Glop

This was my pet peeve with my mobile phone and java software. Everytime a java application attempted to access the filesystem on the phone, a permission request dialog pops up. For a mapping application that uses tiles of around 256×256 pixels, it needs to access the filesystem with great regularity and thus great annoyance ensues.

The correct way to solve this problem is for the application writer to sign the java application with a certificate, obtained from the likes of Thawte or Verisign. The problem with this is:

• It costs money to get a certificate
• It appears that only a commerical entity can purchase a cert. for signing j2me applications.

There are alternatives to this that I spent most of the day investigating. The best way seemed to be to creates ones own private key and certificate. Upload the certificate to the root store on the mobile phone and sign the application with the private key. Tedious perhaps, especially seeing as I’d have to sign every application and every new version of the application I’d put on the phone, but I was happy enough to do that.

However. There is no support for adding ones own certificates to the K750i/W800i. No official support that is. After much googling and trawling through the forums at http://www.esato.com I found software to do this. An application called FAR Manager in conjunction with plugin called SEFP. The FAR Manager application is a generic file system manager, but it supports plugins for accessing various filesystem types other than a standard hard drive. Network filesystems, FTP, etc.

The SEFP, Sony Ericsson Flash Plugin, is able to connect to a K750i/W800i phone over the stock DCU-60 cable and offer access to the filesystem on the onboard flash memory.

There is a brief guide available showing the basics of using FAR Manager in conjunction with the SEFP.

Once this is up and running on the mobile phone (You’ll need to install the Sony Ericsson Update Manager first if you haven’t already. This contains the USB flash drivers the plugin uses to access the phone), it’s possible to copy files to/from the mobile phone flash memory. It’s then a simple matter of uploading a .cer file to the correct directory on the phone, modifying a customize.xml file on the phone to list the certificate, and reseting the phone using a master reset.

Supposedly. This doesn’t actually work. The certificate does not get added to the root repository as some import function needs to be run. I couldn’t figure out how to do this, it appears that the phones firmware needs to be completely flashed and the certificate copied over before the phone is started. This way, when it’s started for the first time with the new firmware, it initializes the certificate database.

So I returned to the forums and kept trawling. I found an easier method, but this is a real hack. The flash plugin has some extra features that allow one to edit the raw flash memory directly, at a bit level. (Extremely useful for obtaining a good forensic image of a Sony Ericsson mobile phone I’d imagine). The plugin also has support for small .vkp scripts that when run, will patch a location in the flash with certain values, so simple automation of memory editing. A number of these scripts have been created that perform a number of actions. And one of those actions is.. you’ve guessed it, to disable requests for file system access.

I downloaded the script from this forum article and installed it using the FAR Manager with plugin. (In the application, press enter on the flash link, press tab to select the other pane, browse to and select the .vkp file. Press F5 to copy and when prompted select the run .vkp file option.)

Success ! No more filesystem prompts. Now I just need to figure out where j2memap looks for map files on the memory card and I’m away in a hack.

This entry was posted on Saturday, December 16th, 2006 at 2:02 am and is filed under GPS. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.