Index: usr.bin/write/write.c
===================================================================
--- usr.bin/write/write.c
+++ usr.bin/write/write.c
@@ -46,18 +46,23 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/capsicum.h>
+#include <sys/file.h>
 #include <sys/signal.h>
 #include <sys/stat.h>
-#include <sys/file.h>
 #include <sys/time.h>
+
 #include <ctype.h>
 #include <err.h>
+#include <errno.h>
 #include <locale.h>
+#include <nl_types.h>
 #include <paths.h>
 #include <pwd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <unistd.h>
 #include <utmpx.h>
 #include <wchar.h>
@@ -71,9 +76,12 @@
 void search_utmp(char *, char *, char *, uid_t);
 int utmp_chk(char *, char *);
 
+static int devfd;
+
 int
 main(int argc, char **argv)
 {
+	cap_rights_t rights;
 	time_t atime;
 	uid_t myuid;
 	int msgsok, myttyfd;
@@ -81,6 +89,37 @@
 
 	(void)setlocale(LC_CTYPE, "");
 
+	devfd = open(_PATH_DEV, O_RDONLY);
+	if (devfd < 0)
+		err(1, "open(/dev)");
+	cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_LOOKUP,
+	    CAP_PWRITE);
+	if (cap_rights_limit(devfd, &rights) < 0 && errno != ENOSYS)
+		err(1, "can't limit devfd rights");
+
+	cap_rights_init(&rights, CAP_FSTAT, CAP_IOCTL, CAP_READ, CAP_WRITE);
+	if ((cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS) ||
+	    (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS) ||
+	    (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS))
+		err(1, "can't limit stdio rights");
+
+	/*
+	 * Cache NLS data, for strerror, for err(3), before entering capability
+	 * mode.
+	 */
+	(void)catopen("libc", NL_CAT_LOCALE);
+
+	/*
+	 * Cache UTX database fds.
+	 */
+	setutxent();
+
+	/* Cache timezone. */
+	tzset();
+
+	if (cap_enter() < 0 && errno != ENOSYS)
+		err(1, "cap_enter");
+
 	while (getopt(argc, argv, "") != -1)
 		usage();
 	argc -= optind;
@@ -222,12 +261,10 @@
 term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
 {
 	struct stat s;
-	char path[MAXPATHLEN];
 
-	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
-	if (stat(path, &s) < 0) {
+	if (fstatat(devfd, tty, &s, 0) < 0) {
 		if (showerror)
-			warn("%s", path);
+			warn("%s%s", _PATH_DEV, tty);
 		return(1);
 	}
 	*msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0;	/* group write bit */
@@ -245,8 +282,9 @@
 	char *nows;
 	struct passwd *pwd;
 	time_t now;
-	char path[MAXPATHLEN], host[MAXHOSTNAMELEN];
+	char host[MAXHOSTNAMELEN];
 	wchar_t line[512];
+	int fd;
 
 	/* Determine our login name before we reopen() stdout */
 	if ((login = getlogin()) == NULL) {
@@ -256,9 +294,13 @@
 			login = "???";
 	}
 
-	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
-	if ((freopen(path, "w", stdout)) == NULL)
-		err(1, "%s", path);
+	fd = openat(devfd, tty, O_WRONLY);
+	if (fd < 0)
+		err(1, "openat(%s%s)", _PATH_DEV, tty);
+	fclose(stdout);
+	stdout = fdopen(fd, "w");
+	if (stdout == NULL)
+		err(1, "%s%s", _PATH_DEV, tty);
 
 	(void)signal(SIGINT, done);
 	(void)signal(SIGHUP, done);