Archive for category Computing History

IPv6 – CGN and Teredo Considered Harmful

There, I said it. The so-called “IPv6 transition strategies” are making it harder, more complicated and less secure to deploy IPv6 than just “doing the right thing”.

Carrier Grade NAT (CGN) and Teredo (among others) are the last gasps of an IPv4 world, and have no place in the modern Internet. While they may have short-term advantages to network operators, they will cause problems for their end users until they are finally phased out. Dual stack would be a better transition process, especially for customers.

keep-calm-and-dual-stackCGN is, as much as anything else, a way for carriers with a large network or large installed base of end users to make the fewest (and hopefully least expensive) changes in their networks. They are betting that by introducing a small number of large-scale NAT devices on the border between their networks and the Internet that they can avoid making sweeping internal network changes, or upgrading CPE (Customer Premise Equipment).

At best, even when working correctly, CGN breaks end-user accountability, geo-location and the end user experience. On top if that, it will slow IPv6 adoption, and force “true IPv6” users to adopt a host operational work-arounds and complicate deployment of next generation mobile and Internet applications.

CGN is inherently selfish on the part of the network operators that deploy it. They are saying “I want to spend less money, so I’m going to force everyone else to make changes or suffer in order to continue to talk to my customers.”

Or, as Owen Delong put it in his excellent look at the tradeoffs in CGN:

Almost all of the advantages of the second approach [transition to CGN and avoid investing in IPv6 deployment] are immediate and accrue to the benefit of the provider, while almost all of the immediate drawbacks impact the subscriber.

The next part of my rant has to do with Teredo, a “last resort transition technology”.

Like CGN, Teredo promises to allow end-user equipment to connect to the public IPv6 Internet over IPv4. It does this by “invisibly” tunneling your IPv6 traffic over the public Internet, to a “Teredo gateway”. A Teredo gateway performs a 4to6 network translation and passes your traffic onto the desired IPv6 destination. Teredo is implemented transparently in some Microsoft operating systems and can by default provide an IPv4 tunnel to the outside world for your IPv6 traffic.  It can, also provide an “invisible” tunnel from the outside world back into the heart of your network. And of course, all your network traffic could be intercepted at the Teredo gateway.

Teredo security has been a hot topic for years, with some concerns being raised shortly after Teredo’s standardization in 2006, and RFC6169 finally providing IETF consensus in 2011. Sadly, Teredo security must still be discussed, even though it is 0.01% of network traffic to dual-stacked resources. Fortunately, there’s a move in IETF to declare 6to4 technologies (including Teredo) as “historic”. Teredo will complicate network security until it is gone.

I for one, cannot wait for both CGN and Teredo to be consigned to the dustbin of history.

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It was 30 years ago today….

… that I logged into a UNIX system for the first time. It was also three days after the ARPANET transitioned to TCP/IP, and my first day at a new job.

The place was Logicon, in San Diego. The system was Programmers Work Bench (PWB) UNIX on a DEC PDP-11/70. The system was in single user mode, since the root filesystem was corrupt and the senior programmers who might have been able to help had quit during the month before. I think that the last one was out of the country for the next 3 weeks. And, my new (completely non-technical) boss had actually been hired after I was; but he was starting at Logicon the same day. It was an interesting beginning to my new job.

I spent that first week at my new job learning enough UNIX to figure out the icheck, dcheck and ncheck commands to repair the filesystem. I eventually got the root filesystem fixed, was able to create an account for myself and bring the system back up into multi-user mode. File systems were much simpler then. So simple in fact that I later learned to use the ed editor to repair (or just change) filenames by editing the directory files.

As soon as the PWB system came back up, I learned that we were now “off net” as the ARPANET had transitioned from NCP to TCP/IP on the 1st of January, and there was no one to port and debug the needed TCP/IP stack for our system. We needed that connection to communicate with our government customer, deliver software and work on our contract for the US Navy.

Fortunately, Logicon re-hired one of the senior programmers; he spent January and part of February working on the TCP/IP code to get us back on the ARPANET. We shared an IMP with the Naval Ocean Systems Center (NOSC, now part of SPAWAR) and UCSD. I met two long-time friends, Ron (@NOSC) and Brian (@UCSD) through our ARPANET connection, and we still keep in touch.

I always remember “ARPANET flag day“, because that’s when I got my start with UNIX and the ARPANET. That led to work on the Internet, HPC, and computer security.

Strangely enough, part of my current job is to work on a transition to IPv6. I have now had direct experience with IPv4, IPv5 and IPv6.

I owe a large debt  to all the people I’ve worked with and the USENIX (and later LOPSA) community of friends. You’ve all been wonderfully helpful, often insightful, and always friendly. Thank you all.

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Security – why programmers should study computing history

You can now add LinkedIn, eHarmony and to the long list of major sites that have had poor password security in their user database designs.  The saddest part is that in the case of LinkedIn, at least, this was apparently completely avoidable. (I haven’t found enough details to comment on the others, yet.)

Protecting stored user passwords is not rocket science.  This problem was pretty much solved in the 80s and 90s: Use a salted one-way hash function of sufficient strength to resist a dictionary attack.

(LinkedIn’s mistake was to use hashes, but to not salt them. )

That’s it.  Really.  UNIX has been using a salted hash since about 1985, initially with a hash based on DES. Since that time, as computing speeds have increased, new (salted) hash functions based on MD5, Blowfish, and SHA-2 have all been introduced.

In other words, stored password security has been a solved problem for at least 25 years. The concept is the same, only the algorithms have needed to be updated as Moore’s Law has dictated.

This is just one reason that programmers (and sysadmins) should study history, if only the history of computer security. Oh, if you’re not a cryptologist, for security-critical functions, please use well-vetted library functions.

A few references:

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