[bug#56690] [PATCH] gnu: seatd-service-type: Should use seat group.

[muradm <mail@muradm.net>]

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From e733977a5cbd2bb34cf129908b16a4a0af830f02 Mon Sep 17 00:00:00 2001
From: muradm <mail@muradm.net>
Date: Fri, 22 Jul 2022 07:09:54 +0300
Subject: [PATCH v3] gnu: seatd-service-type: Should use seat group.
To: 56690@debbugs.gnu.org

* gnu/services/desktop.scm (seatd-service-type): Uses "seat" group.
[extensions]: Added account-service-type with seatd-accounts.
(seatd-accounts): Conditionally produces list with "seat" group.
(<seatd-configuration>):
[user] Removed user field, since it is not going to be used.
[group] Change default value to "seat".
* doc/guix.texi: Mention that users may need to become members of
"seat" group and update default value for group field. Add
explanation on seatd.sock file. Remove dropped user field.
---
 doc/guix.texi            | 29 +++++++++++++++++++++++++----
 gnu/services/desktop.scm | 14 +++++++++-----
 gnu/tests/desktop.scm    |  9 +++++++++
 3 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 9a6a5c307d..92701fca10 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -23171,6 +23171,30 @@ input), without requiring the applications needing access to be root.
   %base-services)
 
 @end lisp
+
+@code{seatd} operates over a UNIX domain socket, with @code{libseat}
+providing the client-side of the protocol. Then applications dealing
+with seat management (e.g. @code{sway}) connects to @code{seatd} via
+mentioned socket.
+
+When seat management is provided by @code{seatd}, @code{libseat} users
+that acquire resources provided by @code{seatd} should have permissions
+to access its UNIX domain socket. By default, @code{seatd-service-type}
+provides ``seat'' group. And @code{libseat} user should become its
+member.
+
+@lisp
+(user-account
+  (name "alice")
+  (group "users")
+  (supplementary-groups '("wheel"   ;allow use of sudo, etc.
+                          "seat"    ;interact with seatd
+                          "audio"   ;sound card
+                          "video"   ;video devices such as webcams
+                          "cdrom")) ;the good ol' CD-ROM
+  (comment "Bob's sister"))
+@end lisp
+
 @end defvr
 
 @deftp {Data Type} seatd-configuration
@@ -23180,10 +23204,7 @@ Configuration record for the seatd daemon service.
 @item @code{seatd} (default: @code{seatd})
 The seatd package to use.
 
-@item @code{user} (default: @samp{"root"})
-User to own the seatd socket.
-
-@item @code{group} (default: @samp{"users"})
+@item @code{group} (default: @samp{"seat"})
 Group to own the seatd socket.
 
 @item @code{socket} (default: @samp{"/run/seatd.sock"})
diff --git a/gnu/services/desktop.scm b/gnu/services/desktop.scm
index 29a3722f1b..fbd5a46a06 100644
--- a/gnu/services/desktop.scm
+++ b/gnu/services/desktop.scm
@@ -13,7 +13,7 @@
 ;;; Copyright © 2020 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;; Copyright © 2020 Reza Alizadeh Majd <r.majd@pantherx.org>
 ;;; Copyright © 2021 Brice Waegeneire <brice@waegenei.re>
-;;; Copyright © 2021 muradm <mail@muradm.net>
+;;; Copyright © 2021, 2022 muradm <mail@muradm.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -1645,8 +1645,7 @@ (define-record-type* <seatd-configuration> seatd-configuration
   make-seatd-configuration
   seatd-configuration?
   (seatd seatd-package (default seatd))
-  (user seatd-user (default "root"))
-  (group seatd-group (default "users"))
+  (group seatd-group (default "seat"))
   (socket seatd-socket (default "/run/seatd.sock"))
   (logfile seatd-logfile (default "/var/log/seatd.log"))
   (loglevel seatd-loglevel (default "info")))
@@ -1660,7 +1659,6 @@ (define (seatd-shepherd-service config)
          (provision '(seatd elogind))
          (start #~(make-forkexec-constructor
                    (list #$(file-append (seatd-package config) "/bin/seatd")
-                         "-u" #$(seatd-user config)
                          "-g" #$(seatd-group config))
                    #:environment-variables
                    (list (string-append "SEATD_LOGLEVEL="
@@ -1670,9 +1668,14 @@ (define (seatd-shepherd-service config)
                    #:log-file #$(seatd-logfile config)))
          (stop #~(make-kill-destructor)))))
 
+(define seatd-accounts
+  (match-lambda
+    (($ <seatd-configuration> _ group)
+     (list (user-group (name group) (system? #t))))))
+
 (define seatd-environment
   (match-lambda
-    (($ <seatd-configuration> _ _ _ socket)
+    (($ <seatd-configuration> _ _ socket)
      `(("SEATD_SOCK" . ,socket)))))
 
 (define seatd-service-type
@@ -1683,6 +1686,7 @@ (define seatd-service-type
 applications needing access to be root.")
    (extensions
     (list
+     (service-extension account-service-type seatd-accounts)
      (service-extension session-environment-service-type seatd-environment)
      ;; TODO: once cgroups is separate dependency we should not mount it here
      ;; for now it is mounted here, because elogind mounts it
diff --git a/gnu/tests/desktop.scm b/gnu/tests/desktop.scm
index 25971f9225..6fe6ec21be 100644
--- a/gnu/tests/desktop.scm
+++ b/gnu/tests/desktop.scm
@@ -255,6 +255,15 @@ (define (sock-var-sock var)
                    (socks (map wait-for-unix-socket-m socks)))
                 (and (= 2 (length socks)) (every identity socks)))))
 
+          (test-equal "seatd.sock ownership"
+            '("root" "seat")
+            `(,(marionette-eval
+                '(passwd:name (getpwuid (stat:uid (stat "/run/seatd.sock"))))
+                marionette)
+              ,(marionette-eval
+                '(group:name (getgrgid (stat:gid (stat "/run/seatd.sock"))))
+                marionette)))
+
           (test-assert "greetd is ready"
             (begin
               (marionette-type "ps -C greetd -o pid,args --no-headers > ps-greetd\n"
-- 
2.37.1


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Liliana Marie Prikler <liliana.prikler@ist.tugraz.at> writes:

> Am Sonntag, dem 07.08.2022 um 23:05 +0300 schrieb muradm:
>
>> * gnu/services/desktop.scm (seatd-service-type): Uses "seat" 
>> group.
>> [extensions]: Added account-service-type with seatd-accounts.
>> (seatd-accounts): Conditionally produces list with "seat" 
>> group.
>> (<seatd-configuration>):
>> [user] Drop user field, since it is not going to be used.
> Removed field.
done

>> [group] Change default value to "seat".
>> [existing-group?] Add field which controls if group should be
>> created or not.
> Would be Added field, but see below.
obsolete

>> * doc/guix.texi: Mention that users may need to become members 
>> of
>> "seat" group and update default value for group field. Add
>> explanation on seatd.sock file. Remove dropped user field.
>
>> +When seat mamanagement is provided by @code{seatd}, users that
>> acquire
> management.
done

>> +resources provided by @code{seatd} should have permissions to 
>> access
>> +its UNIX domain socket. By default, @code{seatd-service-type}
>> provides
>> +``seat'' group. And user should become its member.
> Which user?  Closely related, who acquires resources provided by
> @code{seatd}?  Just the greeter?  A regular user logging in?
> What access level is needed/provided?  Read access?  Write 
> access?
While I understand what you are saying, for me user is fine, and I
can't come up with better description, as my eyes too blurred on
this subject. Anyway for now I specified it as "libseat user".

>> +  (group seatd-group (default "seat"))
>> +  (existing-group? seatd-existing-group? (default #f))
> AFAIK this is not necessary.  accounts-service-type can handle 
> multiple
> eq? groups, so as long as you're careful with what you put into 
> group,
> you shouldn't get an error.
ok field removed

> Cheers


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