Cupfighter.net

The Key to My Mind (11/12) a CC image from Tony the Misfit's Flickr stream

The private key is supposed to be private. It is what proves that the services and the certificate belong to each other. As an attacker you want to obtain this key in order to spoof the identity of the service.

When you import a certificate with private key or generate a private key via the Microsoft Crypto API (CAPI) you can mark it as non-exportable. But are these keys really non-exportable or is this just a GUI option to give administrators a false sense of security?

In order to find out how an attacker can export a non-exportable key RSA key, we need to dive into the CAPI calls.

Disassembling the CAPI functions shows that there are flags in memory that specify that the key is not exportable. It appears that these flags are stored on the same memory location and user the same function. And you can actually temper with this information and set these flags back to being exportable.

The situation is a bit different in the CAPI: Next generation (CNG). Again a disassembly of these functions shows that the CliCryptExportKey() via the c_SrvRpcCryptExportKey function get the private key from the KeyISO or KeyIsolation RPC service that is meant to isolate the RSA keys from the client memory.

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The MSS: settings used to be here...

I recently got involved in a project where I defined the Baseline Security settings for windows and Linux. I used the settings provided by the Center for Internet Security (CIS).

We decided on the following approach:

• Based on the CIS templates we created a baseline document specific to our company
• I, in my security role, created a Nessus .audit file, so we could audit compliance to our own baseline with Seccubus
• The windows administrator created GPOs to apply the settings.

When creating in the GPOs we did a strange discovery. In a windows the settings that are normally marked as MSS: in the category Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options do not appear in a domain if its functional level is Windows 2008.

This made us wonder, have these setting become irrelevant ? If this is not the case, how can we still set them, preferably via group policy?

The settings are not irrelevant, as e.g. Peter van Eeckhoutte’s blog points out. Windows 2008 does not forward IPv4 packets that have source routing on them,  but it does accept them if the machine is the final destination. However for IPv6 Windows 2008 will forward these packets by default.

So if the settings are not irrelevant, how can we apply them if they are not in the Group Policy Editor? For this purpose we created an .adm file, which can be loaded into the Group Policy editor as a Classic Administrative template. Read more…

Last night I attended the Microsoft Security Response Team webcast regarding the Out Of Band patch for the ASP.net padding Oracle vulnerability discovered by Juliana Rizzo and Thai Duong 11 days before.

My main objective in watching the webcast (which is not my usual habit) was to find out if systems that have the described workaround applied still need to apply the patch. The webcast did not give a definitive answer but this YouTube video and the Netifera website and the twitter accounts Thai Duong provide the answer: Yes you should apply the patch a.s.a.p!

However the Q&A section of the talk did give me, as a security operations guy, quite some food for thought. I made some notes in my own Twitter feed, which I have summarized here.

Q: Why did Microsoft release and OOB update for a vulnerability rated “only” as important?
A: The vulnerability itself is rated as Important because it is not a vulnerability that directly leads to remote code execution on the vulnerable system, however exploitation of the vulnerability will lead to disclosure of all information in the webroot including web.config. This information can be used for session hijacking, compromising backend databases and to attack associations between websites, e.g. the association of a website with PayPal. Hence an out of band patch was warranted.

Q: Why only release to the download center and not to WSUS etc?
A: We felt we needed to get this update out quickly, the people that need to apply this patch quickly are mainly enterprises who are capable of applying patches without the aid of WSUS. Developing the WSUS capabilities would add another few days of delay to the deployment of this patch.

Q: Is the attack actively used?

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By Mark Curphey

Mark starts of by giving a very funny overview of his very impressive career. He currently has a non-security security job at Microsoft running the MSDN subscription services department. Being away from security has given him room to think about information security more.

His talk is about 10 crazy ideas that might change the state of information security. These ideas all cost little money, but may have a big impact.

#1 – Adopt Chinese Medicine Business Model

In China the doctor gets paid to keep you healthy, not to cure you. There are currently actually two companies that are experimenting with this business model.

#2 – Stop Human Pattern Matching

Humans seen things they expect so see. The brain is wired to see what it is expecting to see. This is why optical illusions work, which was demonstrated to the audience with two illusions. Security people do his all the time. I have XSS, this is going to happen, this vulnerability will cause this worm.

#3 – Community Driven Statistical modelling

An example of this is http://freerisk.org. It allows people to input and consume financial modelling data. In the security world there is no data that will give us some predictable model of how security behaves. Wine quality can actually be captured in a formula: Wine Quality = 12.145 + 0.00117 * winter rainfall + 0.0614 average growing season – 0.00386 harverst rainfall. Where is the equivalent of security? Rubbish you say? Well, the formula for wine quality is actually used in the field now

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By Yaniv Miron

lolcat adaptation #3, a Creative Commons Attribution No-Derivative-Works (2.0) image from kevinsteele's photostream

Exploit wednessday ois the day after patch Tuesday, the second Tuesday of the month when Microsoft releases its patches. While some people say it’s impossible to write an attack in one day, Yaniv has seen it happen and tries to explain how.

This process is based on diffing. Diffing means finding the differences between the old and the patched version of the binary file.

This could be done on the same machine, or between two different versions of the OS (e.g. Windows XP and Vista).

The toolkit for a typical patch analysis consists of:

• Diff programs
• Compare programs
• Decompiles  and compilers
• Different versions of windows

Yaniv, then went off to demonstrate a to us the creation of an exploit for MS10-005.

First of all information from public source was gathered to find out which program was effected, what the root cause of the vulnerability was and in which version of Windows the problem is present.

The next part is extracting the patch and analyzing it. First this that needs to be done is finding the files that will be updated. The these files will be compared against the original file, just to find which functions have been changed.

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By David Lindsay & Eduardo Vela Nava

The talk is about abusing the anti-XSS filters built into IE8 to always be able to perform XSS.

Microsoft decided to implement anti-XSS measures in IE because XSS is so common. On the other hand the wanted to be careful not to break the web and to keep things performant and the solution itself had to be secure.

So how do these filters work?
•    Examine all outbound requests for XSS patterns using heuristics filters.
•    If something matches the filter a dynamic signature is generated
•    If the signature matches then the response is neutered.
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As part of my work I was installing a Microsoft PKi infrastructure with two tiers. A root CA and an issuing CA.

Since the root CA is in another domain then the issuing CA, it took some fiddling and tweaking around with my CDP and AIA extensions, but that is another blogpost all together.

I knew I was in for some fun when when the following happened:

• I installed my Issuing CA and generated the certificate request
• I issued the request to my Root CA and generated the Issuing CA certificate
• I tried to install the Issuing CA certificate and got the following error:

Cannot verify certificate chain. Do you whish to ignore the error and continue? The revocation function was unable to check revocation because the revocation server was offline. 0x80092013 (-2168885613)

My first reaction was to call one of the network guest and notify him that I needed http access to the Issuing CA to the CDP location. But whil on the phone, I decided to try and to my surprise I was actually able to manually pull down the crl.

Intregued, I decided to check a few things:

• I could download the CRL from both CDP locations with Internet Exporer
• I could open the downloaded CRLs
• I could telnet to port 80 of the both webservers
• I could telnet to port 80 manually issue the GET /crl/CRLname.crl HTTP/1.0 command and get data back

O.K. what is going on here… Lets open PKI view, which is now included in Windows 2008 and Vista and can be downloaded for Windows 2000 and 2003.

It seemed that PKI view as in agreement, it too could not download the CRL from the CDP location

PKI view shows "Unable To Download" for both CDP locations

This did sent me on a wild goose chase:

• Microsoft own documentation, clearly blames it on unavailability of the CDP location, something I, by now, had triple checked four times and refused to believe
• This “Network Builders” forum and many others, simply suggest to turn off revocation checking, but that is clearly not a worthy solution either.
• Apparently there is also an issue with serving delta CRLs threw IIS because the + sign at the end of the basename of a delta CRL file leads to so called “double escaping”. I could rule this out by looking at the IIS logs.
• In the end this technet forum post, about OCSP reponders Brian Komar points out:

But, as stated, I would use certutil to get the “best” answer on how is my configuration.
Certutil -verify -urlfetch “certfile.cer” will check *every* CDP and AIA URL (including OCSP) and tell you how they are all doing *at that specific instance in time” since it goes to the URLs immediately.
Brian

I exported the Issuing CA certificate from the certificate database of the Root CA and ran the command against is and this is what I found

E:\>certutil -verify -urlfetch <certfile>.cer
Issuer:
CN=Root CA
Subject:
CN=Issuing CA
Cert Serial Number: 115d5f6400020000000b
<snip>

—————-  Certificate AIA  —————-
Verified “Certificate (0)” Time: 0
[0.0] http://IIS1.domain1local/crl/Root-CA.crt

Verified “Certificate (0)” Time: 0
[1.0] http://IIS2.domain1.local/crl/Root-CA.crt

—————-  Certificate CDP  —————-
Wrong Issuer “Base CRL (13)” Time: 0
[0.0] http://IIS1.domain1.local/crl/Root-CA.crl

Wrong Issuer “Base CRL (13)” Time: 0
[1.0] http://IIS2.domain1.local/crl/Root-CA.crl

<snip>
E:\>

So while PKI view and the other error messages I was getting all pointed to the most common cause, it actually turned out that the CRl did get downloaded, but was not cryptographically relevant to what the system believes is the Root CA certificate.

Root cause

Inspection of the CRLs generated and the Root certificates installed showed what had caused the problem. In order to test the CDP extensions I had reissued the Root CA certificate, causing the Root CA to have three active certificates. Each with a different key.

This CA has three CA certificates

When validating the Issuing CA certificate, validation would end at the last certificate issued, however the CA still signs its CRLs with the key pair of the first certificate.

I guess for me there is nothing left but to reinstall the entire chain.

Schuberg Philis has sent me and 4 colleagues to Berlin to attend the TECH-ED over there.

Together with another 7000 techies, this is a week of planning, running, eating, experiencing all kinds of (new) technologies presented by Microsoft guys.

Feeling some blisters already, because I’m not used to running so much on a day, especially with a Lenovo T500 on my shoulder. The Berlin Messe is a huge place. But the overall sense of the MCE’s is that we are enjoying the sessions. Not all session are that good, but for instance Mark Minasi is good fun to watch and hear.  The food and beverages (very important) are good and plenty.
Technically we are not always that challenged, in many occasions the depth is lacking, but then again, it is a mass-event and not everybody is a (potential) MCE.

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Late October PowerShell V2 was released for almost all Windows platforms. Check out http://support.microsoft.com/kb/968929 and download the version you need.

Happy scripting!

Some cupfighters are going to TechEd Europe 2009. In fact the company we work for, Schuberg Philis, organizes the dutch country drink together with Microsoft.

We will blog during this event, and try to post major announcements, being made during TechEd, on this site as fast as we can. So keep an eye on this site or twitter!

http://www.schubergphilis.com/countrydrink

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