Date: Sat, 9 Dec 2000 04:22:19 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Joerg Wunsch <joerg_wunsch@interface-business.de> Cc: freebsd-security@FreeBSD.ORG Subject: Re: Please review a change to lock(1) Message-ID: <Pine.BSF.4.21.0012090406120.9818-100000@besplex.bde.org> In-Reply-To: <20001207115835.V4709@B7173150.DeutschePost.de>
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On Thu, 7 Dec 2000, J Wunsch wrote:
> i think everybody's happy when seeing those dead processes running
> around forever, eating up all CPU time -- since they are too stupid to
> notice the tty they're trying to read from is gone. lock(1) is one of
> those culprits, as i just noticed. You can easily prove this by
> ... Please review the following, and make a better
> suggestion if you think i didn't honor all security-related issues
> here. Btw., after the tty is gone, fread() returns NULL but ferror()
> doesn't return 1 (!),
This is correct. read(2) on a dead terminal should return 0/no-error
(i.e., EOF).
and isatty(fileno(stdin)) also still yields 1.
I think isatty() should work. isatty() is implemented using tcgetattr()
which is implented using an ioctl. I'm not sure what dead_ioctl() does.
> So the only way i found was to justify based on errno.
> Index: lock.c
> ===================================================================
> RCS file: /home/ncvs/src/usr.bin/lock/lock.c,v
> retrieving revision 1.8
> diff -u -r1.8 lock.c
> --- lock.c 1999/10/12 13:53:30 1.8
> +++ lock.c 2000/12/07 10:49:28
> @@ -61,6 +61,7 @@
> #include <sys/time.h>
> #include <sys/signal.h>
> #include <err.h>
> +#include <errno.h>
> #include <ctype.h>
> #include <pwd.h>
> #include <sgtty.h>
> @@ -189,7 +190,11 @@
>
> for (;;) {
> (void)printf("Key: ");
> + errno = 0;
> if (!fgets(s, sizeof(s), stdin)) {
> + if (errno == EIO)
> + /* Our terminal is gone; good-bye. */
> + exit(1);
> clearerr(stdin);
> hi();
> continue;
>
This should have no effect :-). It can only work if the VISTTY test in
dead_read() is broken again.
Bruce
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