Qemu CCID Device Documentation.

Contents
1. USB CCID device
2. Building
3. Using ccid-card-emulated with hardware
4. Using ccid-card-emulated with certificates
5. Using ccid-card-passthru with client side hardware
6. Using ccid-card-passthru with client side certificates
7. Passthrough protocol scenario
8. libcacard

1. USB CCID device

The USB CCID device is a USB device implementing the CCID specification, which
lets one connect smart card readers that implement the same spec. For more
information see the specification:

 Universal Serial Bus
 Device Class: Smart Card
 CCID
 Specification for
 Integrated Circuit(s) Cards Interface Devices
 Revision 1.1
 April 22rd, 2005

Smartcard are used for authentication, single sign on, decryption in
public/private schemes and digital signatures. A smartcard reader on the client
cannot be used on a guest with simple usb passthrough since it will then not be
available on the client, possibly locking the computer when it is "removed". On
the other hand this device can let you use the smartcard on both the client and
the guest machine. It is also possible to have a completely virtual smart card
reader and smart card (i.e. not backed by a physical device) using this device.

2. Building

The cryptographic functions and access to the physical card is done via NSS.

Installing NSS:

In redhat/fedora:
    yum install nss-devel
In ubuntu/debian:
    apt-get install libnss3-dev
    (not tested on ubuntu)

Configuring and building:
    ./configure --enable-smartcard && make

3. Using ccid-card-emulated with hardware

Assuming you have a working smartcard on the host with the current
user, using NSS, qemu acts as another NSS client using ccid-card-emulated:

    qemu -usb -device usb-ccid -device ccid-card-emualated

4. Using ccid-card-emulated with certificates

You must create the certificates. This is a one time process. We use NSS
certificates:

    certutil -d /etc/pki/nssdb -x -t "CT,CT,CT" -S -s "CN=cert1" -n cert1

Note: you must have exactly three certificates.

Assuming the current user can access the certificates (use certutil -L to
verify), you can use the emulated card type with the certificates backend:

    qemu -usb -device usb-ccid -device ccid-card-emulated,backend=certificates,cert1=cert1,cert2=cert2,cert3=cert3

5. Using ccid-card-passthru with client side hardware

on the host specify the ccid-card-passthru device with a suitable chardev:

    qemu -chardev socket,server,host=0.0.0.0,port=2001,id=ccid,nowait -usb -device usb-ccid -device ccid-card-passthru,chardev=ccid

on the client run vscclient, built when you built the libcacard library:
    libcacard/vscclient <qemu-host> 2001

6. Using ccid-card-passthru with client side certificates

Run qemu as per #5, and run vscclient as follows:
(Note: vscclient command line interface is in a state of change)

    libcacard/vscclient -e "db=\"/etc/pki/nssdb\" use_hw=no soft=(,Test,CAC,,cert1,cert2,cert3)" <qemu-host> 2001

7. Passthrough protocol scenario

This is a typical interchange of messages when using the passthru card device.
usb-ccid is a usb device. It defaults to an unattached usb device on startup.
usb-ccid expects a chardev and expects the protocol defined in
cac_card/vscard_common.h to be passed over that.
The usb-ccid device can be in one of three modes:
 * detached
 * attached with no card
 * attached with card

A typical interchange is: (the arrow shows who started each exchange, it can be client
originated or guest originated)

client event      |      vscclient           |    passthru    |     usb-ccid  |  guest event
----------------------------------------------------------------------------------------------
                  |      VSC_Init            |                |               |
                  |      VSC_ReaderAdd       |                |     attach    |
                  |                          |                |               |  sees new usb device.
card inserted ->  |                          |                |               |
                  |      VSC_ATR             |   insert       |     insert    |  see new card
                  |                          |                |               |
                  |      VSC_APDU            |   VSC_APDU     |               | <- guest sends APDU
client<->physical |                          |                |               |
card APDU exchange|                          |                |               |
client response ->|      VSC_APDU            |   VSC_APDU     |               |  receive APDU response
                                                    ...
                                    [APDU<->APDU repeats several times]
                                                    ...
card removed  ->  |                          |                |               |
                  |      VSC_CardRemove      |   remove       |    remove     |   card removed
                                                    ...
                                    [(card insert, apdu's, card remove) repeat]
                                                    ...
kill/quit         |                          |                |               |
  vscclient       |                          |                |               |
                  |      VSC_ReaderRemove    |                |    detach     |
                  |                          |                |               |   usb device removed.


8. libcacard

ccid-card-passthru and vscclient use libcacard as the card emulator.
libcacard implements a completely virtual CAC (DoD standard for smart cards)
compliant card and uses NSS to actually retrive certificates and do any
encryption using the backend (real reader + card or file backed certificates).

For documentation of cac_card see README in libcacard subdirectory.