These are some tools to play with the Yubico U2F-only ("NEO Sky") USB dongle sold for $5 thru the github promotional in October 2015.

• a shell to interact with the dongle, using python and pyusb
• (PLANNED) a shell to interact with the dongle, using FIDO U2F javascript API
• (PLANNED) a "spy" that reports on the dongle's activity as your browser

###communication stack +------------------+ | U2F | TRANSACTIONS | | (encapsulated in U2FHID_MSG) | | +------------------+ | U2FHID | MESSAGES | | - logical channels: 0 (reserved), ..., 0xFFFFFFFF (broadcast) | | - commands: U2FHID_INIT, U2FHID_PING, U2FHID_WINK | | - initialization and continuation packets +------------------+ | USB REPORT | PACKETS | | - IN and OUT endpoints | | - 64-byte chunks (HID_RPT_SIZE) +------------------+ | LINUX USB SUBSYS | +------------------+ | USB BUS | +------------------+ | DONGLE | +------------------+

###device structure

• one HID device, one config, one interface, two endpoints, lsbusb gives:

device descr (Bus 002 Device 012: ID 1050:0120 Yubico.com)
  config descr
    interface descr (class: HID)
      endpoint descr (addr: 0x04 EP 4 OUT) (pkt size: 64)
      endpoint descr (addr: 0x84 EP 4 IN)  (pkt size: 64)

###debugging USB presence issues

• simple dmesg to watch insertion, example output:

[771880.315804] usb 2-2.2: new full-speed USB device number 9 using uhci_hcd
[771880.531468] usb 2-2.2: New USB device found, idVendor=1050, idProduct=0120
[771880.531473] usb 2-2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[771880.531475] usb 2-2.2: Product: Security Key by Yubico
[771880.531477] usb 2-2.2: Manufacturer: Yubico
[771880.550951] hid-generic 0003:1050:0120.0002: hiddev0,hidraw1: USB HID v1.10 Device [Yubico Security Key by Yubico] on usb-0000:02:00.0-2.2/input0

• lsusb to find your device
• lsusb -v -d 1050:0120 for details

###debugging protocol issues

• find fido-u2f-u2f.h and fido-u2f-u2fhid.h
• https://fidoalliance.org/specifications/download/

###debugging pylib issues

• find docs with pydoc usb or within python help(usb)
• code (in my case) is in /usr/local/lib/python2.7/dist-packages/pyusb-1.0.0b2-py2.7.egg (treat like zip file)

###pitfalls

• don't use yubico-python; though it has knowledge of product id 0x120 (NEO_SKY), it won't detect, and if you patch it to detect, it will hang waiting for some status bits to clear during a protocol step
• don't use the yubikey personalizatoin tool in OSX, it simply won't detect the thing
• don't use the yubikey personalization tool in Linux, 'cause it's impossible to compile!
• don't use the command-line personalization tool in Linux (ykpers), it won't detect
• DON'T THINK THIS IS ANYTHING LIKE A TYPICAL YUBICO PRODUCT, IT'S U2F ONLY
• don't be scared of USB like I was, there's an indispensable guide called "USB in a NutShell" at http://www.beyondlogic.org/usbnutshell/usb1.shtml and you just have to skim the "device descriptors" section for cursory idea of what device, configuration, interface, and endpoint mean