The forgotten art of error checking

Posted on 2010/06/17 by niemeyer

I was just rambling randomly yesterday, in the usual microblogging platforms, about how result checking seems to be ignored or done badly. The precise wording was:

It’s really amazing how little attention error handling receives in most software development. Even *tutorials* often ignore it.

It indeed does amaze me. It sometimes feels like we write code for theoretical perfect worlds.. “If the processor executes exactly in this order, and the weather is calm, this program will work.”. There are countless examples of bad assumptions.. someday I will come with some statistics of the form “Every N seconds someone forgets to check the result of write().”.

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Posted in Architecture, Go, Java, Lua, Perl, Python, Ruby, Snippet, Test | 10 Comments

Xpresser – Python library for GUI automation with image matching

Posted on 2010/05/18 by niemeyer

In a hurry?

Go check it out!

The context

A while ago I found out about Sikuli, a very interesting project which allows people to script actions in GUIs based on screenshot excerpts. The idea is that you basically take images representing portions of your screen, like a button, or a label, or an icon, and then create a script which can detect a position in the screen which resembles one of these images, and perform actions on them, such as clicking, or hovering.

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Posted in Project, Python, Test | 16 Comments

Recovering a bootable EBS image

Posted on 2010/03/09 by niemeyer

Scott Moser has just announced this week that the new Ubuntu images which boot out of an EBS-based root filesystem in EC2, and thus will persist across reboots, are available for testing.

As usual with something that just left the oven and is explicitly labeled for testing purposes, there was a minor bug in the first iteration of images which was even mentioned in the announcement itself. The bug, if not worked around as specified in the announcement, will prevent the image from rebooting.

Having an bootable EBS image which can’t reboot is a quite interesting (and ironic) problem. You have an image which persists, but suddenly you have no way to see what is inside the image anymore because you can’t boot it. Naturally, even if the said bug didn’t exist in the first place, it’s fairly easy to get into such a situation accidentally if you’re fiddling with the image configuration.

So, in this post we’ll see how to recover from a situation where a bootable EBS image can’t boot.

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Posted in Article, Cloud | 1 Comment

Breaking into an Android password manager – Practice

Posted on 2009/12/05 by niemeyer

In the last post, we’ve seen some security issues which exist in the Android password manager gbaSafe version 1.1.0a, by analyzing the security description provided in its web site. As described there, even though the system depends on a “master key” which might be secure, the security of the system is seriously compromised by the encouragement of very weak keys (a few digits only) in what is named an “unlock key”, used to encrypt the master key itself. All of that in an application which claims to strongly protect people’s data from unwanted eyes.

In this post, we will play a bit with the Linux-based Android OS to actually explore these security deficiencies, demonstrating that such issues are very real, and that the claims of being hard to unveil the data is unfounded. Since the most serious weakness lies in the key itself, we’ll run a simple brute force attack to try to find arbitrary unlock keys.

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Posted in Architecture, Mobile, Puzzle, Security | 8 Comments

Breaking into an Android password manager – Theory

Posted on 2009/12/01 by niemeyer

For some time now I’ve been wanting to research more deeply about the internals of Android. Until now, though, this was just a sentiment. Then, a couple of weeks ago I’ve finally managed to replace my iPhone for an Android phone, and that was the final motivator for me to actually get into learning more about the inner workings of the Linux-based OS.

Now, I just had to pick an actual task for digging into. The Dalvik VM is certainly one of the most innovative and advertised technical details about the OS, so something around it would be a nice start.. some kind of bytecode fiddling perhaps, but what? Luckily, even without trying too hard, I eventually stumbled upon an interesting case for researching upon.

The “victim” of this research is the application gbaSafe version 1.1.0a, which claims to protect user passwords using unbreakable algorithms (how’s that for a hint of a Snake oil case?).

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Posted in Architecture, Java, Mobile, Puzzle, Security | 5 Comments

The last 4 years (and the next N?)

Posted on 2009/11/25 by niemeyer

Some interesting changes have been happening in my professional life, so I wanted to share it here to update friends and also for me to keep track of things over time (at some point I will be older and will certainly laugh at what I called “interesting changes” in the ol’days). Given the goal, I apologize but this may come across as more egocentric than usual, so please feel free to jump over to your next blog post at any time.

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Posted in Architecture, Cloud, Java, Project, Python | 5 Comments

Google won’t kill standalone GPS

Posted on 2009/10/30 by niemeyer

It was already dead. In some senses, anyway.

Google announced a couple of days ago that they’re advancing into the business of GPS guided navigation, rather than staying with their widely popular offering of mapping and positioning only. This announcement affected the rest of the industry immediately, and some of the industry leaders in the area have quickly taken a hit on their share value.

As usual, Slashdot caught up on the news and asked the question: Will Google and Android kill standalone GPS?

Let me point out that the way the facts were covered by Slashdot was quite misguided. Google may be giving a hand to change the industry dynamics a bit faster, but both Garmin and TomTom, the companies which reportedly had an impact in their share value, have phone-based offerings of their own, so it’s not like Google suddenly had an idea for creating a phone-based navigation software which will replace every other offering. The world is slowly converging towards a multi-purpose device for quite a while, and these multi-purpose devices are putting GPSes in the hands of people that in many cases never considered buying a GPS.

The real reason why these companies are taking a hit in their shares now is because Google announced it will offer for free something that these companies charge quality money for at the moment, being it in a standalone GPS or not.

Posted in Cloud, GPS | Leave a comment

Geocaching on the Easter Island

Posted on 2009/10/13 by niemeyer

This post is not about what you think it is, unfortunately. I actually do hope to go to the Easter Island at some point, but this post is about a short story which involves geohash.org, Groundspeak (from geocaching.com), and very very poor minded behavior.

The context

So, before anything else, it’s important to understand what geohash.org is. As announced when the service was launched (also as a post on Groundspeak’s own forum), geohash.org offers short URLs which encode a latitude/longitude pair, so that referencing them in emails, forums, and websites is more convenient, and that’s pretty much it.

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Posted in GPS, Mobile, Project | 2 Comments

Virtual Private Cloud is not the Private Cloud

Posted on 2009/08/27 by niemeyer

More than 40 years ago, a guy named Douglas Parkhill described the concept of utility computing. He described it as containing features such as:

  • Essentially simultaneous use of the system by many remote users.
  • Concurrent running of different multiple programs.
  • Availability of at least the same range of facilities and capabilities at the remote stations as the user would expect if he where the sole operator of a private computer.
  • A system of charging based upon a flat service charge and a variable charge based on usage.
  • Capacity for indefinite growth, so that as the customer load increases, the system can expanded without limit by various means.

Fast forward 40 years, and we now name pretty much this same concept as Cloud Computing, and everyone is very excited about the possibilities that exist within this new world. Different companies are pushing this idea in different ways. One of the pioneers in that area is of course Amazon, which managed to create a quite good public cloud offering through their Amazon Web Services product.

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Posted in Architecture, Cloud | 4 Comments

Accessing RESTful information efficiently

Posted on 2009/07/23 by niemeyer

Alright, so I appreciate the idea of RESTful Web Services, but I’ve got a small dilemma I’d appreciate some opinions on.

In the RESTful Web Services book, by Leonard Richardson and Sam Ruby, there’s emphasis on making the programmable web look like the human web, by following an architecture oriented to having addressable resources rather than oriented to remote procedure calls. Through the book, the RPC (or REST-RPC, when mixed with some RESTful characteristics), is clearly downplayed. In some cases, though, it’s unclear to me what’s the extent of this advice. Humans and computers are of course very different in the nature of tasks they perform, and how well they perform them. To illustrate the point clearly, let me propose a short example.

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Posted in Architecture | 28 Comments