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login: check that after tty reopen we still work with a terminal 

* the login code assumes that stdin is a terminal, it's better to
   check (by isatty()) that after tty reopen we still have a terminal

 * this patch also removes very old obscure fallback for situations where
   ttyname() returns nothing (then ttyn = "/dev/tty??"). I guess that the
   fake string was originally for utmp records or so. Currently (in last 10
   years...) code requires that the tty name is a real open-able file.
   It means the fake tty name is completely useless.

Reported-by: Yann Droneaud <yann@droneaud.fr>
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2010-01-28 16:25:52 +01:00
parent 453b36147b
commit 8bee984a93
1 changed files with 13 additions and 9 deletions
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22
login-utils/login.c
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@ -200,6 +200,13 @@ opentty(const char * tty) {
exit(1);
}
if (!isatty(fd)) {
close(fd);
syslog(LOG_ERR, _("FATAL: %s is not a terminal"), tty);
sleep(1);
exit(1);
}
flags = fcntl(fd, F_GETFL);
flags &= ~O_NONBLOCK;
fcntl(fd, F_SETFL, flags);
@ -222,7 +229,9 @@ static void
check_ttyname(char *ttyn) {
struct stat statbuf;
if (lstat(ttyn, &statbuf)
if (ttyn == NULL
|| *ttyn == '\0'
|| lstat(ttyn, &statbuf)
|| !S_ISCHR(statbuf.st_mode)
|| (statbuf.st_nlink > 1 && strncmp(ttyn, "/dev/", 5))
|| (access(ttyn, R_OK | W_OK) != 0)) {
@ -378,7 +387,7 @@ main(int argc, char **argv)
int ask, fflag, hflag, pflag, cnt, errsv;
int quietlog, passwd_req;
char *domain, *ttyn;
char tbuf[MAXPATHLEN + 2], tname[sizeof(_PATH_DEV_TTY) + 10];
char tbuf[MAXPATHLEN + 2];
char *termenv;
char *childArgv[10];
char *buff;
@ -495,14 +504,9 @@ main(int argc, char **argv)
for (cnt = getdtablesize(); cnt > 2; cnt--)
close(cnt);
/* note that libc checks that the file descriptor is a terminal, so we don't
* have to call isatty() here */
ttyn = ttyname(0);
if (ttyn == NULL || *ttyn == '\0') {
/* no snprintf required - see definition of tname */
snprintf(tname, sizeof(tname), "%s??", _PATH_DEV_TTY);
ttyn = tname;
}
check_ttyname(ttyn);
if (strncmp(ttyn, "/dev/", 5) == 0)