hack.c

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <termios.h>
#include <fcntl.h>
#include "libcli.h"

#define DO 0xfd
#define WONT 0xfc
#define WILL 0xfb
#define DONT 0xfe
#define CMD 0xff
#define CMD_ECHO 1
#define CMD_WINDOW_SIZE 31

#define CLITEST_PORT 8000
#define BUFLEN 20

extern struct cli_def *cli;

static struct termios tin;

void sleep_us(int microseconds);

void negotiate(int sock, unsigned char *buf, int len) 
{
    int i;
     
    if (buf[1] == DO && buf[2] == CMD_WINDOW_SIZE) 
    {
        unsigned char tmp1[10] = {255, 251, 31};
        if (send(sock, tmp1, 3 , 0) < 0)
            exit(1);
         
        unsigned char tmp2[10] = {255, 250, 31, 0, 80, 0, 24, 255, 240};
        if (send(sock, tmp2, 9, 0) < 0)
            exit(1);
        return;
    }
     
    for (i = 0; i < len; i++) 
    {
        if (buf[i] == DO)
            buf[i] = WONT;
        else if (buf[i] == WILL)
            buf[i] = DO;
    }
 
    if (send(sock, buf, len , 0) < 0)
        exit(1);
}

static void terminal_set(void) 
{
    // save terminal configuration
    tcgetattr(STDIN_FILENO, &tin);
     
    static struct termios tlocal;
    memcpy(&tlocal, &tin, sizeof(tin));
    cfmakeraw(&tlocal);
    tcsetattr(STDIN_FILENO,TCSANOW,&tlocal);
}
 
static void terminal_reset(void) 
{
    // restore terminal upon exit
    tcsetattr(STDIN_FILENO,TCSANOW,&tin);
}

void *start_server(void *arg)
{
    int s, x;
    int on = 1;
    struct sockaddr_in addr;
    
    if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) 
    {
        perror("socket");
        exit(1);
    }

    if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) 
    {
        perror("setsockopt");
    }

    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port = htons(CLITEST_PORT);
    if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) 
    {
        perror("bind");
        exit(1);
    }

    if (listen(s, 50) < 0) 
    {
        perror("listen");
        exit(1);
    }
    
    //printf("Listening on port %d\n", CLITEST_PORT);
    
    while ((x = accept(s, NULL, 0))) 
    {
        cli_loop(cli, x); 
        cli_done(cli);
        exit(0);
    }
}

void cli_start()
{
    pthread_t server_thread;
    pthread_create(&server_thread, NULL, start_server, NULL);
    
	//sleep for a bit
	sleep_us(100000);
	
    //Little TELNET code to connect to itself
    int sock;
    struct sockaddr_in server;
    unsigned char buf[BUFLEN + 1];
    int len;
    int i;
 
    //Create socket
    sock = socket(AF_INET , SOCK_STREAM , 0);
    if (sock == -1) 
    {
        perror("Could not create socket. Error");
        exit(1);
    }
 
    server.sin_addr.s_addr = inet_addr("127.0.0.1");
    server.sin_family = AF_INET;
    server.sin_port = htons(CLITEST_PORT);
 
    //Connect to remote server
    if (connect(sock , (struct sockaddr *)&server , sizeof(server)) < 0) 
    {
        perror("connect failed. Error");
        exit(1);
    }
    //puts("Connected...\n");
 
    // set terminal
    terminal_set();
    atexit(terminal_reset);
     
    struct timeval ts;
    ts.tv_sec = 1; // 1 second
    ts.tv_usec = 0;
 
    while (1) 
    {
        // select setup
        fd_set fds;
        FD_ZERO(&fds);
        if (sock != 0)
            FD_SET(sock, &fds);
        FD_SET(0, &fds);
 
        // wait for data
        int nready = select(sock + 1, &fds, (fd_set *) 0, (fd_set *) 0, &ts);
        if (nready < 0) 
        {
            perror("select. Error");
            exit(1);
        }
        else if (nready == 0) 
        {
            ts.tv_sec = 1; // 1 second
            ts.tv_usec = 0;
        }
        else if (sock != 0 && FD_ISSET(sock, &fds)) 
        {
            // start by reading a single byte
            int rv;
            if ((rv = recv(sock , buf , 1 , 0)) < 0)
                exit(1);
            else if (rv == 0) 
            {
                printf("Connection closed by the remote end\n\r");
                exit(0);
            }
 
            if (buf[0] == CMD) 
            {
                // read 2 more bytes
                len = recv(sock , buf + 1 , 2 , 0);
                if (len  < 0)
                    exit(1);
                else if (len == 0) 
                {
                    printf("Connection closed by the remote end\n\r");
                    exit(0);
                }
                negotiate(sock, buf, 3);
            }
            else 
            {
                len = 1;
                buf[len] = '\0';
                printf("%s", buf);
                fflush(0);
            }
        }
         
        else if (FD_ISSET(0, &fds)) 
        {
            buf[0] = getc(stdin); //fgets(buf, 1, stdin);
            if (send(sock, buf, 1, 0) < 0)
                exit(1);
            if (buf[0] == '\n') // with the terminal in raw mode we need to force a LF
                putchar('\r');
        }
    }
    close(sock);
    exit(0);
}