NeXT rexd, /private/etc, Username me Vulnerabilities
Original issue date: May 14, 1991
Last revised: September 18, 1997
Attached copyright statement
A complete revision history is at the end of this file.
The Computer Emergency Response Team/Coordination Center (CERT/CC) and
NeXT Computer, Inc. have received information concerning three
vulnerabilities in NeXT computers running various releases (see below)
of NeXTstep software. For more information, please contact your
authorized support center. If you are an authorized support provider,
please contact NeXT through your normal channels.
PROBLEM 1 Description
By default, rexd(8C) is enabled in NeXTstep
versions 2.0 and 2.1.
(Note that no NeXT software uses rexd.)
PROBLEM 1 Impact Leaving rexd enabled allows remote users to execute
processes on a NeXT computer.
PROBLEM 1 Solution Comment out or remove the rexd line in
/etc/inetd.conf (unless you're using the remote execution facility),
and either restart the computer or cause inetd to re-read it's
configuration file, using:
kill -HUP <inetd pid>
PROBLEM 2 Description The /private/etc directory is shipped with
group write permission enabled in all NeXTstep versions through and
PROBLEM 2 Impact
Group write permission in /private/etc enables any
user in the "wheel" group to modify files in the /private/etc
PROBLEM 2 Solution Turn off group write permission for the
/private/etc directory, using the command:
chmod g-w /private/etc
or the equivalent operations from the Workspace Manager's Inspector
PROBLEM 3 Description Username "me" is a member of the "wheel" group
in all NeXTstep versions through and including 2.1.
PROBLEM 3 Impact Having username "me" in the "wheel" group enables
"me" to use the su(8) command to become root (the user must still know
the root password, however).
PROBLEM 3 Solution Unless you have specific reason(s) not to, remove
the user "me" from the wheel group.
The CERT/CC would like to thank NeXT Computer, Inc. for their response
to this vulnerability. CERT/CC would also like to thank Fuat Baran
for his technical assistance.
This document is available from:
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September 18,1997 Attached Copyright Statement