tsocks is a cool Linux utility. Using LD_PRELOAD, it intercepts calls to the OS’s socket-related functions (connect() and co.), and transparently tunnels them through a SOCKS proxy. Example usage:
As it happens, curl supports SOCKS proxies, but tsocks allows you to add support to programs that know nothing about them (like, say, wget).
Sadly, it’s no longer maintained.
Marc Abramowitz got it working on OS X (patch) back in 2006 by switching to DYLD_INSERT_LIBRARIES, among other things, but even this port has succumbed to bit-rot.
Feel like calling your company something like Cashcoup, Feebany, Bunkapps, Morpone, Realance or Afative? Combining CrunchBase, Mathematica and stochastic matrices yields the Web 2.0 Company Name Generator:
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My first attempt at automated name generation used a few Gutenberg books, which yielded appropriately Victorian-sounding names. CrunchBase seems to work better. If you want to experiment with the code, download the notebook.
Anyway, the cool news is that he’s now going to be spending some time hacking on the offline Wikipedia iPhone app. Stay tuned to see what cool features he cooks up.
Back To My Mac seemed like a neat feature when Steve demoed it back at WWDC 07, but very little attention seems to have been paid to it since.
Remote NAT traversal for screen sharing and AFP is cool and all, but the most useful part is hardly mentioned anywhere: Back To My Mac can automatically establish on-the-fly tunnels to any machine with Back To My Mac enabled. You can just ssh foobar.joebloggs.members.mac.com, or curl something directly from the web server, or whatever. So long as you can make outgoing connections, it should work around any routers, firewalls, and other wrinkles in the network topology.
The catch is that it only works over IPv6. sshd on OS X has IPv6 enabled by default, as does Apache, but a lot of other stuff doesn’t.
I haven’t figured out how it works yet. It’s definitely not a straight IPv6 tunnel—the source IP of any connection is a private address (which kinda seems to defeat the purpose of using IPv6 in the first place). Any info or pointers appreciated.
Update: In the comments, JH points out that it’s not a private address, but an RFC 4193 unique local address.
I’ve seen third-party iPhone developers complaining that this trick is only available to Apple; they want to use it too. The technical reason why they can’t is that because application bundles are cryptographically signed, you can’t modify the contents of the application bundle (by, in this case, changing the default.png resource file) without breaking the digital signature. Apple could enable this feature for signed applications by providing for a way to specify a dynamic default.png that exists outside the application bundle, somewhere in the application’s private Library folder.
With a bit of hackery, it turns out that you can actually create dynamic Default.png files that don’t cause problems. Here’s a demo of it in action:
This is possible because OS X’s codesign binary (I’ve had far too many run-ins with it while writing the offline Wikipedia browser), used to sign and verify bundles, doesn’t traverse symlinks:
$ codesign -vv Rememberer.app
Rememberer.app: valid on disk
$ touch Rememberer.app/test
$ codesign -vv Rememberer.app
Rememberer.app: a sealed resource is missing or invalid
/Users/patrick/Projects/Rememberer/build/Debug-iphoneos/Rememberer.app/test: resource added
$ rm Rememberer.app/test
$ codesign -vv Rememberer.app
Rememberer.app: valid on disk
$ ls -l Rememberer.app/randomfile
lrwxr-xr-x 1 patrick staff 24 8 Nov 17:21 Rememberer.app/randomfile -> ../Documents/randomfile
$ dd if=/dev/random of=Documents/randomfile count=1
1+0 records in
1+0 records out
512 bytes transferred in 0.000095 secs (5382165 bytes/sec)
$ codesign -vv Rememberer.app
Rememberer.app: valid on disk
This is somewhat understandable; the symlink itself doesn’t change. But if “randomfile” is instead something like “Default.png”, the OS will happily load it from the default path in the application bundle—and follow the symlink—even though the file is actually stored in an area (Documents) that’s dynamically modifiable.
I’m guessing that Apple will consider this a bug, and fix it in some future version of the OS. If that happens, though, the downside will probably be nothing worse than losing your dynamic Default.png.
To get it to work in Xcode, you can just add a Run Script phase to the Target:
Here’s the Xcode project for the above demo. (Code is public domain.)
Update (Nov 19): TechCrunch pointed out some wider implications of this vulnerability. Although the article was met with some skepticism, they’re basically right. There’s a good summary of the situation on the McAfee Avert Labs Blog.
I wrote the offline Wikipedia browser back before there was any official iPhone SDK documentation (or SDK, for that matter), and figuring out the APIs was a bit of a challenge. So in trying to get a handle on things, I wrote an API explorer for showing a rough outline of the system’s classes. It started out as a bare-bones script, and since then I’ve gradually bolted various bits on to it.
Unlike many compiled languages, Objective-C supports pretty powerful runtime introspection. The explorer uses this to present the implemented protocols, methods and instance variables of every loaded class. In addition, if the class responds to initWithFrame: (these are usually subclasses of UIView), you can draw and resize an instance, to get a basic feel for what it does.
It’s all more easily explained with a short screencast:
If you want to play around with it (it works in both the simulator and on the devices themselves), you can download the code.
Economic theory suggests that financial innovation must lead to failures. And, in particular, since successful innovations are hard to predict, the infrastructure necessary to support innovation needs to lag the innovations themselves, which increases the probability that controls will be insufficient at times to prevent breakdowns in governance mechanisms. Failures, however, do not lead to the conclusion that re-regulation will succeed in stemming future failures. Or that society will be better off with fewer freedoms. Although governments are able to regulate organisational forms, they are unable to regulate the services provided by competing entities, many yet to be born. Organisational forms change with financial innovations. Although functions of finance remain static and are similar in Africa, Asia, Europe and the United States, their provision is dynamic as entities attempt to profit by providing services at lower cost and greater benefit than competing alternatives.
Back at the start of the year, I blogged about an app I wrote that allows you to store a complete copy of Wikipedia on an iPhone/iPod Touch.
The app got more attention than I expected, with tens of thousands of downloads in the first month, which I think made it one of the more popular apps for the jailbroken iPhone. (Not anticipating any of this, the non-existent documentation and installer ensured many were confused, and so someone made a YouTube installation tutorial that has over 57,000 views at time of writing. I’m not sure if that’s good or bad.)
I also released the app’s source code, and it’s been pretty fun to work with a lot of talented people in improving it. The OLPC crew took an interest in it, and thanks to some cool work from Chris Ball and Wade Brainerd, the iPhone application was ported to the XO laptop. Chris announced in June that:
We’re going to be shipping the result to Peru on tens of thousands of laptops in the near future, and it should go up to hundreds of thousands if the other South American countries with OLPC deployments decide to include it in their builds too.
When the iPhone 3G was announced, I didn’t originally intend to port the application to the new version of the OS. The original app was a short Christmas project, and now that I’m working at Live Current, I don’t have much spare time to hack. But after a few hundred emails enquiring about a new version, I eventually felt too guilty not to. So I spent a weekend porting it to iPhone OS 2.0, added a handful of new features, and I’m happy to say that the end result is now available in the App Store.
While working on some web analytics software a few weeks ago, I wrote a dirty hack to enable pictures in SLIME REPLs. The implementation is ugly, but I think the concept is neat:
Update (22/06): To clarify in response to the reddit thread, this is a dirty proof-of-concept that resulted from an hour of hacking, and obviously shouldn’t be merged into mainline SLIME as it stands. See the slime-devel thread for the discussion surrounding it. With that said, it should be fairly straightforward to rework it as a saner contrib module.
Some sweet work by Chris Ball and Wade Brainerd has resulted in the iPhone app I wrote for offline browsing of Wikipedia being ported to the OLPC. From Chris’s email:
We’re going to be shipping the result to Peru on tens of thousands of laptops in the near future, and it should go up to hundreds of thousands if the other South American countries with OLPC deployments decide to include it in their builds too.
