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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu system linux)
#:use-module (guix records)
#:use-module (guix derivations)
#:use-module (guix gexp)
#:use-module (ice-9 match)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-26)
#:use-module ((guix utils) #:select (%current-system))
#:export (pam-service
pam-entry
pam-services->directory
unix-pam-service
base-pam-services))
;;; Commentary:
;;;
;;; Configuration of Linux-related things, including pluggable authentication
;;; modules (PAM).
;;;
;;; Code:
;; PAM services (see
;; <http://www.linux-pam.org/Linux-PAM-html/sag-configuration-file.html>.)
(define-record-type* <pam-service> pam-service
make-pam-service
pam-service?
(name pam-service-name) ; string
;; The four "management groups".
(account pam-service-account ; list of <pam-entry>
(default '()))
(auth pam-service-auth
(default '()))
(password pam-service-password
(default '()))
(session pam-service-session
(default '())))
(define-record-type* <pam-entry> pam-entry
make-pam-entry
pam-entry?
(control pam-entry-control) ; string
(module pam-entry-module) ; file name
(arguments pam-entry-arguments ; list of string-valued g-expressions
(default '())))
(define (pam-service->configuration service)
"Return the derivation building the configuration file for SERVICE, to be
dumped in /etc/pam.d/NAME, where NAME is the name of SERVICE."
(define (entry->gexp type entry)
(match entry
(($ <pam-entry> control module (arguments ...))
#~(format #t "~a ~a ~a ~a~%"
#$type #$control #$module
(string-join (list #$@arguments))))))
(match service
(($ <pam-service> name account auth password session)
(define builder
#~(begin
(with-output-to-file #$output
(lambda ()
#$@(append (map (cut entry->gexp "account" <>) account)
(map (cut entry->gexp "auth" <>) auth)
(map (cut entry->gexp "password" <>) password)
(map (cut entry->gexp "session" <>) session))
#t))))
(computed-file name builder))))
(define (pam-services->directory services)
"Return the derivation to build the configuration directory to be used as
/etc/pam.d for SERVICES."
(let ((names (map pam-service-name services))
(files (map pam-service->configuration services)))
(define builder
#~(begin
(use-modules (ice-9 match)
(srfi srfi-1))
(mkdir #$output)
(for-each (match-lambda
((name file)
(symlink file (string-append #$output "/" name))))
;; Since <pam-service> objects cannot be compared with
;; 'equal?' since they contain gexps, which contain
;; closures, use 'delete-duplicates' on the build-side
;; instead. See <http://bugs.gnu.org/20037>.
(delete-duplicates '#$(zip names files)))))
(computed-file "pam.d" builder)))
(define %pam-other-services
;; The "other" PAM configuration, which denies everything (see
;; <http://www.linux-pam.org/Linux-PAM-html/sag-configuration-example.html>.)
(let ((deny (pam-entry
(control "required")
(module "pam_deny.so"))))
(pam-service
(name "other")
(account (list deny))
(auth (list deny))
(password (list deny))
(session (list deny)))))
(define unix-pam-service
(let ((unix (pam-entry
(control "required")
(module "pam_unix.so"))))
(lambda* (name #:key allow-empty-passwords? motd)
"Return a standard Unix-style PAM service for NAME. When
ALLOW-EMPTY-PASSWORDS? is true, allow empty passwords. When MOTD is true, it
should be a file-like object used as the message-of-the-day."
;; See <http://www.linux-pam.org/Linux-PAM-html/sag-configuration-example.html>.
(let ((name* name))
(pam-service
(name name*)
(account (list unix))
(auth (list (if allow-empty-passwords?
(pam-entry
(control "required")
(module "pam_unix.so")
(arguments '("nullok")))
unix)))
(password (list (pam-entry
(control "required")
(module "pam_unix.so")
;; Store SHA-512 encrypted passwords in /etc/shadow.
(arguments '("sha512" "shadow")))))
(session (if motd
(list unix
(pam-entry
(control "optional")
(module "pam_motd.so")
(arguments
(list #~(string-append "motd=" #$motd)))))
(list unix))))))))
(define (rootok-pam-service command)
"Return a PAM service for COMMAND such that 'root' does not need to
authenticate to run COMMAND."
(let ((unix (pam-entry
(control "required")
(module "pam_unix.so"))))
(pam-service
(name command)
(account (list unix))
(auth (list (pam-entry
(control "sufficient")
(module "pam_rootok.so"))))
(password (list unix))
(session (list unix)))))
(define* (base-pam-services #:key allow-empty-passwords?)
"Return the list of basic PAM services everyone would want."
;; TODO: Add other Shadow programs?
(append (list %pam-other-services)
;; These programs are setuid-root.
(map (cut unix-pam-service <>
#:allow-empty-passwords? allow-empty-passwords?)
'("su" "passwd" "sudo"
"xlock" "xscreensaver"))
;; These programs are not setuid-root, and we want root to be able
;; to run them without having to authenticate (notably because
;; 'useradd' and 'groupadd' are run during system activation.)
(map rootok-pam-service
'("useradd" "userdel" "usermod"
"groupadd" "groupdel" "groupmod"))))
;;; linux.scm ends here
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