/dev/tty keeps changing permissions..?

[Thomas Park]

...Wow - this is definitely what I'd call going above and beyond the
call of duty.  

Thanks so much for your insights; I'll try this patch and let you know
if it works!  ^_^

Best,
thomas



> -----Original Message-----
> From: Matthew D. Fuller [mailto:fullermd at over-yonder.net] 
> Sent: Monday, June 09, 2003 10:48
> To: Thomas Park
> Cc: freebsd-questions at FreeBSD.ORG
> Subject: Re: /dev/tty keeps changing permissions..?
> 
> 
> On Mon, Jun 09, 2003 at 09:59:18AM -0700 I heard the voice of
> Thomas Park, and lo! it spake thus:
> > 
> > By God, I see that you're right!
> 
> This is what I've been telling you    8-}
> 
> 
> > I think the problem arises when I su into another account 
> and try to ssh
> > outbound.  Which should arguably be possible without having 
> to do arcane
> > manipulations to the tty device, IMHO..?
> 
> Well, it should be, yah.
> 
> 
> Here's what's happening (after a quick foray into the source):
> 
> In the routine (readpassphrase(), readpassphrase.c) where it 
> reads in a
> password, it tries to open() /dev/tty, and if THAT fails, then use
> stdin/stdout:
> 
> ----
>     if ((input = output = open(_PATH_TTY, O_RDWR)) == -1) {
>         if (flags & RPP_REQUIRE_TTY) {
>             errno = ENOTTY;
>             return(NULL);
>         }
>         input = STDIN_FILENO;
>         output = STDERR_FILENO;
>     }
> ----
> 
> So, if it can't open /dev/tty (which it can't), and the 
> RPP_REQUIRE_TTY
> flag is set, then it returns NULL here.  From what I can see, 
> that gets
> passed up, so it ends up sending nothing as the password, which is why
> you see it looping a few times there like:
> 
> > debug1: Next authentication method: password
> > debug2: we sent a password packet, wait for reply
> > debug1: Authentications that can continue:
> > publickey,password,keyboard-interactive
> > Permission denied, please try again.
> 
> 
> So, why is that flag set?  Let's look upward:
> 
> readpassphrase() is called from read_passphrase() 
> (readpass.c), just to
> confuse you with naming.  That sets the RPP_REQUIRE_TTY flag, 
> unless IT
> is passed RP_ALLOW_STDIN.  read_passphrase() is called in 
> this case from
> userauth_passwd (sshconnect2.c), with the flags set to 0:
> ----
> password = read_passphrase(prompt, 0);
> ----
> 
> So, according to my reading, if you change that '0' to 
> 'RP_ALLOW_STDIN'
> there (line 458 in sshconnect2.c from the openssh-portable/ 
> port, after
> 'make patch'), then make/make install it, you SHOULD be able 
> to use that
> ssh(1) binary, and get out just fine, I think.
> 
> 
> You can probably patch it in the base source tree too (it's in
> src/crypto/openssh/), then 'make clean objdir all install' in
> src/secure/usr.bin/ssh/ to install it.
> 
> 
> -- 
> Matthew Fuller     (MF4839)   |  fullermd at over-yonder.net
> Systems/Network Administrator |  http://www.over-yonder.net/~fullermd/
> 
> "The only reason I'm burning my candle at both ends, is because I
>       haven't figured out how to light the middle yet"
>