app signing and automatic app updates

[oberstet]

Is there a "best-practice" way of achieving the following?

An application is first installed by a signed SIS file.

After that, the application upon startup (and available wireless internet connection) connects to an update server to check for app updates. If updates are available, app components (files) are downloaded, overwriting/complementing existing app files. No SIS file is involved.

On the Maemo platform, a convenient automatic update mechanism (Debian package management) is available which roughly implements described process.

How is this to be done on the S60 platform?

Thanks for any hints,
Tobias

[wizard_hu_]

In Symbian, there is no installation without the SWI (Software Installer subsystem). And the only public interface of SWI is using sis files.

[oberstet]

Is it then impossible to overwrite an existing file (the main app executable for instance) in the filesystem from an update application (given the right capabilities)?

I cannot (better: I'd like not to) believe ..

So there is no way of having an application update itself automatically?

[wizard_hu_]

You need TCB capability for (over)writing files in \sys\bin. However after that they will not be accepted by the OS, since it also stores some checksum about installed binaries.
Actually you can try it with the memory card, since you can access its contents in Data Transfer mode: install some application (like Hello World) on e:, then modify it a bit (for example to print "Hello Word" instead), re-build, and manually overwrite the old executable with the new one in Data Transfer mode. After releasing the device try to execute the application. It will not work.

[oberstet]

thx for your explanation. you think symbian executable signing is waterproof (= in no case non-signed code will be run)?

1. In no case will symbian run an executable file that has not been installed via SIS _and_ which checksum has not changed since installation?

2. It is not possible for an "correctly installed" executable to dynamically load a shared-library that was not also "correctly installed"?

So how am I supposed to do automatic app updates? Would this work?

1. App on startup checks server for new incremental SIS file (is there s.th. like incremental SIS files?)

2. App asks user if she wishes to download

3. if yes, incremental SIS is downloaded to device, app shuts down, but S60 SW installer is launched automatically with new SIS

Thank alot for your hints!

[wizard_hu_]

thx for your explanation. you think symbian executable signing is waterproof (= in no case non-signed code will be run)?

Yes, that is what I "think".

1. In no case will symbian run an executable file that has not been installed via SIS _and_ which checksum has not changed since installation?

The way of installation does not matter, the checksum does.

2. It is not possible for an "correctly installed" executable to dynamically load a shared-library that was not also "correctly installed"?

No, plug-ins also have to be installed.

So how am I supposed to do automatic app updates? Would this work?

1. App on startup checks server for new incremental SIS file (is there s.th. like incremental SIS files?)

There is PU (Partial Upgrade)

2. App asks user if she wishes to download

Asking a question is certainly possible

3. if yes, incremental SIS is downloaded to device, app shuts down, but S60 SW installer is launched automatically with new SIS

You can find some ideas about "launching" a .sis file in the Wiki, and the plugin packs (http://wiki.forum.nokia.com/index.php/SDK_API_Plug-in) also contain related API. The bad news is that you need a separate "upgrader" application for launching the install.

[oberstet]

thx again for your hints.

so I need "partial upgade" PU packages. I'll read the wiki stuff ..

IMHO, seamless app upgrade should be handled by the software installer.
for instance, one could provide a HTTP URL within the PKG definition, which the software installer could use to automatically find (if net connection is there), download and (upon user ok) install PU SIS files.

since this is not there, many people will need to reinvent the wheel ..

I'm quite suprised that this is all much less thought through than Debian (Maemo) package management system. ok, Debian doesn't do signing ..

jst my 2cts