安卓逆向 -- 自吐算法(MAC) - Kirin博客

安卓逆向 -- 自吐算法(MAC)

作者: Bee

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一、MAC算法源码

import javax.crypto.Macimport javax.crypto.spec.SecretKeySpecString bs= "逆向有你a";SecretKeySpec key = new SecretKeySpec("12345".getBytes(StandardCharsets.UTF_8), "HmacSHA256");//申请一个密钥,长度内容随便写Mac mac = Mac.getInstance("HmacSHA256");//告诉系统我用的加密码方式是HmacSHA256mac.init(key);byte[] macres = mac.doFinal(bs.getBytes(StandardCharsets.UTF_8));//开始加密System.out.println("HmacSHA1加密(字节):"+Arrays.toString(macres));System.out.println("HmacSHA1加密(字符串):"+bytes2HexString(macres));SecretKeySpec key1 = new SecretKeySpec("12345".getBytes(StandardCharsets.UTF_8), "HmacSHA256");//申请一个密钥,长度内容随便写Mac mac1 = Mac.getInstance("HmacSHA256");//告诉系统我用的加密码方式是HmacSHA256mac1.init(key1);mac1.update("逆向".getBytes(StandardCharsets.UTF_8));mac1.update("有你".getBytes(StandardCharsets.UTF_8));byte[] macres1 = mac1.doFinal("a".getBytes(StandardCharsets.UTF_8));System.out.println(bytes2HexString(macres1));

二、分析源码,需hook的内容

1、hook类是javax.crypto.Mac,javax.crypto.spec.SecretKeySpec

2、hook的方法:SecretKeySpec,doFinal


三、hook源码

XposedBridge.hookAllMethods(XposedHelpers.findClass("javax.crypto.Mac", loadPackageParam.classLoader) , "doFinal", new XC_MethodHook() { @Override protected void afterHookedMethod(MethodHookParam param) throws Throwable { super.afterHookedMethod(param); Log.e("逆向有你", "Stack:", new Throwable("stack dump")); if(param.args.length==2) return; Mac mc = (Mac) param.thisObject;//实例化 String algorithm = mc.getAlgorithm();//获取加密算法的名称 if (param.args.length == 2) { byte[] params = (byte[]) param.args[0]; String data = new String(params); String datahex = b2s(params); String datab64 = Base64.encodeToString(params, 0); Log.d("逆向有你",algorithm+"data:"+data); Log.d("逆向有你",algorithm+"datahex:"+datahex); Log.d("逆向有你",algorithm+"datab64:"+datab64); } byte[] res=(byte[])param.getResult(); String reshex = b2s(res); String resb64 = Base64.encodeToString(res, 0); Log.d("逆向有你",algorithm+"resulthex:"+reshex); Log.d("逆向有你",algorithm+"resultb64:"+resb64); Log.d("逆向有你","========================================================================"); } });XposedBridge.hookAllConstructors(XposedHelpers.findClass("javax.crypto.spec.SecretKeySpec", loadPackageParam.classLoader) , new XC_MethodHook() { @Override protected void afterHookedMethod(MethodHookParam param) throws Throwable { super.afterHookedMethod(param); Log.e("逆向有你", "Stack:", new Throwable("stack dump")); byte[] secretKey = (byte[]) param.args[0]; int offset=0; int size=0; String algorithm=null; if (param.args.length != 2) { offset = ((Integer) param.args[1]).intValue(); size = ((Integer) param.args[2]).intValue(); algorithm = (String) param.args[3]; }else { size=secretKey.length; algorithm= (String) param.args[1]; } byte[] keyres=new byte[size]; System.arraycopy(secretKey,offset,keyres,0,size); String keyreshex = b2s(keyres); String keyresb64 = Base64.encodeToString(keyres, 0); Log.d("逆向有你",algorithm+"secretkey:"+new String(keyres)); Log.d("逆向有你",algorithm+"secretkeyhex:"+keyreshex); Log.d("逆向有你",algorithm+"secretkeyb64:"+keyresb64); Log.d("逆向有你","========================================================================"); } });

四、运行结果


禁止非法,后果自负

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作者: Bee, 转载或复制请以 超链接形式 并注明出处 Kirin博客
原文地址: 《安卓逆向 -- 自吐算法(MAC)》 发布于2021-9-29

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