RE: [ActiveDir] Read-Only Domain Controller and Server Core

[Eric Fleischman]

To add a bit more…   > The part that makes me wonder about the "story" is if it stores no secrets is the server doing anything for me?   The short answer is yes. The bulk of the work that a DC does, even in the auth code path, may not involve the secret. So even if the secret checking work is “outsourced” to a hub DC, there is a lot more work that the local DC can perform for the user. For example, if it is an interactive logon, consider all of the GP work alone that is done that is now local.   At the end of the day, you have a knob….you can make real security trade-offs based upon what attack surface you can accept & mitigate, what administrative story you want, etc. You get to choose what secrets end up on the RODC. The product is built such that you can turn these knobs as you see fit but the default knob setting is “more secure”.   I hope between my response and Dmitri’s you are clear that the belief that it stores “nothing locally” is incorrect. If more clarity is required please just holler.   ~Eric     From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dmitri Gavrilov Sent: Friday, July 28, 2006 9:48 AM To: ActiveDir@mail.activedir.org Subject: RE: [ActiveDir] Read-Only Domain Controller and Server Core   The set of passwords that *can* be sent down to the RODC is controlled by password replication policy. The passwords are sent down by RODC’s request, but the hub also checks whether the user (whose pwd is being requested) actually attempted to authenticate at RODC (the hub can induce this info from the traffic is sees). The pwd hash is sent down only if both are satisfied: pwd policy allows it and the user actually attempted to logon there.   Pwd policy is “empty” by default, i.e. nobody is in “allowed to reveal” list. It is admin’s responsibility to populate this list. We might have some UI that helps with this process.   Once the hash is sent down, there’s no way to remove it from RODC, basically because we do not trust that RODC will remove it, even if instructed to do so. Therefore, the only way to “expire” the hash is to change the password. We store the list of passwords that were sent down to RODC in an attribute on the RODC computer object (the hub DC updates the list when it sends a pwd). So, if the RODC is stolen, you can enumerate whose passwords were down there, and make these users reset their passwords. There’s a constructed attribute that returns only the users whose *current* passwords appear to be on the RODC.   WRT what data is sent down – currently, we send everything, sans a handful of “secret” attributes, which are controlled by pwd replication policy. There’s a DCR to be able to configure the list of attributes that can go down to RODC (aka RODC PAS), but it is not yet clear if we will get it done or not.  Note that the client data access story on RODC becomes quite convoluted because you don’t know if you are seeing the whole object or only a subset of it. We do not normally issue referrals due to “partial reads”.   From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, July 28, 2006 8:22 AM To: ActiveDir@mail.activedir.org Subject: RE: [ActiveDir] Read-Only Domain Controller and Server Core   RODC stores password hashes only for a pre defined list of users and they are not stored on a permanent basis. [I'm unclear how the latter is achieved.]   The goal is such that if the RODC were removed from the office then no password secrets could be extracted from that machine.     neil   From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Al Mulnick Sent: 28 July 2006 16:08 To: ActiveDir@mail.activedir.org Subject: Re: [ActiveDir] Read-Only Domain Controller and Server Core The part that makes me wonder about the "story" is if it stores no secrets is the server doing anything for me? Is there a point to deploying the server in a remote office other than just being able to point to it in the closet and say, "see, I do to earn my paycheck!"     I'm sure there's more, but I don't yet know which parts are public information and which are NDA.   Can you tell I'm concerned about the story being created? I like stories; don't get me wrong.  But I'm concerned that the story being spun up might be missing the mark and lead a few people astray.   Safe to note that there are some features that differentiate the RODC from a NT4 BDC and that make it appealing in some cases. But if it actually does not store anything locally, ever, then I'm not sure it's worth the time to deploy one now is it?   Al     On 7/27/06, Susan Bradley, CPA aka Ebitz - SBS Rocks [MVP] <[EMAIL PROTECTED]> wrote: FYI: http://blogs.msdn.com/jolson/archive/2006/07/27/679801.aspx          Read-Only Domain Controller and Server Core List info   : http://www.activedir.org/List.aspx List FAQ    : http://www.activedir.org/ListFAQ.aspx List archive: http://www.activedir.org/ml/threads.aspx   PLEASE READ: The information contained in this email is confidential and intended for the named recipient(s) only. 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