Re: [RHSA-1999:028-01] Buffer overflow in libtermcap tgetent()

[carenas () CHASQUI LARED NET PE (Carlo M. Arenas Belon)]

<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