Get machine SID (including primary domain controller)

Question

I need to get the SID of a computer (not the SID of a computer account) in C #. The computer is listed as the host name, it is not necessarily the local computer, and it can be a domain computer or a workgroup computer. I use this helper class to call the LookupAccountName API function:

private static class Helper { internal enum SID_NAME_USE { SidTypeUser = 1, SidTypeGroup, SidTypeDomain, SidTypeAlias, SidTypeWellKnownGroup, SidTypeDeletedAccount, SidTypeInvalid, SidTypeUnknown, SidTypeComputer } [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)] private static extern bool LookupAccountName( string systemName, string accountName, byte[] sid, ref int sidLen, System.Text.StringBuilder domainName, ref int domainNameLen, out SID_NAME_USE peUse); public static SecurityIdentifier LookupAccountName( string systemName, string accountName, out string strDomainName, out SID_NAME_USE accountType) { const int ERROR_INSUFFICIENT_BUFFER = 122; int lSidSize = 0; int lDomainNameSize = 0; //First get the required buffer sizes for SID and domain name. LookupAccountName(systemName, accountName, null, ref lSidSize, null, ref lDomainNameSize, out accountType); if (Marshal.GetLastWin32Error() == ERROR_INSUFFICIENT_BUFFER) { //Allocate the buffers with actual sizes that are required //for SID and domain name. byte[] sid = new byte[lSidSize]; var sbDomainName = new System.Text.StringBuilder(lDomainNameSize); if (LookupAccountName(systemName, accountName, sid, ref lSidSize, sbDomainName, ref lDomainNameSize, out accountType)) { strDomainName = sbDomainName.ToString(); return new SecurityIdentifier(sid, 0); } } throw new Win32Exception(); } } 

and using it as follows:

 Helper.SID_NAME_USE accountType; string refDomain; SecurityIdentifier sid = Helper.LookupAccountName("falcon.mydomain.local", "falcon", out refDomain, out accountType); //Domain computer SecurityIdentifier sid = Helper.LookupAccountName("rat", "rat", out refDomain, out accountType); //Workgroup computer 

My only problem is that this does not work if the computer is the primary domain controller (in this case I need to get the domain SID).

Answer 1

It looks like for most computers you are doing the following:

LookupAccountName ("," ComputerName ", ...); ConvertSidToStringSid (...)

But for domain controllers, you need to add a dollar sign to the computer name parameter, and then delete the last segment in the returned SID.