Passing input with netcat to a simple server - ruby

Question

I am trying to write an Ruby script to pass strings to a simple server running in a VM and I am stuck at passing the strings without creating inifinite loops in my server program.
The Content of the Server(written in C):
#include <stdio.h>
#include <strings.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#define PORTNO 12346
int h=0,b=0,p=0;
#define BUFFER_SIZE 512
int checksec(FILE* f){
FILE* key;
char buf[1024];
if(h&b&p){
key=fopen("easy_key","r");
fread(buf,1024,1,key);
fprintf(f,"%s",buf);
fclose(key);
return 0;
}
return 1;
}
void hekers(FILE* f){
volatile int zeroWeekend;
char buf[32];
fprintf(f,"So you want to be an 31337 Hax0r?\n");
fgets(buf,40,f);
switch(strcmp("y3$\n",buf)){
case 0:
fprintf(f,"First you must get power\n");
break;
default:
fprintf(f,"Well then go away\n");
break;
}
if(zeroWeekend==0xcafebabe){
h=1;
}
return;
}
void batmenss(FILE* f){
volatile int batsignet;
char buf[32];
fprintf(f,"So you want to be the batman?\n");
fgets(buf,40,f);
switch(strcmp("YESSSSSSS\n",buf)){
case 0:
fprintf(f,"First you must get rich\n");
break;
default:
fprintf(f,"Well then go away\n");
break;
}
if(batsignet==0x12345678){
b=1;
}
return;
}
void pokemans(FILE* f){
volatile int pikachy;
char buf[32];
fprintf(f,"So you want to be the best there ever was?\n");
fgets(buf,40,f);
switch(strcmp("catchemall\n",buf)){
case 0:
fprintf(f,"First you must get respect\n\n");
break;
default:
fprintf(f,"Well then go away\n");
break;
}
if(pikachy==0xfa75beef){
p=1;
}
return;
}
void readInput(int sock){
int msg;
char choice[4];
char buffer[BUFFER_SIZE];
FILE* fptr = fdopen(sock, "r+");
char* prompt="Do you want to be a?\n"
"1.) Pokemon Master\n"
"2.) Elite Hacker\n"
"3.) The Batman\n";
while(checksec(fptr)){
fprintf(fptr,"%s",prompt);
fgets(choice,4,fptr);
switch(choice[0]){
case '1':
pokemans(fptr);
break;
case '2':
hekers(fptr);
break;
case '3':
batmenss(fptr);
break;
default:
fprintf(fptr,"\nThat is not one of the choices\n");
fflush(fptr);
}
}
fprintf(fptr, "%s", buffer);
fflush(fptr);
fclose(fptr);
return;
}
int main(int argc, char *argv[])
{
char buffer[BUFFER_SIZE];
int sockfd, newsockfd, portno, pid;
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
/*
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
*/
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0){
perror("ERROR opening socket");
exit(1);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
//portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = inet_addr("0.0.0.0");
serv_addr.sin_port = htons(PORTNO);
if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0){
perror("ERROR on binding");
exit(1);
}
listen(sockfd,5);
clilen = sizeof(cli_addr);
while (1) {
newsockfd = accept(sockfd,
(struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
perror("ERROR on accept");
pid = fork();
if (pid < 0)
perror("ERROR on fork");
if (pid == 0) {
close(sockfd);
readInput(newsockfd);
return;
}
else close(newsockfd);
waitpid(-1,NULL,WNOHANG);
} /* end of while */
close(sockfd);
return 0; /* we never get here */
}
When I connect to the server, it looks like this:
user#DESKTOP-LINUX:~/Documents/tob/ctf/exploits/binary1_workshop/easy$ nc 192.168.178.40 12346
Do you want to be a?
1.) Pokemon Master
2.) Elite Hacker
3.) The Batman
Now the Program waits for an input and another string will be printed and then the Program waits for another input and so on...
Now the real problem comes when I try to use a Ruby Script that should dictate the input that the Program should get.
I tried it with this Ruby Script (Filename: script.rb):
#!/usr/bin/env ruby
firstinput = "1"
puts select + "\r\n"
secondinput = "2"
puts secondinput + "\r\n"
And executed it with this command:
user#DESKTOP-LINUX:~/Documents/Code/binary1_workshop_exploits$ ./script.rb | nc 192.168.178.40 12346
But the output is just an infinite loop of the "main menu"...
How do I fix this problem?
P.S. I am running Ubuntu 14.04 64-Bit and the VM with the Server is running Ubuntu 14.04 32-Bit