Re: overwrite any file with updatedb

[jcmurphy () SMURFLAND CIT BUFFALO EDU (Jeff Murphy)]

this is actually the sort command (which uses the qsort()) call that is
making this files. one work around is to set the TMPDIR environment
variable to a directory that only root can access. sort will then write
its temporary files to that directory instead of /tmp

jeff


Cain <cain () TASAM COM> writes:

> If this is already known, my apologies. It seemed very strange that this
> worked, so I thought it would be mentionable.
>
> On many linux systems(Redhat imparticularly) updatedb is run nightly
> around 1:00. When it sorts the files that find gets, it creats a few files
> in /tmp called sort0<pid>000{1,2,etc}. Each is around 512k. The
> first file is created and filled, then if necassary, another is created
> and so on until it has your whole filesystem into a nice database. Well,
> once the first file is created you can easily guess what the next filename
> will be called as only the last character will change. If you create a
> link to say, the shadow password file, updatedb will kindly overwrite it
> for you. Ex:
>
> <assuming updatedb is running in the background>
> $ ls /tmp
> sort012340000 sort012340001
>
> $ ln -s /etc/shadow /tmp/sort012340002
> <wait for awhile to give updatedb time to write to our link>
>
> $ ls /tmp
> sort012340000 sort012340001 sort012340002 sort012340003
>
> It's done, it will now clear out it's files from /tmp. Now go look at the
> shadow password file. It will be quite larger then it was before. About
> 512k is it's new size. I played with this for awhile but couldn't find
> anyway to write anything useful to any file except /etc/shells so you can
> ftp into the system no matter what your specified shell is.