Bug in luatex handling of hidden dirs in TEXMFVAR

[Max Chernoff]

Hi Volker,

On Tue, 2025-11-18 at 09:38 +1300, Volker Kuhlmann wrote:
> On Fri 07 Nov 2025 01:26:07 NZDT +1300, Max Chernoff via tex-live wrote:
> >     - When is set to ‘r’ (for “restricted”), filenames beginning with
> >       ‘.’ are disallowed.
>
> File or directory names starting with "." are not special and don't have
> a higher security risk (I'd like an example of this if I'm wrong).

If writing to dot files were allowed and you were to compile a document
from the root of your home directory, an attacker could overwrite your
".bashrc" file, which would trivially allow arbitrary code execution.
The only alternative solutions would be to disallow compiling documents
from the root of your home directory (not possible due to backwards
compatibility concerns, plus this is genuinely useful in some
circumstances) or hardcoding a list of specific dot file (also not
possible since there are dozens of possible "dangerous" files).

Thanks,
-- Max