Thanks everyone for the advice. Here's a sanitized version of what I put
together for my end user customer. Feel free to use any of this text as you
Here's the scoop with IdM and AD trusts. It's an "official" 2-way trust with
the currently shipping IdM version - I think it's 3.3.5 right now. It's an
official 2-way trust, but de-facto it's only one way because IdM doesn't have
all the pieces it needs yet to allow AD to trust IdM. So IdM can trust AD but
right now AD cannot trust IdM. Red Hat Support told us that in the support
case and I confirmed it with the upstream community. So even though it says
it's a 2-way trust, it's really only one way.
Somewhere in the future, around version 4.3 or so, so it's a long way away, the
plan is for IdM to have the pieces it needs for AD to trust IdM. When that
time comes, there are a number of options for ***?. One is to stick with
today's current version. "If it ain't broke, don't fix it." Another is to
continue upgrading to the current versions as they become available and redo
the trust to be an official one way trust when the time comes. Another option
- just leave it as a 2-way trust.
The decision doesn't come up for a long time - if I had to guess, I'd put it
sometime after 2015. That's just my guess because the people doing the
development don't know themselves and they're the ones building this stuff.
It's a long time out. And even then, it's not a huge decision. Let's say ***?
decides to leave it as a 2-way trust. What are the consequences? Are there
now suddenly 2 sources of truth? Is there a security hole? Is AD suddenly
My answer would be no, no, and no.
On sources of truth - There will always be a few unique users in the Linux IdM
domain. User root, for example, and probably a few others. This is true
whether there is no trust, a one-way trust, or a 2-way trust. IdM is like a
Windows forest with one domain. And AD is a forest with at least one domain.
By definition, both forests have their own individual entities.
On security holes - with a 2-way trust, the AD Administrator now has the
ability to regulate access to AD resources from IdM users and groups. If the
AD Admin takes no action, then nobody on the IdM side can access anything on
the AD side. Just because the AD administrator has this ability does not
imply the he will use it. If he doesn't use it - the default action - nothing
Is AD suddenly vulnerable? No. Even with a 2-way trust, the AD Admin has to
take specific actions in cooperation with others to allow anyone from IdM to
access anything inside AD.
My opinion isn't worth the disk space to store this text and free opinions are
worth what you pay for them. So test it yourself. ***? has the tools right
now. Build a Windows forest - independent of your Dev forest - and do some
experiments with 2-way cross forest trusts. Set up and destroy a few trust
relationships with your existing Dev domain/forest and my proposed test forest
and grant permissions to a few groups from one side into the other side. You
can do it with one Windows VM. Now substitute IdM for that test Windows forest
when the time comes and the issues are exactly the same.
One more point on vulnerability. I know the choice to copy AD users into IdM
is well-known, safe, and comfortable at ***?. That's the way they did it last
time. But this choice requires non Microsoft software on the ***? AD domain
controllers. So thinking it through - which represents the most risk? Setting
up a cross forest trust where the AD administrator retains total control over
everything, or putting foreign software on the Windows domain controllers to
copy user passwords to an untrusted entity?
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