一种inlineHook检测方案

定义

inlinehook是修改内存中的机器码来实现hook的方式

我们用frida查看一个函数hook之前和hook之后的机器码,这里以open函数为例:

let bytes_count = 32let address = Module.getExportByName("libc.so","open")
let before = ptr(address)console.log("")console.log("[*] before hook: ")console.log(hexdump(before, { offset: 0, length: bytes_count, header: true, ansi: true}));
let isOutput = false
Interceptor.attach(address, {onEnter:function(args){ if(isOutput) return;let after = ptr(address) console.log("")console.log("[*] after hook: ") console.log(hexdump(after, { offset: 0, length: bytes_count, header: true, ansi: true })) isOutput = true},onLeave:function(retv){}});

hook之前:

一种inlineHook检测方案

hook之后:

一种inlineHook检测方案

可见,hook之后,函数开头的字节被修改了

思考

inlinehook只修改了内存中的机器码,而内存中的机器码是从文件加载而来的,所以我们可以将函数在内存中字节和本地对应的字节进行比较,如果不一致,那么可以认为内存中的字节被修改了,即被inlinehook了。

实现

#ifdef __LP64__   const char *lib_path = "/system/lib64/libc.so";#else   const char *lib_path = "/system/lib/libc.so";#endif#define CMP_COUNT 8   const char *sym_name = "open";
struct local_dlfcn_handle *handle = static_cast<local_dlfcn_handle *>(local_dlopen(lib_path));
off_t offset = local_dlsym(handle,sym_name);
FILE *fp = fopen(lib_path,"rb"); char file_bytes[CMP_COUNT] = {0}; if(fp != NULL){ fseek(fp,offset,SEEK_SET); fread(file_bytes,1,CMP_COUNT,fp); fclose(fp); }
void *dl_handle = dlopen(lib_path,RTLD_NOW); void *sym = dlsym(dl_handle,sym_name);
int is_hook = memcmp(file_bytes,sym,CMP_COUNT) != 0;
local_dlclose(handle); dlclose(dl_handle);
char text[128] = {0}; snprintf(text,128,"Function "%s" is Hook: %s",sym_name,is_hook ? "true" : "false");

这里local_开头的函数是读取本地符号偏移库,库代码:https://github.com/luoyesiqiu/local_dlfcn

用frida hook测试demo:frida-trace -U -i "open" -f com.luoye.localdlfcn

一种inlineHook检测方案

原文始发于微信公众号(luoyesiqiu):一种inlineHook检测方案

版权声明:admin 发表于 2023年1月7日 下午2:42。
转载请注明:一种inlineHook检测方案 | CTF导航

相关文章

暂无评论

暂无评论...