Per-project sudo policies using sudo-ldap and puppet

LDAP, MediaWiki, OpenStack, Virtualization, Wikimedia

In Wikimedia Labs, we don’t manage authentication and authorization in the normal public cloud way. We don’t assume that an instance creator is managing auth for instances they create. Instead, all of Labs uses a single auth system for all projects and instances and a community manages project membership and auth.

In the original design, being a project member in specific projects would automatically give you root via sudo and being a project member in a global project would give you shell, but not root. We were handling this through puppet configuration. This was a fairly limiting system. Giving fine grained permissions wasn’t easy. The instances knew which users were a member of a project since the projects were also posix groups; however, they didn’t know which users were in the roles of that project, so there was no fined grained way to handle this.

sudo-ldap to the rescue. With sudo-ldap, we can manage sudo policies in LDAP, and those can be done in a per-project basis. Let me explain how we’re handling this while also ensuring the original assumed design still applies to old projects.

Handling the sudo policies in LDAP

To make sudo work per-project, we need to make a sudoers OU for each project. Projects are located at ou=projects,dc=wikimedia,dc=org. We have an example project at cn=testproject,ou=projects,dc=wikimedia,dc=org. We can create a new sudoers OU for this project, with a default policy (for backwards compatibility):

dn: ou=sudoers,cn=testproject,ou=projects,dc=wikimedia,dc=org
ou: sudoers
objectclass: organizationalunit
objectclass: top

dn: cn=default,ou=sudoers,cn=testproject,ou=projects,dc=wikimedia,dc=org
cn: default
objectClass: sudorole
objectClass: top
sudoCommand: ALL
sudoHost: ALL
sudoUser: ALL

The above creates a sudoers OU underneath the project’s object and creates a default policy for that project that gives all users the ability to run all commands via sudo.

For every pre-existing specific project, I created an OU and a default policy, then for every pre-existing global project I only created the OU, ensuring everything continued working how things worked in the original design. Whenever a project is created the OU and a default policy is also now automatically created with the project.

Configuring sudo on the instances

Now we must configure the instances to pull their sudo policies from this OU. Here’s the puppet template we’re using for /etc/sudo-ldap.conf:

BASE            <%= basedn %>
URI             <% servernames.each do |servername| -%>ldap://<%= servername %>:389 <% end -%>

BINDDN          cn=proxyagent,ou=profile,<%= basedn %>
BINDPW          <%= proxypass %>
SSL             start_tls
TLS_CHECKPEER   yes
TLS_REQCERT     demand
TLS_CACERTDIR   /etc/ssl/certs
TLS_CACERTFILE  /etc/ssl/certs/<%= ldap_ca %>
TLS_CACERT      /etc/ssl/certs/<%= ldap_ca %>
<% if ldapincludes.include?('sudo') then %>SUDOERS_BASE    <%= sudobasedn %><% end %>

The sudobasedn variable is being set as this:

$sudobasedn = "ou=sudoers,cn=${instanceproject},ou=projects,${basedn}"

For a more in-context view, you can clone our repo, or browse it via gitweb.

Managing the sudo policies

In the trunk version of the OpenStackManager extension, I’ve added support for managing per-project sudo. Users must be a member of the sysadmin role to do so.

No Comments

Leave a Reply