BBCTF 2018 ROP crazy

gg.c

/*
 * gg.c
 *
 * Copyright 2018 Sudhakar Verma <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 *
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <assert.h>

int main(int argc, char **argv){
    int fd, i;
    char *psc;
    void (*f)();
    psc = mmap(NULL, 0x1000, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    assert(psc != NULL);
    printf("%p\n", psc);
    fflush(stdout);
    while(1){
    fd = open("/dev/urandom", O_RDONLY);
    read(fd, psc, 0x1000);
    write(1, psc, 0x1000);
    for(i=0; i< 0x1000 ;i+= sizeof(int)){
        psc[i] = '\xc3';
        }
    read(0, &f, 8);
    read(0, psc,8);
    f();
    }
    return 0;
}