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diff --git a/docs/u2f.txt b/docs/u2f.txt new file mode 100644 index 0000000000..f60052882e --- /dev/null +++ b/docs/u2f.txt @@ -0,0 +1,101 @@ +QEMU U2F Key Device Documentation. + +Contents +1. USB U2F key device +2. Building +3. Using u2f-emulated +4. Using u2f-passthru +5. Libu2f-emu + +1. USB U2F key device + +U2F is an open authentication standard that enables relying parties +exposed to the internet to offer a strong second factor option for end +user authentication. + +The standard brings many advantages to both parties, client and server, +allowing to reduce over-reliance on passwords, it increases authentication +security and simplifies passwords. + +The second factor is materialized by a device implementing the U2F +protocol. In case of a USB U2F security key, it is a USB HID device +that implements the U2F protocol. + +In Qemu, the USB U2F key device offers a dedicated support of U2F, allowing +guest USB FIDO/U2F security keys operating in two possible modes: +pass-through and emulated. + +The pass-through mode consists of passing all requests made from the guest +to the physical security key connected to the host machine and vice versa. +In addition, the dedicated pass-through allows to have a U2F security key +shared on several guests which is not possible with a simple host device +assignment pass-through. + +The emulated mode consists of completely emulating the behavior of an +U2F device through software part. Libu2f-emu is used for that. + + +2. Building + +To ensure the build of the u2f-emulated device variant which depends +on libu2f-emu: configuring and building: + + ./configure --enable-u2f && make + + +3. Using u2f-emulated + +To work, an emulated U2F device must have four elements: + * ec x509 certificate + * ec private key + * counter (four bytes value) + * 48 bytes of entropy (random bits) + +To use this type of device, this one has to be configured, and these +four elements must be passed one way or another. + +Assuming that you have a working libu2f-emu installed on the host. +There are three possible ways of configurations: + * ephemeral + * setup directory + * manual + +Ephemeral is the simplest way to configure, it lets the device generate +all the elements it needs for a single use of the lifetime of the device. + + qemu -usb -device u2f-emulated + +Setup directory allows to configure the device from a directory containing +four files: + * certificate.pem: ec x509 certificate + * private-key.pem: ec private key + * counter: counter value + * entropy: 48 bytes of entropy + + qemu -usb -device u2f-emulated,dir=$dir + +Manual allows to configure the device more finely by specifying each +of the elements necessary for the device: + * cert + * priv + * counter + * entropy + + qemu -usb -device u2f-emulated,cert=$DIR1/$FILE1,priv=$DIR2/$FILE2,counter=$DIR3/$FILE3,entropy=$DIR4/$FILE4 + + +4. Using u2f-passthru + +On the host specify the u2f-passthru device with a suitable hidraw: + + qemu -usb -device u2f-passthru,hidraw=/dev/hidraw0 + + +5. Libu2f-emu + +The u2f-emulated device uses libu2f-emu for the U2F key emulation. Libu2f-emu +implements completely the U2F protocol device part for all specified +transport given by the FIDO Alliance. + +For more information about libu2f-emu see this page: +https://github.com/MattGorko/libu2f-emu. |