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Category Archives for "Security"

Should Firewalls Track TCP Sequence Numbers?

It all started with a tweet by Stephane Clavel:

Trying to fit my response into the huge Twitter reply field I wrote “Tracking Seq# on FW should be mostly irrelevant with modern TCP stacks” and when Gal Sagie asked for more elaboration, I decided it’s time to write a blog post.

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Some notes on the Norse collapse

Recently, cybersec company "Norse Security" imploded. Their leaders and most the employees were fired, and their website is no longer available. I thought I'd write up some notes on this.

All VC-funded startups are a scam

Here's how VCs think. They see that there is a lot of industry buzz around "threat intel". They'll therefore fund a company in that space. This company will spend a 5% of that money to create a cool prototype, and 95% in marketing and sales. They'll have fancy booths at trade shows. They'll have a PR blitz to all the reporters who cover the industry. They'll bribe Gartner to be named a Cool Vendor or Magic Quadrant Leader. They'll win industry kudos. They have some early sales 'wins' with some major customers. These customers will give glowing reviews of the product they bought -- even before turning it on.

In other words, it's a perfect "Emperor Has No Clothes" story, where neither customers, nor Gartner, nor the press is competent to realize the Emperor is not wearing clothes.

VCs know it's a scam, but they are hoping it'll become real. As a well-known leader in this space, employees with the needed expertise will flock Continue reading

Yubikey 4 for SSH with physical presence proof

This is another post in the series of how to protect SSH keys with hardware, making them impossible to steal.

This means that you know that your piece of hardware (e.g. Yubikey or TPM inside your laptop) was actively involved in the transaction, and not, say, turned off and disconnected from the Internet at the time (like in a safe or on an airplane).

What’s new this time is that we can now have a physical presence test on every use of the key. That means that even if someone hacks your workstation completely and installs a keylogger to get your PIN, unless they also break into your home they can’t use the key even while the machine is on and connected. Evil hackers in another country are out of luck.

Intro

Most of this is a repeat of official docs (see references).

If it looks like a command is hanging, check to see if the Yubikey is flashing. If it is, then touch it.

The touch feature is optional. If you don’t want a key to require it, you can chose to generate a key that doesn’t.

Install yubico-c, ykpersonalization, and yubico-piv-tool

sudo apt-get install help2man gengetopt libtool  Continue reading

Net ring-buffers are essential to an OS

Even by OpenBSD standards, this rejection of 'netmap' is silly and clueless.

BSD is a Linux-like operating system that powers a lot of the Internet, from Netflix servers to your iPhone. One variant of BSD focuses on security, called "OpenBSD". A lot of security-related projects get their start on OpenBSD. In theory, it's for those who care a lot about security. In practice, virtually nobody uses it, because it makes too many sacrifices in the name of security.

"Netmap" is a user-space network ring-buffer. What that means is the hardware delivers network packets directly to an application, bypassing the operating system's network stack. Netmap currently works on FreeBSD and Linux. There are projects similar to this known as "PF_RING" and "Intel DPDK".


The problem with things like netmap is that it means the network hardware no longer is a shareable resource, but instead must be reserved for a single application. This violates many principles of a "general purpose operating system".

In addition, it ultimately means that the application is going to have to implement it's own TCP/IP stack. That means it's going to repeat all the same mistakes of the past, such as "ping of death" when a Continue reading

How not to be a better programmer

Over at r/programming is this post on "How to be a better programmer". It's mostly garbage.


Don't repeat yourself (reuse code)


Trying to reuse code is near the top of reasons why big projects fail. The problem is that while the needs of multiple users of a module may sound similar, they are often different in profound ways that cannot be reconciled. Trying to make the same bit of code serve divergent needs is often more complex and buggy than multiple modules written from the ground up for each specific need.

Yes, we adhere to code cleanliness principles (modularity, cohesion) that makes reuse easier. Yes, we should reuse code when the needs match close enough. But that doesn't mean we should bend over backwards trying to shove a square peg through a round hole, and the principle that all pegs/holes are the same.


Give variables/methods clear names


Programmers hate to read other code because the variable names are unclear. Hence the advice to use "clear names" that aren't confusing.

But of course, programmers already think they are being clear. No programmer thinks to themselves "I'm going to be deliberately obtuse here so that other programmers won't understand". Therefore, Continue reading

Security ‘net: Digital Copyright Edition

security-netThe world of digital copyright is somewhat tangential to “real” security, but it’s a culture issue that impacts every network engineer in myriad ways. For instance, suppose you buy a small home router, and then decide you really want to run your own software on it. For instance, let’s say you really want to build your own router because you know what you can build will outperform what’s commercially available (which, by the way, it will). But rather than using an off box wireless adapter, like the folks at ARS, you really want to have the wireless on board.

Believe it or not, this would be considered, by some folks, as a pretty large act of copyright infringement. For instance, the hardware manufacturer may object to you replacing their software. Or the FCC or some other regulatory agency might even object because they think you’re trying to hog wireless spectrum, or because you don’t like what the wireless providers are doing. The EFF has a good piece up arguing that just such tinkering as replacing the operating system on a commercially purchased device is at the heart of digital freedom.

One of the most crucial issues in the fight for Continue reading

Whatever Happened to “Do No Harm”?

A long time ago in a podcast far, far away one of the hosts saddled his pony unicorn and started explaining how stateful firewalls work:

Stateful firewall is a way to imply trust… because it’s possible to hijack somebody’s flows […] and if the application changes its port numbers… my source port changes when I’m communicating with my web server - even though I’m connected to port 80, my source port might change from X to Y. Once I let the first one through, I need to track those port changes […]

WAIT, WHAT? Was that guy really trying to say “someone can change a source port number of an established TCP session”?

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IPv6 Microsegmentation in Data Center Environments

The proponents of microsegmentation solutions would love you to believe that it takes no more than somewhat-stateful packet filters sitting in front of the VMs to get rid of traditional subnets. As I explained in my IPv6 Microsegmentation talk (links below), you need more if you want to have machines from multiple security domains sitting in the same subnet – from RA guard to DHCPv6 and ND inspection.

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Flawed From the Start & Missing the Mark: Georgia’s Proposed Anti-Drone Legislation

Bad state laws can have the same chilling effect on technology as bad federal laws.  In this guest post, friend of Errata Elizabeth Wharton (@lawyerliz) discusses the latest anti-drone law introduced here in the Georgia legislature and how one bill manages to kill innovation across several key Georgia industries. 




By Elizabeth Wharton 
Georgia’s newly proposed anti-drone legislation is an economic and research buzz kill.  The bill, HB 779, through poorly crafted provisions places unnecessary red tape for use of drones by the film industry and by cellular, telephone, and cable utility companies.  It also completely shuts down Georgia's aerospace defense industry research (and related funding) conducted by universities including Georgia Tech and all related manufacturing by companies such as Lockheed Martin.  Biting the industry hands that bring billions of dollars into Georgia’s economy seems a bold move for state legislators, particularly during an election year.    

Gaps between technology policy and technology practice at the federal level such as the Commerce Department’s proposed Wassenaar Arrangement rules, extend to the states as well.  With over 168 drone-related bills considered by 45 states in 2015 according to the National Conference of State Legislatures, 2016 is already off to a Continue reading

Some notes C in 2016

On r/programming was this post called "How to C (as of 2016)". It has some useful advice, but also some bad advice. I thought I'd write up comments on the topic. As somebody mentioned while I was writing this, only responsible programmers should be writing in C. Irresponsible programmers should write other languages that have more training wheels. These are the sorts of things responsible programmers do.


Use a debugger


The #1 thing you aren't doing, that you should be doing, is stepping through each line of code in a source level debugger as soon as you write it. If you only pull out the debugger to solve particularly difficult problems, then you are doing it wrong.

That means using an IDE like Visual Studio, XCode, or Eclipse. If you are only using an editor (without debugging capabilities), you are doing it wrong. I mention this because so many people are coding in editors that don't have debuggers. I don't even.

It's a concern for all language, but especially with C. When memory gets corrupted, you need to be able to dump structures and memory in order to see that. Why is x some weird value like 37653? Continue reading

The Schelling Game

At the Shmoocon conference, a vendor ("Breach Intelligence") is putting a card in ever schwag bag with an "IoC". The game works by giving everyone a different IoC, in pairs. If you find your matching IoC and come to their booth, they'll give you a free quadcopter.

This is like the "Schelling Point", a question in game theory. You are supposed to meet somebody New York City, but neither of you have been told where to meet. So where do you go? The trick is to estimate the most logical place that the other person, using the same information as you, would make. Most people agree that the answer is the "information booth at Grand Central Station".

So how do you find your matching IoC to win the prize? One guy is walking around asking strangers to match cards. That's useful, because a lot of people who don't want to play the game simply give him their cards, so he's got an ever expanding list of possible matches.

My solution is to tweet the IoC, and of course, blog about it:

If my partner searches Twitter, they will Continue reading

Automating VMware NSX Security Rules Creation using Splunk and Some Code

The VMware NSX network virtualization platform allows us to build sophisticated networking and security constructs in software. NSX has a rich RESTful API which allows one to build highly flexible and automated environments. In this blog, we’re going to focus on operations and automation; we’ll demonstrate one example of automation around security policies/rules that can be done with NSX.

VMware NSX allows for micro-segmentation with a distributed firewall service (DFW). The DFW is a kernel-level module and allows for enhanced segmentation and security across a virtualized environment. One of the common questions we get asked is, “how do I decide what rules to build?” NSX allows for multiple options to create rules such as the use of NSX flow-monitoring or analyzing traffic patterns via logging to create the rules.

We’ll demonstrate how the VMware NSX DFW can be monitored with the popular Splunk platform. Further, we’ll demonstrate, along with using Splunk for monitoring traffic passing through the DFW, how the NSX REST API can be leveraged to automate workflows and creation of DFW rules. Continue reading

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