shellz.c

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

#define AMOUNT_OF_STUFF 40

//Learned my lesson! No more easy flags
/*void win(){
    system("/bin/cat ./flag.txt");    
}*/


void vuln(){
    char * stuff = (char *)mmap(NULL, AMOUNT_OF_STUFF, PROT_EXEC|PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
    if(stuff == MAP_FAILED){
        printf("Failed to get space. Please talk to admin\n");
        exit(0);
    }
    printf("Give me %d bytes:\n", AMOUNT_OF_STUFF);
    fflush(stdout);
    int len = read(STDIN_FILENO, stuff, AMOUNT_OF_STUFF);
    if(len == 0){
        printf("You didn't give me anything :(");
        exit(0);
    }
    void (*func)() = (void (*)())stuff;
    func();      
}

int main(int argc, char*argv[]){
    printf("My mother told me to never accept things from strangers\n");
    printf("How bad could running a couple bytes be though?\n");
    fflush(stdout);
    vuln();
    return 0;
}