CreateDirectory uses custom security descriptor for parents

[iSazonov]

Currently Unix code was changed to create parent directories with DefaultUnixCreateDirectoryMode but Windows code continue to inherit .Net Framework behavior and assign custom security descriptor if presents.

On Windows we usually prefer to inherit permissions and set custom ones only on leaf folder or file. I'd expect the CreateDirectory should follow this too.

Related to #61954

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Issue Details

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Currently Unix code was changed to create parent directories with DefaultUnixCreateDirectoryMode but Windows code continue to inherit .Net Framework behavior and assign custom security descriptor if presents.

On Windows we usually prefer to inherit permissions and set custom ones only on leaf folder or file. I'd expect the CreateDirectory should follow this too.

Author:	iSazonov
Assignees:	-
Labels:	area-System.IO
Milestone:	-

[jozkee]

Windows code continue to inherit .Net Framework behavior and assign custom security descriptor if presents.

What do you mean by "assign custom security descriptor"? All callsites of FileSystem.CreateDirectory do not provide a security descriptor at all, so it is always null. Is the Windows API the one implicitly inheriting the permissions?

We usually need a good reason to change defaults that are in place since .NET Framework. Can you provide a use case of why this is important? The only reason I see now is to align Windows' CreateDirectory with Unix but at the expense of breaking a legacy default that may impact customers migrating from old fw to modern .NET.

[iSazonov]

What do you mean by "assign custom security descriptor"?

I say about creating parent folders if they are not exist. Right behavior is to inherit security descriptor for them and set custom security descriptor only for most level folder as we do on Unix now.
If we create c:\exist\noexist1\noexist2\work the noexist1 must inherits security descriptor from c:\exists, then the noexist2 from noexist2 and then we should assign custom security descriptor for work` folder.

If the change is a breaking change why was the change approved for Unix? This kills portability - now we have to write different code for different platform to get the same behavior.