Re: Bug#23576: tetex-base: no write-permissions on public font directories
Olaf Weber writes:
> christoph martin writes:
> > krisrose@sauternes.ens-lyon.fr writes:
>
> >> Package: tetex-base
> >> Version: 0.9-7
> >>
> >> When the user first hits an ungenerated font then "permission denied"
> >> messages are plentiful... :)
>
> > The fonts get generated correctly, but it is a security problem to let
> > everybody write the ls-R file.
>
> But how much of a security risk is it? It would mean a normal user
> could clobber the file if he wanted to, which is a kind of denial of
> service attack. But are there any other risks?
A normal user could replace the file with a link to some other file
say /vmlinuz or a file in another user homedir. Then if root or this
other user tries to write ls-R he/she would write to /vmlinuz or
other files.
BTW it is Debian policy to not have word-writable files.
>
> And how do those risks compare with the ability to base a denial of
> service attack on /var/cache/fonts (or whatever you call it) being
> world-writable? (mode 1777)
Here you can only write to files which you yourself have created.
>
> > TeX can find the generated fonts even without them noted in the ls-R
> > file. But to speed it up they can be in the ls-R file. For this reason
> > there is a cronjob every day which updates the ls-R files.
>
> Note that it is possible to create a texmf.cnf which ensures that
> generated fonts not mentioned in the ls-R file _won't_ be found. Just
> use !! in the definition of VARTEXFONTS.
If you want this you can do it, but it is not standard.
Christoph
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