81 lines
3.0 KiB
Java
81 lines
3.0 KiB
Java
package com.bjlx.armcloudaf;
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import java.io.ByteArrayOutputStream;
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import java.util.Arrays;
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import javax.crypto.Cipher;
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import javax.crypto.SecretKeyFactory;
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import javax.crypto.spec.IvParameterSpec;
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import javax.crypto.spec.PBEKeySpec;
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import javax.crypto.spec.SecretKeySpec;
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public class AESPatchHelper {
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private static final byte[] SALT = new byte[8]; // 全零 salt
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private static final int PADDING_LEN = 8;
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private static final int IV_LEN = 16;
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public static byte[] extractIV(byte[] data) {
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int ivPos = data.length - PADDING_LEN - IV_LEN;
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return Arrays.copyOfRange(data, ivPos, ivPos + IV_LEN);
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}
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public static byte[] extractPadding(byte[] data) {
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int padPos = data.length - PADDING_LEN - IV_LEN - PADDING_LEN;
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if (padPos < 0) padPos = data.length - PADDING_LEN - IV_LEN;
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return Arrays.copyOfRange(data, data.length - PADDING_LEN - IV_LEN, data.length - IV_LEN);
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}
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public static byte[] extractCiphertext(byte[] data) {
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int ctLen = data.length - PADDING_LEN - IV_LEN;
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return Arrays.copyOfRange(data, 0, ctLen);
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}
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private static SecretKeySpec deriveKey(String password) throws Exception {
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return new SecretKeySpec(
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SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1")
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.generateSecret(new PBEKeySpec(password.toCharArray(), SALT, 10000, 128))
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.getEncoded(),
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"AES"
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);
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}
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public static byte[] decryptRaw(byte[] ciphertext, byte[] iv, String password) throws Exception {
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SecretKeySpec key = deriveKey(password);
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Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
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cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
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return cipher.doFinal(ciphertext);
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}
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public static byte[] encryptRaw(byte[] plaintext, byte[] iv, String password) throws Exception {
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SecretKeySpec key = deriveKey(password);
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Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
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cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
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return cipher.doFinal(plaintext);
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}
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/**
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* 入口函数：
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* 提取 data 中 IV + padding + 密文 → 解密 → 加密 → 再拼装成结构化数据
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*/
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public static byte[] patchAndReEncrypt(byte[] data, String password) throws Exception {
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if (data == null || data.length <= (PADDING_LEN + IV_LEN)) return null;
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byte[] iv = extractIV(data);
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byte[] padding = extractPadding(data);
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byte[] ciphertext = extractCiphertext(data);
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// 解密
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byte[] plaintext = decryptRaw(ciphertext, iv, password);
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// 可在此修改 plaintext（如篡改某些字段）
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// 再加密
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byte[] newCiphertext = encryptRaw(plaintext, iv, password);
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// 拼装为结构：[newCiphertext] + [padding] + [iv]
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ByteArrayOutputStream out = new ByteArrayOutputStream();
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out.write(newCiphertext);
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out.write(padding);
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out.write(iv);
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return out.toByteArray();
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}
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}
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