bookmark_borderAuthentication & Authorization is complex

Could there be any more straight forward topic than authentication & authorization? The user provides user name and password and clicks “login”, the backend checks if credentials are valid. Invalid credentials are not authorized, valid credentials are authorized and identified (authenticated). End of story. Right? Well… in many cases, it’s not that trivial.

As a user, I want to be informed if I have to change my password soon.

As a security officer, I want accounts blocked for some time after a certain amount of failed login attempts. I also want passwords to expire after a certain time. I also want login sessions to expire if client IP address or browser identity changes.

As an integrator, I want to enhance the system to digest certificates, Shibboleth, SAML or OpenID Connect, Bearer Tokens, JWTs or even Kerberos Tickets.

As a support person, I want to silently normalize user login names, lowercase them or append domain names to login names.

As a usability consultant, I want to leverage the user database for UI, make user names searchable and browseable.

As a site administrator, I want to be able to filter out certain or most users from the backend even if they provide valid credentials or block login for all but a few users, i.e. for site maintenance.

As an innovator I want to join user bases from two different authentication sources and possibly migrate them on next login seamlessly, without them noticing.

As a sales person, I want to allow a limited guest user experience prior to login rather than force everbody to the login screen.

As a returning user, I want to transparently log in through a remember me cookie, but maybe make the application aware of that limited trust, asking for real login for sensitive operations.

As a developer, I want to be flexible and allow any combination of criteria. Users may login with a global password or a purpose-limited token, I want them to use a second factor like TOTP if they have set up one but pass if they haven’t, unless I don’t allow it.

For business reasons, I want to rate limit API access per hour, per day and per month with individual thresholds each.

As an auditor, I want each request’s authorization process to be logged for evidence.

There is a lot more to consider, but I will stop here.

Authentication is any means of making sure of a requester’s identity. The most common practice in computers asking for a username (identity) and a password (proof). Another common practice is asking some external authority we trust, an Identity Provider. When we look at a person’s passport to compare his photo or fingerprint with his actual face or finger, this involves the same aspect: The name written on the passport for identity. The photo or fingerprint for proof. And, implicitly, we trust the party who created the passport (Identity Provider) and maybe have some means to check the integrity of the document. But if somebody has no passport but a driver’s license, a club membership card, we might instead use this for verification.

Transparent Authentication is a special case where we can identify the user without explicitly interacting with him. This can be achieved whenever the request carries credible identifying information like a pre-established cookie, a certificate, a passport token whose integrity can be validated or other methods.

Authorization is any decision making if a requester has access to a resource. Simply being authenticated might not be enough. Guests without authentication may be eligible for certain areas of your application, but maybe not if they are from a certain IP range or country. A person may be too young or too old to use a certain facility. A person may be old enough to buy alcohol but cannot currently present a sufficient document to proof this. On the other hand, the bearer of a ticket may be eligible to visit some concert, with no interest in his actual identity. A software user may need to both be authenticated and part of a certain privilege group “administrators” to access a configuration screen.

Both requirements can be linked to each other, as well as all those aspects mentioned above.

In another article I will look at how Horde does it and discuss if this approach is still right for modern use cases.

bookmark_borderHorde’s HTTP component goes PSR

This weekend, I gave the horde/http component a some major redesign. See how things escalated. Oh my.
My minimum goals were namespacing, PSR-4 (Revised Autoloading Standard) and some minor, schematic adjustments. The final result is quite different. I ended up implementing PSR-7 (HTTP Message Interface), PSR-17 (HTTP Factories) and PSR-18 (HTTP Client). The code largely complies with PSR-12 (Extended Coding Style Guide) and thus, implicitly, PSR-1 (Basic Coding Standard). I am sure you will find some deviations and issues, so I welcome any Pull Requests against my repo. You will find the new code in /src/. The original, incompatible implementation is untouched and resides in /lib/. They can coexist as they are so different (namespaced vs unnamespaced, among others).

This is not a total rewrite. I could leverage most of the existing code base with some tweaks. This work would not exist without the foundation by Chuck Hagenbuch and all the contributions from the different Horde maintainers over the years. You will also notice similarities to other php PSR-7/18 implementations out there. I checked out Guzzle, httplug/php-http and some others. It was a great learning experience and I will not pretend I am not influenced by it.

As with all my modernisation activities, I made use of features allowed by PHP 7.4. This excludes Constructor Property Promotion and, sadly, Union Types as both are PHP 8. Union Types have been relegated to phpdoc annotations or check methods. Please mind most of the PSR’s target compatibility with PHP releases older than PHP 7.4 and thus do not sport return types or scalar type hints. I followed these signatures where applicable.

One major change between the old codebase and the new one is clients and Request/Response classes.
In the old implementation, there would be one client but different Request/Response implementations using different backing technologies like pecl/http, fopen or curl. The new implementation moves transport code to clients implementing PSR-18. Optionally, they can be wrapped by a Horde\Http\HordeClientWrapper which exposes the PSR-18 itself, but otherwise mimics the old Horde_Http_Client class.

Horde/http is used by very different parts of Horde, including the horde/dav adapter to SabreDAV, various service integrations (Gravatar, Twitter, …), the horde/feed library and application code all over the place. I intend to upgrade those use cases to the new implementation. I am looking forward to criticism or acceptance of that approach.

The goal of this project is more far-reaching. While Horde 4 and Horde 5 already had horde/controller, they made very limited use of it. In my non-public projects, I relied heavily on controllers and I made several attempts at improving the way controllers are set up in horde/core. However, I always felt the results were clunky and not really what I wished to achieve. While horde/controller knows prefilters and postfilters, these are not easy to use and there are few examples. While doing research, I made up my mind. I want to replace Controller/Prefilter/Postfilter with their PSR-15 (HTTP Handlers and Middleware) equivalents. Controllers will be Handlers, Pre/Postfilters will be Middlewares. Together they will be stacks. Authentication, Authorization, Logging etc will be relegated to Middlewares. There will be a default stack to mimic the default controller behaviour in Horde 5 (Be authenticated or be relegated to the login page). You will be able to define application-specific default stacks or request-specific stacks. As Middlewares are a public standard, we might be able to leverage middlewares existing out in the wild or attract microframework users to some horde built middlewares. I want to make it easier for coders to build horde apps without relearning everything they needed to learn for laravel, laminas or symfony. I also want to make it easier for everyone to cooperate. Horde is among the oldest framework vendors, predating most of PEAR and Zend. I think we still have some bits to offer.

Missing Bits:

  • While I did some implementation of UploadedFileInterface, it is still quite basic
  • UploadedFileFactoryInterface is missing as I have not yet built the server side use cases
  • Unit Tests need to be adapted to the new code base. Is there some PSR Acid Test out there?
  • I began implementing the ext-http (PECL_HTTP) backend but stopped as I am unsure about it. That extension is in version 4 now and still services version 3, but we have backends for versions 1 and 2. I need to learn more about it and decice if it makes sense to invest into that aspect.

bookmark_borderMaintaina Horde: Fourth Of July Additions

I packaged some more exotic horde apps and libraries for use with the composer installer and the FRAMEWORK_6_0 codebase. This was mostly formal conversion work, no actual testing was done. Some of these items might not even be very useful to most administrators. Nevertheless, I want to close the gap between what is available in the horde git-tools install and what can be installed through the horde installer plugin for composer.

These apps are now available:

  • refactor (refactoring utility)
  • trean (bookmarks)
  • ulaform (Forms app)
  • sesha (H4ish inventory app)
  • skeleton (template application)
  • sam (Spam Assassin Integration app)
  • operator (phone call details reader)
  • pastie (simple H4ish pastebin app)

The libraries were previously not available for H6 and now have seen their alpha release:

  • horde/thrift
  • horde/service_urlshortener
  • horde/service_vimeo
  • horde/service_facebook
  • horde/service_twitter
  • horde/scribe
  • horde/reflection
  • horde/pgp
  • horde/rampage
  • horde/oauth
  • horde/kolab_resource
  • horde/pdf
  • horde/lens
  • horde/openxchange
  • horde/mongo
  • horde/memcache

I wish you all a joyful fourth of july.

There are still some items missing, including the Klutz cartoon reader app and some Kolab related libraries.

bookmark_borderNo more master branch in maintaina horde

I am changing the default branch in all maintaina-com/ horde repos to be the FRAMEWORK_6_0 branch. In a separate next step, the master branch on these repos will be removed.

This is not due to any semantic discussion of technical terms like “master”. I am simply acknowledging reality. At the moment I cannot hope to get all those changes merged into horde’s proper master branches. I do incorporate their advances into maintaina but it is not going to the tight feedback loop I would wish to have.

I have no use for a branch pretending to be something different than or beyond the FRAMEWORK_6_0 venture. I had README’s in all those master branches warning against using them. It is way better to simply get rid of them now.

bookmark_borderHorde/Rdo ORM: PSR-4 and BC Breaks

Summary: Horde/Rdo ORM got upgraded for Namespaces. User code conversion is straight-forward. Backward Compatibility is limited.

If you ever wondered, RDO stands for Rampage Data Objects. This has been on my list for quite long, but it took some time to get it right. The horde/rdo library is horde’s Object Relational Mapping (ORM) solution. It allows you to store objects into sql databases or retrieve them without writing SQL. Originally, it has been written by Chuck Hagenbuch way back in the PHP 4 days and I have been a heavy user for years. If you know Laravel’s Eloquent, Doctrine, Hibernate, ActiveRecord, nHydrate or Dapper, this one is Chuck’s “as light as possible” implementation of the concept. Colleagues from B1 Systems have been users and contributors over the years. However, it has long been time to rethink Rdo in the light of newer capabilities of PHP 7.4 or even PHP 8. This time is now.

But you should not fear upgrading. First, the library still keeps the unnamespaced PSR-0 code, at least for the time being. Second, there is a straight-forward upgrade path for existing users.

Horde_Rdo_Base -> Horde\Rdo\Base
Horde_Rdo_Mapper -> Horde\Rdo\BaseMapper
Horde_Rdo_Factory -> Horde\Rdo\Factory
Horde_Rdo_List -> Horde\Rdo\DefaultList
Horde_Rdo_Iterator -> Horde\Rdo\DefaultIterator
Horde_Rdo_Query -> Horde\Rdo\DefaultQuery
Horde_Rdo_Exception -> Horde\Rdo\RdoException
Horde_Rdo:: -> Horde\Rdo\Constants::

It’s about as easy as it looks. Converting an application took me a few minutes. You might have noticed the names do not exactly match. Some names were not practical to simply turn into namespaced classes. In other cases, I turned class names into interface names. I found myself implementing the same enhancements over and over in multiple projects and I found myself wishing there was an easy way to do some others.

Less Boilerplate Mappers and Entities

Rdo is much more fun than some other ORMs as it comes with very little configuration. The library autodetects properties from the table columns. Datetime fields are automatically cast to Horde_Date objects. By default, Rdo tries for a convention over configuration approach for mapping table names, mappers, entities etc. Unfortunately, for most of my projects, that default does not fit too well to the class structure and file layout I choose. But still, implementing a new pair of mappers and entities takes two files and only two or three settings I ever need to think about.

Most often, subclassing the base mapper and the base entity is the right thing to do. But sometimes, you do not really care. If all you ever do to your entity is call ->toArray() and serialize it to json, you would be served very well by a generic entity instead. This is something on my list. I would even go one step further: If all you are changing to a mapper is subclassing and telling it the name of its database table and entity class, why subclass at all? Yes, I would want to turn the optional Factory class into something smarter. It will give you your mapper, be it an instance of the generic mapper with the right table name or something very customized.

Custom List Objects

Rdo queries always return a Horde\Rdo\List. This is a good default implementation and it makes common tasks easy. However, there are situations where you want your list of entities to be specific to an entity type or maybe a subclass of some base list class completely external to Rdo. Maybe you want to manipulate a list or merge results from two different queries.

Custom Entities
Sometimes the default entity implementation does not serve you well. There’s a range of things you would want.
– You want to inherit from a base class to attach behavior to your data. So you attach an interface and a trait to that foreign class to make it Rdo aware.
– You want to implement your own behaviour altogether
– You want Rdo to implement a proper repository with strongly encapsulated, less chatty domain objects. Rdo should provide a mechanism to produce those objects for you rather than having you cast or wrap Rdo\Base objects into your actual models. But it should not force you to think about such concepts before you really need them.

NoSql backends
Remember the name Rampage Data Objects? Rdo is mostly about mapping data to objects. It’s not about autogenerating the smartest SQL for the most obscure use cases. But once you have your prototype version ready, your first feedback comes in, you think about new features – and suddenly you want to support a new backend for some of your domain objects. Be it a NoSql database, a key/value store, a limited scope within a directory like LDAP or even a REST service. In a traditional horde application, you would wrap Rdo into a Driver called Driver/Rdo or Driver/Sql and implement a different backend. But what if you do not want to flip all your data to the new backend? Only the shopping list should go to the nosql backend but not the customers or the product inventory? You end up implementing individual drivers with individual backends. But you used Rdo’s relations feature … things get messy.

To achieve these capabilities, I want to make the Mapper less dominant. The formerly optional Factory gets promoted to take care of managing the right mappers, entities, backends, list types. This is what these interfaces are for. Mappers should mostly take care of mapping between an object class and a plain data format. Currently the mapper and query do too much, tightly coupled with the single mandatory list type. This will change.

Rampage Data Objects provides out of the box defaults for easy and common use cases. It gets you started really quick. We will add the capabilities needed when your application is maturing and your use cases get more demanding. This will be fun.

Backward Compatibility Breaks
The Horde\Rdo\Base* classes and their return types will be your best bet for backward compatibility. If you don’t try to use entities and mappers for side effects, you will be very safe. Factory’s constructor will change very soon. Factory should best be created from a Dependency Injector. Mappers should be created from Factory.

You should not rely on mappers exposing adapter or factory for creating other objects. Also, trying to manipulate sql session modes or transactions through Rdo’s adapter is not a good idea.

bookmark_borderWhat’s new in Maintaina Horde: Status 3/2021

  • CalDAV and CardDAV now run off SabreDAV 4 rather than SabreDAV 2
  • We now support both the Composer installer versions 1 and 2.
  • Nothing still depends on the PEAR protocol.
  • The Horde Icalendar Library now supports vCard 4. Still, importing/exporting vCard 4 or using it in CardDAV in the addressbook App Turba is not yet done. This requires good test coverage, syncing is not something I’d like to break
  • PHPUnit Tests are being upgraded from PHPUnit 4 to PHPUnit 9.
  • All libraries and groupware-related libraries are now packaged as “alpha” versions from the FRAMEWORK_6_0 branch

bookmark_borderMaintaina Horde: Now on Leap 15.2

I changed the Horde Images to use openSUSE Leap 15.2 instead of openSUSE Tumbleweed as a base. You should not experience any issues but I have not yet tested much. The change was necessary as I had build failures since 2021-02-17 in the github actions CI builds. It’s something about the docker used in ubuntu-latest being too old or github’s security settings being too strict. I did invest some weekend hours, but could not really solve it. I intend to switch back to tumbleweed at some point.

Update July 2021: I can now build tumbleweed-based images again.

bookmark_borderDAVx5 CalDAV may break with Unicode symbols in Horde/Kronolith syncs.

If you get user complaints about broken CalDAV syncs with Horde, there’s many places to look at. In one particular instance, an event was created from travelling app Transportr into the stock android Calendar app. Through the DAVx5 sync app, the user wanted to push these events to Horde’s SabreDAV interface – and from there, also sync it to his desktop email solution, Mozilla Thunderbird.

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However, his sync application told him about an error. The server administrator saw a 500 status code in the server log. - user [24/Jan/2021:18:48:26 +0000] "PUT /horde/rpc/calendars/user/calendar~KL14jYhCMpbet4ecYzAg1bn/2bace303-f0d8-4df6-9652-baa5fb9e86c4.ics HTTP/1.1" 500 892 "-" "DAVx5/3.3.8-ose (2021/01/13; dav4jvm; okhttp/4.9.0) Android/11

The root cause was actually not in the software code but in the MariaDB database configuration. The calendar entry from Transportr included some Unicode icon characters like a fast train and some arrows. These characters are part of the standard unicode encoding, utf-8.

Now you might wonder: New installations of mysql and MariaDB default to a character set they call utf-8 since 2010 or so. This shouldn’t be an issue. However, what they call utf-8 is not what you would expect.

Some years ago, TV sets which did not support the full HD resolution were marketed as “HD ready”. In some sense, the default character set is “unicode ready” at best. The default data type saves on disk space by encoding a subset of utf-8 into up to three bytes. While this supports most natural language characters, it is only a fraction of what Unicode can offer. Database manufacturers are well aware that this is not something you should run nowadays that unicode icons like the hamburger are all over the place is user generated content. The mysql manual even says:

“Please use utf8mb4 instead. Although utf8 is currently an alias for utf8mb3, at some point utf8 is expected to become a reference to utf8mb4. To avoid ambiguity about the meaning of utf8, consider specifying utf8mb4 explicitly for character set references instead of utf8.”

Now that’s what I did. First I changed horde’s database encoding to utf8mb4 in conf.php:

$conf['sql']['protocol'] = 'tcp';
$conf['sql']['charset'] = 'utf8mb4';

Then I changed the mysql server’s and client’s default charset:

cat /etc/mysql/my.cnf
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
default-character-set = utf8mb4
default-character-set = utf8mb4
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

I have obviously stripped a lot of file content not relevant to our story. After reloading the database, all new connections should use the real utf8 encoding and new tables should be created with the new standard. But what about existing content? We need to convert all tables and all their text-like columns, varchars, mediumtexts etc.

First, it’s backup time – better safe than sorry.

Then, let’s find all tables in our db server and feed them conversion commands.

mysql --database=horde -B -N -e "SHOW TABLES" | awk '{print "ALTER TABLE", $1, "CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"}' | mysql --database=horde

Do this in a downtime or ensure HA some way or other. It will take some time. Some sources suggest it might be sensible to also rebuild the tables with the optimize command. I am not very convinced, but it won’t harm.

mysqlcheck --auto-repair --optimize --user="hidden" -p --databases mysql horde

After this, repeat the sync test. It should work this time.

bookmark_borderHorde Development Review: October 2020

October was a very busy month in Horde development, even though a lot of things happened under the hood and cannot be accessed right now.

  • A decision was made that Horde RPC will default to json-rpc and deprecate xmlrpc in upcoming releases, maybe already dropping xmlrpc in Horde 6. PHP8 will remove xmlrpc from the core distribution and move it into PECL, giving it much less of an installation base.
  • B1 Systems GmbH released a typescript client for the Horde Ajax Framework
  • Horde Injector: I continued my work from September. The Maintaina version of Injector now supports PSR-4, PSR-11, PSR-12 specifications. Backward compatibility is good. The unit tests have been converted to namespaced versions – see
  • Horde Components: The Components tool has been converted for PSR-4 autoloading in a composer setup. Also, some minor improvements on the composer file generator have been added
  • I worked on upgrading Diana Hille’s DNS library for the horde framework, giving it the same PSR-4 makeover, converted it from wrapping AWS cli to wrapping AWS Route53 SDK. I think we can opensource the component soon.
  • I created a little testbed application for the improved controller/routes handling in recent horde/core. horde/frogsie is the first Horde application stub to feature a RESTish interface. Frogsie writes iptables rules to implement a TCP/UDP Front Proxy in plain linux.
    It doesn’t sport web UI or CLI though as it’s both a case study and a stop-gap utility. However, it’s a good example to learn from.
  • Horde Installer Plugin v1.1.0 supports both composer 1.x and composer 2.0 – This is mostly based on work by Kieran Brahney of SupportPal. I also began working on converting horde-deployment to remove the last bits of PEAR and make it compatible with composer 2.0. It’s not released yet.
  • I am looking at the old vilma application at the moment. This will most likely not materialize before november. Vilma is a simple mailbox manager along the lines of postfixadmin. My primary interest is using it together with hordectl for a turnkey default setup. Vilma will get the PSR-4 treatment and likely I will want to change some of the architecture. Focus is on a minimum viable product that nicely integrates with my groupware bundle and fulfills very limited needs. I appreciate the work of Christian Bolz on PostfixAdmin and I do not intend to build a full scale replacement.

What’s next?

  • More library conversions to PSR-4, PHP7 features.
  • Most likely I will upgrade unit tests to a more recent PHPunit
  • Release Cleanup / Upstreaming efforts for existing non-released code.
  • Better theme support for horde-installer-plugin

Results first, more talk later.

bookmark_borderAutowiring Vfs in a Horde App

The Horde Vfs is an abstraction around storing and retrieving files. Calling code does not care about where the Vfs is actually stored, be it a remote filesystem, a dav resource, a database or a path in the local filesystem. Autowiring means the Injector knows how to create a class using some other class without having it explicitly defined

For this article, I want to get an instance of Horde\MyApp\ReportGenerator which uses the VFS to store reports.

First let’s create the ReportGenerator.


namespace Horde\MyApp;
class ReportGenerator
    private $driver;
     public function __construct(\Horde_Vfs_Base $driver
         $this--->driver = $driver;

When a controller in the app wants a report generator, it would require it through the dependency injector like this:

$reportGenerator = $injector->getInstance('Horde\MyApp\ReportGenerator');

Autowiring allows the injector to return an instance even if it has not been explicitly bound to the injector. For this to work, all required dependencies must be interfaces which have either been registered with the injector or can themselves be created from registered interfaces or have no dependencies themselves.

Now, Horde_Vfs_Base is the common base class of all Horde Vfs drivers.

However, Horde does not provide a default binding for Horde_Vfs_Base even though Horde_Core has a default factory Horde_Core_Factory_Vfs.

Thus, we need to define one. In Application.php, look for a method _bootstrap(). We will use it to setup the injector binding. Normally, we would just want to use the existing factory through $injector->bindFactory($interface, $factory, $method);

We cannot do this in this case. The Vfs Factory’s create method has two string parameters to allow creating multiple Vfs instances. For our app, we just want to get the default configured in horde base. But this doesn’t work. bindFactory would automatically pass a child injector to the create method. This would override the default first parameter “horde”. In the end, we would receive the factory’s exception saying we should configure a backend first – even if we did.

To work around this, we could create an own factory class in our app which uses Horde_Core_Factory_Vfs as a dependency. Horde_Injector would just know what to do. But let’s not do this as it’s quite some boilerplate just for creating a Vfs with default configuration.

Instead, let’s use the closure binder.

protected function _bootstrap()
     $injector = $GLOBALS['injector'];
     $vfsClosure = function(\Horde_Injector $injector) {
     return $injector->getInstance('Horde_Core_Factory_Vfs')->create();
$injector->bindClosure('Horde_Vfs_Base', $vfsClosure);

Now injector knows how to provide a Horde_Vfs_Base implementation which the ReportGenerator requires. We can ask injector to provide an instance. Injector will look if it already has an instance from a previous call, otherwise runs the closure to create the dependency, then create the actual ReportGenerator instance.