Re: Logfile symlink vulnerability

[Harold L Hunt II <huntharo at msu dot edu>]

Eran Tromer wrote:

> Hi,
>
> If /tmp/XWin.log is a symlink, XWin will merrily follow it and write to
> whatever it's pointing to (see LogInit() in os/log.c). This allows
> standard symlink-following attacks.
>
> Example: Alice runs "ln -s /home/Bob/phd-thesis.tex /tmp/XWin.log" under
> her account. Later Bob runs XWin under his account; XWin fails for some
> reasons and writes to /tmp/XWin.log; Bob life's work gets overwritten.

In theory, but have you actually tried it and confirmed that it works 
with two different users that did not already both have permissions to 
overwrite the file in question?

Harold