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Re: vixie cron...
From: Szilveszter Adam <sziszi () PETRA HOS U-SZEGED HU>
Date: Fri, 17 Nov 2000 11:14:38 +0100

On Fri, Nov 17, 2000 at 05:41:32AM +0100, Michal Zalewski wrote:

Attached shell-script exploits fopen() + preserved umask vulnerability in
Paul Vixie's cron code. It will work on systems where /var/spool/cron is
user-readable (eg. 0755) - AFAIR Debian does so. RedHat (at least 6.1 and
previous) have mode 0700 on /var/spool/cron, and thus it isn't exploitable
in its default configuration... (ahmm, but this does NOT mean it is a
problem of o+rx bits, but of insecure umask() and fopen() calls).

I have no information about other distributions or systems - this exploit
should automagically detect if you are vulnerable or not (checking
/var/spool/cron, looking for Paul Vixie's crontab, etc). Please report
your findings to me and/or to BUGTRAQ.

Hello everybody!

Upon testing and inspection of the CVS repository, I have found that FreeBSD
2.1.x, 2.2.x, 3.x, 4.x and -CURRENT are not vulnerable to this exploit if it
is launched by normal users, since the /var/cron directory is 0750 by
default. Members of the wheel group may still launch it successfully,
though. If this is a big risk in itself can be debated.

Note1: The script will not work by default on FreeBSD, because here /bin/sh
is *not* bash, bash is not even installed by default. Directory location is
also different. This in itself does not mean much though:-)

Note2: I do not speak for the FreeBSD Security Officer, but just wanted to
let you know fast.


Szilveszter ADAM
Szeged University
Szeged Hungary

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