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前言

蝉妈妈app v2.6.1 安卓逆向分析之sign破解

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提示：以下是本篇文章正文内容，下面案例可供参考

1.抓包

接口: https://api-service.chanmama.com/v1/douyin/live/rank/realtime

由图可见Headers中关键参数sign

2. 定位分析

2.1 package

package=‘com.chandashi.chanmama’

第一步先获取package为下一步hook分析做准备

2.2 jadx-gui

打开jadx-gui 将蝉妈妈.apk拖进去等待片刻，搜索关键词:“sign”，结果如下: 关键代码arrayMap.put(“sign”, x.R0(sb2, “cmmad!@@#”)); 由此可见 sign = x.R0(sb2, “cmmad!@@#”),

咱们直接看 x.R0()函数代码

jadx代码如下：

    public static String R0(@NonNull String str, String str2) {
        if (TextUtils.isEmpty(str)) {
            return "";
        }
        try {
            String str3 = "";
            for (byte b2 : MessageDigest.getInstance("MD5").digest((str + str2).getBytes())) {
                String hexString = Integer.toHexString(b2 & 255);
                if (hexString.length() == 1) {
                    hexString = MessageService.MSG_DB_READY_REPORT + hexString;
                }
                str3 = str3 + hexString;
            }
            return str3;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return "";
        }
    }

3. hook

Frida代码如下：

import frida, sys

def on_message(message, data):
    if message['type'] == 'send':
        print("[*] {0}".format(message['payload']))
    else:
        print(message)




jscode_hook = """
    Java.perform(
        function(){
            var class_obj = Java.use("d.j.d.x");
            console.log(class_obj);
            if (class_obj != undefined) {
                class_obj.R0.overload('java.lang.String', 'java.lang.String').implementation = function (s1, s2) {
                    console.log("参数1: ---> "+ s1);
                    console.log("参数2: ---> "+ s2);
                    var res = this.R0(s1, s2);
                    console.log("加密: ---> "+res);
                    return res;
                }
            }
        }

    )
"""

process = frida.get_usb_device().attach('com.chandashi.chanmama')
script = process.create_script(jscode_hook)
script.on('message', on_message)
print('[*] Hook Start Running')
script.load()
sys.stdin.read()

str1 = “YqH3DGpu1644394648003” YqH3DGpu+毫秒级时间戳 str2 = “” 结果 md5(str1)最后转大写

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总结

加密都在java层且是标准md5，大家有兴趣可以动手做下。