Review Request 120202: [OS X] improvements to the kwallet/OSX keychain integration

Thu Sep 25 14:58:45 BST 2014

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https://git.reviewboard.kde.org/r/120202/
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(Updated Sept. 25, 2014, 3:58 p.m.)

Review request for KDE Software on Mac OS X and kdelibs.

Changes
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I have addressed the idleTimer's slot issue by making the WalletPrivate class inherit QObject in addition to QOSXKeychain.h . For that I've had to move it to a new headerfile, `kwallet_mac.h`, a header I could have created earlier given the complexity `kwallet_mac.cpp` has attained. In the end this I thought this was the cleanest solution.

Now that this is out of the way (I hope), I'd appreciate some feedback on the 2 open questions:

1- what is missing from my DBus implementation that could explain why I see the slots and signals in qdbusviewer but calls sent to the slots never arrive in my code? Or rather, how do I get it to work?

2- how to complete the DBus-free wallet-user registry? The only thing missing is a method to share the structure in distributed memory without a central server. I'd need something like QSharedMemory with resizing capabilities.
Should I stop looking and share the reference to another QSharedMemory instance rather than share the registry's representation directly? A kind of shared handle (pointer to pointer, in old Apple speak from pre-MMU days).
The requirements are simple: each application having a Wallet open should be able to read the current registry contents ("user list"), and add or remove oneself to/from it.
All those operations can be performed on a copy freshly checked out of shared (and locked) memory but I fear it'd be rather delicate and race-condition prone. Each client will need to attach to the shared reference as well as the shared resource (to which that reference refers), and I think they'd all need to release the shared resource when the shared reference changes.

Any thoughts?

There was some demand from the kde-mac community to try and come up with an approach not requiring a central server (kwalletd), so I'd probably want to get approach 2 working even if we get approach 1 to function.

Repository: kdelibs

Description
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I'm still working on (the KDE4-based version of) my OS X keychain backend for kwallet. I'm at a point where I think I can present a work-in-progress in an RR because at least one feature has been improved enough to be of interest for everyone, and also because I could use feedback on how to proceed.
I'm currently focussing on 2 settings that are configured in the kwallet KCM (SystemSettings), and for which I'm working on an implementation not requiring kwalletd and/or DBus.

- idle time closing of wallets. This feature was not supported in the commited version presented in https://git.reviewboard.kde.org/r/119838/ The present patch adds an idleTimer and a shared lastAccessTime member. The idleTimer is reset each time a client performs one of a series of actions that I count as wallet accesses, and before resetting I update the idle timeout value from KConfig. When the timer fires, the elapsed time is compared to the shared last access time, and if it is >= the timeout, the wallet is closed. This applies only to "KDE keychains", so keychains used by OS X applications should not be affected.

- "close when last application exits". This requires maintaining a "user list" which keeps track of what application has what wallet open. I've implemented an "internal" version of such a registry, mapping wallet name to application names and the list of wallets they have open (a list of wallet reference, pid per application name). The registry is functional, but I have not yet decided (read: figured out) how to make a distributed representation of it.

So the work-in-progress concerns the distributed user registry. The idea would be to maintain the registry in shared memory, meaning it'd be reset (= disappear) when the last application exits, contrary to a file which can go stale. This would be simple if QSharedMemory objects could be resized, but apparently they cannot, so I'll have to look at other solutions possibly involving OS X frameworks (NSData and it's non-objectiveC version CFDataRef or CFMutableDataRef might be candidates). Suggestions welcome.

Other work in progress concerns a less wheel-reinventing approach that builds on kwalletd and DBus. I don't see why the code used in `kwallet.cpp` wouldn't work, but I must still misunderstand its finer details. The present patch contains outcommented code that does indeed cause kwalletd to be launched and slots and signals to become visible e.g. in `qdbusviewer`. But they don't work, which in turn makes the whole kwallet layer dysfunctional. Here too feedback is welcome on how what I'm missing and/or how to get this to work.
Once kwalletd works, wallet idle timeout closing and closing when the last client exits should work out-of-the-box, or at least I suppose.

Diffs (updated)
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  kdeui/util/kwallet.h d7f703f 
  kdeui/util/kwallet_mac.cpp 8344ebb 
  kdeui/util/qosxkeychain.h d0934e6 
  kdeui/util/qosxkeychain.cpp 7cb9a22 

Diff: https://git.reviewboard.kde.org/r/120202/diff/

Testing
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OS X 10.6.8, kdelibs 4.14.1 git/master, KDE/MacPorts 4.12.5 .
Once finalised, all changes should port easily to KF5's kwallet_mac.cpp .

Thanks,

René J.V. Bertin

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