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#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
const char* TARGET_PKG_JSON = "resources/app/package.json";
const char* ORIGINAL_MAIN = "\"main\": \"./application.asar/app_launcher/index.js\"";
const char* NEW_MAIN = "\"main\": \"./loadNapCat.js\"";
static char* g_modified_package_json = nullptr;
static size_t g_modified_len = 0;
#define EXPORT_HOOK __attribute__((visibility("default")))
static bool ends_with(const char* path, const char* suffix)
{
if (!path || !suffix)
return false;
size_t path_len = strlen(path);
size_t suffix_len = strlen(suffix);
if (path_len < suffix_len)
return false;
return strcmp(path + path_len - suffix_len, suffix) == 0;
}
static void init_modified_packagejson(const char* real_path)
{
if (g_modified_package_json)
return;
static FILE* (*real_fopen)(const char*, const char*) = nullptr;
if (!real_fopen)
real_fopen = (FILE * (*)(const char*, const char*)) dlsym(RTLD_NEXT, "fopen");
FILE* fp = real_fopen(real_path, "r");
if (!fp)
return;
fseek(fp, 0, SEEK_END);
long file_size = ftell(fp);
fseek(fp, 0, SEEK_SET);
char* buffer = (char*)malloc(file_size + 1);
if (!buffer) {
fclose(fp);
return;
}
size_t bytes_read = fread(buffer, 1, file_size, fp);
buffer[bytes_read] = 0;
fclose(fp);
char* main_pos = strstr(buffer, ORIGINAL_MAIN);
if (!main_pos) {
g_modified_package_json = buffer;
g_modified_len = bytes_read;
return;
}
size_t prefix_size = main_pos - buffer;
size_t new_main_len = strlen(NEW_MAIN);
size_t suffix_size = strlen(main_pos + strlen(ORIGINAL_MAIN));
size_t new_size = prefix_size + new_main_len + suffix_size;
g_modified_package_json = (char*)malloc(new_size + 1);
if (g_modified_package_json) {
memcpy(g_modified_package_json, buffer, prefix_size);
memcpy(g_modified_package_json + prefix_size, NEW_MAIN, new_main_len);
memcpy(g_modified_package_json + prefix_size + new_main_len, main_pos + strlen(ORIGINAL_MAIN), suffix_size);
g_modified_package_json[new_size] = '\0';
g_modified_len = new_size;
}
free(buffer);
}
static int create_memfd(const char* name, const char* content, size_t length)
{
if (!content)
return -1;
int fd = syscall(SYS_memfd_create, name, 0);
if (fd < 0)
return -1;
if (write(fd, content, length) != (ssize_t)length) {
close(fd);
return -1;
}
lseek(fd, 0, SEEK_SET);
return fd;
}
static int handle_target_file(const char* pathname)
{
if (pathname && ends_with(pathname, TARGET_PKG_JSON)) {
init_modified_packagejson(pathname);
if (g_modified_package_json) {
return create_memfd("mem_package_json", g_modified_package_json, g_modified_len);
}
}
return -1;
}
extern "C" {
EXPORT_HOOK int open(const char* pathname, int flags, ...)
{
static int (*real_open)(const char*, int, ...) = nullptr;
if (!real_open)
real_open = (int (*)(const char*, int, ...))dlsym(RTLD_NEXT, "open");
int target_fd = handle_target_file(pathname);
if (target_fd >= 0)
return target_fd;
int mode = 0;
if (flags & (O_CREAT | O_TMPFILE)) {
va_list args;
va_start(args, flags);
mode = va_arg(args, int);
va_end(args);
return real_open(pathname, flags, mode);
}
return real_open(pathname, flags);
}
EXPORT_HOOK int open64(const char* pathname, int flags, ...)
{
static int (*real_open64)(const char*, int, ...) = nullptr;
if (!real_open64)
real_open64 = (int (*)(const char*, int, ...))dlsym(RTLD_NEXT, "open64");
int target_fd = handle_target_file(pathname);
if (target_fd >= 0)
return target_fd;
int mode = 0;
if (flags & (O_CREAT | O_TMPFILE)) {
va_list args;
va_start(args, flags);
mode = va_arg(args, int);
va_end(args);
return real_open64(pathname, flags, mode);
}
return real_open64(pathname, flags);
}
EXPORT_HOOK int openat(int dirfd, const char* pathname, int flags, ...)
{
static int (*real_openat)(int, const char*, int, ...) = nullptr;
if (!real_openat)
real_openat = (int (*)(int, const char*, int, ...))dlsym(RTLD_NEXT, "openat");
int target_fd = handle_target_file(pathname);
if (target_fd >= 0)
return target_fd;
int mode = 0;
if (flags & (O_CREAT | O_TMPFILE)) {
va_list args;
va_start(args, flags);
mode = va_arg(args, int);
va_end(args);
return real_openat(dirfd, pathname, flags, mode);
}
return real_openat(dirfd, pathname, flags);
}
EXPORT_HOOK int openat64(int dirfd, const char* pathname, int flags, ...)
{
static int (*real_openat64)(int, const char*, int, ...) = nullptr;
if (!real_openat64)
real_openat64 = (int (*)(int, const char*, int, ...))dlsym(RTLD_NEXT, "openat64");
int target_fd = handle_target_file(pathname);
if (target_fd >= 0)
return target_fd;
int mode = 0;
if (flags & (O_CREAT | O_TMPFILE)) {
va_list args;
va_start(args, flags);
mode = va_arg(args, int);
va_end(args);
return real_openat64(dirfd, pathname, flags, mode);
}
return real_openat64(dirfd, pathname, flags);
}
EXPORT_HOOK FILE* fopen(const char* pathname, const char* mode)
{
static FILE* (*real_fopen)(const char*, const char*) = nullptr;
if (!real_fopen)
real_fopen = (FILE * (*)(const char*, const char*)) dlsym(RTLD_NEXT, "fopen");
int target_fd = handle_target_file(pathname);
if (target_fd >= 0) {
FILE* fp = fdopen(target_fd, mode);
if (!fp)
close(target_fd);
return fp;
}
return real_fopen(pathname, mode);
}
EXPORT_HOOK FILE* fopen64(const char* pathname, const char* mode)
{
static FILE* (*real_fopen64)(const char*, const char*) = nullptr;
if (!real_fopen64)
real_fopen64 = (FILE * (*)(const char*, const char*)) dlsym(RTLD_NEXT, "fopen64");
int target_fd = handle_target_file(pathname);
if (target_fd >= 0) {
FILE* fp = fdopen(target_fd, mode);
if (!fp)
close(target_fd);
return fp;
}
return real_fopen64(pathname, mode);
}
} // extern "C"
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