[Full-Disclosure] RE: NetWare Screensaver Authentication Bypass From The Local Console
geoff at cadzow.com.au
Tue Dec 14 22:32:37 GMT 2004
Unpublished Immutable Laws of Security
Number 16: "No matter what the security fault, how exploitable it is or what the workarounds are, there will ALWAYS be someone somewhere who will argue strenuously that it's not a fault, doesn't need fixing and couldn't be exploited, and furthermore they will seem to be taking it personally."
Number 16(a): "Usually this will be Microsoft."
"In order for a hacker to exploit this, they would need to (and you're not going to believe this): (1) Convince someone to click a link in an email message, AND (unbelievable) (2) view a web page with their web browser. See, we told you how incredibly stupid this so-called exploit is."
We all know physical security is important, but there's a huge difference between walking up to a machine and gaining access with a few keystrokes and ripping the hard disk out and examining in a lab offsite. The former is very easy and the latter is very hard. It should NOT be possible to compromise a machine by hacking the screensaver.
From: Brad Bendily [mailto:brad at selu.edu]
Sent: Wednesday, 15 December 2004 03:31
To: Adam Gray
Cc: full-disclosure at lists.netsys.com; bugtraq at securityfocus.com;
vulnwatch at vulnwatch.org
Subject: Re: NetWare Screensaver Authentication Bypass From The Local
As we all know security comes in layers. The only way this exploit will
work is if someone is standing at the server's console. In this way
all servers are subject to vulnerability and I have discovered this
method of hacking servers. Ok, not really. But I can tell you that if I
have access to the server console then I can get access to the box.
This vulnerability is not new, I had to legitimately hack the password
for a couple of my NetWare servers and I did it 3-4 years ago using
this same hack. Preferrably I would rather Novell NOT fix this. It's
a great "just in case" tool.
I think this is a waste of bandwidth.
On Sun, 12 Dec 2004, Adam Gray wrote:
> Novacoast Security Advisory
> Novell Netware 5/5.1/6.0/6.5 Vulnerability
> Novacoast has discovered a vulnerability in the Novell NetWare Operating
> System screen saver software. The vulnerability allows a local attacker
> to bypass authentication and access the system console.
> The Novell Operating System uses the screen saver nlm with lock enabled
> to protect access to the console. When the screen saver is locked only a
> user in the e-directory tree with supervisor rights to the server object
> has the ability to unlock it. It is possible to bypass this
> authentication scheme by entering the debugger within NetWare while the
> screensaver is running, kill the screensaver process, and resume the
> operating system without the screen saver or the access control still
> Affected Version:
> Novell NetWare 5.1
> Novell Netware 6
> Novell NetWare 6.5
> with the screensaver nlm running and in enable lock mode press alt shift
> shift esc. Find the screen saver process in memory. Kill it using the
> debugger. If you are not sure how to use the NetWare debugger then just
> kill the server with the q key and restart it without the autoexec.ncf
> running (server -na) edit the autoexec.ncf to keep the screensaver from
> running in the future and restart the server normally. The screen saver
> will not start again.
> Recommended Solution:
> Install the Bordermanager ICSA Compliance kit
> They put the screensaver fix into that patch
> This bug has been submitted to, acknowledged by, and a fix has been
> created and included with the Bordermanager ICSA Compliance toolkit.
> Additional information can be found at the following location:
> Novacoast accepts no liability or responsibility for the
> content of this report, or for the consequences of any
> actions taken on the basis of the information provided
> within. Dissemination of this information is granted
> provided it is presented in its entirety. Modifications
> may not be made without the explicit permission of
> Adam Gray
> Novacoast, Inc.
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