35.安卓逆向-壳-Frida脚本脱壳

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内容参考于：图灵Python学院

本人写的内容纯属胡编乱造，全都是合成造假，仅仅只是为了娱乐，请不要盲目相信。第一次接触安卓逆向写的很烂，后面有机会再全部重写。

工具下载：

链接：https://pan.baidu.com/s/1rEEJnt85npn7N38Ai0_F2Q?pwd=6tw3

提取码：6tw3

复制这段内容后打开百度网盘手机App，操作更方便哦

上一个内容：34.安卓逆向-壳-frida-Dexdump脱壳

上一个内容里写了使用frida-Dexdump脱壳，使用frida-Dexdump脱壳的时候下载源码的时候会报错，报错之后dex源码在jadx-gui里就没法识别了，这个问题可以使用下方的Frida脚本下载源码来解决，源码下载的位置在电脑控制台，如下图红框，源码文件下载到了手机里，所以需要手动把手机里的源码文件复制到电脑里，然后再使用jadx-gui反编译源码，注意脚本运行的时候需要在app里刷一刷（就是玩一玩app，玩到不会再下载新的dex文件为止）

frida下载app源码脚本，指令 frida -UF -l 这里写js文件名（也就是下方Frida脚本的文件名和目录），运行这个指令之后会把手机上当前运行的app的源码下载下来

function get_self_process_name() {
    var openPtr = Module.getExportByName('libc.so', 'open');
    var open = new NativeFunction(openPtr, 'int', ['pointer', 'int']);

    var readPtr = Module.getExportByName("libc.so", "read");
    var read = new NativeFunction(readPtr, "int", ["int", "pointer", "int"]);

    var closePtr = Module.getExportByName('libc.so', 'close');
    var close = new NativeFunction(closePtr, 'int', ['int']);

    var path = Memory.allocUtf8String("/proc/self/cmdline");
    var fd = open(path, 0);
    if (fd != -1) {
        var buffer = Memory.alloc(0x1000);

        var result = read(fd, buffer, 0x1000);
        close(fd);
        result = ptr(buffer).readCString();
        return result;
    }

    return "-1";
}


function mkdir(path) {
    var mkdirPtr = Module.getExportByName('libc.so', 'mkdir');
    var mkdir = new NativeFunction(mkdirPtr, 'int', ['pointer', 'int']);

    var opendirPtr = Module.getExportByName('libc.so', 'opendir');
    var opendir = new NativeFunction(opendirPtr, 'pointer', ['pointer']);

    var closedirPtr = Module.getExportByName('libc.so', 'closedir');
    var closedir = new NativeFunction(closedirPtr, 'int', ['pointer']);

    var cPath = Memory.allocUtf8String(path);
    var dir = opendir(cPath);
    if (dir != 0) {
        closedir(dir);
        return 0;
    }
    mkdir(cPath, 755);
    chmod(path);
}

function chmod(path) {
    var chmodPtr = Module.getExportByName('libc.so', 'chmod');
    var chmod = new NativeFunction(chmodPtr, 'int', ['pointer', 'int']);
    var cPath = Memory.allocUtf8String(path);
    chmod(cPath, 755);
}

function dump_dex() {
    var libart = Process.findModuleByName("libart.so");
    var addr_DefineClass = null;
    var symbols = libart.enumerateSymbols();
    for (var index = 0; index < symbols.length; index++) {
        var symbol = symbols[index];
        var symbol_name = symbol.name;
        //这个DefineClass的函数签名是Android9的
        //_ZN3art11ClassLinker11DefineClassEPNS_6ThreadEPKcmNS_6HandleINS_6mirror11ClassLoaderEEERKNS_7DexFileERKNS9_8ClassDefE
        if (symbol_name.indexOf("ClassLinker") >= 0 &&
            symbol_name.indexOf("DefineClass") >= 0 &&
            symbol_name.indexOf("Thread") >= 0 &&
            symbol_name.indexOf("DexFile") >= 0) {
            console.log(symbol_name, symbol.address);
            addr_DefineClass = symbol.address;
        }
    }
    var dex_maps = {};
    var dex_count = 1;

    console.log("[DefineClass:]", addr_DefineClass);
    if (addr_DefineClass) {
        Interceptor.attach(addr_DefineClass, {
            onEnter: function(args) {
                var dex_file = args[5];
                //ptr(dex_file).add(Process.pointerSize) is "const uint8_t* const begin_;"
                //ptr(dex_file).add(Process.pointerSize + Process.pointerSize) is "const size_t size_;"
                var base = ptr(dex_file).add(Process.pointerSize).readPointer();
                var size = ptr(dex_file).add(Process.pointerSize + Process.pointerSize).readUInt();

                if (dex_maps[base] == undefined) {
                    dex_maps[base] = size;
                    var magic = ptr(base).readCString();
                    if (magic.indexOf("dex") == 0) {

                        var process_name = get_self_process_name();
                        if (process_name != "-1") {
                            var dex_dir_path = "/data/data/" + process_name + "/files/dump_dex_" + process_name;
                            mkdir(dex_dir_path);
                            var dex_path = dex_dir_path + "/class" + (dex_count == 1 ? "" : dex_count) + ".dex";
                            console.log("[find dex]:", dex_path);
                            var fd = new File(dex_path, "wb");
                            if (fd && fd != null) {
                                dex_count++;
                                var dex_buffer = ptr(base).readByteArray(size);
                                fd.write(dex_buffer);
                                fd.flush();
                                fd.close();
                                console.log("[dump dex]:", dex_path);

                            }
                        }
                    }
                }
            },
            onLeave: function(retval) {}
        });
    }
}

var is_hook_libart = false;

function hook_dlopen() {
    Interceptor.attach(Module.findExportByName(null, "dlopen"), {
        onEnter: function(args) {
            var pathptr = args[0];
            if (pathptr !== undefined && pathptr != null) {
                var path = ptr(pathptr).readCString();
                //console.log("dlopen:", path);
                if (path.indexOf("libart.so") >= 0) {
                    this.can_hook_libart = true;
                    console.log("[dlopen:]", path);
                }
            }
        },
        onLeave: function(retval) {
            if (this.can_hook_libart && !is_hook_libart) {
                dump_dex();
                is_hook_libart = true;
            }
        }
    })

    Interceptor.attach(Module.findExportByName(null, "android_dlopen_ext"), {
        onEnter: function(args) {
            var pathptr = args[0];
            if (pathptr !== undefined && pathptr != null) {
                var path = ptr(pathptr).readCString();
                //console.log("android_dlopen_ext:", path);
                if (path.indexOf("libart.so") >= 0) {
                    this.can_hook_libart = true;
                    console.log("[android_dlopen_ext:]", path);
                }
            }
        },
        onLeave: function(retval) {
            if (this.can_hook_libart && !is_hook_libart) {
                dump_dex();
                is_hook_libart = true;
            }
        }
    });
}


setImmediate(dump_dex);