IRMDS not supported

[GPHemsley-RELX]

It looks like this library does not support opening files encrypted according to Information Rights Management Data Space (IRMDS), which does not use EncryptionInfo.

The spec is here:
https://learn.microsoft.com/en-us/openspecs/office_file_formats/ms-offcrypto/518785bc-a76d-410e-b6f2-9f6b6b077d23

The file I have (which I can't share) looks like this, according to olefile:

'Root Entry' (root) 320 bytes
  '\x06DataSpaces' (storage)
    'DataSpaceInfo' (storage)
      'DRMEncryptedDataSpace' (stream) 56 bytes
    'DataSpaceMap' (stream) 104 bytes
    'TransformInfo' (storage)
      'DRMEncryptedTransform' (storage)
        '\x06Primary' (stream) 46880 bytes
    'Version' (stream) 76 bytes
  'EncryptedPackage' (stream) 7598088 bytes

Note that the spec for the encryption that this library does support is also available:
https://learn.microsoft.com/en-us/openspecs/office_file_formats/ms-offcrypto/e47faaed-ee58-4309-9033-88b342df5469

[nolze]

Thank you for the report!
I’d definitely like to implement this in the future. There are a few challenges to work through at the moment, but it’s something I’m interested in exploring.
As always, pull requests are very welcome.