full-disclosure - Symlink attack techniques

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Date: Thu Dec 15 17:28:05 2005
From: j.schipper at math.uu.nl (Joachim Schipper)
Subject: Symlink attack techniques

On Thu, Dec 15, 2005 at 01:09:49PM +0000, Werner Schalk wrote:
> Hi,
> 
> thanks for all the replies, I really appreciate this.

> basically the cronjob is something like:
> 
> 15 4 ?* * 6 ?root ?/usr/bin/find /home/userA -type f -print > /tmp/report.txt
> 
> Consequently as userB I have no way of influencing what information is printed 
> by the find command to /tmp/report.txt but I can surely 
> control /tmp/report.txt. Any other ideas of how to exploit this to gain root 
> access?

This is not generally possible. It's likely to viewed, though, and you
can attack the viewing application (bad email clients, old vim versions,
and most browsers apply).

Of course, symlinking it to /etc/passwd is fun but ultimately pretty
useless.

		Joachim