[bug#47155] [PATCH] gnu: Respect DataDirectoryGroupReadable option of tor.

[Maxime Devos]

On Sat, 2021-03-27 at 06:37 +0000, raid5atemyhomework wrote:
> > > If you reconfigure your OS without restarting the tor service,
> > > the directory permissions are reset due to the activation code being
> > > re-run and resetting the directory permissions.
> > > This change simply does not chmod if the directory already exists.
> > 
> > I believe it would be more transparent to introduce a
> > (data-directory-group-readable? #t/#f), with #f as default,
> > to tor-configuration (adjusting tor-configuration->torrc)
> > and change the permission bits passed to chmod appropriately.
> > 
> > (Documentation & reproducible system configuration & one integrated
> > system (in the software sense) and all that)
> 
> But really though, the primary reason for this is to use the "cookie"
> authentication scheme with a control port on 9051.  This is supported
> by most daemons, as the "control unix socket" (that is currently supported
> by `control-socket?` option) seems to be relatively new (Tor 0.2.7.1).
> 
> This requires adding:
> 
>     ControlPort 9051
>     CookieAuthentication 1
>     CookieAuthFileGroupReadable 1
>     DataDirectoryGroupReadable 1
> 
> In https://issues.guix.gnu.org/46549 which implements `control-socket?` the
> author expressed doubt as to the safety of this mechanism.  Looking at the Tor
>  manpage regarding `ControlPort`:
> 
> ```
> Note: unless you also specify one or more of HashedControlPassword or 
> CookieAuthentication,
> setting this option will cause Tor to allow any process on the local
> host to control it. (Setting both authentication methods means either method 
> is sufficient
> to authenticate to Tor.) This option is required for many Tor controllers; 
> most use
> the value of 9051.
> ```
> 
> Basically, this is safe as long as you use *either* `HashedControlPassword` 
> *or*
> `CookieAuthentication` *or* both; in the case of `CookieAuthentication` only 
> users
> with read access to the cookie file can access it.  Nearly every daemon that 
> needs
> control access over Tor (usually to set up their own hidden service using 
> their own
> privkey) expects `CookieAuthentication` and reads from 
> `/var/lib/tor/control_auth-_cookie`,
> which requires that `/var/lib/tor` be readable (else it can't look up the 
> filename).  It
> becomes just as safe as the control-unix-socket option, as that is similarly 
> gated by
> file permissions.

I believe this addresses the security concerns Christopher Lemmer Webber had.

> Note in particular that Bitcoin Core supports `ControlPort` and not 
> `ControlSocket`, so
> this is needed for Bitcoin Core support.  From what I can see more daemons 
> support
> `ControlPort` than `ControlSocket`.

Ok, but take a look at
<https://gitlab.torproject.org/legacy/trac/-/wikis/doc/bitcoin>.
Maybe its out of date though: 
<https://blog.torproject.org/tor-heart-cryptocurrencies>

This patch looks good to me, except for some minor aesthetic issues in the 
commit message.
I ran "make system-check TESTS=tor" with this patch, which succeeded.

> Thanks
> raid5atemyhomework
> 
> 
> From d9bea7635594654e1e631e4db55422c511f0220a Mon Sep 17 00:00:00 2001
> From: raid5atemyhomework <raid5atemyhomework@protonmail.com>
> Date: Sat, 27 Mar 2021 14:29:31 +0800
> Subject: [PATCH] gnu: Add 'control-port?' setting to Tor.
> 
> * gnu/services/networking.scm (tor-configuration): Add `control-port?` field.
> (tor-configuration->torrc): Support `control-port?` field.
> (tor-activation): Allow group access to data directory if `control-port?`.
> * doc/guix.texi (Networking Services)[Tor]: Describe new `control-port?` 
> field.

Usually we `quote', 'quote', "quote" or ‘quote’, but never `quote`.
I recommend 'quote', as in

commit 43937666ba6975b6c847be8e67cecd781ce27049
Author: Ludovic Courtès <ludo@gnu.org>
Date:   Fri Mar 19 14:23:57 2021 +0100

    download: 'tls-wrap' treats premature TLS termination as EOF.
    
    This is a backport of Guile commit
    076276c4f580368b4106316a77752d69c8f1494a.
    
    * guix/build/download.scm (tls-wrap)[read!]: Wrap 'get-bytevector-n!'
    call in 'catch' and handle 'error/premature-termination' GnuTLS errors.

Greetings, Maxime.

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