPasswordLength(passwordLength);
this.modDivisor = pl.getModDivisor();
this.formatString = pl.getFormatString();
this.passwordLength = passwordLength;
}
private enum PasswordLength {
SIX(6, 1_000_000, "%06d"),
SEVEN(7, 10_000_000, "%07d"),
EIGHT(8, 100_000_000, "%08d"),;
private int passwordLength;
private int modDivisor;
private String formatString;
private PasswordLength(int passwordLength, int modDivisor, String formatString) {
this.passwordLength = passwordLength;
this.modDivisor = modDivisor;
this.formatString = formatString;
}
public int getPasswordLength() {
return passwordLength;
}
public int getModDivisor() {
return modDivisor;
}
public String getFormatString() {
return formatString;
}
public static PasswordLength getByPasswordLength(int passwordLength) {
for (PasswordLength pl : values()) {
if (passwordLength == pl.getPasswordLength()) {
return pl;
}
}
return SIX;
}
public static List<Integer> getValidPasswordLength() {
return Stream.of(values()).map(PasswordLength::getPasswordLength).collect(Collectors.toList());
}
}
public int genHOTP(final String data, final long counter) throws Exception {
return genHOTP(new SecretKeySpec(data.getBytes(), "AES"), counter);
}
public int genHOTP(final Key key, final long counter) throws Exception {
final Mac mac = getMac();
final ByteBuffer buffer = ByteBuffer.allocate(mac.getMacLength());
buffer.putLong(0, counter);
final byte[] array = buffer.array();
mac.init(key);
mac.update(array, 0, 8);
mac.doFinal(array, 0);
final int offset = buffer.get(buffer.capacity() - 1) & 0x0f;
return (buffer.getInt(offset) & 0x7fffffff) % this.modDivisor;
}
private Mac getMac() {
try {
return (Mac)this.prototypeMac.clone();
} catch (CloneNotSupportedException e) {
try {
return Mac.getInstance(this.prototypeMac.getAlgorithm());
} catch (final NoSuchAlgorithmException ex) {
throw new RuntimeException(ex);
}
}
}
public String genHOTPString(final String data, final long counter) throws Exception {
return this.genHOTPString(data, counter, Locale.getDefault());
}
public String genHOTPString(final String data, final long counter, final Locale locale) throws Exception {
return this.formatOTP(genHOTP(data, counter), locale);
}
public String genHOTPString(final Key key, final long counter) throws Exception {
return this.genHOTPString(key, counter, Locale.getDefault());
}
public String genHOTPString(final Key key, final long counter, final Locale locale) throws Exception {
return this.formatOTP(genHOTP(key, counter), locale);
}
private String formatOTP(final int oneTimePassword, final Locale locale) {
return String.format(locale, formatString, oneTimePassword);
}
public int getPasswordLength() {
return this.passwordLength;
}
public String getAlgorithm() {
return this.prototypeMac.getAlgorithm();
}
}
|
