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-rw-r--r--term-utils/write.c368
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diff --git a/term-utils/write.c b/term-utils/write.c
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+/*
+ * Copyright (c) 1989, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * Modified for Linux, Mon Mar 8 18:16:24 1993, faith@cs.unc.edu
+ * Wed Jun 22 21:41:56 1994, faith@cs.unc.edu:
+ * Added fix from Mike Grupenhoff (kashmir@umiacs.umd.edu)
+ * Mon Jul 1 17:01:39 MET DST 1996, janl@math.uio.no:
+ * - Added fix from David.Chapell@mail.trincoll.edu enabling daemons
+ * to use write.
+ * - ANSIed it since I was working on it anyway.
+ * 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
+ * - added Native Language Support
+ *
+ */
+
+#include <errno.h>
+#include <getopt.h>
+#include <paths.h>
+#include <pwd.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <unistd.h>
+#include <utmpx.h>
+
+#include "c.h"
+#include "carefulputc.h"
+#include "closestream.h"
+#include "nls.h"
+#include "strutils.h"
+#include "ttyutils.h"
+#include "xalloc.h"
+
+static sig_atomic_t signal_received = 0;
+
+struct write_control {
+ uid_t src_uid;
+ const char *src_login;
+ const char *src_tty_path;
+ const char *src_tty_name;
+ const char *dst_login;
+ char *dst_tty_path;
+ const char *dst_tty_name;
+};
+
+static void __attribute__((__noreturn__)) usage(void)
+{
+ FILE *out = stdout;
+ fputs(USAGE_HEADER, out);
+ fprintf(out,
+ _(" %s [options] <user> [<ttyname>]\n"),
+ program_invocation_short_name);
+
+ fputs(USAGE_SEPARATOR, out);
+ fputs(_("Send a message to another user.\n"), out);
+
+ fputs(USAGE_OPTIONS, out);
+ printf(USAGE_HELP_OPTIONS(16));
+ printf(USAGE_MAN_TAIL("write(1)"));
+ exit(EXIT_SUCCESS);
+}
+
+/*
+ * check_tty - check that a terminal exists, and get the message bit
+ * and the access time
+ */
+static int check_tty(const char *tty, int *tty_writeable, time_t *tty_atime, int showerror)
+{
+ struct stat s;
+
+ if (stat(tty, &s) < 0) {
+ if (showerror)
+ warn("%s", tty);
+ return 1;
+ }
+ if (getuid() == 0) /* root can always write */
+ *tty_writeable = 1;
+ else {
+ if (getegid() != s.st_gid) {
+ warnx(_("effective gid does not match group of %s"), tty);
+ return 1;
+ }
+ *tty_writeable = s.st_mode & S_IWGRP;
+ }
+ if (tty_atime)
+ *tty_atime = s.st_atime;
+ return 0;
+}
+
+/*
+ * check_utmp - checks that the given user is actually logged in on
+ * the given tty
+ */
+static int check_utmp(const struct write_control *ctl)
+{
+ struct utmpx *u;
+ int res = 1;
+
+ utmpxname(_PATH_UTMP);
+ setutxent();
+
+ while ((u = getutxent())) {
+ if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) == 0 &&
+ strncmp(ctl->dst_tty_name, u->ut_line, sizeof(u->ut_line)) == 0) {
+ res = 0;
+ break;
+ }
+ }
+
+ endutxent();
+ return res;
+}
+
+/*
+ * search_utmp - search utmp for the "best" terminal to write to
+ *
+ * Ignores terminals with messages disabled, and of the rest, returns
+ * the one with the most recent access time. Returns as value the number
+ * of the user's terminals with messages enabled, or -1 if the user is
+ * not logged in at all.
+ *
+ * Special case for writing to yourself - ignore the terminal you're
+ * writing from, unless that's the only terminal with messages enabled.
+ */
+static void search_utmp(struct write_control *ctl)
+{
+ struct utmpx *u;
+ time_t best_atime = 0, tty_atime;
+ int num_ttys = 0, valid_ttys = 0, tty_writeable = 0, user_is_me = 0;
+ char path[sizeof(u->ut_line) + 6];
+
+ utmpxname(_PATH_UTMP);
+ setutxent();
+
+ while ((u = getutxent())) {
+ if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) != 0)
+ continue;
+ num_ttys++;
+ sprintf(path, "/dev/%s", u->ut_line);
+ if (check_tty(path, &tty_writeable, &tty_atime, 0))
+ /* bad term? skip */
+ continue;
+ if (ctl->src_uid && !tty_writeable)
+ /* skip ttys with msgs off */
+ continue;
+ if (strcmp(u->ut_line, ctl->src_tty_name) == 0) {
+ user_is_me = 1;
+ /* don't write to yourself */
+ continue;
+ }
+ if (u->ut_type != USER_PROCESS)
+ /* it's not a valid entry */
+ continue;
+ valid_ttys++;
+ if (best_atime < tty_atime) {
+ best_atime = tty_atime;
+ free(ctl->dst_tty_path);
+ ctl->dst_tty_path = xstrdup(path);
+ ctl->dst_tty_name = ctl->dst_tty_path + 5;
+ }
+ }
+
+ endutxent();
+ if (num_ttys == 0)
+ errx(EXIT_FAILURE, _("%s is not logged in"), ctl->dst_login);
+ if (valid_ttys == 0) {
+ if (user_is_me) {
+ /* ok, so write to yourself! */
+ if (!ctl->src_tty_path)
+ errx(EXIT_FAILURE, _("can't find your tty's name"));
+ ctl->dst_tty_path = xstrdup(ctl->src_tty_path);
+ ctl->dst_tty_name = ctl->dst_tty_path + 5;
+ return;
+ }
+ errx(EXIT_FAILURE, _("%s has messages disabled"), ctl->dst_login);
+ }
+ if (1 < valid_ttys)
+ warnx(_("%s is logged in more than once; writing to %s"),
+ ctl->dst_login, ctl->dst_tty_name);
+}
+
+/*
+ * signal_handler - cause write loop to exit
+ */
+static void signal_handler(int signo)
+{
+ signal_received = signo;
+}
+
+/*
+ * write_line - like fputs(), but makes control characters visible and
+ * turns \n into \r\n.
+ */
+static void write_line(char *s)
+{
+ while (*s) {
+ const int c = *s++;
+
+ if ((c == '\n' && fputc_careful('\r', stdout, '^') == EOF)
+ || fputc_careful(c, stdout, '^') == EOF)
+ err(EXIT_FAILURE, _("carefulputc failed"));
+ }
+}
+
+/*
+ * do_write - actually make the connection
+ */
+static void do_write(const struct write_control *ctl)
+{
+ char *login, *pwuid;
+ struct passwd *pwd;
+ time_t now;
+ struct tm *tm;
+ char *host, line[512];
+ struct sigaction sigact;
+
+ /* Determine our login name(s) before the we reopen() stdout */
+ if ((pwd = getpwuid(ctl->src_uid)) != NULL)
+ pwuid = pwd->pw_name;
+ else
+ pwuid = "???";
+ if ((login = getlogin()) == NULL)
+ login = pwuid;
+
+ if ((freopen(ctl->dst_tty_path, "w", stdout)) == NULL)
+ err(EXIT_FAILURE, "%s", ctl->dst_tty_path);
+
+ sigact.sa_handler = signal_handler;
+ sigemptyset(&sigact.sa_mask);
+ sigact.sa_flags = 0;
+ sigaction(SIGINT, &sigact, NULL);
+ sigaction(SIGHUP, &sigact, NULL);
+
+ host = xgethostname();
+ if (!host)
+ host = xstrdup("???");
+
+ now = time((time_t *)NULL);
+ tm = localtime(&now);
+ /* print greeting */
+ printf("\r\n\a\a\a");
+ if (strcmp(login, pwuid))
+ printf(_("Message from %s@%s (as %s) on %s at %02d:%02d ..."),
+ login, host, pwuid, ctl->src_tty_name,
+ tm->tm_hour, tm->tm_min);
+ else
+ printf(_("Message from %s@%s on %s at %02d:%02d ..."),
+ login, host, ctl->src_tty_name,
+ tm->tm_hour, tm->tm_min);
+ free(host);
+ printf("\r\n");
+
+ while (fgets(line, sizeof(line), stdin) != NULL) {
+ if (signal_received)
+ break;
+ write_line(line);
+ }
+ printf("EOF\r\n");
+}
+
+int main(int argc, char **argv)
+{
+ int tty_writeable = 0, c;
+ struct write_control ctl = { 0 };
+
+ static const struct option longopts[] = {
+ {"version", no_argument, NULL, 'V'},
+ {"help", no_argument, NULL, 'h'},
+ {NULL, 0, NULL, 0}
+ };
+
+ setlocale(LC_ALL, "");
+ bindtextdomain(PACKAGE, LOCALEDIR);
+ textdomain(PACKAGE);
+ atexit(close_stdout);
+
+ while ((c = getopt_long(argc, argv, "Vh", longopts, NULL)) != -1)
+ switch (c) {
+ case 'V':
+ printf(UTIL_LINUX_VERSION);
+ return EXIT_SUCCESS;
+ case 'h':
+ usage();
+ default:
+ errtryhelp(EXIT_FAILURE);
+ }
+
+ if (get_terminal_name(&ctl.src_tty_path, &ctl.src_tty_name, NULL) == 0) {
+ /* check that sender has write enabled */
+ if (check_tty(ctl.src_tty_path, &tty_writeable, NULL, 1))
+ exit(EXIT_FAILURE);
+ if (!tty_writeable)
+ errx(EXIT_FAILURE,
+ _("you have write permission turned off"));
+ tty_writeable = 0;
+ } else
+ ctl.src_tty_name = "<no tty>";
+
+ ctl.src_uid = getuid();
+
+ /* check args */
+ switch (argc) {
+ case 2:
+ ctl.dst_login = argv[1];
+ search_utmp(&ctl);
+ do_write(&ctl);
+ break;
+ case 3:
+ ctl.dst_login = argv[1];
+ if (!strncmp(argv[2], "/dev/", 5))
+ ctl.dst_tty_path = xstrdup(argv[2]);
+ else
+ xasprintf(&ctl.dst_tty_path, "/dev/%s", argv[2]);
+ ctl.dst_tty_name = ctl.dst_tty_path + 5;
+ if (check_utmp(&ctl))
+ errx(EXIT_FAILURE,
+ _("%s is not logged in on %s"),
+ ctl.dst_login, ctl.dst_tty_name);
+ if (check_tty(ctl.dst_tty_path, &tty_writeable, NULL, 1))
+ exit(EXIT_FAILURE);
+ if (ctl.src_uid && !tty_writeable)
+ errx(EXIT_FAILURE,
+ _("%s has messages disabled on %s"),
+ ctl.dst_login, ctl.dst_tty_name);
+ do_write(&ctl);
+ break;
+ default:
+ errtryhelp(EXIT_FAILURE);
+ }
+ free(ctl.dst_tty_path);
+ return EXIT_SUCCESS;
+}
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