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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);

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