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From dav...@apache.org
Subject Some thoughts around adding security for Karaf Shell Commands
Date Thu, 15 Aug 2013 14:26:15 GMT
Hi all,

In the context of KARAF-2442 I started looking at securing the commands in
the shell. I wanted to do something similar to what I did for the JMX
access (KARAF-2435) in that this should be configurable by a Karaf
administrator. I also really wanted a generic solution that would work with
all commands, so that there would not be a big burden on the command
developer. I know that there was discussion about this in the context of
Karaf before, my approach here is a bit different...

Here's what I came up with…
Karaf Commands are implemented OSGi services and one of the lesser known
features of the OSGi service registry is the fact that you can control
service registrations through service registry hooks. This effectively
allows you to change registrations, control who sees what registrations and
also proxy service objects with some interceptor [1].
I thought that this might be a nice tool to use to add security to the
Karaf Commands from the outside, so I started an experimental
implementation with this:
* The roles that a specific Karaf Command needs in order to be executable
are defined in a ConfigAdmin config file in the etc/ directory. So this can
easily be modified by an administrator. E.g I have a file that controls who
can use the feature command, some example content:
  list = manager, viewer
  install = manager
  uninstall = admin
* I added a mechanism that effectively changes command service
registrations to add the required roles for the specific command - based on
the ConfigAdmin data specified, e.g. the Service Registration for a
features:list command is turned into the following:
* The CommandProcessorImpl class in Karaf keeps track of what commands are
there. Previously this was a global instance, but now we need one instance
per shell console that selects the right commands for the user of that
console. It does this by reading off the current RolePrincipal objects
(that were put there by the JAAS login) and only selecting those commands
that have these roles by simply adding these as additional conditions to
the OSGi Service Registry selection filter.
* From there on everything works as normal. Tab completion etc, 'just

The commands themselves are not modified. The required roles are added
externally, which is really easy for the command developer.
It's also pretty easy to change the required roles for commands either
directly in the etc/...cfg files or via the ConfigAdmin API...

There are still a few things that I need to look at in more detail
(including defaults), but I wanted to run this by everyone to see what
people think, so feedback is appreciated!
If you're interested, I implemented this on a branch here:



[1] Detail: you don't really change a service registration, but can hide it
from bundles and replace it with an alternative, which gives this effect… I
wrote a blog about this a while ago:

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