[tor-dev] Re: can tor use secondary groups to read FamilyKeyDirectory?

[Nick Mathewson via tor-dev <tor-dev@xxxxxxxxxxxxxxxxxxxx>]

On Thu, Apr 3, 2025 at 6:29 PM nusenu via tor-dev
<tor-dev@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> given the following example, tor fails to access the familykeydir folder.
>
> familykeydir has the following permissions:
>
> drwxr-x--- 2 root tor_reader
>
> id _tor
> uid=996(_tor) gid=993(_tor) groups=993(_tor),994(tor_reader)
>
> Is tor able to use secondary groups?
>
> When using sudo to switch to user _tor manually, it is possible to read files in that folder without problems.
>
> The problem does not happen when _tor's primary group is set to 'tor_reader'.
> Tested on debian.

Hm.  In src/lib/process.setuid.c, it looks like we're only calling
setgroups() with a single gid from the password database, not with any
additional groups.  So I don't think the C tor implementation is set
up to handle _switching_ to secondary groups when you're telling it to
setuid.


-- 
Nick
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