That Was The First Security Fix For Hyper-V

By the way, when I posted about the security fix for Hyper-V last night, I should have mentioned that it was the first such on for the hypervisor itself in the 18 or so months since it RTM’d in Windows Server 2008.  Not bad!

There’s some debate about how important it is.  Basically, if someone can log into a VM running on a host and has admin rights in that VM, then they can run a DOS attack on the hypervisor on that host.  Most scenarios will probably be safe enough.

I would guess that most companies that deployed virtualisation are running it for internal server virtualisation purposes.  The people who log into those machines are trusted administrators and extremely unlikely to go postal.

Funny phrase that.  I once worked with a guy who was the son of post employees and he didn’t know what it meant.  He got highly offended!

Virtualised “terminal services”, or to put it correctly using the current phrase, Remote Desktop Services Session Hosts *gasps for air*,  will likely only have users logging in with limited rights so they will be safe.

Some VDI implementations will have users logging in with administrative rights.  That means that they are vulnerable.  And those operating cloud services (server hosting) based on Hyper-V are vulnerable.  Those operating private clouds with large numbers of unknown administrators also face a risk.  It’s inevitable that someone will write an attack script/program for this.

I fall into one of those vulnerable scenarios so our normal patching process was put to one side today.  The update was approved in WSUS for all groups, not just our testing group.  Using Operations Manager and VMM we put clustered hosts into maintenance mode.  This allows VMM to use Live Migration to move VM’s from the host that will be worked on to another host.  If you don’t have VMM then you need to Live Migrate each of the VM’s, one by one.  OpsMgr maintenance mode prevents false alarms.  This is done in turn with all hosts in the cluster.  No customers have down time and the security fix gets deployed.  Nice and tidy.

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KB977894: VERY Important Hyper-V Security Update

One of the patches released by Microsoft is a critical security fix for Hyper-V.  It affects all installation types on both Windows Server 2008 and Windows Server 2008 R2.

“This security update resolves a privately reported vulnerability in Windows Server 2008 Hyper-V and Windows Server 2008 R2 Hyper-V. The vulnerability could allow denial of service if a malformed sequence of machine instructions is run by an authenticated user in one of the guest virtual machines hosted by the Hyper-V server. An attacker must have valid logon credentials and be able to log on locally into a guest virtual machine to exploit this vulnerability. The vulnerability could not be exploited remotely or by anonymous users”.

Basically, if a person has rights to log into a VM hosted on a vulnerable server, then they could cause a Denial-of-Service (DOS) attack. 

The update is supplied via Windows Update.  Check your updates either on the host, Configuration Manager, WSUS or whatever your update service is.

I’ll be pushing it out first thing tomorrow morning.  Live Migration with VMM 2008 R2 maintenance mode makes it really easy to update clustered hosts.  Standalone hosts will have some downtime for their VM’s.  Most VM’s will be set up to go into a saved state when the host shuts down.  That limits interruption to them in a way.

Worried About Hyper-V Security or Reliability? Don’t!

I’ve previously mentioned that Windows Server 2008 Hyper-V is secure.  It was designed from the ground up to be secure.  The German Federal government certainly thought so.  I’ve had excellent experiences.  But why take my word?

There’s one country out there that takes security more seriously than any other.  I’m not talking about the USA, the UK, China or France, and certainly not Ireland.  It’s Israel.  And what part of the nation do you think would value reliability more than anything else?  Yeap, the military.  The Israeli Defence Forces (IDF) just spent a bunch of money to deploy a Hyper-V cluster.  If it’s secure and reliable enough for them then it should be for you too.

Microsoft – Cloud Computing Security Considerations

One or two people out there are talking about something called Cloud Computing.  I doubt it’s important 😉

Microsoft published a document on cloud computing security:

“A high-level discussion of the fundamental challenges and benefits of cloud computing security, plus some of the questions that cloud service providers and organisations using cloud services need to consider when evaluating a new move, or expansion of existing services, to the cloud. This document presumes that the reader is familiar with the core concepts of cloud computing and basic principles of cloud security. It is not the goal of this paper to provide all the answers to the questions of security in the cloud or to provide an exhaustive framework for cloud security“.

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Setting Up Public Key Based SSH Access To SLES

I needed to set up key based, rather than password based, access to SUSE Linux Enterprise Server.  It’s more secure because it uses a public/private key pair rather than a password.  The user’s private key is stored on the client.  The private key for the user is stored on the Linux machines.  When they connect using an SSH client there is no need to enter a password.  You can optionally (and it’s recommended) store a passphrase with the private key so that it cannot be used without knowing the private key.

The solutions starts at the client.  I normally used Putty but I couldn’t get it to work properly with this type of solution.  Instead I turned to Poderosa.  Using it I create a public and private key pair.  From there I saved the public key in OpenSSH format and the private key.

Save the private key somewhere safe, e.g. a backed up location on your PC or on your home drive on a file server.  Make sure the location is secure.

Now you need to copy the text of the public key.  Note that it is a single line.  Log into the SLES machine and browse to your home directory.  For example:

  • For root browse to ~/.ssh
  • For any other user browse to /home/<username>/.ssh

Use a text editor (like vi) to create a file called authorized_keys in that home directory.  Copy the text from your private key and paste it into the file.  Save it.

You now need to enable SSH to allow logons using keys.  The configuration for SSH is stored in a text file: /etc/ssh/sshd_config.  Edit that and you’ll have a few entries to modify.  We’ll start by allowing public keys to be used for authentication.  This is done by setting PubkeyAuthentication to “yes”.  I had to remove the # (comment/remark) symbol from the start of the line.

PubkeyAuthentication yes

I restarted the SSH daemon or service by running rcsshd restart.  That’s required to load the new settings for authentication. 

I configured the SSH client to log in as my user to this server with my private copy of the key.  I started the connection and I was logged in without using a password.  It authenticated me using the private key (and the passphrase for the key if you set it).

Now it is possible to disable log via SSH on using passwords.  You’ll do this to force people to us their private key instead of a weaker password that could be subject to brute force attacks.

The first is to change PasswordAuthentication to have a value of “no”.  You may need to remove the comment/remark symbol of # from the start of the line.  I also found that I had to set UsePam to a value of “no”.  That meant these two lines were in the file in different locations:

PasswordAuthentication no

UsePam no

Again I restarted SSH using rcsshd restart.  Now I tested two things:

  1. I tried to login using Putty and my username and password.  The initial connection failed.
  2. I logged in using my private key.  That worked.

Perfect.  Now I can use SSH to log into the Linux box without the worry of weak passwords being used by users on the machine.  They are forced into using stronger public/private key pairs.  And I can sleep safe knowing that the machine is not vulnerable to brute force password attacks.

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The BitLocker “Crack”

Microsoft releases a new operating system and everyone wants to make a headline.  It happened 2 years ago and it’s happening again.

This time some people are claiming they’ve broken BitLocker.  Their attack vectors work two ways:

  1. Attack the machine while it’s running and a user is logged in.  That way they can scan the RAM for cached BitLocker keys.  If you have the machine while it’s logged in then you have access to the data.  Pointless.
  2. Gain access to the machine to attack the hardware.  Install something to capture the PIN as the machine boots up.  Then steal the machine or gain access to it again and use the captured data to access the hard disk data.

That last one would be a threat, admittedly.  It’s a far fetched one for laptops but it feasible.  I’m guessing that BitLocker with a Smart Card would beat that one assuming the smart card is not kept with the laptop.  We know how lazy people can be so – eek.  And potentially the latter approach is one to attack on-premises physical servers. 

I guess we’ll see.

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WSUS: The Update Could Not Be Found

I was re-installing the WSUS role on our security server (W2008 R2) today and hit this error as soon as the installation started:

“The update could not be found”.

It’s a bit of a weird one for a role installation.  I hadn’t the foggiest so I did a quick search and found the solution:

  • Delete the “WindowsUpdate” key from the registry at HKLMSoftwarePoliciesMicrosoftWindows.  I’d recommend you export this to a .reg file to be safe.
  • Restart the Windows Update service.

Now you can go ahead and install WSUS.

The problem and fix applies to previous versions of Windows.  The issue is that the installer is checking Windows Updates but it has found a circular reference.  You’ve uninstalled WSUS from the server and it is configured to update from itself.  How can it?  Make sure you do the install before GPO applies those settings again during an automatic refresh.

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Microsoft Responds to Black Screen of Death Claims

It was widely reported that a UK company was claiming that one of last weeks security updates by Microsoft was causing a “black screen of death” where Explorer would show nothing when you logged in.  Microsoft responded overnight:

“While these reports weren’t brought to us directly, from our research into them, it appears they’re saying that our security updates are making permission changes in the registry to the value for the HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogonShell  key.

We’ve conducted a comprehensive review of the November Security Updates, the Windows Malicious Software Removal Tool, and the non-security updates we released through Windows Update in November. That investigation has shown that none of these updates make any changes to the permissions in the registry. Thus, we don’t believe the updates are related to the “black screen” behavior described in these reports.

We’ve also checked with our worldwide Customer Service and Support organization, and they’ve told us they’re not seeing “black screen” behavior as a broad customer issue. Because these reports were not brought to us directly, it’s impossible to know conclusively what might be causing a “black screen” in those limited instances where customers have seen it”.

There you have it.  Prevx didn’t do the responsible thing, i.e. contact Microsoft directly, and instead decided to generate some publicity for themselves.  Their claims have been refuted so this leads me to wonder: are these developers more of the same who don’t comply with documented standards and just write rubbish code and to hell with their customers?  I don’t know them, never dealt with them and certainly never heard of them before yesterday.  You decide 🙂

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Black Screen of Death

I’ve read a few reports on this today.  It’s being claimed by Prevx that one of Microsoft’s recent security updates causes issues on machines.  The machine boots up OK, but you get nothing but a black screen when you log in.  The have posted a “fix” (it’s not something MS has authorised).  Note that this is an issue that can be caused by a lot of things.  I’ve personally seen it a few times over the years.

Microsoft are reported to be investigating.

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