二段階認証コードの生成処理を実装

src/main/java/com/sedmelluq/discord/lavaplayer/source/nico/TOTPGenerator.java

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+package com.sedmelluq.discord.lavaplayer.source.nico;/*
+ *  Copyright 2024 Cosgy Dev (info@cosgy.dev).
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+import java.nio.ByteBuffer;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.time.Instant;
+import java.util.*;
+
+public class TOTPGenerator {
+
+    private static final int DIGIT = 6;
+    private static final int TIME_STEP = 30;
+    private static final Map<Character, Integer> base32table = new HashMap<>();
+
+    static {
+        base32table.put('A', 0); base32table.put('B', 1); base32table.put('C', 2); base32table.put('D', 3);
+        base32table.put('E', 4); base32table.put('F', 5); base32table.put('G', 6); base32table.put('H', 7);
+        base32table.put('I', 8); base32table.put('J', 9); base32table.put('K', 10); base32table.put('L', 11);
+        base32table.put('M', 12); base32table.put('N', 13); base32table.put('O', 14); base32table.put('P', 15);
+        base32table.put('Q', 16); base32table.put('R', 17); base32table.put('S', 18); base32table.put('T', 19);
+        base32table.put('U', 20); base32table.put('V', 21); base32table.put('W', 22); base32table.put('X', 23);
+        base32table.put('Y', 24); base32table.put('Z', 25); base32table.put('2', 26); base32table.put('3', 27);
+        base32table.put('4', 28); base32table.put('5', 29); base32table.put('6', 30); base32table.put('7', 31);
+    }
+
+    // Main method to get the TOTP code
+    public static String getCode(String key) {
+        byte[] decodedKey = base32decode(key.toUpperCase());
+        return totp(decodedKey, Instant.now());
+    }
+
+    // TOTP generation function
+    private static String totp(byte[] key, Instant instant) {
+        long counter = instant.getEpochSecond() / TIME_STEP;
+        return hotp(key, counter);
+    }
+
+    // HOTP generation function
+    private static String hotp(byte[] key, long counter) {
+        ByteBuffer buffer = ByteBuffer.allocate(8);
+        buffer.putLong(counter);
+
+        byte[] hash = hmacSha1(key, buffer.array());
+        int truncatedHash = truncate(hash);
+        return String.format("%06d", truncatedHash);
+    }
+
+    // Truncate function as defined in RFC 4226
+    private static int truncate(byte[] hash) {
+        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 % (int) Math.pow(10, DIGIT);
+    }
+
+    // HMAC-SHA1 calculation
+    private static byte[] hmacSha1(byte[] key, byte[] data) {
+        try {
+            Mac mac = Mac.getInstance("HmacSHA1");
+            SecretKeySpec secretKeySpec = new SecretKeySpec(key, "HmacSHA1");
+            mac.init(secretKeySpec);
+            return mac.doFinal(data);
+        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    // Base32 decoding function
+    private static byte[] base32decode(String str) {
+        str = str.replaceAll("[^A-Z2-7]", ""); // Only keep valid base32 characters
+        int outputLength = str.length() * 5 / 8;
+        byte[] result = new byte[outputLength];
+
+        int buffer = 0;
+        int bitsLeft = 0;
+        int index = 0;
+
+        for (char c : str.toCharArray()) {
+            buffer <<= 5;
+            buffer |= base32table.get(c) & 31;
+            bitsLeft += 5;
+
+            if (bitsLeft >= 8) {
+                result[index++] = (byte) (buffer >> (bitsLeft - 8));
+                bitsLeft -= 8;
+            }
+        }
+
+        return result;
+    }
+
+    public static void main(String[] args) {
+        // Example usage
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("二段階認証のシークレットキーを入力してください。");
+        String secretKey = scanner.next(); // Sample Base32 secret key
+
+        Timer timer = new Timer();
+        timer.schedule(new TimerTask() {
+            @Override
+            public void run() {
+                String code = getCode(secretKey);
+                long current = (Instant.now().getEpochSecond() % TIME_STEP);
+                String gauge = "=".repeat((int) current) + "-".repeat(TIME_STEP - (int) current);
+                System.out.printf("\rTOTP Code: %s [%s]", code, gauge);
+            }
+        }, 0, 500); // 0ミリ秒で開始し、500ミリ秒ごとに更新
+    }
+}
+