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TLS renegotiation status update

It’s been a while since I last checked any news or used a computer. I was away for more than a month spending time with our new baby daughter and almost completely disconnected from the tubes of the net.

Now that I’m back, I wanted to point to a patch from Microsoft that allows admins to disable TLS renegotiation on both the client and the server side. The security advisory is 977377 and MSRC has published a blog post with a bit more details.

The new RFC that will outline the changes needed to the TLS protocol to fix the problem is almost there and should be out “real soon now”.

TLS Renegotiation Test

The new TLS/SSL man-in-the-middle (MiTM) attack targets the renegotiation part of the protocol. There are two variations of the renegotiation – client initiated and server initiated. This tool allows you to test any web server (input as server:port) for client initiated renegotiation support, as server initiated renegotiation depends on specific server configuration. As currently there is no fix other than disabling renegotiation, this will pretty much tell you whether the server is vulnerable or not to this type of renegotiation attack

Update (2014-09-19): The TLS renegotiation vulnerability is now five years old and should be fixed by most TLS stacks and hopefully all Internet facing servers have been updated. Thus, I have removed my own test for the renegitiation flaw. I would suggest using, which has a much better scanner for the overall configuration of servers.

A tale of commercial security product

I want to share a story that had me completely puzzled and frustrated. I had to install PGP Desktop for something I’m playing with. I was amazed by PGP (the company) because I thought those guys understand security, the concept of digital signatures, and the crypto area in general. Well, believe it or not I had changed my opinion. After receiving the PGP Desktop zip file, I cracked it open to install the software. What do I find? Another zip file inside it along with a PGP signature file.

Contents of the PGP Desktop zip file

This is all good and the idea is that you should verify the signature of the installer to ensure it comes from the actual author. But this is a chicken/egg problem. I need to PGP to verify the installer, but I cannot since I’m trying to install PGP. I moved on, since there was no way (without using some other PGP package) to verify the installer zip file. So I fire up the installer on a test machine to see how it will go. To my surprise the installer comes from “Unknown Publisher”.


Hmm, I would think PGP being a security company selling encryption/signing software would definitely sign their code, but I guess I assumed too much. Since this was on a test machine, I decided to go through the entire process and see what happens. Maybe they launch another installer from inside it that is signed. They do have a MSI package inside it that gets installed, but it is still not signed :(


Total failure in my book for PGP. After I installed the software, I decided to verify the signature on the zip, since I now had PGP Desktop installed : ). Here comes the next surprise. PGP automatically looks up the key that has signed the package (cool), downloads it (cool), and verifies the package (cool). But what do I see in the log?


The key is invalid?!? Turns out that I have to explicitly download the PGP Release Key into my keyring for it to verify properly and say the key is valid. I wouldn’t mind doing this step (even though some of the PGP keys should be really shipping with the product), but if you are going to do the download for me, please do it properly. It only worked after I had manually copied the key ID from the invalid key, downloaded it to my keyring, and tried verifying the file again. (Nevermind that the log doesn’t have timestamp associated with it).

Successfull verification of PGP installer

My usual approach is to always double check things that seem as weird as this. I thought I might have missed some support article or some other resource outlining the proper way to verify and install PGP. So I hop on support chat with PGP. I would leave it up to you to interpret the chat log yourself:

SupportTech: Hi, my name is SupportTech. How may I help you?
Nasko: Hello
Nasko: I wanted to ask a question about the installation of PGP Desktop
Nasko: I got the zip file that contains another zip file and a .sig file (the signature)
Nasko: How do I verify the signature ?
Nasko: It seems it is PGP signature, but me trying to install PGP, it seems like the chicken/egg problem
SupportTech: Unfortunately the only way to verify the signature is by having a previous version of PGP Desktop installed or after installing the software.
Nasko: Well, if I’m first time customer, there is no way for me to verify the zip file
Nasko: And what bothers me even more
Nasko: your installer is not signed, so it comes from “Untrusted” source
Nasko: How do I know what I am installing is indeed PGP Desktop from PGP?
SupportTech: For one, you need to login to LEMS in order to receive the download link. Since this is a secure site you can verify from the certificates that you are indeed downloading from PGP Corporation.
Nasko: is the actual download performed over https?
Nasko: Even if it is, I would feel a lot more comfortable if the installer is a signed binary
Nasko: such that Windows actually recognizes the author
Nasko: PGP is a security company after all
Nasko: and, no, the download link is not HTTPS
Nasko: what prevents a man-in-the-middle to replace the file on the wire ?
SupportTech: I understand that concern but it is currently not available in the installer. I do not have any information on if our development team plan to incorporate it.
SupportTech: Correct, it is not an HTTPS download.
Nasko: Is there any way customers can file issues or requests for the product?
SupportTech: Yes, there is this form: Which goes directly to our developers.
Nasko: Thanks

I would give them props for at least having a way to relay feedback to the developers. This was the only ray of light in this whole mess.

In conclusion, I wouldn’t be bothered as much by all of this if the product was free. But for the steep price I expect polished product, not something I have to wrestle with for a day just to get up and going. So if you are security conscious and don’t have existing PGP software, you just don’t have any way to trust the product!

P.S. I am skipping the whole problem of PGP Desktop messing up my networking stack. You can get the idea from this  KB article, though the installer failed to create the rollback file, so I had to do all this by hand : (.

TLS 1.2 in Windiows 7

Windows 7 includes support for TLS 1.1 and TLS 1.2. I’ve been running with enabled 1.2 support for a while now and no problems at all, so I figured I’d share how to enable it. You need to import these 4 reg keys:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Client]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.1\Server]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]

This will allow Win7 to use TLS 1.1 and 1.2, but that will work for apps that don’t explicitly ask for the TLS version they want to use. IE is one of those that want to be in control, so you need to tell it explicitly that you want it to use the new versions of TLS. To do that, you need to check the 1.1 and 1.2 checkboxes under Tools->Internet Options->Advanced->Security.

After you’ve done that, one may wonder how to check if this actually works. You can go to one of the few TLS interop servers available on the net. Here are a few that I know of which support TLS 1.2:

In general, you can check the page’s properties for the connection info. Going to Mike’s toolbox site IE shows “TLS 1.2, AES with 128 bit encryption (High); RSA with 1024 bit exchange”.

Hopefully enough people will support TLS1.2 soon enough so the world can move on : )

Mixed mode content settings for IE and Firefox

I recently installed a plugin for my blog to help with one of the daily tasks I do, only to find out that it is improperly coded, such that it requests resources using HTTP, even though I access my admin section through HTTPS. With all the latest findings on how insecure the web is and the CookieMonster tool by Mike Perry in the wild, this is not a risk I’m willing to accept. The developers of the plugin are completely unresponsive, so I figured I’ll just block my browser from loading mixed mode content (HTTP and HTTPS).

Here comes the fun part. I am a heavy Firefox user and use IE only occasionally. The problem is that Firefox doesn’t have such a feature. It has a dialog box warning you about mixed mode content, but it doesn’t prevent downloading plaintext content. It is rarely that I feel IE is doing much better than Firefox*, but in this case I have to give it the thumbs up, since it actually has a setting to disallow loading of insecure content.

After hunting around the web for a way to disable mixed mode content from loading in Firefox, the only thing I could find is an extension developed by Standford people - ForceHTTPS. Their paper is an informative read if you are not familiar with the problems with mixing content, but alas their extension does not work with the latest version of Firefox : (. I tried contacting them, but so far I haven’t gotten any response. I wish Firefox will include such a setting in the core browser, but if not, I might be forced to write a similar extension myself. If someone knows of other extensions that do this, let me know.

* After this year’s DefCon, I must say that IE has gained some points on its scoreboard when it comes to security.

State of computer security

In case you haven’t seen it yet, zf0 summer of hax was released in the last few days. While scanning through the content, I read a paragraph in the “Industry Check” section that perfectly sums up the state of computer security these days:

Are you professional types really this out of touch? I see all these papers
about how to protect yourself from these super-fucking-advanced techniques and
exploits that very few people can actually develop, and most hackers will NEVER
USE. It's the simple stuff that works now, and will continue to work years into
the future. Not only is it way easier to dev for simple mistakes, but they are
easier to find and are more plentiful.

It is indeed much easier to look for a misconfiguration in the web app than to hack the actual web server software (be it apache, IIS or some other). It is much easier to guess the secret questions of a person and gain access to their account than it is to hack the actual service (be it web mail or something else). At the end of the day, people should be looking at security as an end-to-end picture, not just focus on parts of it. The tried and true “a chain is as strong as its weakest link” is in full force here.

It is important to identify attack vectors

I recently read a paper on the topic of strong passwords. While going through it, it hit me that very often people will discuss a way of solving some problem (phishing for example), but they fail to enumerate what the attack vectors are and subsequently how the solution addresses these attack vectors. I like how the paper actually lists the threats at the very beginning and discusses them throughout. When solving a problem or coming up with a security product, one should be very clear as to what it is protecting against. It is not often that you see this clearly addressed.

I don’t quite agree with all the views presented in this paper, but it was overall a very interesting read. The idea of brute-forcing not only a single account but all accounts based on statistics was an approach I had not seen before.