Tuesday, November 10, 2009

Accessing the KDE Wallet from the Cmdline

I needed to write a script that would contact my Exchange server at work via IMAP and list all the messages in the Calendar folder. The idea was to see if it was possible to perform a one-way sync from the Exchange server to a specific calendar in Kontact. I was going to embed my IMAP password in the script - security hole, I know - but we have a password policy that requires the password to change every 30 days. Since I didn't want to edit the script every month I decided to see if it was possible to use the password for kmail that's already stored in my KDE wallet.

I didn't have any luck finding a perl interface to the KDE wallet. However, thanks to the good folks at #kde on freenode, I found that the KDE wallet - and lots of other applications as well - expose their interfaces over D-Bus. This was the first time I'd dealt with D-Bus so it took some getting used to but I figured out how to read my kmail password from my KDE wallet. KDE comes with the handy qdbus program that allows command-line testing of the D-Bus interface.

What follows are step-by-step instructions on how to use qdbus to open your KDE wallet and read your kmail password. I'll incorporate this into my one-way sync experiment using the Net::DBus perl module but I wanted to put this out there in case someone else was looking at that.

Introduction to qdbus
A quick intro to qdbus before we get started so you can explore other options instead of just kwalletd:

The following command shows all applications exposing a DBus interface:

$ qdbus




The numbers and strings refer to applications, however since most applications expose a recognizable string it's common to use just the strings and ignore the numbers.

The following command lists all the DBus paths exposed by the kwalletd application:

$ qdbus org.kde.kwalletd

The /MainApplication path is mainly used when you want to interact with the application itself and you'll find many applications that expose a /MainApplication path. I haven't explored this much but it looks like it should be interesting.

With that introduction to qdbus you should have enough to explore further on your own.

Getting a Password from a KDE Wallet
The following steps will open your default KDE wallet and get your kmail password. Each step will have an explanation, the command issued and the output of that command.

We will use the /modules/kwalletd path in the DBus interface for org.kde.kwalletd for all our password-getting needs. You can get a list of all the methods and signals exposed in the /modules/kwalletd path by using the following command:

$ qdbus org.kde.kwalletd /modules/kwalletd

method bool org.kde.KWallet.isOpen(QString wallet)
method bool org.kde.KWallet.isOpen(int handle)
method bool org.kde.KWallet.keyDoesNotExist(QString wallet, QString folder, QString key)
method QString org.kde.KWallet.localWallet()

method QString org.kde.KWallet.networkWallet()
method int org.kde.KWallet.open(QString wallet, qlonglong wId, QString appid)
method int org.kde.KWallet.openAsync(QString wallet, qlonglong wId, QString appid, bool handleSession)
method int org.kde.KWallet.openPath(QString path, qlonglong wId, QString appid)

Formatting's a bit messed up going forward. Not sure why :-(

However, let's get to work obtaining the password. First, we will open the default KDE wallet - called kdewallet. We will call the org.kde.KWallet.open method which expects a wallet name string, what appears to be a wallet id (similar to a file handle it seems) and finally an application id string. We will use "kdewallet" as the wallet name since that's the name of the default wallet in KDE. We don't know the value of the wallet id so we'll just specify 0. The application id is interesting because KDE wallet prompts the currently logged in user with the application id of any applications that call the org.kde.KWallet.open method which we're abbreviating to just open since that uniquely identifies it in the method list for the /modules/kwalletd path. Specifying a meaningful id here goes a long way to helping the user click on "Allow", "Allow Once" or "Allow Never". With all that in mind, let's use the following command:

$ qdbus org.kde.kwalletd /modules/kwalletd org.kde.KWallet.open kdewallet 0 "KOrganizer-Exchange 1-way Sync"


This results in popping up a dialog box like so:

For the purpose of these experiments, I chose "Allow Once". Once I've allowed it, the qdbus call returns a wallet id - similar to a file handle - that we'll use in all our other method calls. I did see that if I waited too long the dialog box remains visible but qdbus times out. However, the next time you make the
org.kde.KWallet.open call it returns a valid wallet id without prompting which means the permission grant is persistent. I'll have to deal with the timeouts in my perl code somehow. The next step is to see what's stored in my wallet. This isn't strictly necessary if you already know what you want but serves to walk through my own discovery process. Notice I'm passing in the newly given wallet id as well as the full application id as I sent earlier.

$ qdbus org.kde.kwalletd /modules/kwalletd folderList 470467109 "KOrganizer-Exchange 1-way Sync"

Form Data
Network Management Passwords

Let's list the contents of the kmail folder:

$ qdbus org.kde.kwalletd /modules/kwalletd entryList 470467109 kmail "KOrganizer-Exchange 1-way Sync"


I know the account-242017858 account is the one I need the password from because the other account is older. So let's see how to retrieve that password:

$ qdbus org.kde.kwalletd /modules/kwalletd readPasswordList 470467109 kmail account-242017858 "KOrganizer-Exchange 1-way Sync"

account-242017858: [the password here]

There you go folks! That's all it takes. Please let me know if you found this helpful.

Monday, November 9, 2009

Mythbuntu 9.10 Diskless Frontend

With Mythbuntu 9.10 out (simultaneously with Ubuntu 9.10), apparently the "Diskless Server" plugin for the Mythbuntu Control Center is missing. According to this thread on the Ubuntu forums, it's because the developer who was working on that has had to step away from it for the moment. However, manually building the diskless client/server setup still works. That same thread has all the relevant information. Thanks blackoper!

Saturday, November 7, 2009

Seagate FreeAgent USB Drives and Linux

I don't particularly like the Seagate FreeAgent line of drives. Ever since I tried the first one - a 500GB specimen - and it died on me while still connected to a machine running CentOS. One moment it was fine, the next it was gone or remounted read-only. I figured out it happened whenever the drive went idle. I've stayed away from them ever since.

Lately, however, I had to work with a FreeAgent drive again and this time I found this solution to the problem by trolav that uses the power of udev and sysfs to keep the drive working whether or not it's idle. While the solution is posted on an Ubuntu forum, it works well on CentOS 5 as well.