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Allowing Normal Users to Manage SMF Services: Part 2 Comments Off on Allowing Normal Users to Manage SMF Services: Part 2

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In Part 1, I covered setting up RBAC with a custom role that would allow us to manage an SMF service as a non-privileged user. Now I’ll cover the steps required to setup the SMF part.

Note that, in the previous post, for management of the Sun MC Agent, we didn’t add a specific command – we added an authorisation to the Profile.

Although this will configure RBAC to support this nicely, it actually won’t do anything – we need to specifically configure SMF on each host to support this extra authorisation.

Basically SMF has an all or nothing approach – applying the authorisation solaris.smf.manage will allow you to manage any SMF service – very much not what we want.

Instead we want to configure a specific SMF service – in this case, sunmcagent – to allow an authorisation string that lets us specifically manage this service – and just this service.

We do this by using the svcprop command on the specific host to directly edit the properties of the service.

First of all let’s list the service’s properties:

[email protected] # svcprop -p general sunmcagent
general/enabled boolean true
general/entity_stability astring Evolving
general/single_instance boolean true

All fairly straightforward – the above tells us:

  • the service is enabled
  • it’s an evolving service, so the stability of it’s properties isn’t guaranteed
  • there can only be a single discreet instance of this service

We want to add an additional property, our authorisation string.

We use the svccfg command to do this:

[email protected] # svccfg -s sunmcagent setprop general/action_authorization=astring: 'solaris.smf.manage.sunmcagent'

Having done this, it won’t take effect until we refresh the service.

Check for yourself:

[email protected] # svcprop -p general sunmcagent
general/enabled boolean true
general/entity_stability astring Evolving
general/single_instance boolean true

Then we refresh the service:

[email protected] # svcadm refresh sunmcagent

And then check again:

[email protected] # svcprop -p general sunmcagent
general/enabled boolean true
general/entity_stability astring Evolving
general/single_instance boolean true
general/action_authorization astring solaris.smf.manage.sunmcagent

Behold our authorisation string! Now SMF will recognise this string when passed from RBAC, realise we only want to manage this specific service, and the magic happens.

However – we still can’t disable this service.

That’s because the ‘disable’ action modifies the SMF service (by changing the value of the general/enabled property) – the other actions are all temporary, but disable is persistent across reboots.

To get round this we need to add another property, value/authorization, will gives us authority to modify the values for properties for that specific service when managing it.

Similar sort of options to svcprop to affect this change:

[email protected] # svccfg -s sunmcagent setprop general/value_authorization=astring: 'solaris.smf.manage.sunmcagent'

Then we can refresh and review the change:

[email protected] # svcadm refresh sunmcagent
[email protected] # svcprop -p general sunmcagent
general/enabled boolean true
general/entity_stability astring Evolving
general/single_instance boolean true
general/action_authorization astring solaris.smf.manage.sunmcagent
general/value_authorization astring solaris.smf.manage.sunmcagent

So now the authorisation ‘solaris.smf.manage.sunmcagent’ is allowed to perform temporary actions and permanently modify the values of the sunmcagent service.

There’s a good BigAdmin article on configuring custom RBAC roles in Solaris here – highly recommended reading.

Allowing Normal Users to Manage SMF Services: Part 1 Comments Off on Allowing Normal Users to Manage SMF Services: Part 1

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RBAC doesn’t just let you give mortal users the power to execute commands as a privileged user – it can also be used to allow them power over other areas of the Solaris OE. A recurring task is allowing a normal user the power to start/stop an SMF service.

In this example I’ll work through how to allow a non-privileged user to manage the SMF service using by the Sun Management Centre (SMC) agent. We do this by modifying the SMF service to add an authorisation, and then defining with RBAC who is able to use that authorisation.

Setting up RBAC for this will involve modifying three of the RBAC configuration files:

  • /etc/security/prof_attr (where RBAC Profiles are defined)
  • /etc/security/auth_attr (where authorisations used by RBAC are defined)
  • /etc/user_attr (where user attributes are defined)

First of all, we need to edit /etc/security/prof_attr to add a new profile for the SMC agent. The syntax is simple: the name of the profile, a description, and then any authorisations that are needed. Adding the following line will do the trick:

SunMC Management:::Manage SunMC:auths=solaris.smf.manage.sunmcagent

Authorisations are extra tags that are added to an SMF service’s properties – they’re the ‘glue’ that ties together the profile and the SMF service.

Next up we need to add a definition for the new authorisation, by editing /etc/security/auth_attr and adding the following line:

solaris.smf.manage.sunmcagent:::Manage SunMC Agent::

Finally, we edit /etc/user_attr to add in a new role, and then assign our newly created SMC Profile to the role. Add the following line to the file:

smcmgmt::::type=role;profiles=SunMC Management,All

Also within /etc/user_attr we need to assign the role to our users. Add in an entry for each user you want to be able to use the role, like this:

tom::::type=normal;roles=smcmgmt

The final stage required to setup RBAC is to add the role details to /etc/passwd and to add a group entry to /etc/group. This should be standard stuff, so I’ll just show the lines added to each file:

/etc/passwd

smcmgmt:x:10003:10003:SunMC Management RBAC Role:/export/home/smcmgmt:/bin/pfksh

/etc/shadow

smcmgmt:lku7RuB1d71jY:13162::::::

/etc/group

smcmgmt::10003:

As always for RBAC, it’s good practice to create a role, and get users to su to that, rather than tacking profiles onto existing users and pre-pending pfexec to each command.

That’s all for part one – we’ve setup RBAC and we’re ready to roll. Part 2 will cover how we actually modify the SMF service and tie everything together.

Update: You should also head over to Ben Summers’ blog, where he wrote up an excellent end-to-end guide on how to Control untrusted processes with Solaris SMF

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