On Wed, May 2, 2012 at 11:15 PM, Pete Batard <p...@akeo.ie> wrote: > On 2012.05.02 16:11, Pete Batard wrote: >> Thanks for the info. >> >> On 2012.05.02 06:03, Xiaofan Chen wrote: >>> Q5: When using interface control requests (LIBUSB_RECIPIENT_INTERFACE), >>> WinUSB overrides the low byte of wIndex with the destination interface. >>> Ref: http://www.lvr.com/forum/index.php?topic=331 >>> >>> A5: this is so you only target your interface on a composite device. >>> Letting a >>> user mode stack manipulate a sibling interface is bad security and >>> encapsulation, no? >> >> Interesting. >> >> I could have sworn I saw some documentation indicating that >> bmRequestType was supposed to be set to 0xC1 (=> recipient = interface) >> when attempting to retrieve the Extended Properties OS Feature >> Descriptor from a device. As a matter of fact, this is the info I >> currently provide on the WCID page [1]. However, checking on the latest >> MS documentation [2], it seems that Microsoft do state that it should be >> set to 0xC0 (=> recipient = device), in which case the WinUSB override >> does not occur. > > Just to clarify the above, and how it relates to Q5, the retrieval of > the Extended Properties OS Feature Descriptor requires setting wIndex to > 0x05, which results in an override if using an interface request with > WinUSB.
Also Tim's view on this topic in the OSR mailing list / forum. http://www.osronline.com/showthread.cfm?link=223812 +++++++ One can also argue that this is a security measure. The USB spec requires that the low byte of wIndex be set to the interface number when the recipient is set to "interface". Devices that use that field for other purposes are broken. ++++++++ -- Xiaofan ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ libusbx-devel mailing list libusbx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libusbx-devel
