July 2nd, 2015

Is a SID with zero subauthorities a valid SID? It depends whom you ask

Raymond Chen
Raymond Chen

Here’s an interesting table.

Function Is Sub­Authority­Count=0 valid?
IsValidSid Yes
Convert­Sid­To­String­Sid Yes
ConvertString­­Sid­To­Sid No

That last entry creates the unfortunate situation where a SID with no subauthorities can be converted to a string, but cannot be converted back.

If it’s any consolation, SIDs with no subauthorities aren’t encountered in normal usage, so if you ever accidentally reject one of these, it’s not going to inconvenience anyone.

Oh, and the answer to the question at the top: Yes, a SID with zero subauthorities is technically valid. It’s a degenerate case that’s not very interesting, but it is technically valid.

Category
Old New Thing
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Author

Raymond Chen

Raymond has been involved in the evolution of Windows for more than 30 years. In 2003, he began a Web site known as The Old New Thing which has grown in popularity far beyond his wildest imagination, a development which still gives him the heebie-jeebies. The Web site spawned a book, coincidentally also titled The Old New Thing (Addison Wesley 2007). He occasionally appears on the Windows Dev Docs Twitter account to tell stories which convey no useful information.

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