抖音app协议逆向分析

1.准备工具

• 抖音app（app下载连接) 提取码：6666

博客所写的所有算法还原均已开源在GitHub，地址

https://github.com/YotaGit/AlgorithmRestore

2.本次主要演示抓取某个话题下的数据

没有图片的话是将图片过滤掉了，这样加载会更快

3.先抓包

话题首页

GET http://aweme.snssdk.com/aweme/v1/challenge/aweme/?ch_id=1603132116358228&query_type=0&cursor=0&count=20&type=5&retry_type=retry_http&iid=361063819794455&device_id=1126379551206542&ac=wifi&channel=yingyonghui&aid=2329&app_name=douyin_lite&version_code=180&version_name=1.8.0&device_platform=android&ssmix=a&device_type=Nexus+6P&device_brand=google&language=zh&os_api=25&os_version=7.1.1&openudid=df2eb2a465f9b18f&manifest_version_code=180&resolution=1440*2392&dpi=560&update_version_code=1800&_rticket=771495793&ts=1630245339&as=aac81339d8000bc5a7c813&cp=3a28c81339d8c8133a2032&mas=0133332319a3f3f3b323f9b9b93fef9cdaf3b323f9d3b993f97933 HTTP/1.1
Accept-Encoding: gzip
X-SS-QUERIES: dGMCA76ot3awALq29Cjed6Wxk9vvcxlI%2BcrVbsSshXPE367hsCodObDobByuYNDsyCWTS76ot3awAOm2rKzdv5e1E7B4tcJ4rILc5cqsABMctdUrsE%2BsYPhZcFX06I%2F6XKH1ew%3D%3D
X-SS-REQ-TICKET: 771495805
Cookie: 你自己的cookie
X-Gorgon: 03742f2b00051aeec7dc6b6c24d8a111044edde107abede12ba7
X-Khronos: 771495
Host: aweme.snssdk.com
Connection: Keep-Alive
User-Agent: okhttp/3.10.0.1

翻页后的请求与响应

GET http://aweme.snssdk.com/aweme/v1/challenge/aweme/?ch_id=1603132116358228&query_type=0&cursor=20&count=20&type=5&retry_type=retry_http&iid=361063819794455&device_id=1126379551206542&ac=wifi&channel=yingyonghui&aid=2329&app_name=douyin_lite&version_code=180&version_name=1.8.0&device_platform=android&ssmix=a&device_type=Nexus+6P&device_brand=google&language=zh&os_api=25&os_version=7.1.1&openudid=df2eb2a465f9b18f&manifest_version_code=180&resolution=1440*2392&dpi=560&update_version_code=1800&_rticket=771550466&ts=1630245393&as=aac81339d8000bc5dec813&cp=3a28c81339d8c8133a2032&mas=0133332319a3f3f3b323f9b9b93fef9c44f3b323f9991993f97933 HTTP/1.1
Accept-Encoding: gzip
X-SS-QUERIES: dGMCA76ot3awALq29Cjed6Wxk9vvcxlI%2BcrVbsSshXPE367hsCodObDobByuYNDsyCWTS76ot3awAOm2rKzdv5e1E7B4tcJ4rILc5cqsABMctdUrsE%2BsYPhZcFX06I%2F6XKH1ew%3D%3D
X-SS-REQ-TICKET: 771550474
Cookie:你自己的cookie
X-Gorgon: 03742f2b000547608bad6b6c24d8a111044edde107abede1b5f4
X-Khronos: 771550
Host: aweme.snssdk.com
Connection: Keep-Alive
User-Agent: okhttp/3.10.0.1

跑一段时间你会发现出不了数据
逐步替换url请求参数会发现是as cp mas这三个参数失效了，得逆向分析一波

4.逆向分析步骤

查壳

查壳的方式很多种，可以先用apktool解开查看特侦，如果应用被加固了，那么需要脱壳
脱壳的教程很多，可以优先考虑FDex2

5.jadx使用搜索大法搜索as cp mas三个参数

搜索需要讲究技巧，先搜索as和cp会直接死亡

在搜索时按照java的尿性会有以下几种形式(仅供参考)先找长字符的搜索

"mas
"mas=
"mas"
="mas"

果然给蒙对了

双击进入发现就是我们想要的

上图的代码如下

package com.ss.android.ugc.aweme.app.a;

import android.text.TextUtils;
import com.meituan.robust.ChangeQuickRedirect;
import com.meituan.robust.PatchProxy;
import com.meituan.robust.PatchProxyResult;
import com.meizu.cloud.pushsdk.notification.model.AdvanceSetting;
import com.ss.android.common.applog.EagleEye;
import com.ss.android.common.applog.GlobalContext;
import com.ss.android.common.applog.UserInfo;
import com.ss.android.deviceregister.a;
import com.ss.android.ugc.aweme.app.AwemeApplication;
import com.ss.android.ugc.aweme.app.b.e;
import com.ss.sys.ces.out.ISdk;
import com.ss.sys.ces.out.StcSDKFactory;
import e.t;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.List;

/* compiled from: ApiAntiSpamUtils */
public final class b {

    /* renamed from: a  reason: collision with root package name */
    public static ChangeQuickRedirect f13081a;

    public static t a(t tVar, List list, int i) {
        String str;
        PatchProxyResult proxy = PatchProxy.proxy(new Object[]{tVar, list, new Integer(i)}, null, f13081a, true, 866, new Class[]{t.class, List.class, Integer.TYPE}, t.class);
        if (proxy.isSupported) {
            return (t) proxy.result;
        }
        String decode = URLDecoder.decode(tVar.toString());
        String b2 = a.b();
        if (b2 == null) {
            b2 = "";
        }
        if (decode.contains("&device_id=") || decode.contains("?device_id=")) {
            str = UserInfo.getUserInfo(i, decode, (String[]) list.toArray(new String[list.size()]), b2);
        } else {
            str = UserInfo.getUserInfo(i, decode, (String[]) list.toArray(new String[list.size()]), "");
        }
        t.a k = tVar.k();
        int length = str.length();
        if (TextUtils.isEmpty(str)) {
            k.a(AdvanceSetting.ADVANCE_SETTING, "a1iosdfgh").a("cp", "androide1");
        } else if (length % 2 == 0) {
            int i2 = length >> 1;
            String substring = str.substring(0, i2);
            ISdk sdk = StcSDKFactory.getSDK(GlobalContext.getContext(), (long) AwemeApplication.p().m());
            sdk.setSession(e.a());
            k.a(AdvanceSetting.ADVANCE_SETTING, substring).a("cp", str.substring(i2, length)).a("mas", EagleEye.byteArrayToHexStr(sdk.encode(substring.getBytes())));
        } else {
            k.a(AdvanceSetting.ADVANCE_SETTING, "a1qwert123").a("cp", "cbfhckdckkde1");
        }
        return k.b();
    }

    public static List a(String str) {
        int i = 0;
        PatchProxyResult proxy = PatchProxy.proxy(new Object[]{str}, null, f13081a, true, 867, new Class[]{String.class}, List.class);
        if (proxy.isSupported) {
            return (List) proxy.result;
        }
        ArrayList arrayList = new ArrayList();
        while (i <= str.length()) {
            int indexOf = str.indexOf(38, i);
            if (indexOf == -1) {
                indexOf = str.length();
            }
            int indexOf2 = str.indexOf(61, i);
            if (indexOf2 == -1 || indexOf2 > indexOf) {
                arrayList.add(URLDecoder.decode(str.substring(i, indexOf)));
                arrayList.add(null);
            } else {
                arrayList.add(URLDecoder.decode(str.substring(i, indexOf2)));
                arrayList.add(URLDecoder.decode(str.substring(indexOf2 + 1, indexOf)));
            }
            i = indexOf + 1;
        }
        return arrayList;
    }

    public static String b(String str) {
        PatchProxyResult proxy = PatchProxy.proxy(new Object[]{str}, null, f13081a, true, 868, new Class[]{String.class}, String.class);
        if (proxy.isSupported) {
            return (String) proxy.result;
        }
        if (TextUtils.isEmpty(str)) {
            return str;
        }
        try {
            return URLDecoder.decode(str, "UTF-8");
        } catch (UnsupportedEncodingException e2) {
            com.google.b.a.a.a.a.a.a(e2);
            return URLDecoder.decode(str);
        }
    }
}

这里有一个AdvanceSetting.ADVANCE_SETTING
我们查找一下声明

这一节我们只做fridaRpc调用下一节我们直接用python还原这三个参数

现在我们已经很清楚需要hook UserInfo.getUserInfo()这个方法

import os
import sys

import frida



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


js_code = """
Java.perform(function(){
    var UserInfo = Java.use('com.ss.android.common.applog.UserInfo');
    UserInfo.getUserInfo.overload('int', 'java.lang.String', '[Ljava.lang.String;', 'java.lang.String').implementation=function(a,b,c,d){
        send('a:'+a);
        send('b:'+b);
        send('c:'+c);
        send('d:'+d);
        user=this.UserInfo(a,b,c,d);
        return user;
    }
});
"""

process = frida.get_remote_device().attach('com.ss.android.ugc.aweme.lite')
script = process.create_script(js_code)
script.on('message', on_message)
script.load()
sys.stdin.read()

getUserInfo的各个参数如下

第一个是时间戳
第二个是你传入的请求url
第三个是请求的参数构成的字符串
第四个是一堆数字其实就是deviceId,从下面这个if else可以得知

frida.rpc hook模板如下

hook_code = '''
rpc.exports = {
    getSign: function(str){
        send('getSign');
        Java.perform(function(){
				
            
        }
    )
    }
};
'''

于是结合djax代码可的代码如下

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


js_code = """
rpc.exports = {
    getsign: function (timestamps, base_url, params, device_id) {
        var sig = "aa";
        Java.perform(
            function () {
                send('getsign');
                var StcSDKFactory = Java.use('com.ss.sys.ces.out.StcSDKFactory');
                var GlobalContext = Java.use('com.ss.android.common.applog.GlobalContext');
                var AwemeApplication = Java.use('com.ss.android.ugc.aweme.app.AwemeApplication');
                var EagleEye = Java.use('com.ss.android.common.applog.EagleEye');
                var sdk = StcSDKFactory.getSDK(GlobalContext.getContext(), AwemeApplication.p().m());
                var UserInfo = Java.use('com.ss.android.common.applog.UserInfo');
                
                var aac=params.toArray(params.length);
                
                var user_info = UserInfo.getUserInfo(timestamps,base_url,params,device_id);

                var as = user_info.substring(0, 22);
                var cp = user_info.substring(22, user_info.length);
                var mas = EagleEye.byteArrayToHexStr(sdk.encode(getBytes(as)));
                sig = '&as='+as+'&cp='+cp+'&mas='+mas;
            }
        )
        return sig;
    }
}


function getBytes(s) {
        var bytes = [];
            for (var i = 0; i < s.length; i++) {
                bytes.push(s.charCodeAt(i));
            }
        return bytes;
}

"""

process = frida.get_remote_device().attach('com.ss.android.ugc.aweme.lite')
script = process.create_script(js_code)
script.on('message', on_message)
script.load()

a= int(time.time())

b="https://aweme-eagle.snssdk.com/aweme/v1/feed/?type=0&max_cursor=0&min_cursor=0&count=6&volume=0.0&pull_type=1&need_relieve_aweme=0&filter_warn=0&ts=1630343714&app_type=lite&os_api=25&device_platform=android&device_type=Xiaomi&iid=361063819794455&ssmix=a&manifest_version_code=180&dpi=560&version_code=180&app_name=douyin_lite&version_name=1.8.0&openudid=df2eb2a465f9b18f&device_id=1126379551206542&resolution=1440*2392&os_version=7.1.1&language=zh&device_brand=google&ac=wifi&update_version_code=1800&aid=2329&channel=yingyonghui&_rticket=1630343715767"

c="type,0,max_cursor,0,min_cursor,0,count,6,volume,0.0,pull_type,1,need_relieve_aweme,0,filter_warn,0,ts,1630343714,app_type,lite,os_api,25,device_platform,android,device_type,Xiaomi,iid,361063819794455,ssmix,a,manifest_version_code,180,dpi,560,version_code,180,app_name,douyin_lite,version_name,1.8.0,openudid,df2eb2a465f9b18f,device_id,1126379551206542,resolution,1440*2392,os_version,7.1.1,language,zh,device_brand,google,ac,wifi,update_version_code,1800,aid,2329,channel,yingyonghui,_rticket,1630343715767"

d="1126379551206542"
sig = script.exports.getsign(a, b, c, d)
print(sig)

最终的结果如下图所示，每一次的调用都是生成不同的参数