Bugtraq mailing list archives
Re: [RHSA-1999:028-01] Buffer overflow in libtermcap tgetent()
From: carenas () CHASQUI LARED NET PE (Carlo M. Arenas Belon)
Date: Tue, 24 Aug 1999 18:45:21 -0400
<SNIP>
The problem with telnetd is that you can pass a terminal name that indicates 'use a local file'. Now the ncurses library then goes 'ok leading slash all well and good', Im not suid uid==euid, lets open it as root and read a few bytes. You can't do much with it - you can rewind the machines tape drive for example however. Also if your termcap parser has bugs you can hit those.This is fixed in the latest (pre-)release of ncurses-5.0. From the release notes posted to bug-ncurses mailing list (as of last night) from da man hissef: 990821 pre-release + updated configure macros CF_MAKEFLAGS, CF_CHECK_ERRNO + minor corrections to beterm terminfo entry. + modify lib_setup.c to reject values of $TERM which have a '/' in them. So, version 5.0 will no longer accept $TERM that has a slash in it at all, much less a leading one. I haven't looked closely at the source code, but a similar change to the 4.2 sources, the version most distributions are using now, should address this at least where tgetent() is concerned.
from a COL2.2 system ldd /usr/sbin/in.telnetd libncurses.so.4 => /lib/libncurses.so.4 (0x40018000) libc.so.6 => /lib/libc.so.6 (0x4005a000) /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000) i think someone should fix the last post on Caldera's homepage regarding this vulnerability http://www.calderasystems.com/news/security/CSSA-1999:020.0.txt .... Olaf? ;)
It is a very nice example of why saying "lets ignore XYZ variable" is not security but a quick fix for emergencies. If you don't fix the code it will get you..Yep...
wise words Carlo
Current thread:
- Re: [RHSA-1999:028-01] Buffer overflow in libtermcap tgetent() Carlo M. Arenas Belon (Aug 24)