Native开发与逆向第四篇 - hook JNI函数GetStringUTFChars

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修改测试demo
通过GetStringUTFChars 获取java层传入的字符串参数。

extern "C" JNIEXPORT jstring JNICALL
Java_com_mycode_nativehello_MainActivity_stringFromJNI(JNIEnv* env,jobject /* this */,jstring s) {std::string hello = env->GetStringUTFChars(s, 0);return env->NewStringUTF(hello.c_str());
}

目标hook GetStringUTFChars 打印字符串。
hook 代码如下：

function hook_jni_3(){var symbols = Process.getModuleByName("libart.so").enumerateSymbols();var addr_GetStringUTFChars = NULL;for (var index = 0; index < symbols.length; index++) {const symbols_one = symbols[index];if (symbols_one.name.indexOf("art") >= 0){if (symbols_one.name.indexOf("checkJNI") == -1 && symbols_one.name.indexOf("GetStringUTFChars")>= 0){console.log("GetStringUTFChars ",JSON.stringify(symbols_one));addr_GetStringUTFChars = symbols_one.address;console.log("GetStringUTFChars address = " + addr_GetStringUTFChars); break}}    }Interceptor.attach(addr_GetStringUTFChars,{onEnter:function(args){var env = args[0];var param1 = args[1];console.log("env :",env,"param1 ", Java.vm.getEnv().getStringUtfChars(param1, null).readCString());},onLeave:function (retval) {console.log("GetStringUTFChars retval :", ptr(retval).readCString());}})
}
setImmediate(hook_jni_3);