Microsoft OS descriptors

04 Apr 2016

OS support

• Microsoft OS 1.0 Descriptors are supported by:
  • Windows 8.1
  • Windows 8
  • Windows 7
  • Windows Vista, Windows Server 2008
  • Windows XP with Service Pack 1 (SP1), Windows Server 2003
• Microsoft OS 2.0 Descriptors are supported by Windows 8.1 onwards

String Descriptor Request

• Index: 0xEE, langid: 0
• u”MSFT100?”, ? is bMS_VendorCode, which will be used for subsequent OS feature vendor request

OS Feature descriptor

• Genre (0x1)
  • Used by HID devices to provide detailed configuration data. - Not implemented
• Extended Compact ID (0x4), e.g. “WINUSB”, “RNDIS”
• Extended Properties (0x5), e.g. URLs, icons, help pages, GUIDs
  • Class level
  • devnode level

Debugging

• The OS only query 0xEE once
  • because OS will cache the result at HLKM\SYSTEM\CurrentControlSet\Control\UsbFlags\
  • Refer USB Device Registry Entries for details
• Make sure the length of CID descriptor is 0x28 for single interface configuration