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Diffstat (limited to 'src/mcron/crontab.scm')
| -rw-r--r-- | src/mcron/crontab.scm | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/src/mcron/crontab.scm b/src/mcron/crontab.scm new file mode 100644 index 0000000..6be5c61 --- /dev/null +++ b/src/mcron/crontab.scm @@ -0,0 +1,228 @@ +;; Copyright (C) 2003, 2014 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. + +(let ((hit-server + (lambda (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. + + (in-access-file? + (lambda (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. + + (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.")) + + + + (let ( + + + ;; Iff the --user option is given, the crontab-user may be different + ;; from the real user. + + (crontab-user (option-ref options 'user crontab-real-user)) + + + ;; So now we know which crontab file we will be manipulating. + + (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. + + (get-yes-no (lambda (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."))) + + +)) ;; End of file-level let-scopes. |