520bac7ed0
This addresses a potential security issue, where a compromised service could trick the activation code in changing the permissions, owner and group of arbitrary files. However, this patch is currently only a partial fix, due to a TOCTTOU (time-of-check to time-of-use) race, which can be fixed once guile has bindings to openat and friends. Fixes: <https://lists.gnu.org/archive/html/guix-devel/2021-01/msg00388.html> * gnu/build/activation.scm: new procedure 'mkdir-p/perms'. * gnu/services/authentication.scm (%nslcd-activation, nslcd-service-type): use new procedure. * gnu/services/cups.scm (%cups-activation): likewise. * gnu/services/dbus.scm (dbus-activation): likewise. * gnu/services/dns.scm (knot-activation): likewise. Signed-off-by: Ludovic Courtès <ludo@gnu.org>
386 lines
16 KiB
Scheme
386 lines
16 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
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;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (gnu services dbus)
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#:use-module (gnu services)
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#:use-module (gnu services shepherd)
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#:use-module (gnu system shadow)
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#:use-module (gnu system pam)
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#:use-module ((gnu packages glib) #:select (dbus))
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#:use-module (gnu packages polkit)
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#:use-module (gnu packages admin)
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#:use-module (guix gexp)
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#:use-module ((guix packages) #:select (package-name))
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#:use-module (guix records)
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#:use-module (guix modules)
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#:use-module (srfi srfi-1)
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#:use-module (ice-9 match)
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#:export (dbus-configuration
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dbus-configuration?
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dbus-root-service-type
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dbus-service
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wrapped-dbus-service
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polkit-service-type
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polkit-service))
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;;;
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;;; D-Bus.
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;;;
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(define-record-type* <dbus-configuration>
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dbus-configuration make-dbus-configuration
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dbus-configuration?
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(dbus dbus-configuration-dbus ;<package>
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(default dbus))
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(services dbus-configuration-services ;list of <package>
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(default '())))
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(define (system-service-directory services)
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"Return the system service directory, containing @code{.service} files for
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all the services that may be activated by the daemon."
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(computed-file "dbus-system-services"
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(with-imported-modules '((guix build utils))
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#~(begin
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(use-modules (guix build utils)
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(srfi srfi-1))
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(define files
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(append-map (lambda (service)
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(find-files
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(string-append
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service
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"/share/dbus-1/")
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"\\.service$"))
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(list #$@services)))
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(mkdir #$output)
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(for-each (lambda (file)
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(symlink file
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(string-append #$output "/"
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(basename file))))
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files)
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#t))))
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(define (dbus-configuration-directory services)
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"Return a directory contains the @code{system-local.conf} file for DBUS that
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includes the @code{etc/dbus-1/system.d} directories of each package listed in
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@var{services}."
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(define build
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#~(begin
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(use-modules (sxml simple)
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(srfi srfi-1))
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(define-syntax directives
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(syntax-rules ()
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;; Expand the given directives (SXML expressions) only if their
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;; key names a file that exists.
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((_ (name directory) rest ...)
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(let ((dir directory))
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(if (file-exists? dir)
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`((name ,dir)
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,@(directives rest ...))
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(directives rest ...))))
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((_)
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'())))
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(define (services->sxml services)
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;; Return the SXML 'includedir' clauses for DIRS.
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`(busconfig
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(servicehelper "/run/setuid-programs/dbus-daemon-launch-helper")
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;; First, the '.service' files of services subject to activation.
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;; We use a fixed location under /etc because the setuid helper
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;; looks for them in that location and nowhere else. See
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;; <https://bugs.freedesktop.org/show_bug.cgi?id=92458>.
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(servicedir "/etc/dbus-1/system-services")
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,@(append-map (lambda (dir)
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(directives
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(includedir
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(string-append dir "/etc/dbus-1/system.d"))
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(includedir
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(string-append dir "/share/dbus-1/system.d"))
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(servicedir ;for '.service' files
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(string-append dir "/share/dbus-1/services"))))
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services)))
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(mkdir #$output)
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;; Provide /etc/dbus-1/system-services, which is where the setuid
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;; helper looks for system service files.
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(symlink #$(system-service-directory services)
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(string-append #$output "/system-services"))
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;; 'system-local.conf' is automatically included by the default
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;; 'system.conf', so this is where we stuff our own things.
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(call-with-output-file (string-append #$output "/system-local.conf")
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(lambda (port)
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(sxml->xml (services->sxml (list #$@services))
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port)))))
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(computed-file "dbus-configuration" build))
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(define (dbus-etc-files config)
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"Return a list of FILES for @var{etc-service-type} to build the
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@code{/etc/dbus-1} directory."
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(list `("dbus-1" ,(dbus-configuration-directory
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(dbus-configuration-services config)))))
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(define %dbus-accounts
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;; Accounts used by the system bus.
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(list (user-group (name "messagebus") (system? #t))
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(user-account
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(name "messagebus")
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(group "messagebus")
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(system? #t)
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(comment "D-Bus system bus user")
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(home-directory "/var/run/dbus")
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(shell (file-append shadow "/sbin/nologin")))))
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(define dbus-setuid-programs
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;; Return the file name of the setuid program that we need.
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(match-lambda
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(($ <dbus-configuration> dbus services)
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(list (file-append dbus "/libexec/dbus-daemon-launch-helper")))))
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(define (dbus-activation config)
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"Return an activation gexp for D-Bus using @var{config}."
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(with-imported-modules (source-module-closure
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'((gnu build activation)
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(guix build utils)))
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#~(begin
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(use-modules (gnu build activation)
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(guix build utils))
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(let ((user (getpwnam "messagebus")))
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;; This directory contains the daemon's socket so it must be
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;; world-readable.
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(mkdir-p/perms "/var/run/dbus" user #o755))
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(unless (file-exists? "/etc/machine-id")
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(format #t "creating /etc/machine-id...~%")
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(invoke (string-append #$(dbus-configuration-dbus config)
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"/bin/dbus-uuidgen")
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"--ensure=/etc/machine-id")))))
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(define dbus-shepherd-service
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(match-lambda
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(($ <dbus-configuration> dbus)
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(list (shepherd-service
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(documentation "Run the D-Bus system daemon.")
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(provision '(dbus-system))
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(requirement '(user-processes syslogd))
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(start #~(make-forkexec-constructor
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(list (string-append #$dbus "/bin/dbus-daemon")
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"--nofork" "--system" "--syslog-only")
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#:pid-file "/var/run/dbus/pid"))
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(stop #~(make-kill-destructor)))))))
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(define dbus-root-service-type
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(service-type (name 'dbus)
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(extensions
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(list (service-extension shepherd-root-service-type
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dbus-shepherd-service)
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(service-extension activation-service-type
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dbus-activation)
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(service-extension etc-service-type
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dbus-etc-files)
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(service-extension account-service-type
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(const %dbus-accounts))
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(service-extension setuid-program-service-type
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dbus-setuid-programs)))
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;; Extensions consist of lists of packages (representing D-Bus
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;; services) that we just concatenate.
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(compose concatenate)
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;; The service's parameters field is extended by augmenting
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;; its <dbus-configuration> 'services' field.
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(extend (lambda (config services)
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(dbus-configuration
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(inherit config)
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(services
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(append (dbus-configuration-services config)
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services)))))
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(default-value (dbus-configuration))
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(description "Run the system-wide D-Bus inter-process message
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bus. It allows programs and daemons to communicate and is also responsible
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for spawning (@dfn{activating}) D-Bus services on demand.")))
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(define* (dbus-service #:key (dbus dbus) (services '()))
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"Return a service that runs the \"system bus\", using @var{dbus}, with
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support for @var{services}.
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@uref{http://dbus.freedesktop.org/, D-Bus} is an inter-process communication
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facility. Its system bus is used to allow system services to communicate and
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be notified of system-wide events.
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@var{services} must be a list of packages that provide an
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@file{etc/dbus-1/system.d} directory containing additional D-Bus configuration
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and policy files. For example, to allow avahi-daemon to use the system bus,
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@var{services} must be equal to @code{(list avahi)}."
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(service dbus-root-service-type
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(dbus-configuration (dbus dbus)
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(services services))))
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(define (wrapped-dbus-service service program variables)
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"Return a wrapper for @var{service}, a package containing a D-Bus service,
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where @var{program} is wrapped such that @var{variables}, a list of name/value
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tuples, are all set as environment variables when the bus daemon launches it."
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(define wrapper
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(program-file (string-append (package-name service) "-program-wrapper")
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#~(begin
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(use-modules (ice-9 match))
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(for-each (match-lambda
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((variable value)
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(setenv variable value)))
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'#$variables)
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(apply execl (string-append #$service "/" #$program)
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(string-append #$service "/" #$program)
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(cdr (command-line))))))
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(define build
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(with-imported-modules '((guix build utils))
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#~(begin
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(use-modules (guix build utils))
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(define service-directory
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"/share/dbus-1/system-services")
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(mkdir-p (dirname (string-append #$output
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service-directory)))
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(copy-recursively (string-append #$service
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service-directory)
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(string-append #$output
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service-directory))
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(symlink (string-append #$service "/etc") ;for etc/dbus-1
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(string-append #$output "/etc"))
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(for-each (lambda (file)
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(substitute* file
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(("Exec[[:blank:]]*=[[:blank:]]*([[:graph:]]+)(.*)$"
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_ original-program arguments)
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(string-append "Exec=" #$wrapper arguments
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"\n"))))
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(find-files #$output "\\.service$")))))
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(computed-file (string-append (package-name service) "-wrapper")
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build))
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;;;
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;;; Polkit privilege management service.
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;;;
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(define-record-type* <polkit-configuration>
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polkit-configuration make-polkit-configuration
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polkit-configuration?
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(polkit polkit-configuration-polkit ;<package>
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(default polkit))
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(actions polkit-configuration-actions ;list of <package>
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(default '())))
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(define %polkit-accounts
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(list (user-group (name "polkitd") (system? #t))
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(user-account
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(name "polkitd")
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(group "polkitd")
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(system? #t)
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(comment "Polkit daemon user")
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(home-directory "/var/empty")
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(shell "/run/current-system/profile/sbin/nologin"))))
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(define %polkit-pam-services
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(list (unix-pam-service "polkit-1")))
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(define (polkit-directory packages)
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"Return a directory containing an @file{actions} and possibly a
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@file{rules.d} sub-directory, for use as @file{/etc/polkit-1}."
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(with-imported-modules '((guix build union))
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(computed-file "etc-polkit-1"
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#~(begin
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(use-modules (guix build union) (srfi srfi-26))
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(union-build #$output
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(map (cut string-append <>
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"/share/polkit-1")
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(list #$@packages)))))))
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(define polkit-etc-files
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(match-lambda
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(($ <polkit-configuration> polkit packages)
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`(("polkit-1" ,(polkit-directory (cons polkit packages)))))))
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(define polkit-setuid-programs
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(match-lambda
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(($ <polkit-configuration> polkit)
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(list (file-append polkit "/lib/polkit-1/polkit-agent-helper-1")
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(file-append polkit "/bin/pkexec")))))
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(define polkit-service-type
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(service-type (name 'polkit)
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(extensions
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(list (service-extension account-service-type
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(const %polkit-accounts))
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(service-extension pam-root-service-type
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(const %polkit-pam-services))
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(service-extension dbus-root-service-type
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(compose
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list
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polkit-configuration-polkit))
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(service-extension etc-service-type
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polkit-etc-files)
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(service-extension setuid-program-service-type
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polkit-setuid-programs)))
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;; Extensions are lists of packages that provide polkit rules
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;; or actions under share/polkit-1/{actions,rules.d}.
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(compose concatenate)
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(extend (lambda (config actions)
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(polkit-configuration
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(inherit config)
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(actions
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(append (polkit-configuration-actions config)
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actions)))))
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(default-value (polkit-configuration))
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(description
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"Run the
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@uref{http://www.freedesktop.org/wiki/Software/polkit/, Polkit privilege
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management service}, which allows system administrators to grant access to
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privileged operations in a structured way. Polkit is a requirement for most
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desktop environments, such as GNOME.")))
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(define* (polkit-service #:key (polkit polkit))
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"Return a service that runs the
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@uref{http://www.freedesktop.org/wiki/Software/polkit/, Polkit privilege
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management service}, which allows system administrators to grant access to
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privileged operations in a structured way. By querying the Polkit service, a
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privileged system component can know when it should grant additional
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capabilities to ordinary users. For example, an ordinary user can be granted
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the capability to suspend the system if the user is logged in locally."
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(service polkit-service-type
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(polkit-configuration (polkit polkit))))
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;;; dbus.scm ends here
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