Linux-kernel mailing list archive 1998-49,: Re: Linux login security approaches

# Re: Linux login security approaches

Clifford Wolf (clifford@clifford.at)
Wed, 9 Dec 1998 08:43:29 +0100 (MET)

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On Tue, 8 Dec 1998, Lenart Gabor wrote:

> And your idea (and even alt-printscreen-k) has got a problem :
> user *CAN* login when he forget to check if it's a trojan (by pressing
> alt-printscreen-k for example). There should be a solution which do not
> allow the begin the login procedure before the key combo !

That's just userlevel stuff. You can add a timeout to the login binary.
As soon as this timeout is reached it will print out a message like

'Login time out -> please press the SAK'

This would give it the same security level as the NT login. Whe pressing
Ctrl-Alt-Del on the NT login screen it gives you the login prompt and
after a while it switches back to the 'Press Ctrl-Alt-Del to login'
message.

One could still write a little program which shows a login prompt and hope
that one user will think that the timeout was not reached till now and
login without pressing the SAK - but NT has the same problem and your
kernel-level solution would have too.

Ad X11: Ctrl-Alt-Backspace terminates the running X Server and xdm starts
a new one. That _exaclty_ the same thing as SAK on a terminal. With SAK
all progs connected to the terminal line will be killed and init starts
a new login prozess. It should be easy to add this timeout stuff to the
xdm login promt too.

happy hacking,

- clifford

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Clifford Wolf (CEO and CTO)
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