Active directory accounts inside a windows container (server 2016 TP5)
So I have Windows Server 2016 TP5 and I’m playing around with the containers. I am able to do basic docker tasks fine. I’m trying to figure out how to containerize some of our IIS-hosted web applications.
Thing is, we usually use integrated authentication for the DB and use domain service accounts for the app pool. I currently don’t have a test VM (that is in a domain) so I can’t test if this will work inside a container.
If the host is joined to an AD domain, are its containers also part of the domain? Can I still run processes using domain accounts?
Also, if I specify the “USER” in the dockerfile, does this mean that my app pool will run using that (instead of the app pool identity)?
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Quick answer – no, containers are not supported as part of AD so you can’t use AD accounts to run processes within a container or authenticate with it
This used to be mentioned on the MS Containers site but the original link now redirects.
Original wording (CTP 3 or 4?):
“Containers cannot join Active Directory domains, and cannot run services or applications as domain users, service accounts, or machine accounts.”
I don’t know if that will change in a later release.
Someone tried to hack around it but with no joy.
There are at least some scenarios where AD-integration in Docker container actually works:
- You need to access network resources with AD credentials.
- Run cmdkey /add:
<pass>under local identity that needs this access
- To apply the same trick to IIS apps without modifying AppPoolIdentity you’ll need a simplest .ashx wrapper around cmdkey (Note: you’ll have to call this wrapper in run-time, e.g.: during ENTRYPOINT, otherwise network credentials will be mapped to different local identity)
- Run cmdkey /add:
- You need to run code under AD user
- Impersonate using ADVAPI32 function LogonUser with LOGON32_LOGON_NEW_CREDENTIALS and LOGON32_PROVIDER_DEFAULT as suggested
- You need transport layer network security, like when making RPC calls (e.g.: MSDTC) to an AD-based resources.
- Set up gMSA by using any guide that suites you best. Note however, that gMSA requires Docker host to be in the domain.
You can’t join containers to a domain but if your app needs to authenticate then you can use managed service accounts. Saves you the hassle of having to deal with packaging passwords.