Deleting a file based on disk ID

Question

As described here, using SetFileInformationByHandle with FILE_DISPOSITION_INFO allows one to set a file with an open handle to be deleted upon all handles being closed.

Answer 1

In order to make FILE_DISPOSITION_INFO work you need to specify the DELETE access in the CreateFile function as reported in https://msdn.microsoft.com/en-us/library/windows/desktop/aa365539(v=VS.85).aspx:

You must specify appropriate access flags when creating the file handle for use with SetFileInformationByHandle. For example, if the application is using FILE_DISPOSITION_INFO with the DeleteFile member set to TRUE, the file would need DELETE access requested in the call to the CreateFile function. To see an example of this, see the Example Code section. For more information about file permissions, see File Security and Access Rights. I.e.

//...
  HANDLE hFile = CreateFile( TEXT("tempfile"), 
                             GENERIC_READ | GENERIC_WRITE | DELETE,  //Specify DELETE access!
                             0 /* exclusive access */,
                             NULL, 
                             CREATE_ALWAYS,
                             0, 
                             NULL);

But it seems that an handle created with OpenFileById() cannot be used because the function cannot accept the DELETE flag.
From https://msdn.microsoft.com/en-us/library/windows/desktop/aa365432(v=vs.85).aspx on OpenFileById() it can be read: dwDesired

Access [in]
The access to the object. Access can be read, write, or both.

Even setting DELETE or GENERIC_ALL the function fails.
If you replace the handle passed to SetFileInformationByHandle with one created with the CreateFile function having the DELETE flag set, as above, it works.

Answer 2

Assume the files are XXX and xxx and you want to delete XXX.

1. MoveFile("XXX", "I think it's XXX")
2. If XXX got renamed, then DeleteFile("I think it's XXX")
3. Otherwise, DeleteFile("XXX"); MoveFile("I think it's XXX", "xxx")

As to OpenFileById, as you noted, there is a potential ambiguity with a file with multiple names (aka hard links). Allowing DELETE access could cause havoc with this, with an unexpected name being deleted (if it were left to the file system to select which one). I suspect they opted for the simple case of never letting DELETE access be granted.

A similar argument could be made for allowing hard links to directories. Sure, you could do it some of the time correctly, but once you created a cycle, things get a lot tougher...

Answer 3

There's a user mode version of the kernel mode ZwCreateFile called NTCreteFile which, among other things will give you all of the access rights you can't get with OpenFileById (but you can get with CreateFile). It can do everything CreateFile can do and more. For example, it can even create directories.

The good part is, there's an immensely hacky (but entertaining) way of specifying a file ID in the POBJECT_ATTRIBUTES argument as well, so you get the best of all worlds...except that it's an even more awkward API to call than your run-of-the-mill awkward Windows APIs.

There are two versions of the documentation. One at:

https://msdn.microsoft.com/en-us/library/bb432380(v=vs.85).aspx

and one at:

https://msdn.microsoft.com/en-us/library/windows/hardware/ff556465(v=vs.85).aspx

...which links to the ZwCreateFile documentation at:

https://msdn.microsoft.com/en-us/library/windows/hardware/ff566424(v=vs.85).aspx

The reason I point this out is that the first article omits some of the goodies (like opening files by ID) that are documented in the last article. I have found this to be common and have also found that most of the documented Zwxxx functionality actually does exists in the equivalent, but incompletely documented NTxxx functions. So you gotta hold your mouth just right to get the requisite functionality.

Answer 4

Have you looked into FILE_FLAG_POSIX_SEMANTICS? It will allow you to open files that differ only in case using CreateFile.

Edit: I guess I should have read your code first as I see you are using said flag.