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Or as said by xkcd:
Category Archives: Technology
Really everything related to technology
Explanation for hjsdhjerrddf.com domains
In case you’ve checked some of your spam mails recently you might’ve discovered how a large amount of them include links to sites using seemingly very random names in the domain names. Like hjsdhjerrddf.com or qwetyqfweyqt.com and so on. Hammering-the-keyboard looking names.
The explanation behind these is quite simple and sad: ICANN allows for a “tasting period” before you pay for the domain. Thus spammers register all sorts of random names, spam the world with mails referring the users to these domains and then they return the domain names again before they’ve paid anything, and go on to the next names.
With a large enough set of people and programs doing this, a large amount of names will constantly be kept in use but not paid for and constantly changing owners.
Conclusion: wherever there’s a loophole in the system, someone is there to exploit it for the purpose of sending spam.
More suggested HTTP fun
I’ve already previously expressed my deepest dislike with where the HTML5 work is going, and just yesterday two new internet-drafts appeared on ietf.org that spurred up discussions all around. They’re claimed to be “part of our effort to remove from HTML5 sections that are more appropriate elsewhere” but I’m thinking they’re rather inappropriate everywhere…
The first one named Content-Type Processing Model hits a subject that I’ve been over before, namely the stupidity of having web browsers guess the content based on what it looks like. IE introduced the “I really mean it property“, the HTML5 team wants to standardize the way of the guessing. Personally, I think the world of web will become a better place if the browsers would instead become stricter and more closer follow what the servers actually say the contents is, and then all users would complain to the site admins if things are wrong and then things should be fixed.
Guessing content types allows for sloppy behaviors, it makes it harder to write browsers for the web and it still features a significant risk of guessing wrong.
The second draft propagates for the new HTTP header “Origin”, which according to the authors would help to guard servers against CSRF (“Cross-Site Request Forgery“). The main author says 3% of users on the Internet gets their Referer header stripped while virtually none gets Origin stripped. I claim this is a bogus argument since they strip Referer beacause it is a known and established header and Origin is not. I also completely fail to see the goodness of this and based on several of the other responses on the ieth-http-wg mailing list I am not alone…
Linux distros consolidate crypto libs
For a while already, the Fedora distribution has fought battles, done lots of work and pushed for a consolidation of all packages that use crypto libs to completely go with Mozilla’s NSS.
Now it seems to be OpenSUSE’s turn. The discussion I link to here doesn’t make any definite conclusions but they seem to lean towards NSS as well, claiming it has the most features. I wonder what they base that statement on – if there’s a public doc anywhere that state exactly which has what that makes any contender better than any other for them?
In the Fedora case it seems they’ve focused on the NSS FIPS license as the deciding factor but the license issue is also often brought up in this discussion.
I’ve personally been pondering on writing some kind of unified crypto layer that would expose a single API to an application and handle the different libs as backends, pretty much the same way we do it internally in libcurl at the moment. It hasn’t taken off (or even been started) since I’ve not had the time nor energy for it yet.
BYO rockbox player partly alive
Jorge “casainho” Pinto is known in the Rockbox circles as the main guy behind the “Rockbox Player” project which strives to build their own portable music player to run Rockbox.
They’ve made some progress latetly, and they’ve now run Rockbox far enough to display stuff on their screen:
Click the image for the full photo. Cortesy of Casainho himself. “I hope to take no more than 1 month to finish the port.“
The target is using an Atmel AT91SAM9260 at 200MHz and the screen is a 12bit color 128×128 one.
IETF http-state group created
Over at the IETF another group was just created named http-state (with an associated mailing list) with the specific goal:
Ultimately, the purpose of this group is to create an updated HTTP State Management Mechanism RFC (aka cookies) that will supersede the Netscape spec, RFCs 2109, 2964, 2965 then add in real-world usage (e.g. HTTPOnly), and possibly add in additional features and possibly merge in draft-broyer-http-cookie-auth-00.txt and draft-pettersen-cookie-v2-03.txt.
I’ve joined the list and I hope to follow and participate in this, as I believe the current state of HTTP cookies is a rather sorry mess and the Netscape spec is still what closest describes how cookies work in the wild. Of course I’ll do it with my libcurl experience in my luggage.
While it perhaps would be cool to join the group in more formal way, there’s no way for me to participate in that IETF meeting in San Francisco in March.
Fun with executable extensions in viewvc
A few years ago I wrote up silly little perl script (let’s call it script.pl) that would fetch a page from a site that returns a “random URL off the internet”. I needed a range of URLs for a test program of mine and just making up a thousand or so URLs is tricky. Thus I wrote this script that I would run and allow to get a range of URLs on each invoke and then run it again later and append to the log file. It wasn’t a fancy script, but it solved my task.
The script was part of a project I got funded to work on, that was improving libcurl back in 2005/2006 so I thought adding and committing the script to CVS felt only natural and served a good purpose. To allow others to repeat what I did.
Fast forward to late 2008. The script is now browsable via viewvc on a site that… eh, doesn’t have “.pl” disabled as a cgi extension in its config! The result of course is that each time someone tries to view the script using the web interface, the web server invokes the script locally!
All of a sudden I get a mail from someone, who apparently is admin or something of the site this old script was using, and he mentions that a machine on our network is hammering his site with many requests per second (38 requests/second apparently) and asked me to stop this. It turns out a search engine crawler has indexed the viewvc output several times, and now some 8 processes or so were running this script.pl and they were all looping around getting a page, outputting the URL, getting another page…
While I think 38 requests second is a bit low to even be considered a DOS, it certainly wasn’t intended nor friendly and I was greatly surprised when I slowly realized how it all came to end up like this! Man I suck! It reminds me of my other extension mess from just a few months ago…
Maybe I’ll learn how to do things right in the future when I grow up!
Rockbox 3.1
After three months of work since the last release, we manage to keep the schedule and ship Rockbox 3.1. The list of news since 3.0 include the following:
- A bitmap scaler was added to Rockbox, which means that album art no longer has to be pre-scaled to the correct dimensions on your computer. See AlbumArt for more information.
- The calendar plugin which has existed for the Archos units for a long time is now available on all devices equipped with a clock.
- The spacerocks plugin which was removed from version 3.0 due to a major bug has been brought back.
- Optimised MP3 decoder on dual-core targets, giving several more hours of battery life in most situations.
- Optimizations for AAC and APE decoding
- Backlight fading is now available on most targets.
- When recording in mono, you can now chose between recording the left or right channel, or a mix of both.
- It is now possible to configure which items are shown in the Quick Screen.
- Several new features were added to the WPS syntax
- The build system received a major overhaul. This only matters for people who compile their own builds.
Of course you can find a more detailed list in the MajorChanges wiki page, and the full release notes for 3.1.
My personal contribution has been very tiny this time around and I’ve basically just built the release builds and admined the distributed build system somewhat.
SSL certs crash without trust
Eddy Nigg found out and blogged about how he could buy SSL certificates for a domain he clearly doesn’t own nor control. The cert is certified by Comodo who apparently has outsourced (parts of) there cert business to a separate company who obviously does very little or perhaps no verification at all of the buyers.
As a result, buyers could buy certificates from there for just about any domain/site name, and Comodo being a trusted CA in at least Firefox would thus make it a lot easier for phishers and other cyber-style criminals to setup fraudulent sites that even get the padlock in Firefox and looks almost perfectly legitimate!
The question is now what Mozilla should do. What Firefox users should expect their browser to do when HTTPS sites use Comodo-verified certs and how Comodo and their resellers are going to deal with everything…
Read the scary thread on the mozilla dev-tech-crypto list.
Update: if you’re on the paranoid/safe side you can disable trusting their certificates by doing this:
Select Preferences -> Advanced -> View Certificates -> Authorities. Search for
AddTrust AB -> AddTrust External CA Root and click “Edit”. Remove all Flags.
10G and Direct Cache Access
As some of you might know, I currently work with a client doing 10G network stuff. 10G as in 10 gigabit/second Ethernet. That’s a lot of data. It’s actually so much data it’s hard to even generate network loads of this magnitude to be able to do good tests, as a typical server using SATA harddrives hardly fills a one gigabit pipe due to “slow” I/O: ordinary SATA drives don’t even reach 100MB/sec. You need RAID solutions or putting the entire thing in RAM first. So generating 10 gigabit network loads thus requires some extraordinary solutions.
Having a server that tries to “eat” a line speed 10G is a big challenge, and in fact we can’t do it as 1.25 GB/sec is just too much and yet we run a quad-core 3.00GHz Xeon thing here which is at least near the best “off-the-shelf” CPU/server you can get at the moment. Of course our software does a little bit more with the data than just receiving it as well.
Anyway, recently I’ve been experimenting with 10G cards from Myricom and when trying to maximize our performance with these beauties, I fell over the three-letter acronym DCA. Direct Cache Access. A terribly overused acronym consisting of often-used words make it hard to research and learn about! But here’s a great document describing some of the gory details:
Direct Cache Access for High Bandwidth Network I/O
Summary: it is an Intel technology for delivering data directly into the CPU’s cache, to reduce the bandwidth requirement to memory (note: it only decreases the bandwidth requirement at that moment, not the total requirement as it still needs to be read from memory into the cache, as noted in a comment below). Using this technique it should be possible to drastically reduce the time for getting the traffic. Support for this tech has been added to the Linux kernel as well since a while back.
It seems DCA is (only?) implemented in Intel’s 7300 chipset family which seems to only exist for Xeon 7300 and 7400. Too bad we don’t have one of these monsters so I haven’t been able to try this out for real yet…
Currently we can generate 10G network loads using two different approaches: one is uploading a specially crafted binary blob embedded with the FPGA image to a Xilinx-equipped board with a 10G MAC that then can do some fiddling with the packages (like increasing a counter) so that they aren’t all 100% identical. It makes a pretty good load test, even if the traffic isn’t at all shaped like the “real” traffic our product will receive. Our other approach has been even less good: upload a custom firmware to the network card and have that send the same Ethernet frame… This latter approach didn’t get better because it was a bit too complicated and badly documented on how to make a really good generator out of it. Even if I liked being able to upload custom code to my network card! 😉
Allow me to also mention that the problems with generating 10G is with small packet sizes, like 100 bytes or so as the main problem in the hardwares seem to the number of packets, not the payload part. Thus it is easier to do full line speed with 9000 bytes packets (jumbo frames) than the tiny ones we are likely to get when this product is in use by customers in the wild.
Update: this article was written in 2008. Please note that many things may have changed since then.