Date: Mon, 9 Jun 2003 12:48:10 -0500 From: "Matthew D. Fuller" <fullermd@over-yonder.net> To: Thomas Park <tpark@drivespeed.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: /dev/tty keeps changing permissions..? Message-ID: <20030609174810.GL28798@over-yonder.net> In-Reply-To: <001101c32ea8$78544d40$11640a0a@titanium> References: <20030609164829.GK28798@over-yonder.net> <001101c32ea8$78544d40$11640a0a@titanium>
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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@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"
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