zen-parseat_private wrote: > If the user has local access to the system, it is possible to get the > program to set arbitrary environment variables in the environment of > /bin/login. e.g. LD_PRELOAD=/tmp/make-rootshell.so To protect against this (and possible bad environment processing within telnetd itself), create some otherwise unused group and make /bin/login setgid to that: # chown root._login_ /bin/login # chmod 6711 /bin/login # ls -l /bin/login -rws--s--x 1 root _login_ 24752 Aug 25 2000 /bin/login (Since telnetd runs as root, login has getuid==geteuid so the OS may follow LD_PRELOAD and similar variables. Using this login has getgid!=getegid and the OS should disallow such trickery.) Paul Szabo - pszat_private http://www.maths.usyd.edu.au:8000/u/psz/ School of Mathematics and Statistics University of Sydney 2006 Australia
This archive was generated by hypermail 2b30 : Thu Aug 09 2001 - 15:51:43 PDT