Computer science, IT, Photography

Pitfalls when running a mail server

When running a mail server, some basic rules have to be followed, e.g. ensuring that the server does not operate as an open relay. These rules are nowadays well known and the default configuration provided with MTA software typically avoids these “big no-nos”. Still, there are many pitfalls when configuring a mail server. In this post I want to share some of those pitfalls that I stumbled across in the last years myself.

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Migrating from ownCloud 9.1.6 to Nextcloud 10

If you are stuck with PHP 5.4 (e.g. because you are still running Debian Wheezy) and want to migrate from ownCloud to Nextcloud, you are probably facing a minor issue. Nextcloud 11 and newer require PHP 5.6 so you have to stick to version 10 instead. Nextcloud 10 reached its end-of-life with version 10.0.5, which internally corresponds to ownCloud version 9.1.5. The most recent version of ownCloud 9 is version 9.1.6 though, so when trying to migrate to Nextcloud you will face the following error:

Downgrading is not supported and is likely to cause unpredictable issues (from to

Looking at the git commits between ownCloud 9.1.5 and 9.1.6 shows that there were no changes to the database layout. So, as a workaround, you can just edit your config/config.php and set version to or lower. Afterwards, you should be able to run the normal upgrade procedure.

Fixing Roundcube’s command execution vulnerability in Debian Wheezy

Recently a quite serious vulnerability (CVE-2016-9920) in Roundcube was reported. Until now (7th Dec) this vulnerability is unfixed in Debian’s roundcube packages (see the corresponding entry in the Debian Security Tracker).

The upstream patch is not directly applicable to version 0.7 which is used in Debian Wheezy but with a little modification it is. Following you find a corresponding patch*.
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Broken calendar migration from Google to ownCloud

For some time now I run a small ownCloud instance to synchronize my contacts and calendars across different devices. When another person tried to migrate his Google calendars to this instance there was an issue though. The .ics files exported from Google contained invalid entries that were copied into ownCloud’s database and broke synchronization with 3rd party applications like Thunderbird’s Lightning extension.

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