1 files changed, 292 insertions, 0 deletions
diff --git a/usr.bin/write/write.c b/usr.bin/write/write.c
new file mode 100644
index 0000000..945e92f
--- /dev/null
+++ b/usr.bin/write/write.c
@@ -0,0 +1,292 @@
+/*	$NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $	*/
+
+/*
+ * 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. 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.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
+ The Regents of the University of California.  All rights reserved.");
+#endif /* not lint */
+
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)write.c	8.2 (Berkeley) 4/27/95";
+#else
+__RCSID("$NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $");
+#endif
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <time.h>
+#include <fcntl.h>
+#include <paths.h>
+#include <pwd.h>
+#include <unistd.h>
+#include <err.h>
+#include <errno.h>
+
+#include "utmpentry.h"
+#include "term_chk.h"
+
+__dead static void done(int);
+static void do_write(int, const char *, const uid_t);
+static void wr_fputs(char *);
+static int search_utmp(char *, char *, uid_t, gid_t);
+static int utmp_chk(const char *, const char *);
+
+int
+main(int argc, char **argv)
+{
+	time_t atime;
+	uid_t myuid, uid;
+	int msgsok, ttyfd;
+	char *mytty;
+	gid_t saved_egid = getegid();
+
+	if (setegid(getgid()) == -1)
+		err(1, "setegid");
+	myuid = getuid();
+	ttyfd = -1;
+
+	mytty = check_sender(&atime, myuid, saved_egid);
+
+	/* check args */
+	switch (argc) {
+	case 2:
+		ttyfd = search_utmp(argv[1], mytty, myuid, saved_egid);
+		break;
+	case 3:
+		if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
+			argv[2] += strlen(_PATH_DEV);
+		if (uid_from_user(argv[1], &uid) == -1)
+			errx(1, "%s: unknown user", argv[1]);
+		if (utmp_chk(argv[1], argv[2]))
+			errx(1, "%s is not logged in on %s",
+			    argv[1], argv[2]);
+		ttyfd = term_chk(uid, argv[2], &msgsok, &atime, 0, saved_egid);
+		if (ttyfd == -1)
+			err(1, "%s%s", _PATH_DEV, argv[2]);
+		if (myuid && !msgsok)
+			errx(1, "%s has messages disabled on %s",
+			    argv[1], argv[2]);
+		break;
+	default:
+		(void)fprintf(stderr, "usage: write user [tty]\n");
+		exit(1);
+	}
+	if (setgid(getgid()) == -1)
+		err(1, "setgid");
+	do_write(ttyfd, mytty, myuid);
+	done(0);
+	/* NOTREACHED */
+#ifdef __GNUC__
+	return (0);
+#endif
+}
+
+/*
+ * utmp_chk - checks that the given user is actually logged in on
+ *     the given tty
+ */
+static int
+utmp_chk(const char *user, const char *tty)
+{
+	struct utmpentry *ep;
+
+	(void)getutentries(NULL, &ep);
+
+	for (; ep; ep = ep->next)
+		if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0)
+			return(0);
+	return(1);
+}
+
+/*
+ * 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 int
+search_utmp(char *user, char *mytty, uid_t myuid, gid_t saved_egid)
+{
+	char tty[MAXPATHLEN];
+	time_t bestatime, atime;
+	int nloggedttys, nttys, msgsok, user_is_me;
+	struct utmpentry *ep;
+	int fd, nfd;
+	uid_t uid;
+
+	if (uid_from_user(user, &uid) == -1)
+		errx(1, "%s: unknown user", user);
+
+	(void)getutentries(NULL, &ep);
+
+	nloggedttys = nttys = 0;
+	bestatime = 0;
+	user_is_me = 0;
+	fd = -1;
+	for (; ep; ep = ep->next)
+		if (strcmp(user, ep->name) == 0) {
+			++nloggedttys;
+			nfd = term_chk(uid, ep->line, &msgsok, &atime, 0,
+			    saved_egid);
+			if (nfd == -1)
+				continue;	/* bad term? skip */
+			if (myuid && !msgsok) {
+				close(nfd);
+				continue;	/* skip ttys with msgs off */
+			}
+			if (strcmp(ep->line, mytty) == 0) {
+				user_is_me = 1;
+				if (fd == -1)
+					fd = nfd;
+				else
+					close(nfd);
+				continue;	/* don't write to yourself */
+			}
+			++nttys;
+			if (atime > bestatime) {
+				bestatime = atime;
+				(void)strlcpy(tty, ep->line, sizeof(tty));
+				close(fd);
+				fd = nfd;
+			} else
+				close(nfd);
+		}
+
+	if (nloggedttys == 0)
+		errx(1, "%s is not logged in", user);
+	if (nttys == 0) {
+		if (user_is_me)			/* ok, so write to yourself! */
+			return fd;
+		errx(1, "%s has messages disabled", user);
+	} else if (nttys > 1)
+		warnx("%s is logged in more than once; writing to %s",
+		    user, tty);
+	return fd;
+}
+
+/*
+ * do_write - actually make the connection
+ */
+static void
+do_write(int ttyfd, const char *mytty, const uid_t myuid)
+{
+	const char *login;
+	char *nows;
+	struct passwd *pwd;
+	time_t now;
+	char host[MAXHOSTNAMELEN + 1], line[512];
+
+	/* Determine our login name before we re-open stdout */
+	if ((login = getlogin()) == NULL) {
+		if ((pwd = getpwuid(myuid)) != NULL)
+			login = pwd->pw_name;
+		else	login = "???";
+	}
+
+	if (dup2(ttyfd, STDOUT_FILENO) == -1)
+		err(1, "dup2");
+
+	(void)signal(SIGINT, done);
+	(void)signal(SIGHUP, done);
+	(void)close(ttyfd);
+
+	/* print greeting */
+	if (gethostname(host, sizeof(host)) < 0)
+		(void)strlcpy(host, "???", sizeof(host));
+	else
+		host[sizeof(host) - 1] = '\0';
+	now = time(NULL);
+	nows = ctime(&now);
+	nows[16] = '\0';
+	(void)printf("\r\n\a\a\aMessage from %s@%s on %s at %s ...\r\n",
+	    login, host, mytty, nows + 11);
+
+	while (fgets(line, sizeof(line), stdin) != NULL)
+		wr_fputs(line);
+}
+
+/*
+ * done - cleanup and exit
+ */
+static void
+done(int signo)
+{
+
+	(void)write(STDOUT_FILENO, "EOF\r\n", sizeof("EOF\r\n") - 1);
+	if (signo == 0)
+		exit(0);
+	else
+		_exit(0);
+}
+
+/*
+ * wr_fputs - like fputs(), but makes control characters visible and
+ *     turns \n into \r\n
+ */
+static void
+wr_fputs(char *s)
+{
+	unsigned char c;
+
+#define	PUTC(c)	if (putchar(c) == EOF) goto err;
+
+	for (; *s != '\0'; ++s) {
+		c = toascii(*s);
+		if (c == '\n') {
+			PUTC('\r');
+		} else if (!isprint(c) && !isspace(c) && c != '\a') {
+			PUTC('^');
+			c ^= 0x40;	/* DEL to ?, others to alpha */
+		}
+		PUTC(c);
+	}
+	return;
+
+err:	err(1, NULL);
+#undef PUTC
+}