Hooking into libc functions from C #73
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nitanmarcel
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Came to this code after a while, but the init status gets set to 9: Maybe I'm missing something important in my mk file. as mentioned I'm using the sources in my code from the added submodule: |
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The following code seems to work. With the exception on apps refusing to fully start after an while #include "bytehook.h"
#include "jni.h"
#include "Logger.h"
#define BYTEHOOK_MODE_AUTOMATIC 0
#define BYTEHOOK_MODE_MANUAL 1
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <stdbool.h>
bytehook_stub_t stub = NULL;
typedef int (*faccessat_t)(int fd, const char *path, int amode, int flag);
int hook_faccessat(int fd, const char *path, int amode, int flag)
{
LOGD("faccessat: %s", path);
int result = BYTEHOOK_CALL_PREV(hook_faccessat, faccessat_t, fd, path, amode, flag);
BYTEHOOK_POP_STACK();
return result;
}
void do_hook()
{
LOGD("do_hook");
int status;
status = bytehook_init(BYTEHOOK_MODE_AUTOMATIC, true);
LOGD("bytehook_init: %d", status);
stub = bytehook_hook_single(
"libc.so",
NULL,
"faccessat",
(void *)(hook_faccessat),
NULL,
NULL
);
if (stub == NULL)
{
LOGD("bytehook_hook_all failed");
return;
}
LOGD("bytehook_hook_all finished %p", stub);
}
void* hook_thread(void* arg) {
do_hook();
return NULL;
}
__attribute__((constructor))
void library_constructor() {
pthread_t detach_thread;
pthread_create(&detach_thread, NULL, hook_thread, NULL);
// pthread_join(detach_thread, NULL); // will fail again.
}Logs |
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Hello. I'm coming here from funchook since this library is more axed on android and I can simply include it's source directly into my shared lib, which saves me a lot of time.
One issue I have is that I don't understand how to really use it, and the documentation is mostly in Chinese. What I need, is to intercept different calls from libc calls and modify their return. The following code is ported from the library I used but I guess I'm not that lucky for it to work.
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