-       0x333 OUTSIDERS SECURITY LABS       -
            -              www.0x333.org              -


~~~~~~~~~ contents ~~~~~~~~~

0x0 Info
0x1 Description
0x2 Stack Overflow in Switch (1)
0x3 Stack Overflow in Switch (2)
0x4 Stack Overflow in $LADSPA_PATH
0x5 Format String Bug in tx_note()
0x6 Solutions
0x7 Vendor Contact 



[0x0 Info]

  author   : c0wboy
  mail     : c0wboy@tiscali.it
  date     : 7 November 2003
  advisory : outsiders-terminatorX-001.txt
  vendor   : http://terminatorX.cx
  category : stack overflow, format bug
  platform : linux, unix


[0x1 Description]

>From terminatorX's offcial web page : "terminatorX is a realtime audio synthesizer that allows
you to "scratch" on digitally sampled audio data (*.wav, *.au, *.ogg, *.mp3, etc.)" . In Last
version (3.8.1) there are still lots of bugs, that could be used by user to execute arbitrary
codes with root privileges.


[0x2 Stack Overflow in Switch (1)]

It is possible to overflow a static buffer, by passing a long string after switch "-f"
(or "--file"). In function parse_args() (src/main.cc) we find the follow piece of code:

    if ((strcmp(argv[i], "-f") == 0) || (strcmp(argv[i], "--file") == 0)) {
      ++i;
      globals.startup_set = argv[i];

The variable "globals.startup_set" will contain our (long) string. After this the variable
will be passed to function load_tt_part() (src/tX_mastergui.cc) which is called by main(): 

int main(int argc, char **argv)
{
...
  if (globals.startup_set) {
    while (gtk_events_pending()) gtk_main_iteration(); gdk_flush();  
    tX_cursor::set_cursor(tX_cursor::WAIT_CURSOR);
    load_tt_part(globals.startup_set);
...

/* src/tX_mastergui.cc */
void load_tt_part(char * buffer)
{
  char idbuff[256];
  char wbuf[PATH_MAX];
...
  strcpy(globals.tables_filename, buffer);
...
      strcpy(idbuff, "Failed to access file: \"");
      strcat(idbuff, globals.tables_filename);
...

In load_tt_part() our string will first be copied in "globals.tables_filename", that will
overflow the static buffer idbuff[256]. User could overwrite eip and executes arbitrary code.


[0x3 Stack Overflow in Switch (2)]

This case is similar to the first one. Here we can overflow a static buffer by passing a
long string after option "-r" (or "--rc-file"). In function parse_args() (src/main.cc) we
find the vulnerable code:


    if ((strcmp(argv[i], "-r") == 0) || (strcmp(argv[i], "--rc-file") == 0)) {
      ...
      globals.alternate_rc = argv[i];

In function get_rc_name() (src/tX_global.c) there is an unchecked strcpy() that will overflow
a static buffer (passed to this function as argument) with the content of "globals.alternate_rc"
variable:

void get_rc_name(char *buffer)
{
  strcpy(buffer,"");
  if (globals.alternate_rc) {
    strcpy(buffer, globals.alternate_rc);
...

This bug can be used to overwrite the eip, and execute arbitrary code.


[0x4 Stack Overflow in $LADSPA_PATH]

In file tX_ladspa.cc, it's possible overflow a static buffer by setting a long "$LADSPA_PATH"
environment variable. As we had before, there is an unchecked strcpy(), in this case a long string
will overflow "ladspa_path[PATH_MAX]":

void LADSPA_Plugin :: init ()
{
  char *ladspa_path_ptr;
  char ladspa_path[PATH_MAX];
...

  /* Finding the LADSPA Path */
  ladspa_path_ptr=getenv("LADSPA_PATH");  
...
  else strcpy(ladspa_path, ladspa_path_ptr);
...

By overflowing "ladspa_path[PATH_MAX]", eip will be overwritten, allowing the execution of
arbitrary code.


[0x5 Format String Bug in tx_note()]

There is a format string bug in function tx_note(), that can be found in src/tX_mastergui.cc. The
problem exists in function "gtk_message_dialog_new()". User can control the contents of "message"
variable, and set it to special format string parameters (for example lots of '%x'). Here's the
vulnerable code :

void tx_note(const char *message, bool isError)
{
  char buffer[4096]="terminatorX ";
  if (isError) {
    strcat(buffer, "note:\n\n");
  } else {
    strcat(buffer, "error:\n\n");
  }
  
  strcat(buffer, message);
  GtkWidget *dialog=gtk_message_dialog_new(GTK_WINDOW(main_window),
    GTK_DIALOG_DESTROY_WITH_PARENT,
    isError ? GTK_MESSAGE_ERROR : GTK_MESSAGE_INFO, GTK_BUTTONS_CLOSE, message);
  gtk_dialog_run(GTK_DIALOG(dialog));                                      /*  |_____ fmt bug  */
  gtk_widget_destroy(dialog);  
}

It is possible to exploit this bug, by passing a crafted string after witch "-f" (or "--file"). TerminatorX
will be run, but it will display a warning-windows showing memory addresses. There will be a segfault.

[c0wboy@0x333 src]$ ./terminatorX -f %x%x%x%x%x%x%n
terminatorX Release 3.81 - Copyright (C) 1999-2003 by Alexander Knig
terminatorX comes with ABSOLUTELY NO WARRANTY - for details read the license.
* tX_error: set_capabilities(): failed to set caps: Operation not permitted.
+ tX_warning: engine_thread_entry(): can't set SCHED_FIFO -> lacking capabilities.
+ tX_warning: engine_thread_entry() - engine has no realtime priority scheduling.
+ tX_warning: LADSPA_PATH not set. Trying /usr/lib/ladspa:/usr/local/lib/ladspa
* tX_error: tX: Error: couldn't access directory "/usr/lib/ladspa".
+ tX_warning: Plugin "Stereo Amplifier" disabled. Not a 1-in/1-out plugin.
+ tX_warning: Plugin "White Noise Source" disabled. Not a 1-in/1-out plugin.
+ tX_warning: Plugin "Sine Oscillator (Freq:audio, Amp:audio)" disabled. Not a 1-in/1-out plugin.
+ tX_warning: Plugin "Sine Oscillator (Freq:control, Amp:control)" disabled. Not a 1-in/1-out plugin.
warning: failed to load external entity "%25x%25x%25x%25x%25x%25x%25n"
Segmentation fault
[c0wboy@0x333 src]$

**NOTE** : There are lots of syntax-wrong gtk_message_dialog_new(), in src/tX_mastergui.cc file.


[0x6 Solutions]

  0x1 (switch "-f"):

  /* src/tX_mastergui.cc */
  void load_tt_part(char * buffer)
  {
    char idbuff[256];
    char wbuf[PATH_MAX];
    xmlDocPtr doc;
  ...
  if (strlen(idbuff) + strlen(buffer) > 256-strlen("Failed to access file: \"")-strlen("\""))
    return;
  else
    strcpy(globals.tables_filename, buffer);
    ...

  This will correctly check the "idbuff" lenght.


  0x2 (switch "-r"):

  void get_rc_name(char *buffer)
  {
    strcpy(buffer,"");
    if (globals.alternate_rc && (strlen(globals.alternate_rc) < sizeof(buffer)-1) ) { /* bof fixed */
      strcpy(buffer, globals.alternate_rc);
  ...

  0x3 ($ env):

  The program already use a funtion to check the environment variables leghnt (checkenv()).
  Just us it in main() also with $LADSPA_PATH.


  0x4 (fmt bug):

  void tx_note(const char *message, bool isError)
  {
    char buffer[4096]="terminatorX ";
    if (isError) {
      strcat(buffer, "note:\n\n");
    } else {
      strcat(buffer, "error:\n\n");
    }

    /* - */ strcat(buffer, message);
    /* + */ strncat(buffer, sizeof(message), message); /* i don't like this strcat() ... */

    GtkWidget *dialog=gtk_message_dialog_new(GTK_WINDOW(main_window), GTK_DIALOG_DESTROY_WITH_PARENT,
    isError ? GTK_MESSAGE_ERROR : GTK_MESSAGE_INFO, GTK_BUTTONS_CLOSE, "%s", message); /* fmt bug fixed */
    ...


[0x7 Vendor Contact]

Vendor was informed about the bugs.