Bugtraq mailing list archives
Re: OpenSSH/PAM timing attack allows remote users identification
From: Nicolas Couture <nc () stormvault net>
Date: 01 May 2003 14:15:38 -0400
On Thu, 2003-05-01 at 05:12, Ethan Benson wrote:
On Wed, Apr 30, 2003 at 04:34:27PM +0200, Marco Ivaldi wrote:root@voodoo:~# 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@voodoo:~# 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:
This is not only true in association with the ssh daemon's configuration. Even if root login is allowed in it's configuration but pam disallow root logins, it'll result in a 2 seconds delay on bad password and reject instantly good password instead of login. The problem is not in the handling of PermitRootLogin but in the handling of login in sshd, adding a 2 seconds delay before login or removing the 2 seconds delay on bad login before sending an error would fix the problem.
$ ssh root@host root@host's password: <- arbitrary (non-null) string [2 secs delay] Permission denied, please try again.a $ ssh root@host root@host'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 verified this on redhat 8, openssh-3.4p1-2(rpm) and sshd is acting just like you described it.
Current thread:
- Re: OpenSSH/PAM timing attack allows remote users identification Ethan Benson (May 01)
- Re: OpenSSH/PAM timing attack allows remote users identification Nicolas Couture (May 02)
- Re: OpenSSH/PAM timing attack allows remote users identification Marco Ivaldi (May 05)
- <Possible follow-ups>
- Re: OpenSSH/PAM timing attack allows remote users identification Nicolas Couture (May 01)
- Re: OpenSSH/PAM timing attack allows remote users identification ilja van sprundel (May 02)
- Re: OpenSSH/PAM timing attack allows remote users identification Thilo Schulz (May 02)
- Re: OpenSSH/PAM timing attack allows remote users identification Marco Ivaldi (May 02)
- Re: OpenSSH/PAM timing attack allows remote users identification Michael Shigorin (May 02)
- Re: OpenSSH/PAM timing attack allows remote users identification Marco Ivaldi (May 02)
- Re: OpenSSH/PAM timing attack allows remote users identification Karl-Heinz Haag (May 02)