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Message-ID: <20150530054446.GA18797@openwall.com>
Date: Sat, 30 May 2015 08:44:46 +0300
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: [john-core] Getting John's stdout unbuffered for Johnny
On Wed, May 27, 2015 at 09:56:23PM +0200, magnum wrote:
> On 2015-05-27 20:57, Shinnok wrote:
> >NB: What I find weird about JtR is that by default, it treats input
> >as a tty(and if not tty then defaults to reading password candidates)
>
> As far as I'm aware it treats input as a TTY if it is indeed a TTY,
> nothing weird about that. It doesn't default to reading candidates,
> there's an option for that.
I am with magnum on this.
> I haven't ever experienced any problems with stdout buffering, perhaps
> it's somewhat different under Windows?
No, what Shinnok describes about stdout buffering is actually the same
on Unix. By default, libc has stdout line buffered when outputting to a
tty and fully buffered when not.
http://www.pixelbeat.org/programming/stdio_buffering/
http://stackoverflow.com/questions/13932932/why-does-stdout-need-explicit-flushing-when-redirected-to-file
> >and output as standard buffered stdout. This discussion will probably
> >evolve towards trying to be more flexible on that front so that
> >wrappers(like Johnny) can properly communicate with it.
>
> My general feeling about this is you shouldn't try to use stdin/stdout
> for things they're not designed to do. If we're about to change JtR
> code, why not add a proper interface of some sort, intead of fflush
> bodges? How hard would that be? (that is a sincere question, not irony).
This makes sense.
However, I don't mind changing stdout to always be line-buffered. This
means JtR will run slower when someone redirects its stdout to a disk
file, but that's not typical and when someone does it for some weird
reason they quite possibly actually want it to be merely line-buffered.
I think setting it to unbuffered is overkill.
Shinnok, just let me know what the Johnny team decides on this. If you
ask me to, I think I'll add a call to:
setvbuf(stdout, NULL, _IOLBF, 0);
to john.c: john_init().
It is important to keep stdout with its default buffering when john is
invoked via one of the un* symlinks, since they're commonly used with
stdout pointing at a disk file.
Alexander
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