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The Machine SID Duplication Myth
toppings writes "Microsoft Technical fellow Mark Russinovich explains why he is now retiring NewSID, which has been used by IT departments for years when deploying Windows to new systems from customized clone images. Russinovich writes: 'The reason that I began considering NewSID for retirement is that, although people generally reported success with it on Windows Vista, I hadn't fully tested it myself and I got occasional reports that some Windows component would fail after NewSID was used. When I set out to look into the reports I took a step back to understand how duplicate SIDs could cause problems, a belief that I had taken on faith like everyone else. The more I thought about it, the more I became convinced that machine SID duplication — having multiple computers with the same machine SID — doesn't pose any problem, security or otherwise. I took my conclusion to the Windows security and deployment teams and no one could come up with a scenario where two systems with the same machine SID, whether in a Workgroup or a Domain, would cause an issue. At that point the decision to retire NewSID became obvious.' He concludes: 'It's a little surprising that the SID duplication issue has gone unquestioned for so long, but everyone has assumed that someone else knew exactly why it was a problem. To my chagrin, NewSID has never really done anything useful and there's no reason to miss it now that it's retired. Microsoft's official policy on SID duplication will also now change and look for Sysprep to be updated in the future to skip SID generation.'"
Maybe slashdot should get rid of the dupe sids, too.
This is coming from the same company that billed my employer to the tune of $250,000 USD in order to create a utility that would move a user profile from the old location to the new one after the user account had been moved to a new NT domain.
And then we found the moveuser.exe utility on the server resource kit and asked them what the $250,000 was for. Not that anyone who pays two hundred and fifty thousand dollars for a few lines of vbscript is smart (the phbs wanted something bonafide), but I'm just sayin'...
A ggreat deal of Microsoft security is unfortunately just like the underwear of Brittany Spears.
If it's even there at all it's needlessly complex and frilly, looks good without actually covering much and is far too easy to get around or remove completely.
The excessive complexity for no good reason of the SID and the way UIDs are implemented on that array of platforms are a good example of this.
"As I said earlier, there’s one exception to rule, and that’s DCs themselves. Every Domain has a unique Domain SID that’s randomly generated by Domain setup, and all machine SIDs for the Domain’s DCs match the Domain SID. So in some sense, that’s a case where machine SIDs do get referenced by other computers. That means that Domain member computers cannot have the same machine SID as that of the DCs and therefore Domain. However, like member computers, each DC also has a computer account in the Domain, and that’s the identity they have when they authenticate to remote systems. All accounts in a Domain, including computers, users and security groups, have SIDs that are based on the Domain SID in the same way local account SIDs are based on the machine SID, but the two are unrelated."
The low ramifications of this as mentioned above may have changed post Win2K and XP. This particular caveat governed our processes as system deployment specialists for Microsoft corporate events. We had to make sure that any potential DC had a unique SID even before the machines were promoted to DC, otherwise we saw (verifiably!) many issues with Workstations failing to join the domain. I seem to recall other more esoteric issues with older Microsoft server products, but that may be delusions based on the mass hysteria we had about unique SIDs at the time.
For what it's worth, using NewSID (or some other technique to accomplish the same thing) was too much trouble to do the first time when push came to deadline and I had to crank out a few hundred WinXP workstations for the college labs. I didn't have any problems. Never gave it another thought.
http://alternatives.rzero.com/
There are several other software packages with a similar problem. Microsoft SMS is a big one, as well as most McAfee Enterprise Virus scan products.
I think Mark's saying this to conveniently avoid updating his software to work with Windows Vista/Windows 7 =)
"I want to get more into theory, because everything works in theory." -John Cash
Did you mean the SusClientId? AFAIK this is the only identifier WSUS uses to distinguish between computers (they also don't have to be on the same domain).
On new clones you only need to delete the SusClientId key under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate; the update service will take care of assigning the machine a new ID.
Speaking from experience, having two machines with the same SID on a single Domain you will have issues related to the computer account in Active Directory. Remove one of these computers from the Domain and the others will experience Netlogon errors and various other issues as a result. Although NewSID may no longer be relevant due to lack of Vista/2008/7/2008R2 support, you should always sysprep /generalize to prevent these issues from occuring.
Not too sure why an MS blogger would have this stance, I've seen it numerous times (10+) with my own eyes. The fix is to either perform an offline workgroup join and generate new SID's on all but 1 affected machine, or to remove machines, NewSID all but one, and rejoin the Domain.
It's not for domain controllers in general it's for the very first domain controller used to initialize a brand new domain. You want to never create a new server with that same SID again. The first domain controller's SID is special, it will be used to generate the domain SID. From then on, all subsequent domain controllers promoted in the domain will have the same machine SID.
So you're good if you create the very first DC with a unique install, and clone all your other servers from an image.
As I said earlier, there’s one exception to rule, and that’s DCs themselves. Every Domain has a unique Domain SID that’s randomly generated by Domain setup, and all machine SIDs for the Domain’s DCs match the Domain SID. So in some sense, that’s a case where machine SIDs do get referenced by other computers. That means that Domain member computers cannot have the same machine SID as that of the DCs and therefore Domain. However, like member computers, each DC also has a computer account in the Domain, and that’s the identity they have when they authenticate to remote systems. All accounts in a Domain, including computers, users and security groups, have SIDs that are based on the Domain SID in the same way local account SIDs are based on the machine SID, but the two are unrelated.
issue is if a distributed application used machine SIDs to uniquely identify computers. No Microsoft software does so and using the machine SID in that way doesn’t work just for the fact that all DC’s have the same machine SID.
Microsoft is now my employer, and I have no reason to cater to the needs of the user community anymore.
If you keep throwing chairs, one day you'll break windows....
I have said this for years, glad its finally being widely accepted. My coworkers when ghosting machines would be fanatical about changing the SId's. I have a bad memory and would often forget to change them with no problems. I finally just started skipping the step of changing SID's and never had any adverse issues. When I told me coworkers about this they would rattle off a liteny of problems that I "could" encounter. After 10 years its nice to know I was right all along. So now a drum roll please...... IN YOUR FACE....MY COWORKERS!
And then we found the moveuser.exe utility on the server resource kit and asked them what the $250,000 was for. Not that anyone who pays two hundred and fifty thousand dollars for a few lines of vbscript is smart (the phbs wanted something bonafide), but I'm just sayin'...
A company was having a problem with one of their machines, so they called in this specialist. The specialist came in, examined the machine, pulled out a hammer and tapped the machine. The specialist then produced a bill for $1,000. When asked why he was charging $1000 for just tapping he machine with a hammer, the specialist replied, "You're paying for me to know where to tap the machine with the hammer."
The bill was paid.
It's NOT me! It's the meds! I'm on 1000mg of Fukitol.
Doesn't it bother anyone else that even Microsoft doesn't have a clue how the OS they developed works anymore? That something like this is even an issue?
I know for a fact that WSUS (Windows Server Update Services... basically a centralized patch server) would do "weird, interesting" things when two machines tried to check into WSUS with the same SID.
I don't even work with Windows servers and I happen to know this from engineering some network infrastructure (load balancing) for the folks in our organization who do manage WSUS. Long story short, what they thought was problematic load balancing across WSUS servers was actually the same SID being used from 1,000+ cloned VMs. WSUS thought they were one machine.
"Nature doesn't care how smart you are. You can still be wrong." - Richard Feynman
A ggreat deal of Microsoft security is unfortunately just like the underwear of Brittany Spears.
GOOGLE IMAGES: britney spears commando
The "subtlety" here is that Windows is extremely complex. I don't think anybody knows exactly how it works. Given that, it is hard to determine conclusively whether something can cause problems or not. Without that knowledge, it is best to err on the safe side.
Please correct me if I got my facts wrong.
This surprises me. I'm not going to say he's wrong, after all the man literally wrote the book on Windows (Windows Internals from Microsoft Press, great book) but it just seems odd. We seem to have problems at work if a system is Ghosted, but not SID walked. It'll join the domain, but exhibit weird problems, like users not able to log in and such. Now maybe GhostWalk does other things too that are what really needs to be done, but it seems to just be a SID change tool.
Personally I'll keep using GhostWalk until Symantec removes it.
You should sysprep the machines to reset their state before joining the machines. Basically, you should create a stock VM that is your disk image right after a "sysprep" and then NEVER EVER do anything with that. Clone it, complete the setup process, and join that cloned machine to the domain.
So in your case, you should have installed each VM from the ISO/CD and joined the domain, or used a first sysprepped disk image, cloned that twice, and used the two clones to join the domain.
The reason is that sysprep does the necessary work to separate two machine's identities in a more significant way than just the SID.
Microsoft's policy is you should never clone a disk image in a domain environment without first running sysprep. NewSID was just a way of doing "sysprep lite."
This is absolutely correct.
Identical machine SIDs and WSUS identifiers (stored in the registry) don't stop the updates from being applied...they just cause the WSUS reports to show only the details for the last cloned machine that connected.
Not so much of Mark, if he doesn't want to maintain it, thats fine, it was free, I get it.
However ... this is typical of MS.
They tell us (developers) that the sid will be unique. We write software that expects this and uses the sid as a unique ID.
Now they come along and say 'naaa, its not important to be unique, use the same sid all you want, no one will notice!'
And then I have to say ... thank god for real OSes where backwards compatibility is a rule for a reason, not just because they need it to maintain compatibility. They throw corner cases to the wind and go back on something they've said for years, completely ignoring the fact that people have built things based on something they said was a requirement.
This is the forth change that will break (or potentially in this case) software I have to maintain. Two patches that remove existing functionality in the name of security with the argument that 'no one uses it that way', to which Google can clearly show to be wrong. Even better is that one of them, a change to the DHTML control breaks some of their own apps, OWA for instance.
Its fucked up when you have to find a hack via Google to fix a bug in MS software that they say doesn't effect anyone ... except everyone that uses one of their more popular clients. Their response is 'patch exchange' which breaks OTHER things.
STOP
CHANGING
BINARY
COMPATIBILITY
you worthless fucks. Yes, I'm annoyed.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
From the article:
This is called generalizing the image, because when you boot an image created using this process, Sysprep specializes the installation by generating a new machine SID, triggering plug-and-play hardware detection, resetting the product activation clock, and setting other configuration data like the new computer name.
Is the product activation clock reset because of Sysprep, or because the SID is changed?
In other words, could NewSID be used to keep unactivated windows installations running indefinately?
<conspiracy_theory> Would that be the real reason for the NewSID retirement? What's the rush of removing the download instead of leaving it unsupported? </conspiracy_theory>
Not that I ever used it to generate a completely new SID, but what I did find it invaluable for was to set a machine's SID back to its old value after a re-install. This did away with the need to change the ownership on all of the user's files still on the hard drive and meant that most of the time their user profile would just keep on working as if nothing had changed.
I ran into this same issue. I've now got a batch script that runs at first logon (post-reimaging) that resets the client ID. Probably overkill at this point (the bad image that was causing this has long since been redone), but it ensure that every machine checks in with a fresh key.
net stop wuauserv /v SusClientId /f /resetauthorization /detectnow
reg delete "HKEY_LOCALMACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Windowsupdate"
net start wuauserv
wuauclt.exe
That does require a more windows update client (the old wuauclt only accepted a couple of options, including detectnow, and ignored the reset. If you typed wuauclt.exe /gogetmeabeerandasteak it wouldn't throw an error, it just looked like it ran).
There's a distinct difference between the SID and the SusClientID.
There are some people that if they don't know, you can't tell 'em.