一、目標(biāo)

有一段時(shí)間沒(méi)有寫unidbg相關(guān)的文章了，這個(gè)樣本挺合適，難度適中，還適當(dāng)給你挖個(gè)小坑。所以后面是一個(gè)系列文章，包含 unidbg補(bǔ)環(huán)境，Trace Block 對(duì)比流程，Trace Code定位差異。掌握好這一系列套路，Native分析可以算入門了。

這次先來(lái)把so用unidbg跑通

v6.1.0

二、步驟

Dump so

IDA打開(kāi) libencrypt.so 去到我們要分析的兩個(gè)函數(shù) checkcode 和 decheckcode 對(duì)應(yīng)的偏移地址 0x24424 , 0x2B1BC 。會(huì)發(fā)現(xiàn)一個(gè)奇怪的問(wèn)題，這兩個(gè)地址上沒(méi)有匯編代碼，都是 0x00。

估計(jì)是殼給我們加戲了，他把這兩個(gè)關(guān)鍵函數(shù)的部分代碼給抽取了，等到運(yùn)行的時(shí)候才會(huì)補(bǔ)回去，這樣就阻礙你去靜態(tài)分析這個(gè)so。

不過(guò)殼怎么加戲，運(yùn)行的時(shí)候是一定會(huì)在內(nèi)存中存在完整的代碼的，否則App是跑不起來(lái)的。

所以我們也加戲，Dump 之

function dumpSo(){
    var libxx = Process.getModuleByName("libencrypt.so");
    console.log("*****************************************************");
    console.log(TAG + "name: " +libxx.name);
    console.log(TAG + "base: " +libxx.base);
    console.log(TAG + "size: " +ptr(libxx.size));

    var file_path = "/data/data/com.xxx.aeri.caranywhere/" + libxx.name + "_" + libxx.base + "_" + ptr(libxx.size) + ".so";
    console.log(TAG + file_path);

    var file_handle = new File(file_path, "wb");
    if (file_handle && file_handle != null) {
        Memory.protect(ptr(libxx.base), libxx.size, 'rwx');
        var libso_buffer = ptr(libxx.base).readByteArray(libxx.size);
        file_handle.write(libso_buffer);
        file_handle.flush();
        file_handle.close();
        console.log(TAG + "[dump]:", file_path);
    }
}

unidbg run so 基本框架

dump出so的完整代碼了，我們開(kāi)始撘unidbg run so的基本框架。unidbg的庫(kù)代碼可以從原作者的github上下載最新的。

public class CaranywhereDemo  extends AbstractJni {
    public AndroidEmulator emulator;
    public VM vm;
    public Module module;
    public DvmClass dvmClass;

    public static void main(String[] args) throws DecoderException, IOException {
        String apkPath = "/Users/fenfei/Desktop/xxx/6.1.0.apk";
        CaranywhereDemo carObj = new CaranywhereDemo(apkPath);
        carObj.destroy();
    }

    public CaranywhereDemo(String apkFilePath) throws DecoderException, IOException {
        //*
        emulator = AndroidEmulatorBuilder.for64Bit()
                .setProcessName("com.xxx.aeri.caranywhere")
                .addBackendFactory(new Unicorn2Factory(true))
                .build(); // 創(chuàng)建模擬器實(shí)例，要模擬32位或者64位，在這里區(qū)分
        //*/

        // 多線程處理  true的情況下 在 faccessat  的時(shí)候就卡死， 所以關(guān)掉, 這個(gè)樣本暫時(shí)也不需要多線程
        emulator.getSyscallHandler().setEnableThreadDispatcher(false);

        final Memory memory = emulator.getMemory();                // 模擬器的內(nèi)存操作接口
        memory.setLibraryResolver(new AndroidResolver(23)); // 設(shè)置系統(tǒng)類庫(kù)解析

        vm = emulator.createDalvikVM(new File(apkFilePath)); // 創(chuàng)建Android虛擬機(jī)
        vm.setJni(this);
        vm.setVerbose(true); // 設(shè)置是否打印Jni調(diào)用細(xì)節(jié)

        new JniGraphics(emulator, vm).register(memory);
        new AndroidModule(emulator, vm).register(memory);

                dvmClass = vm.resolveClass("com/bangcle/comapiprotect/CheckCodeUtil");

                DalvikModule dm = vm.loadLibrary("encrypt", false);

        module = dm.getModule();
        dm.callJNI_OnLoad(emulator);
    }
    private void destroy() {
        try {
            emulator.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

一個(gè)unidbg的Hello World就是這樣，先別著急跑它，之前我們說(shuō)過(guò)，so的關(guān)鍵代碼被抽取了，所以不能直接跑so。得換成我們dump出來(lái)的結(jié)果。

// DalvikModule dm = vm.loadLibrary("encrypt", false);
DalvikModule dm = vm.loadLibrary(new File("/Users/fenfei/Desktop/work/blogCode/xxx/libencrypt.so_0x7634ee7000_0x1d6000.so"), false);

一步一步補(bǔ)unidbg run so環(huán)境

先看第一個(gè)錯(cuò)誤

[07:17:09 068]  WARN [com.github.unidbg.linux.ARM64SyscallHandler] (ARM64SyscallHandler:384) - handleInterrupt intno=2, NR=30, svcNumber=0x16e, PC=unidbg@0xfffe0774, LR=RX@0x40018c9c[libencrypt.so]0x18c9c, syscall=null
java.lang.UnsupportedOperationException: android/app/ActivityThread->currentActivityThread()Landroid/app/ActivityThread;
        at com.github.unidbg.linux.android.dvm.AbstractJni.callStaticObjectMethod(AbstractJni.java:432)
        at com.github.unidbg.linux.android.dvm.AbstractJni.callStaticObjectMethod(AbstractJni.java:421)
        at com.github.unidbg.linux.android.dvm.DvmMethod.callStaticObjectMethod(DvmMethod.java:59)
        at com.github.unidbg.linux.android.dvm.DalvikVM64$111.handle(DalvikVM64.java:1723)
        at com.github.unidbg.linux.ARM64SyscallHandler.hook(ARM64SyscallHandler.java:130)

unidbg的報(bào)錯(cuò)提示非常清晰，說(shuō)明在 callStaticObjectMethod 中調(diào)用 ActivityThread 類的靜態(tài)方法 currentActivityThread，并且返回值是 ActivityThread 類型。

我們?cè)贑aranywhereDemo.java中重載 callStaticObjectMethod 函數(shù)來(lái)解決這個(gè)問(wèn)題：

@Override
    public DvmObject<?> callStaticObjectMethod(BaseVM vm, DvmClass dvmClass, String signature, VarArg varArg) {
        switch (signature) {
            case "android/app/ActivityThread->currentActivityThread()Landroid/app/ActivityThread;":
                return vm.resolveClass("android/app/ActivityThread").newObject(null);
        }
        return super.callStaticObjectMethod(vm, dvmClass, signature, varArg);
    }

我們先不關(guān)心這個(gè) currentActivityThread 要被做什么用，直接返回一個(gè)空的類就行。

繼續(xù)跑，下一個(gè)錯(cuò)誤還是在 callStaticObjectMethod 里面，看上去像是獲取 一些系統(tǒng)信息

java.lang.UnsupportedOperationException: android/os/SystemProperties->get(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
        at com.github.unidbg.linux.android.dvm.AbstractJni.callStaticObjectMethod(AbstractJni.java:432)
        at com.fenfei.test.CaranywhereDemo.callStaticObjectMethod(CaranywhereDemo.java:78)
        at com.github.unidbg.linux.android.dvm.AbstractJni.callStaticObjectMethod(AbstractJni.java:421)
        at com.github.unidbg.linux.android.dvm.DvmMethod.callStaticObjectMethod(DvmMethod.java:59)
        at com.github.unidbg.linux.android.dvm.DalvikVM64$111.handle(DalvikVM64.java:1723)
        at com.github.unidbg.linux.ARM64SyscallHandler.hook(ARM64SyscallHandler.java:130)

補(bǔ)這中有入?yún)⒌暮瘮?shù)可以簡(jiǎn)單粗暴的給他返回一個(gè)空字符串，但是講究人先要把他的入?yún)⒋蛴〕鰜?lái)。

@Override
    public DvmObject<?> callStaticObjectMethod(BaseVM vm, DvmClass dvmClass, String signature, VarArg varArg) {
        switch (signature) {
            case "android/os/SystemProperties->get(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;":
                System.out.println("android/os/SystemProperties->get 入?yún)ⅲ? + varArg.formatArgs());
                return new StringObject(vm, "705KPGS001091");

            case "android/app/ActivityThread->currentActivityThread()Landroid/app/ActivityThread;":
                return vm.resolveClass("android/app/ActivityThread").newObject(null);
        }
        return super.callStaticObjectMethod(vm, dvmClass, signature, varArg);
    }

Tip:

unidbg庫(kù)函數(shù)formatArgs提示不是公有函數(shù)，在VarArg類里面改下 public final String formatArgs()

輸出

android/os/SystemProperties->get 入?yún)ⅲ?ro.serialno", "unknown"

原來(lái)是為了獲取Android序列號(hào)，隨便給他編一個(gè)就好， 由于本樣本只調(diào)用一次，所以就懶得判斷入?yún)⒘恕?/p>

Tip:

adb shell getprop ro.serialno 可以獲取到Android序列號(hào)

這個(gè)報(bào)錯(cuò)和第一個(gè)報(bào)錯(cuò)類似，不過(guò)它是在 callObjectMethod 函數(shù)里面

java.lang.UnsupportedOperationException: android/app/ActivityThread->getSystemContext()Landroid/app/ContextImpl;
        at com.github.unidbg.linux.android.dvm.AbstractJni.callObjectMethod(AbstractJni.java:921)
        at com.github.unidbg.linux.android.dvm.AbstractJni.callObjectMethod(AbstractJni.java:855)
        at com.github.unidbg.linux.android.dvm.DvmMethod.callObjectMethod(DvmMethod.java:74)
        at com.github.unidbg.linux.android.dvm.DalvikVM64$31.handle(DalvikVM64.java:504)
        at com.github.unidbg.linux.ARM64SyscallHandler.hook(ARM64SyscallHandler.java:130)

重載 callObjectMethod 函數(shù)，然后 直接返回 ContextImpl 類型就行

public DvmObject<?> callObjectMethod(BaseVM vm, DvmObject<?> dvmObject, String signature, VarArg varArg) {
        switch (signature) {
            case "android/app/ActivityThread->getSystemContext()Landroid/app/ContextImpl;":
                return vm.resolveClass("android/app/ContextImpl").newObject(null);
        }

        return super.callObjectMethod(vm, dvmObject, signature, varArg);
    }

繼續(xù)報(bào)錯(cuò)，這個(gè)是獲取包管理類

java.lang.UnsupportedOperationException: android/app/ContextImpl->getPackageManager()Landroid/content/pm/PackageManager;
        at com.github.unidbg.linux.android.dvm.AbstractJni.callObjectMethod(AbstractJni.java:921)
        at com.fenfei.test.CaranywhereDemo.callObjectMethod(CaranywhereDemo.java:91)
        at com.github.unidbg.linux.android.dvm.AbstractJni.callObjectMethod(AbstractJni.java:855)
        at com.github.unidbg.linux.android.dvm.DvmMethod.callObjectMethod(DvmMethod.java:74)
        at com.github.unidbg.linux.android.dvm.DalvikVM64$31.handle(DalvikVM64.java:504)
        at com.github.unidbg.linux.ARM64SyscallHandler.hook(ARM64SyscallHandler.java:130)

callObjectMethod 構(gòu)造 PackageManager類返回

case "android/app/ContextImpl->getPackageManager()Landroid/content/pm/PackageManager;":
                return vm.resolveClass("android/content/pm/PackageManager").newObject(null);

下一個(gè)報(bào)錯(cuò)。

java.lang.UnsupportedOperationException: android/app/ContextImpl->getSystemService(Ljava/lang/String;)Ljava/lang/Object;
        at com.github.unidbg.linux.android.dvm.AbstractJni.callObjectMethod(AbstractJni.java:921)
        at com.fenfei.test.CaranywhereDemo.callObjectMethod(CaranywhereDemo.java:93)
        at com.github.unidbg.linux.android.dvm.AbstractJni.callObjectMethod(AbstractJni.java:855)
        at com.github.unidbg.linux.android.dvm.DvmMethod.callObjectMethod(DvmMethod.java:74)

這個(gè)函數(shù)有參數(shù)，老規(guī)矩，打印下參數(shù)看看。

case "android/app/ContextImpl->getSystemService(Ljava/lang/String;)Ljava/lang/Object;":
                System.out.println("android/app/ContextImpl->getSystemService 入?yún)ⅲ? + varArg.formatArgs());
                return vm.resolveClass("java/lang/Object").newObject(null);

參數(shù)打印出來(lái)是

android/app/ContextImpl->getSystemService 入?yún)ⅲ?wifi"

估摸是wifi相關(guān)，先給他返回一個(gè)空的 Object再說(shuō)

后面兩個(gè)報(bào)錯(cuò)就是獲取wifi Mac地址相關(guān)的，直接補(bǔ)上

case "android/net/wifi/WifiInfo->getMacAddress()Ljava/lang/String;":
                return new StringObject(vm, "00:00:00:00:00:00");
            case "java/lang/Object->getConnectionInfo()Landroid/net/wifi/WifiInfo;":
                return vm.resolveClass("android/net/wifi/WifiInfo").newObject(null);

到這里終于把 JNI_OnLoad 給跑通了， 可以干一杯了。

call checkcode

搞了半天才開(kāi)始進(jìn)入正題，我們來(lái)調(diào)用 checkcode

public void callA() {

    String strA = "F{"appInnerVersion":"125","appOutVersion":"6.1.0","deviceType":0,"imeiMD5":"EE6431DEBB1E02FE469FA5E8467CD693","mobileModel":"GOOGLE PIXEL 2 XL","softType":"0"}";
    String strC = "1662109202156";

    String methodName = "checkcode(Ljava/lang/String;ILjava/lang/String;)Ljava/lang/String;";
    DvmObject ret = dvmClass.callStaticJniMethodObject(emulator, methodName,strA,1,strC);
    String strOut = (String)ret.getValue();
    System.out.println("call checkcode: " + strOut);
}

又有新的報(bào)錯(cuò)了

java.lang.UnsupportedOperationException: android/os/Build->MODEL:Ljava/lang/String;
        at com.github.unidbg.linux.android.dvm.AbstractJni.getStaticObjectField(AbstractJni.java:103)
        at com.github.unidbg.linux.android.dvm.AbstractJni.getStaticObjectField(AbstractJni.java:53)
        at com.github.unidbg.linux.android.dvm.DvmField.getStaticObjectField(DvmField.java:106)
        at com.github.unidbg.linux.android.dvm.DalvikVM64$142.handle(DalvikVM64.java:2228)

這次要重載 getStaticObjectField 類了

public DvmObject<?> getStaticObjectField(BaseVM vm, DvmClass dvmClass, String signature) {
        switch (signature){
            case "android/os/Build$VERSION->SDK:Ljava/lang/String;":
                return new StringObject(vm, "23");
            case "android/os/Build->MANUFACTURER:Ljava/lang/String;":
                return new StringObject(vm, "Google");
            case "android/os/Build->MODEL:Ljava/lang/String;":
                return new StringObject(vm, "pixel");
        }
        return super.getStaticObjectField(vm,dvmClass,signature);
    }

這幾個(gè)值比較簡(jiǎn)單，都是字符串型，我們給他賦值一把。

耶，大功告成了

call checkcode: FDAEKCAcOAQcNBgkEAwoCDQgEDQ4JBAgAAA4ODgcJBgkKBwYPBwwEBw4LBwsODQcFDQMMCAUJDAcEDQsADwEDDAIGDgQJAQYNDggNDQsCAQcNAwwIBQkMBwQNCwAPAQMMDQYCDAgBBQwGBAUIAwULBAoHBg8HDAQHDgsHCw4NBwUPAwEADAkPBQcODAcDDgYCDwMJCQUEAAgHDAUIBwEDBwMKDgcGBg4NDAgLBAAEAw8PAwEADAkPBQcODAcDDgYCCAQNDgkECAAADg4OBwkGCQIIAwkLBgACCgoGAgcCAwEMAQoIBw4BBw0GCQQDCgINDwMBAAwJDwUHDgwHAw4GAggHBwEMBAAAAwMJDQUDDQECBg4ECQEGDQ4IDQ0LAgEHDw0ADwMJDgQICAsJAgILBw8NAA8DCQ4ECAgLCQICCwcNBgIMCAEFDAYEBQgDBQsEAgYOBAkBBg0OCA0NCwIBBw==

先別高興的太早了，這個(gè)結(jié)果怎么看都有點(diǎn)不對(duì)勁，和我們hook的結(jié)果相差有點(diǎn)大。

怎么判斷結(jié)果是對(duì)是錯(cuò)？怎么和app對(duì)比來(lái)拿到正確的結(jié)果？ 等待下次的 Trace Block 和 Trace Code 教程吧。

三、總結(jié)

unidbg補(bǔ)環(huán)境實(shí)際是考驗(yàn)?zāi)愕腁ndroid編程能力。

谷歌一下關(guān)鍵字 unidbg + 報(bào)錯(cuò)信息，一般都有同道趟過(guò)坑。

什么？你打不開(kāi)谷歌？我現(xiàn)在勸你改行還來(lái)得及嗎？

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好味止園葵，大歡止稚子。平生不止酒，止酒情無(wú)喜。