Vortex Level 1

#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

#define e(); if(((unsigned int)ptr & 0xff000000)==0xca000000) { \
        setresuid(geteuid(), geteuid(), geteuid()); \
        execlp("/bin/sh", "sh", NULL); \
        printf("%p %p\n", &ptr,ptr); \
}

void print(unsigned char *buf, int len) {
        int i;
        printf("[ ");
        for(i=0; i < len; i++) printf("%x ", buf[i]);
        printf(" ]\n");
}

int main() {
        unsigned char buf[512];
        unsigned char *ptr = buf + (sizeof(buf)/2);
        unsigned int x;

        while((x = getchar()) != EOF) {
                switch(x) {
                        case '\n':
                                print(buf, sizeof(buf));
                                continue;
                                break;
                        case '\\':
                                ptr--;
                                break;
                        default:
                                e();
                                if(ptr > buf + sizeof(buf)) continue;
                                ptr++[0] = x;
                                break;
                }
        }
        printf("All done\n");
        return 0;
}