Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Sun, 28 Feb 2016 16:21:08 -0500
From: Rich Rumble <richrumble@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Changes needed for cygwin (-fork tty problems)

On Sun, Feb 28, 2016 at 12:08 AM, Solar Designer <solar@...nwall.com> wrote:
> Hi Jim,
>
> Thank you for bringing this in here.
>
> On Sat, Feb 27, 2016 at 10:44:36PM -0600, jfoug wrote:
>> This has been a problem for me, since we have gotten cygwin working with
>> -fork.  When complete (with abort with 'q' or the session completes),
>> the cygwin shell is screwed up (tty is in non-echo mode).   I have lived
>> with this, but recently there are other user posts, where I see them
>> doing 'stty sane' calls after a -fork run (cygwin).
>>
>> So I made a change to john.c
>> https://github.com/magnumripper/JohnTheRipper/commit/81e0cce6303cbea87420ccd70151f0779857b564
>> ,  so that when john exited, it did a system 'stty sane' call to clean
>> things up..   This seemed to work fine.  However, magnum question why this
>> was done, and we had some discussion.  Well to put things simply, we found
>> the 'real' bug on why cygwin was left in a tty non-echo mode.   It was
>> fixed here:
>> https://github.com/magnumripper/JohnTheRipper/commit/5aebb0bc4f94e778be5f95599cd47313604a64a9
>> reverting the other 'hack',, and fixing the real problem.  This fix should
>> be pushed down to john core, since this was code code in tty.   It may be
>> that at some time, the getpid() or some other call in cygwin was not
>> working. Well, if this code IS done in cygwin, then when -fork=x runs exit,
>> the tty is left in a sane state.   This code should really be looked at,
>> and likely the #ifndef __CYGWIN__ define should be removed.
>
> This is indeed a better fix, but not necessarily the right fix.  I think
> the problem isn't even limited to Cygwin, it's just hidden by that code.
I will take anything, I have to "stty echo" after I run fork if I do
it in Cygwin, but I don't have to do that when running john as a
standalone from a cmd prompt.
> I think the real problem is that we call tty_init() after fork()'ing,
> and thus per process, rather than just once in the parent process.
> After all, they're supposed to share the same tty, which we only need to
> initialize once.
>
> The fork()'ing is at the end of john_load(), which is the last thing
> called by john_init().  The tty_init() is in john_run(), which is called
> after john_init().  Maybe we need to move the fork()'ing to right after
> where tty_init() is.  However, there's some other initialization code
> right above it, some of which we might (or might not?) want to run per
> process - e.g., the self-test.  This needs some thinking and testing.
>
> For now, Jim's tty.c fix is fine.
Again I am keen to have my shell working inside the cygwin environment
after running fork!
-rich

Powered by blists - more mailing lists

Your e-mail address:

Powered by Openwall GNU/*/Linux - Powered by OpenVZ