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;; Copyright (C) 2003 Dale Mellor
;;
;; This file is part of GNU mcron.
;;
;; GNU mcron 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 mcron 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 mcron. If not, see <http://www.gnu.org/licenses/>.
;; Apart from the collecting of options and the handling of --help and --version
;; (which are done in the main.scm file), this file provides all the
;; functionality of the crontab personality. It is designed to be loaded and run
;; once, and then the calling program can exit and the crontab program will have
;; completed its function.
;; Procedure to communicate with running cron daemon that a user has modified
;; his crontab. The user name is written to the /var/cron/socket UNIX socket.
(define (hit-server user-name)
(catch #t (lambda ()
(let ((socket (socket AF_UNIX SOCK_STREAM 0)))
(connect socket AF_UNIX config-socket-file)
(display user-name socket)
(close socket)))
(lambda (key . args)
(display "Warning: a cron daemon is not running.\n"))))
;; Procedure to scan a file containing one user name per line (such as
;; /var/cron/allow and /var/cron/deny), and determine if the given name is in
;; there. The procedure returns #t, #f, or '() if the file does not exist.
(define (in-access-file? file name)
(catch #t (lambda ()
(with-input-from-file file (lambda ()
(let loop ((input (read-line)))
(if (eof-object? input)
#f
(if (string=? input name)
#t
(loop (read-line))))))))
(lambda (key . args) '())))
;; This program should have been installed SUID root. Here we get the passwd
;; entry for the real user who is running this program.
(define crontab-real-user (passwd:name (getpw (getuid))))
;; If the real user is not allowed to use crontab due to the /var/cron/allow
;; and/or /var/cron/deny files, bomb out now.
(if (or (eq? (in-access-file? config-allow-file crontab-real-user) #f)
(eq? (in-access-file? config-deny-file crontab-real-user) #t))
(mcron-error 6 "Access denied by system operator."))
;; Check that no more than one of the mutually exclusive options are being used.
(if (> (+ (if (option-ref options 'edit #f) 1 0)
(if (option-ref options 'list #f) 1 0)
(if (option-ref options 'remove #f) 1 0))
1)
(mcron-error 7 "Only one of options -e, -l or -r can be used."))
;; Check that a non-root user is trying to read someone else's files.
(if (and (not (eqv? (getuid) 0))
(option-ref options 'user #f))
(mcron-error 8 "Only root can use the -u option."))
;; Iff the --user option is given, the crontab-user may be different from the
;; real user.
(define crontab-user (option-ref options 'user crontab-real-user))
;; So now we know which crontab file we will be manipulating.
(define crontab-file (string-append config-spool-dir "/" crontab-user))
;; Display the prompt and wait for user to type his choice. Return #t if the
;; answer begins with 'y' or 'Y', return #f if it begins with 'n' or 'N',
;; otherwise ask again.
(define (get-yes-no prompt . re-prompt)
(if (not (null? re-prompt))
(display "Please answer y or n.\n"))
(display (string-append prompt " "))
(let ((r (read-line)))
(if (not (string-null? r))
(case (string-ref r 0)
((#\y #\Y) #t)
((#\n #\N) #f)
(else (get-yes-no prompt #t)))
(get-yes-no prompt #t))))
;; There are four possible sub-personalities to the crontab personality: list,
;; remove, edit and replace (when the user uses no options but supplies file
;; names on the command line).
(cond
;; In the list personality, we simply open the crontab and copy it
;; character-by-character to the standard output. If anything goes wrong, it
;; can only mean that this user does not have a crontab file.
((option-ref options 'list #f)
(catch #t (lambda ()
(with-input-from-file crontab-file (lambda ()
(do ((input (read-char) (read-char)))
((eof-object? input))
(display input)))))
(lambda (key . args)
(display (string-append "No crontab for "
crontab-user
" exists.\n")))))
;; In the edit personality, we determine the name of a temporary file and an
;; editor command, copy an existing crontab file (if it is there) to the
;; temporary file, making sure the ownership is set so the real user can edit
;; it; once the editor returns we try to read the file to check that it is
;; parseable (but do nothing more with the configuration), and if it is okay
;; (this program is still running!) we move the temporary file to the real
;; crontab, wake the cron daemon up, and remove the temporary file. If the
;; parse fails, we give user a choice of editing the file again or quitting
;; the program and losing all changes made.
((option-ref options 'edit #f)
(let ((temp-file (string-append config-tmp-dir
"/crontab."
(number->string (getpid)))))
(catch #t (lambda () (copy-file crontab-file temp-file))
(lambda (key . args) (with-output-to-file temp-file noop)))
(chown temp-file (getuid) (getgid))
(let retry ()
(system (string-append
(or (getenv "VISUAL") (getenv "EDITOR") "vi")
" "
temp-file))
(catch 'mcron-error
(lambda () (read-vixie-file temp-file))
(lambda (key exit-code . msg)
(apply mcron-error 0 msg)
(if (get-yes-no "Edit again?")
(retry)
(begin
(mcron-error 0 "Crontab not changed")
(primitive-exit 0))))))
(copy-file temp-file crontab-file)
(delete-file temp-file)
(hit-server crontab-user)))
;; In the remove personality we simply make an effort to delete the crontab and
;; wake the daemon. No worries if this fails.
((option-ref options 'remove #f)
(catch #t (lambda () (delete-file crontab-file)
(hit-server crontab-user))
noop))
;; !!!! This comment is wrong.
;; In the case of the replace personality we loop over all the arguments on the
;; command line, and for each one parse the file to make sure it is parseable
;; (but subsequently ignore the configuration), and all being well we copy it
;; to the crontab location; we deal with the standard input in the same way but
;; different. :-) In either case the server is woken so that it will read the
;; newly installed crontab.
((not (null? (option-ref options '() '())))
(let ((input-file (car (option-ref options '() '()))))
(catch-mcron-error
(if (string=? input-file "-")
(let ((input-string (stdin->string)))
(read-vixie-port (open-input-string input-string))
(with-output-to-file crontab-file (lambda ()
(display input-string))))
(begin
(read-vixie-file input-file)
(copy-file input-file crontab-file))))
(hit-server crontab-user)))
;; The user is being silly. The message here is identical to the one Vixie cron
;; used to put out, for total compatibility.
(else
(mcron-error 15 "usage error: file name must be specified for replace.")))
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