一、前言

AES（高级加密标准）、DES（数据加密标准）、MD5（消息摘要算法5）和SHA-1（安全哈希算法1）都是常见的加密算法，用于数据加密和哈希计算。

二、加密算法实现

1、创建加密函数

java代码实现方式：

package com.yuanrenxue.course6;

import android.util.Base64;

import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.Key;
import java.security.MessageDigest;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class CryptoUtils implements ICryptoUtils {
    @Override
    public String aesEncrypt(String key, String iv, String content) throws Exception {
        // 密钥和IV的处理
        SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(), "AES");
        // Cipher对象的初始化获取Cipher对象，指定了AES算法、CBC模式和PKCS5填充。
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        // iv 偏移量
        IvParameterSpec ivSpec = new IvParameterSpec(iv.getBytes());
        // 初始化
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
        // 加密
        byte[] bytes = cipher.doFinal(content.getBytes());
        return Base64.encodeToString(bytes, Base64.DEFAULT);
    }

    @Override
    public String aesDecrypt(String key, String iv, String content) throws Exception {
        // 密钥和IV的处理
        SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(), "AES");
        // Cipher对象的初始化获取Cipher对象，指定了AES算法、CBC模式和PKCS5填充。
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        // iv 偏移量
        IvParameterSpec ivSpec = new IvParameterSpec(iv.getBytes());
        // 初始化
        cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
        // 解密
        byte[] bytes = cipher.doFinal(Base64.decode(content, Base64.DEFAULT));
        return new String(bytes);
    }

    @Override
    public String desEncrypt(String key, String content) throws Exception {
        // 密钥处理
        SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(), "DES");
        // Cipher对象的初始化获取Cipher对象，指定了AES算法、CBC模式和PKCS5填充。
        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        // 初始化
        cipher.init(Cipher.ENCRYPT_MODE, keySpec);
        // 加密
        byte[] bytes = cipher.doFinal(content.getBytes());
        return Base64.encodeToString(bytes, Base64.DEFAULT);
    }

    @Override
    public String desDecrypt(String key, String content) throws Exception {
        // 密钥处理
        SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(), "DES");
        // Cipher对象的初始化获取Cipher对象，指定了AES算法、CBC模式和PKCS5填充。
        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        // 初始化
        cipher.init(Cipher.DECRYPT_MODE, keySpec);
        // 解密
        byte[] bytes = cipher.doFinal(Base64.decode(content, Base64.DEFAULT));
        return new String(bytes);
    }

    @Override
    public String getMD5(String content) throws Exception {
        // 得到摘要实例
        MessageDigest md = MessageDigest.getInstance("MD5");
        // 摘要运算
        byte[] digest = md.digest(content.getBytes());
        // 返回16进制字符串
        return new BigInteger(1, digest).toString(16);
    }

    @Override
    public String getSHA1(String content) throws Exception {
        // 得到摘要实例
        MessageDigest md = MessageDigest.getInstance("SHA1");
        // 摘要运算
        byte[] digest = md.digest(content.getBytes());
        // 返回16进制字符串
        return new BigInteger(1, digest).toString(16);

        // 第二种写法
        // md.update(content.getBytes());
        // md.update(content2.getBytes());
        // md.update(content3.getBytes());
        // return new BigInteger(1, md.digest()).toString(16);
    }
}

2、hook 加密函数

java代码实现方式：

package com.example.plugintest;

import android.util.Log;

import com.virjar.ratel.api.rposed.IRposedHookLoadPackage;
import com.virjar.ratel.api.rposed.RC_MethodHook;
import com.virjar.ratel.api.rposed.RposedHelpers;
import com.virjar.ratel.api.rposed.callbacks.RC_LoadPackage;

import java.math.BigInteger;
import java.security.MessageDigest;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class HookCryptoEntry implements IRposedHookLoadPackage {
    private static final String TAG = "plugintest-->";

    @Override
    public void handleLoadPackage(RC_LoadPackage.LoadPackageParam lpparam) throws Throwable {
        System.out.println(TAG + "包名是什么：" + lpparam.packageName);
        if (lpparam.packageName.equals("com.yuanrenxue.course6")) {
            System.out.println(TAG + "确认hook的app是：" + lpparam.packageName);

            // 想hook这个：new SecretKeySpec(key.getBytes(),"AES");这里用的是findAndHookConstructor因为new ... 就是一个
            // 实例化的过程，所以需要hook的是构造方法而不是普通方法
            RposedHelpers.findAndHookConstructor(SecretKeySpec.class, byte[].class, String.class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, String.format("SecretKeySpec(%s,%s))", new String((byte[]) param.args[0]), param.args[1]));
                }
            });

            // hook iv:new IvParameterSpec(iv.getBytes());
            RposedHelpers.findAndHookConstructor(IvParameterSpec.class, byte[].class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, String.format("IvParameterSpec(%s)", new String((byte[]) param.args[0])));
                }
            });

            // hook 采用了什么加密算法:Cipher.getInstance("AES/CBC/PKCS5Padding")
            RposedHelpers.findAndHookMethod(Cipher.class, "getInstance", String.class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, "发现使用如下加密算法: " + param.args[0]);
                }
            });

            // hook 加密解密过程：cipher.doFinal(content.getBytes());
            RposedHelpers.findAndHookMethod(Cipher.class, "doFinal", byte[].class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    // 对于加密来说：入参（明文），返回值（密文）
                    // 对于解密来说：入参（密文），返回值（明文） 可以通过这来判断在加密还是在解密
                    // 加密的返回值因为是随机的字节，所以打印出来很可能是鬼画符一样的东西�7sZ������O��像这种，是正常的
                    Log.d(TAG, String.format("入参为：%s,返回值为：%s", new String((byte[]) param.args[0]), new String((byte[]) param.getResult())));
                }
            });

            // hook采用了哪种哈希函数（摘要算法） MessageDigest.getInstance("MD5");
            RposedHelpers.findAndHookMethod(MessageDigest.class, "getInstance", String.class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, "发现使用如下哈希函数: " + param.args[0]);
                }
            });

            // 对于摘要内容的hook
            // 1. md.digest(content.getBytes());
            RposedHelpers.findAndHookMethod(MessageDigest.class, "digest", byte[].class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, "消息内容为: " + new String((byte[]) param.args[0]));
                    Log.d(TAG, "摘要结果为: " + new String((byte[]) param.getResult()));
                    Log.d(TAG, "摘要结果为: " + new BigInteger(1, (byte[]) param.getResult()).toString(16));
                }
            });

            // 2. md.update(content.getBytes());
            RposedHelpers.findAndHookMethod(MessageDigest.class, "update", byte[].class, new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, "2.消息内容为: " + new String((byte[]) param.args[0]));
                }
            });

            RposedHelpers.findAndHookMethod(MessageDigest.class, "digest", new RC_MethodHook() {
                @Override
                protected void afterHookedMethod(MethodHookParam param) throws Throwable {
                    super.afterHookedMethod(param);
                    Log.d(TAG, "2.摘要结果为: " + new BigInteger(1, (byte[]) param.getResult()).toString(16));
                }
            });

        }
    }
}

三、效果