15f0de0581
* gnu/build/activation.scm (activate-ptrace-attach): Check for the existence of /proc/sys/kernel/yama/ptrace_scope before trying to write to it.
404 lines
16 KiB
Scheme
404 lines
16 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
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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 build activation)
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#:use-module (gnu build linux-boot)
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#:use-module (guix build utils)
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#:use-module (ice-9 ftw)
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#:use-module (ice-9 match)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-26)
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#:export (activate-users+groups
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activate-etc
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activate-setuid-programs
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activate-/bin/sh
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activate-modprobe
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activate-firmware
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activate-ptrace-attach
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activate-current-system))
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;;; Commentary:
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;;;
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;;; This module provides "activation" helpers. Activation is the process that
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;;; consists in setting up system-wide files and directories so that an
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;;; 'operating-system' configuration becomes active.
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;;;
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;;; Code:
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(define (enumerate thunk)
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"Return the list of values returned by THUNK until it returned #f."
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(let loop ((entry (thunk))
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(result '()))
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(if (not entry)
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(reverse result)
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(loop (thunk) (cons entry result)))))
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(define (current-users)
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"Return the passwd entries for all the currently defined user accounts."
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(setpw)
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(enumerate getpwent))
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(define (current-groups)
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"Return the group entries for all the currently defined user groups."
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(setgr)
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(enumerate getgrent))
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(define* (add-group name #:key gid password system?
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(log-port (current-error-port)))
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"Add NAME as a user group, with the given numeric GID if specified."
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;; Use 'groupadd' from the Shadow package.
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(format log-port "adding group '~a'...~%" name)
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(let ((args `(,@(if gid `("-g" ,(number->string gid)) '())
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,@(if password `("-p" ,password) '())
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,@(if system? `("--system") '())
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,name)))
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(zero? (apply system* "groupadd" args))))
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(define %skeleton-directory
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;; Directory containing skeleton files for new accounts.
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;; Note: keep the trailing '/' so that 'scandir' enters it.
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"/etc/skel/")
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(define (dot-or-dot-dot? file)
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(member file '("." "..")))
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(define (make-file-writable file)
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"Make FILE writable for its owner.."
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(let ((stat (lstat file))) ;XXX: symlinks
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(chmod file (logior #o600 (stat:perms stat)))))
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(define* (copy-account-skeletons home
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#:optional (directory %skeleton-directory))
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"Copy the account skeletons from DIRECTORY to HOME."
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(let ((files (scandir directory (negate dot-or-dot-dot?)
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string<?)))
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(mkdir-p home)
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(for-each (lambda (file)
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(let ((target (string-append home "/" file)))
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(copy-file (string-append directory "/" file) target)
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(make-file-writable target)))
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files)))
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(define* (make-skeletons-writable home
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#:optional (directory %skeleton-directory))
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"Make sure that the files that have been copied from DIRECTORY to HOME are
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owner-writable in HOME."
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(let ((files (scandir directory (negate dot-or-dot-dot?)
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string<?)))
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(for-each (lambda (file)
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(let ((target (string-append home "/" file)))
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(when (file-exists? target)
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(make-file-writable target))))
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files)))
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(define* (add-user name group
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#:key uid comment home shell password system?
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(supplementary-groups '())
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(log-port (current-error-port)))
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"Create an account for user NAME part of GROUP, with the specified
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properties. Return #t on success."
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(format log-port "adding user '~a'...~%" name)
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(if (and uid (zero? uid))
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;; 'useradd' fails with "Cannot determine your user name" if the root
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;; account doesn't exist. Thus, for bootstrapping purposes, create that
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;; one manually.
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(begin
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(call-with-output-file "/etc/shadow"
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(cut format <> "~a::::::::~%" name))
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(call-with-output-file "/etc/passwd"
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(cut format <> "~a:x:~a:~a:~a:~a:~a~%"
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name "0" "0" comment home shell))
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(chmod "/etc/shadow" #o600)
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(copy-account-skeletons (or home "/root"))
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#t)
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;; Use 'useradd' from the Shadow package.
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(let ((args `(,@(if uid `("-u" ,(number->string uid)) '())
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"-g" ,(if (number? group) (number->string group) group)
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,@(if (pair? supplementary-groups)
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`("-G" ,(string-join supplementary-groups ","))
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'())
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,@(if comment `("-c" ,comment) '())
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,@(if home
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(if (file-exists? home)
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`("-d" ,home) ; avoid warning from 'useradd'
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`("-d" ,home "--create-home"))
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'())
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,@(if shell `("-s" ,shell) '())
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,@(if password `("-p" ,password) '())
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,@(if system? '("--system") '())
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,name)))
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(and (zero? (apply system* "useradd" args))
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(begin
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;; Since /etc/skel is a link to a directory in the store where
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;; all files have the writable bit cleared, and since 'useradd'
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;; preserves permissions when it copies them, explicitly make
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;; them writable.
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(make-skeletons-writable home)
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#t)))))
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(define* (modify-user name group
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#:key uid comment home shell password system?
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(supplementary-groups '())
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(log-port (current-error-port)))
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"Modify user account NAME to have all the given settings."
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;; Use 'usermod' from the Shadow package.
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(let ((args `(,@(if uid `("-u" ,(number->string uid)) '())
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"-g" ,(if (number? group) (number->string group) group)
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,@(if (pair? supplementary-groups)
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`("-G" ,(string-join supplementary-groups ","))
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'())
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,@(if comment `("-c" ,comment) '())
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;; Don't use '--move-home', so ignore HOME.
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,@(if shell `("-s" ,shell) '())
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,name)))
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(zero? (apply system* "usermod" args))))
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(define* (delete-user name #:key (log-port (current-error-port)))
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"Remove user account NAME. Return #t on success. This may fail if NAME is
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logged in."
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(format log-port "deleting user '~a'...~%" name)
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(zero? (system* "userdel" name)))
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(define* (delete-group name #:key (log-port (current-error-port)))
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"Remove group NAME. Return #t on success."
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(format log-port "deleting group '~a'...~%" name)
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(zero? (system* "groupdel" name)))
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(define* (ensure-user name group
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#:key uid comment home shell password system?
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(supplementary-groups '())
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(log-port (current-error-port))
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#:rest rest)
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"Make sure user NAME exists and has the relevant settings."
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(if (false-if-exception (getpwnam name))
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(apply modify-user name group rest)
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(apply add-user name group rest)))
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(define (activate-users+groups users groups)
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"Make sure the accounts listed in USERS and the user groups listed in GROUPS
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are all available.
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Each item in USERS is a list of all the characteristics of a user account;
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each item in GROUPS is a tuple with the group name, group password or #f, and
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numeric gid or #f."
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(define (touch file)
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(close-port (open-file file "a0b")))
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(define activate-user
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(match-lambda
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((name uid group supplementary-groups comment home shell password system?)
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(let ((profile-dir (string-append "/var/guix/profiles/per-user/"
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name)))
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(ensure-user name group
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#:uid uid
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#:system? system?
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#:supplementary-groups supplementary-groups
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#:comment comment
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#:home home
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#:shell shell
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#:password password)
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(unless system?
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;; Create the profile directory for the new account.
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(let ((pw (getpwnam name)))
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(mkdir-p profile-dir)
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(chown profile-dir (passwd:uid pw) (passwd:gid pw))))))))
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;; 'groupadd' aborts if the file doesn't already exist.
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(touch "/etc/group")
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;; Create the root account so we can use 'useradd' and 'groupadd'.
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(activate-user (find (match-lambda
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((name (? zero?) _ ...) #t)
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(_ #f))
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users))
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;; Then create the groups.
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(for-each (match-lambda
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((name password gid system?)
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(unless (false-if-exception (getgrnam name))
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(add-group name
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#:gid gid #:password password
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#:system? system?))))
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groups)
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;; Create the other user accounts.
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(for-each activate-user users)
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;; Finally, delete extra user accounts and groups.
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(for-each delete-user
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(lset-difference string=?
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(map passwd:name (current-users))
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(match users
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(((names . _) ...)
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names))))
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(for-each delete-group
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(lset-difference string=?
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(map group:name (current-groups))
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(match groups
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(((names . _) ...)
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names)))))
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(define (activate-etc etc)
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"Install ETC, a directory in the store, as the source of static files for
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/etc."
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;; /etc is a mixture of static and dynamic settings. Here is where we
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;; initialize it from the static part.
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(define (rm-f file)
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(false-if-exception (delete-file file)))
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(format #t "populating /etc from ~a...~%" etc)
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;; Create the /etc/ssl -> /run/current-system/profile/etc/ssl symlink. This
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;; symlink, to a target outside of the store, probably doesn't belong in the
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;; static 'etc' store directory. However, if it were to be put there,
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;; beware that if /run/current-system/profile/etc/ssl doesn't exist at the
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;; time of activation (e.g. when installing a fresh system), the call to
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;; 'file-is-directory?' below will fail because it uses 'stat', not 'lstat'.
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(rm-f "/etc/ssl")
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(symlink "/run/current-system/profile/etc/ssl" "/etc/ssl")
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(rm-f "/etc/static")
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(symlink etc "/etc/static")
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(for-each (lambda (file)
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(let ((target (string-append "/etc/" file))
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(source (string-append "/etc/static/" file)))
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(rm-f target)
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;; Things such as /etc/sudoers must be regular files, not
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;; symlinks; furthermore, they could be modified behind our
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;; back---e.g., with 'visudo'. Thus, make a copy instead of
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;; symlinking them.
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(if (file-is-directory? source)
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(symlink source target)
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(copy-file source target))
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;; XXX: Dirty hack to meet sudo's expectations.
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(when (string=? (basename target) "sudoers")
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(chmod target #o440))))
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(scandir etc (negate dot-or-dot-dot?)
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;; The default is 'string-locale<?', but we don't have
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;; it when run from the initrd's statically-linked
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;; Guile.
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string<?)))
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(define %setuid-directory
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;; Place where setuid programs are stored.
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"/run/setuid-programs")
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(define (link-or-copy source target)
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"Attempt to make TARGET a hard link to SOURCE; if it fails, fall back to
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copy SOURCE to TARGET."
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(catch 'system-error
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(lambda ()
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(link source target))
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(lambda args
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;; Perhaps SOURCE and TARGET live in a different file system, so copy
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;; SOURCE.
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(copy-file source target))))
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(define (activate-setuid-programs programs)
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"Turn PROGRAMS, a list of file names, into setuid programs stored under
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%SETUID-DIRECTORY."
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(define (make-setuid-program prog)
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(let ((target (string-append %setuid-directory
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"/" (basename prog))))
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(link-or-copy prog target)
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(chown target 0 0)
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(chmod target #o6555)))
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(format #t "setting up setuid programs in '~a'...~%"
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%setuid-directory)
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(if (file-exists? %setuid-directory)
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(for-each (compose delete-file
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(cut string-append %setuid-directory "/" <>))
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(scandir %setuid-directory
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(lambda (file)
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(not (member file '("." ".."))))
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string<?))
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(mkdir-p %setuid-directory))
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(for-each make-setuid-program programs))
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(define (activate-/bin/sh shell)
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"Change /bin/sh to point to SHELL."
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(symlink shell "/bin/sh.new")
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(rename-file "/bin/sh.new" "/bin/sh"))
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(define (activate-modprobe modprobe)
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"Tell the kernel to use MODPROBE to load modules."
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(call-with-output-file "/proc/sys/kernel/modprobe"
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(lambda (port)
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(display modprobe port))))
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(define (activate-firmware directory)
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"Tell the kernel to look for device firmware under DIRECTORY. This
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mechanism bypasses udev: it allows Linux to handle firmware loading directly
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by itself, without having to resort to a \"user helper\"."
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(call-with-output-file "/sys/module/firmware_class/parameters/path"
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(lambda (port)
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(display directory port))))
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(define (activate-ptrace-attach)
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"Allow users to PTRACE_ATTACH their own processes.
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This works around a regression introduced in the default \"security\" policy
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found in Linux 3.4 onward that prevents users from attaching to their own
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processes--see Yama.txt in the Linux source tree for the rationale. This
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sounds like an unacceptable restriction for little or no security
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improvement."
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(let ((file "/proc/sys/kernel/yama/ptrace_scope"))
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(when (file-exists? file)
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(call-with-output-file file
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(lambda (port)
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(display 0 port))))))
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(define %current-system
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;; The system that is current (a symlink.) This is not necessarily the same
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;; as the system we booted (aka. /run/booted-system) because we can re-build
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;; a new system configuration and activate it, without rebooting.
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"/run/current-system")
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(define (boot-time-system)
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"Return the '--system' argument passed on the kernel command line."
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(find-long-option "--system" (linux-command-line)))
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(define* (activate-current-system
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#:optional (system (or (getenv "GUIX_NEW_SYSTEM")
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(boot-time-system))))
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"Atomically make SYSTEM the current system."
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;; The 'GUIX_NEW_SYSTEM' environment variable is used as a way for 'guix
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;; system reconfigure' to pass the file name of the new system.
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(format #t "making '~a' the current system...~%" system)
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;; Atomically make SYSTEM current.
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(let ((new (string-append %current-system ".new")))
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(symlink system new)
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(rename-file new %current-system)))
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;;; activation.scm ends here
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