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React Native Hermes 逆向实践
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发表于: 2022-7-4 21:31
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Android 应用gl，使用了加固i，老版本的应用gl是js源码，新版本更新后，刚开始以为是加密了源码，分析后才知道是使用了Hermes优化引擎。
Hermes是Facebook为React Native开源的一款javascript优化引擎。
原来的index.android.bundle是javascript的，被Hermes优化后变成了Bytecode。
Hermes优化的优化效果如下：
优化前：
优化后：
应用gl使用了加固i，在被root 的手机上运行，闪退。
绕过方法也很简单，在magisk的设置中，开启遵守排除列表，然后在配置排除列表中选择应用gl
应用被添加到排除列表后，将没办法使用lspoed，只能使用frida
抓包可以看到登录接口有个signcode加密参数，69e34d747c5757236142a19f4595d313 是32位字符串，猜测跟md5相关
由于我分析过应用gl前面版本，所以知道它是React Native开发的
但当你们拿到新app的时候，需要先对apk文件，app数据目录进行一次搜索
解压 apk， 使用命令 grep -r "signcode" *，搜索一下apk下有没有signcode，第一次没搜到(备注：应用gl把代码打包到assets/android-rn.zip里了)
在app的数据目录下，使用命令 grep -r "signcode" *，搜索一下，在文件./files/RN/rnbundle/index.android.bundle下搜索到了signcode
把./files/RN/rnbundle/index.android.bundle拿出来
使用010editor打开后，就看到如下图的内容：
刚打开index.android.bundle, 我就猜测这个文件难道被加密了？(备注：在这之前我没有分析过被Hermes优化的应用）。
因为应用gl有加固i，我并没有研究加固，于是只能研究React Native的源码，看不能找到最终加载源码的地方
下载源码 https://github.com/facebook/react-native.git
在源码中搜索 LoadScript，找到2个可疑的函数
这2个函数是native，使用https://github.com/lasting-yang/frida_hook_libart/blob/master/hook_RegisterNatives.js，可以找到函数对应的so
对jniLoadScriptFromAssets和jniLoadScriptFromFile进行hook，需要配合hook_dlopen一起使用，因为frida注入的时候，libreactnativejni.so还没有加载。
jniLoadScriptFromFile被加载，传入参数为index.android.bundle文件路径
继续阅读源码，jniLoadScriptFromFile中会调用loadScriptFromString
loadScriptFromString
hook loadScriptFromString后，可以知道loadSynchronously为0， 继续分析loadBundle
runOnExecutorQueue的参数是一个Lambda表达式，它的回调函数里面调用了loadBundle，在源码中搜索loadBundle，找到了很多处实现代码，这时候我们酒不知道loadBundle具体实现在哪里，继续写hook代码hook_loadBundle
facebook::react::JSIExecutor::loadBundle函数中调用了evaluateJavaScript
hook "*evaluateJavaScript*",
evaluateJavaScriptWithSourceMap函数 在React Native源码中没有搜到，在另一个hermes项目（https://github.com/facebook/hermes）中找到了evaluateJavaScriptWithSourceMap函数和evaluateJavaScript函数
evaluateJavaScript函数对应so的地址0xbb867431 libhermes.so!0x11431
evaluateJavaScriptWithSourceMap函数中调用了prepareJavaScriptWithSourceMap函数, 继续调用isHermesBytecode函数
isHermesBytecode用来判断是否是Hermes的Bytecode
MAGIC和index.android.bunddle的前8个字节是一直的，至此已经知道index.android.bundle并不是被应用gl加密了，而是被Hermes编译成了bytecode
前面的分析过程，已经知道了index.android.bundle是Hermes的bytecode，没办法直接查看源码，需要借助其他工具进行反编译
Hermes官方提供了hbcdump工具，可以进行反编译，但使用起来比较麻烦，有另一个开源工具hbctool可以对hermesbytecode进行反编译与回编译
https://github.com/bongtrop/hbctool 提供了59， 62， 74， 76版本的反编译
https://github.com/niosega/hbctool/tree/draft/hbc-v84 对84版本的Hermes进行补充
安装可以反编译84版本的hbctool
反编译
回编译
bytecode反编译出来的代码如下：搜索两处能md5相关的代码
并不需要深入bytecode，指令详情，了解几个简单指令即可。
只需要写一个打印日志的函数，变成成bytecode，反编译后替换掉这两个函数就能看到这两个md5函数的输入参数
先编译Hermes源码，会得到./build/bin/hermes工具，
test.js
写了一些简单的js代码，把test.js编译成bytecode
010editor打开test.hbc可以看到MAGIC
反编译test.hbc
得到
把反编译出来的bytecode，替换到md5函数中
需要对字符串的id进行修改，字符串对应hbctool反编译出来的string.json中的字符串id
再次回编译，得到index.android.bundle.re
现在替换app目录下的index.android.bundle
结束app, 运行 adb logcat "*:S ReactNative:V ReactNativeJS:V", 再次运行app就可以到得到md5函数的输入参数
算法分析完成
https://github.com/facebook/react-native.git
https://github.com/lasting-yang/frida_hook_libart
https://github.com/facebook/hermes
https://github.com/bongtrop/hbctool
https://github.com/niosega/hbctool/tree/draft/hbc-v84
function hook_ssl() { Java.perform(function () {
var ClassName = "com.android.org.conscrypt.Platform";
var Platform = Java.use(ClassName);
var targetMethod = "checkServerTrusted";
var len = Platform[targetMethod].overloads.length;
console.log(targetMethod, len);
for (var i = 0; i < len; ++i) {
Platform[targetMethod].overloads[i].implementation = function () {
console.log("class:", ClassName, "target:", targetMethod, " i:", i, arguments);
};
}
var ClassName = "com.android.org.conscrypt.TrustManagerImpl";
var Platform = Java.use(ClassName);
var targetMethod = "checkTrustedRecursive";
var len = Platform[targetMethod].overloads.length;
console.log(targetMethod, len);
var ArrayList = Java.use("java.util.ArrayList")
var X509Certificate = Java.use("java.security.cert.X509Certificate");
for (var i = 0; i < len; ++i) {
Platform[targetMethod].overloads[i].implementation = function () {
console.log("class:", ClassName, "target:", targetMethod, " i:", i, arguments);
return ArrayList.$new();
};
}
});
}function hook_ssl() { Java.perform(function () {
var ClassName = "com.android.org.conscrypt.Platform";
var Platform = Java.use(ClassName);
var targetMethod = "checkServerTrusted";
var len = Platform[targetMethod].overloads.length;
console.log(targetMethod, len);
for (var i = 0; i < len; ++i) {
Platform[targetMethod].overloads[i].implementation = function () {
console.log("class:", ClassName, "target:", targetMethod, " i:", i, arguments);
};
}
var ClassName = "com.android.org.conscrypt.TrustManagerImpl";
var Platform = Java.use(ClassName);
var targetMethod = "checkTrustedRecursive";
var len = Platform[targetMethod].overloads.length;
console.log(targetMethod, len);
var ArrayList = Java.use("java.util.ArrayList")
var X509Certificate = Java.use("java.security.cert.X509Certificate");
for (var i = 0; i < len; ++i) {
Platform[targetMethod].overloads[i].implementation = function () {
console.log("class:", ClassName, "target:", targetMethod, " i:", i, arguments);
return ArrayList.$new();
};
}
});
}Binary file ./files/RN/rnbundle/index.android.bundle matches
Binary file ./files/RN/rnbundle/index.android.bundle matches
cp ./files/RN/rnbundle/index.android.bundle /data/local/tmp/index.android.bundle
chmod 777 /data/local/tmp/index.android.bundle
adb pull /data/local/tmp/index.android.bundle
cp ./files/RN/rnbundle/index.android.bundle /data/local/tmp/index.android.bundle
chmod 777 /data/local/tmp/index.android.bundle
adb pull /data/local/tmp/index.android.bundle
private native void jniLoadScriptFromAssets(AssetManager assetManager, String assetURL, boolean loadSynchronously);private native void jniLoadScriptFromFile(String fileName, String sourceURL, boolean loadSynchronously);private native void jniLoadScriptFromAssets(AssetManager assetManager, String assetURL, boolean loadSynchronously);private native void jniLoadScriptFromFile(String fileName, String sourceURL, boolean loadSynchronously);[RegisterNatives] java_class: com.facebook.react.bridge.CatalystInstanceImpl name: jniLoadScriptFromAssets sig: (Landroid/content/res/AssetManager;Ljava/lang/String;Z)V fnPtr: 0xb4e99a85 fnOffset: 0x80a85 callee: 0xb4d2021d libhermes-executor-release.so!_ZN8facebook3jni6JClass15registerNativesESt16initializer_listI15JNINativeMethodE+0x20
[RegisterNatives] java_class: com.facebook.react.bridge.CatalystInstanceImpl name: jniLoadScriptFromFile sig: (Ljava/lang/String;Ljava/lang/String;Z)V fnPtr: 0xb4e99aa1 fnOffset: 0x80aa1 callee: 0xb4d2021d libhermes-executor-release.so!_ZN8facebook3jni6JClass15registerNativesESt16initializer_listI15JNINativeMethodE+0x20
这时候会遇到一个问题，callee在libhermes-executor-release.so，使用ida打开libhermes-executor-release.so后，去fnOffset: 0x80a85和fnOffset: 0x80aa1找不到对应的函数。
于是使用frida的 Process.findModuleByAddress(ptr(0xb4e99a85)) 找jniLoadScriptFromAssets函数所在的模块，在libreactnativejni.so里面
{ "base": "0xb4e19000",
"name": "libreactnativejni.so",
"path": "/data/app/~~klydM6uPsWM_heluFCfyKQ==/com.xxxxx.xxx.xxxxxxxxxx.xxxxxx-zC5SUJ_WxA0rwldHieq_fg==/lib/arm/libreactnativejni.so",
"size": 815104
}[RegisterNatives] java_class: com.facebook.react.bridge.CatalystInstanceImpl name: jniLoadScriptFromAssets sig: (Landroid/content/res/AssetManager;Ljava/lang/String;Z)V fnPtr: 0xb4e99a85 fnOffset: 0x80a85 callee: 0xb4d2021d libhermes-executor-release.so!_ZN8facebook3jni6JClass15registerNativesESt16initializer_listI15JNINativeMethodE+0x20
[RegisterNatives] java_class: com.facebook.react.bridge.CatalystInstanceImpl name: jniLoadScriptFromFile sig: (Ljava/lang/String;Ljava/lang/String;Z)V fnPtr: 0xb4e99aa1 fnOffset: 0x80aa1 callee: 0xb4d2021d libhermes-executor-release.so!_ZN8facebook3jni6JClass15registerNativesESt16initializer_listI15JNINativeMethodE+0x20
这时候会遇到一个问题，callee在libhermes-executor-release.so，使用ida打开libhermes-executor-release.so后，去fnOffset: 0x80a85和fnOffset: 0x80aa1找不到对应的函数。
于是使用frida的 Process.findModuleByAddress(ptr(0xb4e99a85)) 找jniLoadScriptFromAssets函数所在的模块，在libreactnativejni.so里面
{ "base": "0xb4e19000",
"name": "libreactnativejni.so",
"path": "/data/app/~~klydM6uPsWM_heluFCfyKQ==/com.xxxxx.xxx.xxxxxxxxxx.xxxxxx-zC5SUJ_WxA0rwldHieq_fg==/lib/arm/libreactnativejni.so",
"size": 815104
}function hook_dlopen(module_name, fun) { var android_dlopen_ext = Module.findExportByName(null, "android_dlopen_ext");
if (android_dlopen_ext) {
Interceptor.attach(android_dlopen_ext, {
onEnter: function (args) {
var pathptr = args[0];
if (pathptr) {
this.path = (pathptr).readCString();
if (this.path.indexOf(module_name) >= 0) {
this.canhook = true;
console.log("android_dlopen_ext:", this.path);
}
}
},
onLeave: function (retval) {
if (this.canhook) {
fun();
}
}
});
}
}function hook_libreactnativejni() { let base_libreactnativejni = Module.findBaseAddress("libreactnativejni.so");
if (base_libreactnativejni == null) {
return;
}
let jniLoadScriptFromAssets = base_libreactnativejni.add(0x80a85);
let jniLoadScriptFromFile = base_libreactnativejni.add(0x80aa1);
//private native void jniLoadScriptFromAssets(AssetManager assetManager, String assetURL, boolean loadSynchronously);
Interceptor.attach(jniLoadScriptFromAssets, {
onEnter(args) {
console.log("jniLoadScriptFromAssets:", Java.vm.tryGetEnv().getStringUtfChars(args[3]).readCString())
}
})
//private native void jniLoadScriptFromFile(String fileName, String sourceURL, boolean loadSynchronously);
Interceptor.attach(jniLoadScriptFromFile, {
onEnter(args) {
console.log("jniLoadScriptFromFile:", Java.vm.tryGetEnv().getStringUtfChars(args[2]).readCString(), Java.vm.tryGetEnv().getStringUtfChars(args[3]).readCString())
}
})
}setImmediate(() => {
hook_dlopen("libreactnativejni.so", hook_libreactnativejni)
hook_libreactnativejni();
})function hook_dlopen(module_name, fun) { var android_dlopen_ext = Module.findExportByName(null, "android_dlopen_ext");
if (android_dlopen_ext) {
Interceptor.attach(android_dlopen_ext, {
onEnter: function (args) {
var pathptr = args[0];
if (pathptr) {
this.path = (pathptr).readCString();
if (this.path.indexOf(module_name) >= 0) {
this.canhook = true;
console.log("android_dlopen_ext:", this.path);
}
}
},
onLeave: function (retval) {
if (this.canhook) {
fun();
}
}
});
}
}function hook_libreactnativejni() { let base_libreactnativejni = Module.findBaseAddress("libreactnativejni.so");
if (base_libreactnativejni == null) {
return;
}
let jniLoadScriptFromAssets = base_libreactnativejni.add(0x80a85);
let jniLoadScriptFromFile = base_libreactnativejni.add(0x80aa1);
//private native void jniLoadScriptFromAssets(AssetManager assetManager, String assetURL, boolean loadSynchronously);
Interceptor.attach(jniLoadScriptFromAssets, {
onEnter(args) {
console.log("jniLoadScriptFromAssets:", Java.vm.tryGetEnv().getStringUtfChars(args[3]).readCString())
}
})
//private native void jniLoadScriptFromFile(String fileName, String sourceURL, boolean loadSynchronously);
Interceptor.attach(jniLoadScriptFromFile, {
onEnter(args) {
console.log("jniLoadScriptFromFile:", Java.vm.tryGetEnv().getStringUtfChars(args[2]).readCString(), Java.vm.tryGetEnv().getStringUtfChars(args[3]).readCString())
}
})
}setImmediate(() => {
hook_dlopen("libreactnativejni.so", hook_libreactnativejni)
hook_libreactnativejni();
})void CatalystInstanceImpl::jniLoadScriptFromFile( const std::string &fileName,
const std::string &sourceURL,
bool loadSynchronously) {
auto reactInstance = instance_;
if (!reactInstance) {
return;
}
switch (getScriptTagFromFile(fileName.c_str())) { //根据文件头判断脚本类型，
case ScriptTag::MetroHBCBundle: {
std::unique_ptr<const JSBigFileString> script;
RecoverableError::runRethrowingAsRecoverable<std::system_error>(
[&fileName, &script]() {
script = JSBigFileString::fromPath(fileName);
});
const char *buffer = script->c_str();
uint32_t bufferLength = (uint32_t)script->size();
uint32_t offset = 8;
while (offset < bufferLength) {
uint32_t segment = offset + 4;
uint32_t moduleLength =
bufferLength < segment ? 0 : *(((uint32_t *)buffer) + offset / 4);
reactInstance->loadScriptFromString(
std::make_unique<const JSBigStdString>(
std::string(buffer + segment, buffer + moduleLength + segment)),
sourceURL,
false);
offset += ((moduleLength + 3) & ~3) + 4;
}
break;
}
case ScriptTag::RAMBundle:
instance_->loadRAMBundleFromFile(fileName, sourceURL, loadSynchronously);
break;
case ScriptTag::String:
default: {
std::unique_ptr<const JSBigFileString> script;
RecoverableError::runRethrowingAsRecoverable<std::system_error>(
[&fileName, &script]() {
script = JSBigFileString::fromPath(fileName);
});
instance_->loadScriptFromString(
std::move(script), sourceURL, loadSynchronously);
}
}
}void CatalystInstanceImpl::jniLoadScriptFromFile( const std::string &fileName,
const std::string &sourceURL,
bool loadSynchronously) {
auto reactInstance = instance_;
if (!reactInstance) {
return;
}
switch (getScriptTagFromFile(fileName.c_str())) { //根据文件头判断脚本类型，
case ScriptTag::MetroHBCBundle: {
std::unique_ptr<const JSBigFileString> script;
RecoverableError::runRethrowingAsRecoverable<std::system_error>(
[&fileName, &script]() {
script = JSBigFileString::fromPath(fileName);
});
const char *buffer = script->c_str();
uint32_t bufferLength = (uint32_t)script->size();
uint32_t offset = 8;
while (offset < bufferLength) {
uint32_t segment = offset + 4;
uint32_t moduleLength =
bufferLength < segment ? 0 : *(((uint32_t *)buffer) + offset / 4);
reactInstance->loadScriptFromString(
std::make_unique<const JSBigStdString>(
std::string(buffer + segment, buffer + moduleLength + segment)),
sourceURL,
false);
offset += ((moduleLength + 3) & ~3) + 4;
}
break;
}
case ScriptTag::RAMBundle:
instance_->loadRAMBundleFromFile(fileName, sourceURL, loadSynchronously);
break;
case ScriptTag::String:
default: {
std::unique_ptr<const JSBigFileString> script;
RecoverableError::runRethrowingAsRecoverable<std::system_error>(
[&fileName, &script]() {
script = JSBigFileString::fromPath(fileName);
});
instance_->loadScriptFromString(
std::move(script), sourceURL, loadSynchronously);
}
}
}void Instance::loadScriptFromString( std::unique_ptr<const JSBigString> string,
std::string sourceURL,
bool loadSynchronously) {
SystraceSection s("Instance::loadScriptFromString", "sourceURL", sourceURL);
if (loadSynchronously) {
loadBundleSync(nullptr, std::move(string), std::move(sourceURL));
} else {
loadBundle(nullptr, std::move(string), std::move(sourceURL));
}
}void Instance::loadScriptFromString( std::unique_ptr<const JSBigString> string,
std::string sourceURL,
bool loadSynchronously) {
SystraceSection s("Instance::loadScriptFromString", "sourceURL", sourceURL);
if (loadSynchronously) {
loadBundleSync(nullptr, std::move(string), std::move(sourceURL));
} else {
loadBundle(nullptr, std::move(string), std::move(sourceURL));
}
}let loadScriptFromString = base_libreactnativejni.add(0xA0BF8 + 1);
Interceptor.attach(loadScriptFromString, {
onEnter(args) {
console.log("loadScriptFromString:", (args[1]), ptr(args[2]).add(Process.pointerSize * 2).readPointer().readCString(), args[3])
}
})
let loadScriptFromString = base_libreactnativejni.add(0xA0BF8 + 1);
Interceptor.attach(loadScriptFromString, {
onEnter(args) {
console.log("loadScriptFromString:", (args[1]), ptr(args[2]).add(Process.pointerSize * 2).readPointer().readCString(), args[3])
}
})
void Instance::loadBundle( std::unique_ptr<RAMBundleRegistry> bundleRegistry,
std::unique_ptr<const JSBigString> string,
std::string sourceURL) {
callback_->incrementPendingJSCalls();
SystraceSection s("Instance::loadBundle", "sourceURL", sourceURL);
nativeToJsBridge_->loadBundle(
std::move(bundleRegistry), std::move(string), std::move(sourceURL));
}//Instance::loadBundle调用了nativeToJsBridge_->loadBundle，
void NativeToJsBridge::loadBundle( std::unique_ptr<RAMBundleRegistry> bundleRegistry,
std::unique_ptr<const JSBigString> startupScript,
std::string startupScriptSourceURL) {
runOnExecutorQueue(
[this,
bundleRegistryWrap = folly::makeMoveWrapper(std::move(bundleRegistry)),
startupScript = folly::makeMoveWrapper(std::move(startupScript)),
startupScriptSourceURL =
std::move(startupScriptSourceURL)](JSExecutor *executor) mutable {
auto bundleRegistry = bundleRegistryWrap.move();
if (bundleRegistry) {
executor->setBundleRegistry(std::move(bundleRegistry));
}
try {
executor->loadBundle(
std::move(*startupScript), std::move(startupScriptSourceURL));
} catch (...) {
m_applicationScriptHasFailure = true;
throw;
}
});
}//NativeToJsBridge::loadBundle里面调用了NativeToJsBridge::runOnExecutorQueue
void Instance::loadBundle( std::unique_ptr<RAMBundleRegistry> bundleRegistry,
std::unique_ptr<const JSBigString> string,
std::string sourceURL) {
callback_->incrementPendingJSCalls();
SystraceSection s("Instance::loadBundle", "sourceURL", sourceURL);
nativeToJsBridge_->loadBundle(
std::move(bundleRegistry), std::move(string), std::move(sourceURL));
}//Instance::loadBundle调用了nativeToJsBridge_->loadBundle，
void NativeToJsBridge::loadBundle( std::unique_ptr<RAMBundleRegistry> bundleRegistry,
std::unique_ptr<const JSBigString> startupScript,
std::string startupScriptSourceURL) {
runOnExecutorQueue(
[this,
bundleRegistryWrap = folly::makeMoveWrapper(std::move(bundleRegistry)),
startupScript = folly::makeMoveWrapper(std::move(startupScript)),
startupScriptSourceURL =
[注意]传递专业知识、拓宽行业人脉——看雪讲师团队等你加入！
最后于 2022-7-4 22:16
被Imyang编辑
，原因：
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已经更新了 |
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更新了 他的key也没变 |
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这个更新是替换md5为log的方法失效了吗，跟着试了一下发现logcat没有输出 |
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在我的星球，有快速获取signcode算法的方法，联系我加入星球 |
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刚试了3.2.0 的signcode |
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https://t.zsxq.com/05JiuFAu7 |
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yang神，打开这个知识星球的连接显示没有权限，能再发一下吗 |
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