Monday, 26 August 2013

What is wrong with security: "don't use bcrypt"

You know, security is lately one of my biggest sources of irritation. More so when I read articles like this one. On the surface, the article is well written, even informative. But it also shows off most of what is currently wrong with computer security.

Security, like most other areas of the IT world, is an area of specialization. If you look around, you'll see that we have database, operating system, embedded system, storage and network experts. While it is true that the job role that has the best future prospect is the generalist that can can also understand and even learn deeply any subject, it is also true that after a few years of working focused on a specific subject, there is a general tendency to develop more deep knowledge in some subjects than others.

Security is no different in that regard, but has one important difference with all the others: what it ultimately delivers is the absence of something that is not even known. While the rest of the functions have more or less clearly defined goals in any project or organization, security can only provide as proof of effectiveness the lack -or a reduction- of security incidents over time. The problem is, while incidents in other areas of computing are always defined by "something that is not behaving as it should", in security an incident is "something that we did not even know could happen is actually happening"

Instead of focusing on what they don't know, the bad security focus on what they know. They know what has been used so far to exploit an application or OS, so here they go with their vulnerability and antivirus scanners and willingly tell you if your system is vulnerable or not. Something that you can easily do yourself, using the exact same tools. But is not often you hear from them an analysis of why a piece of code is vulnerable, or what are the risky practices you should avoid. Or how the vulnerability was discovered.

And that is part of the problem. Another part of the problem is their seemingly lack of any consideration of the environment. In a similar way to the "architecture astronauts" the security people seem to live in a different world. One where there is no actual cost-benefit analysis of anything and you only have a list of know vulnerabilities to deal with, and at best a list of "best practices" to follow. Such as "don't use bcrypt"

And finally, security guys are often unable to communicate in a meaningful way according to their target audience. Outside a few specialist, most people in the IT field (me included) lack the familiarity with the math skills required to understand the subtle points of encryption, much less the results of the years of analysis and heavy number theory required to even attempt to efficiently crack encryption.

Ironically, the article gets some of these points right. At the beginning of the article, there is an estimation of cracking cost vs. derivation method that should help the reader make an informed decision. There is advice about the bcrypt alternatives and how they stack one against each other.

But as I read further the article, it seems to fall into all these security traps: for example, the title says "don't use bcrypt", only to say on its first paragraph "If you're already using bcrypt, relax, you're fine, probably" Hold on, what was the point of the article then? And if you try to read the article comments, my guess is that unless you're very strong on crypto, you'll not fully understand half of them and will come up confused and even more disoriented.

But what better summarizes what is wrong with security is the second paragraph: "I write this post because I've noticed a sort of "JUST USE BCRYPT" cargo cult (thanks Coda Hale!) This is absolutely the wrong attitude to have about cryptography"

How is detailing the reason for using bcrypt a wrong attitude about attitude? The original article is a good description of the tradeoffs of bcrypt against other methods. That is not cargo cult. Not at least in the same way as "just use a SQL database", "just use a NoSQL database", "just use Windows" or "just use Linux" are cargo cult statements. Those statements are cargo cult only when taken out of context. Like the DBA that indexes each and every field in a table in the hope that sacrificing his disk space, memory and CPU to the cargo cult church will speed up things.

But the original article was not cargo cult. Not more than the "don't use bcrypt" article is cargo cult.

I guess that what I'm trying to say is that there are "bad" and "good" security. The "bad" security will tell you all about what is wrong with something and that you should fix all this immediately. The good security should tell you not only what is vulnerable, but also how to avoid creating vulnerabilities in the future. And provide you ready made and usable tools for the job. And articles like "don't use bcrypt" are frustrating in that they give almost what you need, but in a confusing and contradictory way.

When I choose a database, or operating system, or programming language, or whatever tool to do some job, I do it having only a superficial knowledge the trade offs of each option. But I don't have to be an specialist in any of these to decide. I don't know the nuts and bolts of the round robin vs. priority based and how O(1) task schedulers work. Or the details of a B-Tree vs. hash table index implementations. Or the COW strategy for virtual memory. I know the basics and what works best in each situation, mostly out of experience and education. True, with time I will learn the details of some of these as needed. But a lot of the time software developers are making really educated best guesses. And the more complex the subject -and crypto is one of the most- the more difficult these decisions are.

If I want to encrypt something, I want to have an encrypt function, with the encryption method as a parameter and a brief explanation of the trade offs of each method. And make it fool proof, without any way of misusing it. Yes, someone will find a way of misusing it and probably will be a disaster. Find ways of finding these misuses.

So please security guys, give us tools and techniques to prevent security issues. With a balanced view of their costs and benefits. And let the rest of the world sleep safely in their ignorance of 250 years of number theory. That is your real job. Creating huge repositories of vulnerabilities and malware signatures is not good enough. That in fact does little to protect us from future threats. Give us instead the tools to prevent these in the first place. And in a way that everyone can understand them.Thank you.

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