Category Archives: tech

SSH bashers

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Oh yeah, if you ever open up your ssh-server to the interwebs, don’t forget to install a banner. Fail2ban is an excellent tool to prevent this and many other type of attacks:

Jul 11 09:48:45 beeserver sshd[24408]: input_userauth_request: invalid user mitesh [preauth]
Jul 11 09:48:45 beeserver sshd[24408]: Received disconnect from 124.160.194.27: 11: Bye Bye [preauth]
Jul 11 09:48:53 beeserver sshd[24412]: Invalid user webftp from 124.160.194.27
Jul 11 09:48:53 beeserver sshd[24412]: input_userauth_request: invalid user webftp [preauth]
Jul 11 09:48:53 beeserver sshd[24412]: Received disconnect from 124.160.194.27: 11: Bye Bye [preauth]
Jul 11 09:49:01 beeserver sshd[24417]: Invalid user yangjun from 124.160.194.27
Jul 11 09:49:01 beeserver sshd[24417]: input_userauth_request: invalid user yangjun [preauth]
Jul 11 09:49:01 beeserver sshd[24417]: Received disconnect from 124.160.194.27: 11: Bye Bye [preauth]
Jul 11 09:49:09 beeserver sshd[24421]: Invalid user zl from 124.160.194.27
Jul 11 09:49:09 beeserver sshd[24421]: input_userauth_request: invalid user zl [preauth]
Jul 11 09:49:09 beeserver sshd[24421]: Received disconnect from 124.160.194.27: 11: Bye Bye [preauth]
Jul 11 09:49:17 beeserver sshd[24425]: Invalid user zl from 124.160.194.27
Jul 11 09:49:17 beeserver sshd[24425]: input_userauth_request: invalid user zl [preauth]
Jul 11 09:49:18 beeserver sshd[24425]: Received disconnect from 124.160.194.27: 11: Bye Bye [preauth]
Jul 11 09:49:25 beeserver sshd[24429]: Invalid user dr from 124.160.194.27
Jul 11 09:49:25 beeserver sshd[24429]: input_userauth_request: invalid user dr [preauth]

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Home Media Server and Media Center with Raspberry Pis

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More then one year ago, I read about the Raspberry Pi for the first time, before they launched. A couple of days ago I finally bought one (second hand), and currently have it running as a very cheap home server. Sanne and I are going to buy another to make it part of our new Media Centre.

A connected Raspberry Pi

This is a server.

We currently use my old computer as our media centre, But the word old says it all. The hard drive is starting to fail (currently 5 pending sectors) and it consumes way more energy then I’d want. Our television is a 5:4 19″ HD-ready TFT monitor from 2004, which is not ideal to watch movies and other video.  Therefore we started planning on an upgrade of this equipment. Continue reading →

Microsoft Office and it’s VelvetSweatshop password protected files

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Everyone knows that since Office 2007, all file formats from Office have been converted to the OfficeOpen standard, which is nothing more then a zip containing a bunch of XMLs. A lot of IT guys also know that Microsoft and the (password) protection of spreadsheets is nothing more then a tiny user interface lock and one line of code in the underlying XML, which of course is only a real issue to users of Excel. Starting with OpenOffice, there is actually a good encryption built into the file format. It now can use AES encryption, which is currently the standard for encryption.

But what if we’d locked parts of the spreadsheet, but without password-protecting the file  (but just the cell protection)? This would implicitly tell us that Office can open the file without password. Inspecting some of these files I got as an assignment for my job, I found out that Office does encrypt these files. Opening these kind of files as a zip is impossible because they have become some OLE-object instead. Which acts as the encrypted data container.

To unlock these files, you’ll need the password Microsoft used as some hardcoded useless feature in their Office programs, “VelvetSweatshop” (which is ironically enough a wink at critics on Microsoft’s PO policy in 1989). Microsoft Office of course has this feature (try the password and if we fail, ask the user). Luckily I was not the first to find out that Microsoft introduced this password protection. Although it took me some hours of googling to get this knowledge.

I could get my files decrypted using the ooxmlcrypto library of Danilo Mirkovic (plus some minor tweaks to get it running using mono).

Lazy Saturday

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Today, as a first since some time I had a lazy Saturday. Sleeping in till 2 PM, hanging on the couch, catching up some series I follow. The great feeling of having nothing to do other then relax. Turn up the Goo Goo Dolls and write some blog about the joy the Sabbath means for a lazy Western student in the Netherlands. It sounds a bit like I have no life at all, but I actually did achieve some stuff today! For example, I even did some clicking and browsing the internets for my project of the university.

And, I managed to install Google Android on my Touch Diamond. It runs kind of buggy though. But the big advantage of running a dual boot is that you can always switch back to Windows Mobile. I’m really excited about this platform, because it’s very popular right now, which means that a lot of mobile applications are developed for this platform.
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Uitgaan database (Part 1)

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Ik heb voor het uitgaan database project even een ER diagram in elkaar gedraaid (met cacoo :mrgreen:) Ik ben er dus van uitgegaan dat er een verzameling mensen zijn, een verzameling uitgaansplekken en een verzameling consumpties (waarvan een subset drankjes is).
— Sheet 1: 4 entities, 1 parent-child relation

Op Sheet 2 kan je het daadwerkelijke database model zien, wat de relaties:

  • tussen mensen en uitgaansplekken “going_out’s” noemt
  • tussen uitgaansgelegenheden en consumpties een prijs noemt
  • tussen prijzen en going_out’s en users een “buys” noemt

— Sheet 2: Sheet 1 + 3 relaties
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Cacoo

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Vandaag vond ik Cacoo nadat ik erg lang aan het zoeken was geweest voor een beetje handige diagrammensoftware op het internet en plugins voor wordpress. Ik dacht: “Dat is nog eens leuk voor gewone baby diagrammetjes et cetera”, maar het blijkt dus een bijna volledige UML-toolset te bevatten. Het werkt supereenvoudig en is redelijk uitgebreid. Het heeft standaard een set met heel erg leuke items om te gebruiken in een diagram en je kan ze ook nog eens combineren met elk willekeurig ander set.
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Ik heb Wave!

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Ja! Ik heb het! Na ongeveer een week wachten kreeg ik zowaar een invite in mijn inbox! Het is inderdaad allemaal een beetje buggy, maar het is goed te werken in Google Chrome en Firefox. Intussen al 3 mensen een invite gestuurd, maar er zijn echt maar heel weinig mensen op Wave (althans, die ik ken dan). Ik hoop dat het echt een succes gaat worden wanneer het publiek gaat.

Waarom dan?

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Omdat Wave super vet is! Dit mag dan een heel erg lang en redelijk saai filmpje zijn, maar alle technieken die er in beschreven worden zijn redelijk vooruitstrevend. Meer als een Web 2.5

Kijk dat ik de hele tijd http://wave.google.com/ zit te F5en lijkt misschien stom, maar ik wil daar echt zodra het kan op! Dat is nog eens wat anders dan 20 nieuwe emails in je inbox omdat een mailinglist als forum misbruikt wordt. Sounds familiar?