bugtraq - Re: OpenSSH/PAM timing attack allows remote users identification

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Date: Thu, 1 May 2003 01:12:42 -0800
From: Ethan Benson <erbenson@...ska.net>
To: Marco Ivaldi <raptor@...iaservice.net>
Subject: Re: OpenSSH/PAM timing attack allows remote users identification

On Wed, Apr 30, 2003 at 04:34:27PM +0200, Marco Ivaldi wrote:
> root@...doo:~# ssh [valid_user]@lab.mediaservice.net
> [valid_user]@lab.mediaservice.net's password:	<- arbitrary (non-null) string
> [2 secs delay]
> Permission denied, please try again.
> 
> root@...doo:~# ssh [no_such_user]@lab.mediaservice.net
> [no_such_user]@lab.mediaservice.net's password:	<- arbitrary (non-null) string
> [no delay]
> Permission denied, please try again.

ive noticed something similar in its handling of PermitRootLogin, if
this option is set to `no' you get the following behavior:

$ ssh root@...t
root@...t's password: <- arbitrary (non-null) string
[2 secs delay]
Permission denied, please try again.a

$ ssh root@...t
root@...t's password:  <- correct root password
[no delay]
Permission denied, please try again.

i haven't checked the current version to see if this is still true. 

i think you also will get no delay if DenyUsers or so is in use for
accounts your testing.

-- 
Ethan Benson
http://www.alaska.net/~erbenson/

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