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Index: head/usr.bin/write/write.c
===================================================================
--- head/usr.bin/write/write.c
+++ head/usr.bin/write/write.c
@@ -46,12 +46,16 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
+#include <sys/capsicum.h>
+#include <sys/filio.h>
#include <sys/signal.h>
#include <sys/stat.h>
-#include <sys/file.h>
#include <sys/time.h>
+
+#include <capsicum_helpers.h>
#include <ctype.h>
#include <err.h>
+#include <errno.h>
#include <locale.h>
#include <paths.h>
#include <pwd.h>
@@ -64,23 +68,76 @@
#include <wctype.h>
void done(int);
-void do_write(char *, char *, uid_t);
+void do_write(int, char *, char *, const char *);
static void usage(void);
-int term_chk(char *, int *, time_t *, int);
+int term_chk(int, char *, int *, time_t *, int);
void wr_fputs(wchar_t *s);
-void search_utmp(char *, char *, char *, uid_t);
+void search_utmp(int, char *, char *, char *, uid_t);
int utmp_chk(char *, char *);
int
main(int argc, char **argv)
{
+ unsigned long cmds[] = { TIOCGETA, TIOCGWINSZ, FIODGNAME };
+ cap_rights_t rights;
+ struct passwd *pwd;
time_t atime;
uid_t myuid;
int msgsok, myttyfd;
char tty[MAXPATHLEN], *mytty;
+ const char *login;
+ int devfd;
(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");
+
+ /*
+ * Can't use capsicum helpers here because we need the additional
+ * FIODGNAME ioctl.
+ */
+ cap_rights_init(&rights, CAP_FCNTL, 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) ||
+ (cap_ioctls_limit(STDIN_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) ||
+ (cap_ioctls_limit(STDOUT_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) ||
+ (cap_ioctls_limit(STDERR_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) ||
+ (cap_fcntls_limit(STDIN_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) ||
+ (cap_fcntls_limit(STDOUT_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) ||
+ (cap_fcntls_limit(STDERR_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS))
+ err(1, "can't limit stdio rights");
+
+ caph_cache_catpages();
+ caph_cache_tzdata();
+
+ /*
+ * Cache UTX database fds.
+ */
+ setutxent();
+
+ /*
+ * Determine our login name before we reopen() stdout
+ * and before entering capability sandbox.
+ */
+ myuid = getuid();
+ if ((login = getlogin()) == NULL) {
+ if ((pwd = getpwuid(myuid)))
+ login = pwd->pw_name;
+ else
+ login = "???";
+ }
+
+ if (cap_enter() < 0 && errno != ENOSYS)
+ err(1, "cap_enter");
+
while (getopt(argc, argv, "") != -1)
usage();
argc -= optind;
@@ -99,29 +156,27 @@
errx(1, "can't find your tty's name");
if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
mytty += strlen(_PATH_DEV);
- if (term_chk(mytty, &msgsok, &atime, 1))
+ if (term_chk(devfd, mytty, &msgsok, &atime, 1))
exit(1);
if (!msgsok)
errx(1, "you have write permission turned off");
- myuid = getuid();
-
/* check args */
switch (argc) {
case 1:
- search_utmp(argv[0], tty, mytty, myuid);
- do_write(tty, mytty, myuid);
+ search_utmp(devfd, argv[0], tty, mytty, myuid);
+ do_write(devfd, tty, mytty, login);
break;
case 2:
if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV)))
argv[1] += strlen(_PATH_DEV);
if (utmp_chk(argv[0], argv[1]))
errx(1, "%s is not logged in on %s", argv[0], argv[1]);
- if (term_chk(argv[1], &msgsok, &atime, 1))
+ if (term_chk(devfd, argv[1], &msgsok, &atime, 1))
exit(1);
if (myuid && !msgsok)
errx(1, "%s has messages disabled on %s", argv[0], argv[1]);
- do_write(argv[1], mytty, myuid);
+ do_write(devfd, argv[1], mytty, login);
break;
default:
usage();
@@ -170,7 +225,7 @@
* writing from, unless that's the only terminal with messages enabled.
*/
void
-search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
+search_utmp(int devfd, char *user, char *tty, char *mytty, uid_t myuid)
{
struct utmpx *u;
time_t bestatime, atime;
@@ -185,7 +240,7 @@
if (u->ut_type == USER_PROCESS &&
strcmp(user, u->ut_user) == 0) {
++nloggedttys;
- if (term_chk(u->ut_line, &msgsok, &atime, 0))
+ if (term_chk(devfd, u->ut_line, &msgsok, &atime, 0))
continue; /* bad term? skip */
if (myuid && !msgsok)
continue; /* skip ttys with msgs off */
@@ -219,15 +274,13 @@
* and the access time
*/
int
-term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
+term_chk(int devfd, 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 */
@@ -239,26 +292,21 @@
* do_write - actually make the connection
*/
void
-do_write(char *tty, char *mytty, uid_t myuid)
+do_write(int devfd, char *tty, char *mytty, const char *login)
{
- const char *login;
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) {
- if ((pwd = getpwuid(myuid)))
- login = pwd->pw_name;
- else
- 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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