Messages in this thread | | | Subject | Re: Linux login security approaches | Date | Tue, 8 Dec 1998 16:52:10 -0500 (EST) | From | Scott Wood <> |
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Henrik Olsen wrote: > <long letter about protecting against a trojaned login snipped> > > You have a fundamental flaw in your assumptions, since you don't take into > account the fact that unless the security of the system is very badly > messed up already, if a user is able to substitute his own program for > the normal login/getty, he can also exchange his programs for whatevery > else you add to give better "security".
He's not talking about actually replacing the getty or login binaries, but running a regular unprivileged program that makes itself look exactly like a valid login screen.
When the unsuspecting user tries to log in, it saves the username/password, and tells the user that the login failed. It then exits, and the real getty gets respawned by init. The user assumes he mistyped his password and retries, and it works. The person who ran the program then has the user's password, and the user isn't suspicious at all.
This is why the secure attention key exists; it kills anything on that vt and lets init respawn the real getty. It would be pointless if the real getty had been altered.
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