[5/5] ccid: add docs

Message ID 1292497600-16115-6-git-send-email-alevy@redhat.com
State New
Headers show

Commit Message

Alon Levy Dec. 16, 2010, 11:06 a.m.
Add documentation for the usb-ccid device and accompanying two card
devices, ccid-card-emulated and ccid-card-passthru.
 docs/ccid.txt      |  125 ++++++++++++++
 docs/libcacard.txt |  483 ----------------------------------------------------
 2 files changed, 125 insertions(+), 483 deletions(-)
 create mode 100644 docs/ccid.txt
 delete mode 100644 docs/libcacard.txt


Gerd Hoffmann Dec. 16, 2010, 1:01 p.m. | #1
On 12/16/10 12:06, Alon Levy wrote:
> Add documentation for the usb-ccid device and accompanying two card
> devices, ccid-card-emulated and ccid-card-passthru.
> ---
>   docs/ccid.txt      |  125 ++++++++++++++
>   docs/libcacard.txt |  483 ----------------------------------------------------

Guess that isn't intentional, right?

> +A typical interchange is:
> +
> +client event      |      vscclient           |    passthru    |     usb-ccid  |  guest event
> +----------------------------------------------------------------------------------------------
> +                  |      VSC_Init            |                |               |
> +                  |      VSC_ReaderAdd       |                |     attach    |
> +                  |                          |                |               |  sees new usb device.
> +card inserted     |                          |                |               |
> +                  |      VSC_ATR             |                |               |
> +                  |                          |                |               |  guest operation, APDU transfer via CCID
> +                  |                          |   VSC_APDU     |               |
> +                  |      VSC_APDU            |                |               |
> +client<->physical |                          |                |               |
> +card APDU exchange|                          |                |               |
> +                            [APDU<->APDU repeats several times]
> +card removed      |                          |                |               |
> +                  |      VSC_CardRemove      |                |               |
> +kill/quit         |                          |                |               |
> +  vscclient       |                          |                |               |
> +                  |      VSC_ReaderRemove    |                |    detach     |
> +                  |                          |                |               |   usb device removed.

This needs updating, doesn't it?  I think you plugin and -out just the 
cards on the ccid bus instead of the whole usb device, right?

Alon Levy Dec. 16, 2010, 4:52 p.m. | #2
On Thu, Dec 16, 2010 at 02:01:34PM +0100, Gerd Hoffmann wrote:
> On 12/16/10 12:06, Alon Levy wrote:
> >Add documentation for the usb-ccid device and accompanying two card
> >devices, ccid-card-emulated and ccid-card-passthru.
> >---
> >  docs/ccid.txt      |  125 ++++++++++++++
> >  docs/libcacard.txt |  483 ----------------------------------------------------
> Guess that isn't intentional, right?


> >+A typical interchange is:
> >+
> >+client event      |      vscclient           |    passthru    |     usb-ccid  |  guest event
> >+----------------------------------------------------------------------------------------------
> >+                  |      VSC_Init            |                |               |
> >+                  |      VSC_ReaderAdd       |                |     attach    |
> >+                  |                          |                |               |  sees new usb device.
> >+card inserted     |                          |                |               |
> >+                  |      VSC_ATR             |                |               |
> >+                  |                          |                |               |  guest operation, APDU transfer via CCID
> >+                  |                          |   VSC_APDU     |               |
> >+                  |      VSC_APDU            |                |               |
> >+client<->physical |                          |                |               |
> >+card APDU exchange|                          |                |               |
> >+                            [APDU<->APDU repeats several times]
> >+card removed      |                          |                |               |
> >+                  |      VSC_CardRemove      |                |               |
> >+kill/quit         |                          |                |               |
> >+  vscclient       |                          |                |               |
> >+                  |      VSC_ReaderRemove    |                |    detach     |
> >+                  |                          |                |               |   usb device removed.
> This needs updating, doesn't it?  I think you plugin and -out just
> the cards on the ccid bus instead of the whole usb device, right?

actually I'm not sure.. I'll check and update.

> cheers,
>   Gerd


diff --git a/docs/ccid.txt b/docs/ccid.txt
new file mode 100644
index 0000000..791c28c
--- /dev/null
+++ b/docs/ccid.txt
@@ -0,0 +1,125 @@ 
+Qemu CCID Device Documentation.
+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. libcaccard
+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
+ 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
+    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=,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 libcaccard library:
+    libcaccard/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)
+    libcaccard/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.
+A typical interchange is:
+client event      |      vscclient           |    passthru    |     usb-ccid  |  guest event
+                  |      VSC_Init            |                |               |
+                  |      VSC_ReaderAdd       |                |     attach    |
+                  |                          |                |               |  sees new usb device.
+card inserted     |                          |                |               |
+                  |      VSC_ATR             |                |               |
+                  |                          |                |               |  guest operation, APDU transfer via CCID
+                  |                          |   VSC_APDU     |               |
+                  |      VSC_APDU            |                |               |
+client<->physical |                          |                |               |
+card APDU exchange|                          |                |               |
+                            [APDU<->APDU repeats several times]
+card removed      |                          |                |               |
+                  |      VSC_CardRemove      |                |               |
+kill/quit         |                          |                |               |
+  vscclient       |                          |                |               |
+                  |      VSC_ReaderRemove    |                |    detach     |
+                  |                          |                |               |   usb device removed.
+8. libcaccard
+ccid-card-passthru and vscclient use libcaccard as the card emulator.
+libcaccard 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 libcaccard subdirectory.
diff --git a/docs/libcacard.txt b/docs/libcacard.txt
deleted file mode 100644
index 5dee6fa..0000000
--- a/docs/libcacard.txt
+++ /dev/null
@@ -1,483 +0,0 @@ 
-This file documents the CAC (Common Access Card) library in the libcacard
-Virtual Smart Card Emulator
-This emulator is designed to provide emulation of actual smart cards to a
-virtual card reader running in a guest virtual machine. The emulated smart
-cards can be representations of real smart cards, where the necessary functions
-such as signing, card removal/insertion, etc. are mapped to real, physical
-cards which are shared with the client machine the emulator is running on, or
-the cards could be pure software constructs.
-The emulator is structured to allow multiple replacable or additional pieces,
-so it can be easily modified for future requirements. The primary envisioned
-modifications are:
-1) The socket connection to the virtual card reader (presumably a CCID reader,
-but other ISO-7816 compatible readers could be used). The code that handles
-this is in vscclient.c.
-2) The virtual card low level emulation. This is currently supplied by using
-NSS. This emulation could be replaced by implementations based on other
-security libraries, including but not limitted to openssl+pkcs#11 library,
-raw pkcs#11, Microsoft CAPI, direct opensc calls, etc. The code that handles
-this is in vcard_emul_nss.c.
-3) Emulation for new types of cards. The current implementation emulates the
-original DoD CAC standard with separate pki containers. This emulator lives in
-cac.c. More than one card type emulator could be included. Other cards could
-be emulated as well, including PIV, newer versions of CAC, PKCS #15, etc.
-Replacing the Socket Based Virtual Reader Interface.
-The current implementation contains a replacable module vscclient.c. The
-current vscclient.c implements a sockets interface to the virtual ccid reader
-on the guest. CCID commands that are pertinent to emulation are passed
-across the socket, and their responses are passed back along that same socket.
-The protocol that vscclient uses is defined in vscard_common.h and connects
-to a qemu ccid usb device. Since this socket runs as a client, vscclient.c
-implements a program with a main entry. It also handles argument parsing for
-the emulator.
-An application that wants to use the virtual reader can replace vscclient.c
-with it's own implementation that connects to it's own CCID reader.  The calls
-that the CCID reader can call are:
-      VReaderList * vreader_get_reader_list();
-  This function returns a list of virtual readers.  These readers may map to
-  physical devices, or simulated devices depending on vcard the back end. Each
-  reader in the list should represent a reader to the virtual machine. Virtual
-  USB address mapping is left to the CCID reader front end. This call can be
-  made any time to get an updated list. The returned list is a copy of the
-  internal list that can be referenced by the caller without locking. This copy
-  must be freed by the caller with vreader_list_delete when it is no longer
-  needed.
-      VReaderListEntry *vreader_list_get_first(VReaderList *);
-  This function gets the first entry on the reader list. Along with
-  vreader_list_get_next(), vreader_list_get_first() can be used to walk the
-  reader list returned from vreader_get_reader_list(). VReaderListEntries are
-  part of the list themselves and do not need to be freed separately from the
-  list. If there are no entries on the list, it will return NULL.
-      VReaderListEntry *vreader_list_get_next(VReaderListEntry *);
-  This function gets the next entry in the list. If there are no more entries
-  it will return NULL.
-      VReader * vreader_list_get_reader(VReaderListEntry *)
-  This function returns the reader stored in the reader List entry. Caller gets
-  a new reference to a reader. The caller must free it's reference when it is
-  finished with vreader_free().
-      void vreader_free(VReader *reader);
-   This function frees a reference to a reader. Reader's are reference counted
-   and are automatically deleted when the last reference is freed.
-      void vreader_list_delete(VReaderList *list);
-   This function frees the list, all the elements on the list, and all the
-   reader references held by the list.
-      VReaderStatus vreader_power_on(VReader *reader, char *atr, int *len);
-  This functions simulates a card power on. Virtual cards do not care about
-  the actual voltage and other physical parameters, but it does care that the
-  card is actually on or off. Cycling the card causes the card to reset. If
-  the caller provides enough space, vreader_power_on will return the ATR of
-  the virtual card. The amount of space provided in atr should be indicated
-  in *len. The function modifies *len to be the actual length of of the
-  returned ATR.
-      VReaderStatus vreader_power_off(VReader *reader);
-  This function simulates a power off of a virtual card.
-      VReaderStatus vreader_xfer_bytes(VReader *reader, unsigne char *send_buf,
-                                       int send_buf_len,
-                                       unsigned char *receive_buf,
-                                       int receive_buf_len);
-  This functions send a raw apdu to a card and returns the card's response.
-  The CCID front end should return the response back. Most of the emulation
-  is driven from these APDUs.
-      VReaderStatus vreader_card_is_present(VReader *reader);
-  This function returns whether or not the reader has a card inserted. The
-  vreader_power_on, vreader_power_off, and vreader_xfer_bytes will return
-       const char *vreader_get_name(VReader *reader);
-  This function returns the name of the reader. The name comes from the card
-  emulator level and is usually related to the name of the physical reader.
-       VReaderID vreader_get_id(VReader *reader);
-  This function returns the id of a reader. All readers start out with an id
-  of -1. The application can set the id with vreader_set_id.
-       VReaderStatus vreader_get_id(VReader *reader, VReaderID id);
-  This function sets the reader id. The application is responsible for making
-  sure that the id is unique for all readers it is actively using.
-       VReader *vreader_find_reader_by_id(VReaderID id);
-  This function returns the reader which matches the id. If two readers match,
-  only one is returned. The function returns NULL if the id is -1.
-       Event *vevent_wait_next_vevent();
-  This function blocks waiting for reader and card insertion events. There
-  will be one event for each card insertion, each card removal, each reader
-  insertion and each reader removal. At start up, events are created for all
-  the initial readers found, as well as all the cards that are inserted.
-       Event *vevent_get_next_vevent();
-  This function returns a pending event if it exists, otherwise it returns
-  NULL. It does not block.
-Card Type Emulator: Adding a New Virtual Card Type
-The ISO 7816 card spec describes 2 types of cards:
- 1) File system cards, where the smartcard is managed by reading and writing
-data to files in a file system. There is currently only boiler plate
-implemented for file system cards.
- 2) VM cards, where the card has loadable applets which perform the card
-functions. The current implementation supports VM cards.
-In the case of VM cards, the difference between various types of cards is
-really what applets have been installed in that card. This structure is
-mirrored in card type emulators. The 7816 emulator already handles the basic
-ISO 7186 commands. Card type emulators simply need to add the virtual applets
-which emulate the real card applets. Card type emulators have exactly one
-public entry point:
-       VCARDStatus xxx_card_init(VCard *card, const char *flags,
-                               const unsigned char *cert[],
-                               int cert_len[],
-                               VCardKey *key[],
-                               int cert_count);
-  The parameters for this are:
-  card       - the virtual card structure which will prepresent this card.
-  flags      - option flags that may be specific to this card type.
-  cert       - array of binary certificates.
-  cert_len   - array of lengths of each of the certificates specified in cert.
-  key        - array of opaque key structures representing the private keys on
-               the card.
-  cert_count - number of entries in cert, cert_len, and key arrays.
-  Any cert, cert_len, or key with the same index are matching sets. That is
-  cert[0] is cert_len[0] long and has the corresponsing private key of key[0].
-The card type emulator is expected to own the VCardKeys, but it should copy
-any raw cert data it wants to save. It can create new applets and add them to
-the card using the following functions:
-       VCardApplet *vcard_new_applet(VCardProcessAPDU apdu_func,
-                                     VCardResetApplet reset_func,
-                                     const unsigned char *aid,
-                                     int aid_len);
-  This function creates a new applet. Applet structures store the following
-  information:
-     1) the AID of the applet (set by aid and aid_len).
-     2) a function to handle APDUs for this applet. (set by apdu_func, more on
-        this below).
-     3) a function to reset the applet state when the applet is selected.
-        (set by reset_func, more on this below).
-     3) applet private data, a data pointer used by the card type emulator to
-        store any data or state it needs to complete requests. (set by a
-        separate call).
-     4) applet private data free, a function used to free the applet private
-        data when the applet itself is destroyed.
-  The created applet can be added to the card with vcard_add_applet below.
-        void vcard_set_applet_private(VCardApplet *applet,
-                                      VCardAppletPrivate *private,
-                                      VCardAppletPrivateFree private_free);
-  This function sets the private data and the corresponding free function.
-  VCardAppletPrivate is an opaque data structure to the rest of the emulator.
-  The card type emulator can define it any way it wants by defining
-  struct VCardAppletPrivateStruct {};. If there is already a private data
-  structure on the applet, the old one is freed before the new one is set up.
-  passing two NULL clear any existing private data.
-         VCardStatus vcard_add_applet(VCard *card, VCardApplet *applet);
-  Add an applet onto the list of applets attached to the card. Once an applet
-  has been added, it can be selected by it's aid, and then commands will be
-  routed to it VCardProcessAPDU function. This function adopts the applet the
-  passed int applet. Note: 2 applets with the same AID should not be added to
-  the same card. It's permissible to add more than one applet. Multiple applets
-  may have the same VCardPRocessAPDU entry point.
-The certs and keys should be attached to private data associated with one or
-more appropriate applets for that card. Control will come to the card type
-emulators once one of its applets are selected through the VCardProcessAPDU
-function it specified when it created the applet.
-The signature of VCardResetApplet is:
-        VCardStatus (*VCardResetApplet) (VCard *card, int channel);
-  This function will reset the any internal applet state that needs to be
-  cleared after a select applet call. It should return VCARD_DONE;
-The signature of VCardProcessAPDU is:
-        VCardStatus (*VCardProcessAPDU)(VCard *card, VCardAPDU *apdu,
-                                         VCardResponse **response);
-  This function examines the APDU and determines whether it should process
-  the apdu directly, reject the apdu as invalid, or pass the apdu on to
-  the basic 7816 emulator for processing.
-      If the 7816 emulator should process the apdu, then the VCardProcessAPDU
-  should return VCARD_NEXT.
-      If there is an error, then VCardProcessAPDU should return an error
-  response using vcard_make_response and the appropriate 7816 error code
-  (see card_7816t.h) or vcard_make_response with a card type specific error
-  code. It should then return VCARD_DONE.
-      If the apdu can be processed correctly, VCardProcessAPDU should do so,
-  set the response value appropriately for that APDU, and return VCARD_DONE.
-  VCardProcessAPDU should always set the response if it returns VCARD_DONE.
-  It should always either return VCARD_DONE or VCARD_NEXT.
-Parsing the APDU --
-Prior to processing calling the card type emulator's VCardProcessAPDU function, the emulator has already decoded the APDU header and set several fields:
-   apdu->a_data - The raw apdu data bytes.
-   apdu->a_len  - The len of the raw apdu data.
-   apdu->a_body - The start of any post header parameter data.
-   apdu->a_Lc   - The parameter length value.
-   apdu->a_Le   - The expected length of any returned data.
-   apdu->a_cla  - The raw apdu class.
-   apdu->a_channel - The channel (decoded from the class).
-   apdu->a_secure_messaging_type - The decoded secure messagin type
-                                   (from class).
-   apdu->a_type - The decode class type.
-   apdu->a_gen_type - the generic class type (7816, PROPRIETARY, RFU, PTS).
-   apdu->a_ins  - The instruction byte.
-   apdu->a_p1   - Parameter 1.
-   apdu->a_p2   - Parameter 2.
-Creating a Response --
-The expected result of any APDU call is a response. The card type emulator must
-set *response with an appropriate VCardResponse value if it returns VCARD_DONE.
-Reponses could be as simple as returning a 2 byte status word response, to as
-complex as returning a block of data along with a 2 byte response. Which is
-returned will depend on the semantics of the APDU. The following functions will
-create card responses.
-        VCardResponse *vcard_make_response(VCard7816Status status);
-    This is the most basic function to get a response. This function will
-    return a response the consists soley one 2 byte status code. If that status
-    code is defined in card_7816t.h, then this function is guarrenteed to
-    return a response with that status. If a cart type specific status code
-    is passed and vcard_make_response fails to allocate the appropriate memory
-    for that response, then vcard_make_response will return a VCardResponse
-    of VCARD7816_STATUS_EXC_ERROR_MEMORY. In any case, this function is
-    guarrenteed to return a valid VCardResponse.
-        VCardResponse *vcard_response_new(unsigned char *buf, int len,
-                                          VCard7816Status status);
-    This function is similar to vcard_make_response except it includes some
-    returned data with the response. It could also fail to allocate enough
-    memory, in which case it will return NULL.
-        VCardResponse *vcard_response_new_status_bytes(unsigned char sw1,
-                                                       unsigned char sw2);
-    Sometimes in 7816 the response bytes are treated as two separate bytes with
-    split meanings. This function allows you to create a response based on
-    two separate bytes. This function could fail, in which case it will return
-    NULL.
-       VCardResponse *vcard_response_new_bytes(unsigned char *buf, int len,
-                                               unsigned char sw1,
-                                               unsigned char sw2);
-    This function is the same as vcard_response_new except you may specify
-    the status as two separate bytes like vcard_response_new_status_bytes.
-Implementing functionality ---
-The following helper functions access information about the current card
-and applet.
-        VCARDAppletPrivate *vcard_get_current_applet_private(VCard *card,
-                                                             int channel);
-    This function returns any private data set by the card type emulator on
-    the currently selected applet. The card type emulator keeps track of the
-    current applet state in this data structure. Any certs and keys associated
-    with a particular applet is also stored here.
-        int vcard_emul_get_login_count(VCard *card);
-    This function returns the the number of remaing login attempts for this
-    card. If the card emulator does not know, or the card does not have a
-    way of giving this information, this function returns -1.
-         VCard7816Status vcard_emul_login(VCard *card, unsigned char *pin,
-                                          int pin_len);
-    This function logins into the card and return the standard 7816 status
-    word depending on the success or failure of the call.
-         void vcard_emul_delete_key(VCardKey *key);
-     This function frees the VCardKey passed in to xxxx_card_init. The card
-     type emulator is responsible for freeing this key when it no longer needs
-     it.
-         VCard7816Status vcard_emul_rsa_op(VCard *card, VCardKey *key,
-                                           unsigned char *buffer,
-                                           int buffer_size);
-     This function does a raw rsa op on the buffer with the given key.
-The sample card type emulator is found in cac.c. It implements the cac specific
-applets.  Only those applets needed by the coolkey pkcs#11 driver on the guest
-have been implemented. To support the full range CAC middleware, a complete CAC
-card according to the CAC specs should be implemented here.
-Virtual Card Emulator
-This code accesses both real smart cards and simulated smart cards through
-services provided on the client. The current implementation uses NSS, which
-already knows how to talk to various PKCS #11 modules on the client, and is
-portable to most operating systems. A particular emulator can have only one
-virtual card implementation at a time.
-The virtual card emulator consists of a series of virtual card services. In
-addition to the services describe above (services starting with
-vcard_emul_xxxx), the virtual card emulator also provides the following
-    VCardEmulError vcard_emul_init(cont VCardEmulOptions *options);
-  The options structure is built by another function in the virtual card
-  interface where a string of virtual card emulator specific strings are
-  mapped to the options. The actual structure is defined by the virutal card
-  emulator and is used to determine the configuration of soft cards, or to
-  determine which physical cards to present to the guest.
-  The vcard_emul_init function will build up sets of readers, create any
-  threads that are needed to watch for changes in the reader state. If readers
-  have cards present in them, they are also initialized.
-  Readers are created with the function.
-          VReader *vreader_new(VReaderEmul *reader_emul,
-                               VReaderEmulFree reader_emul_free);
-      The freeFunc is used to free the VReaderEmul * when the reader is
-      destroyed.  The VReaderEmul structure is an opaque structure to the
-      rest of the code, but defined by the virtual card emulator, which can
-      use it to store any reader specific state.
-  Once the reader has been created, it can be added to the front end with the
-  call:
-           VReaderStatus vreader_add_reader(VReader *reader);
-      This function will automatically generate the appropriate new reader
-      events and add the reader to the list.
-  To create a new card, the virtual card emulator will call a similiar
-  function.
-           VCard *vcard_new(VCardEmul *card_emul,
-                            VCardEmulFree card_emul_free);
-      Like vreader_new, this function takes a virtual card emulator specific
-      structure which it uses to keep track of the card state.
-  Once the card is created, it is attached to a card type emulator with the
-  following function:
-            VCardStatus vcard_init(VCard *vcard, VCardEmulType type,
-                                   const char *flags,
-                                   unsigned char *const *certs,
-                                   int *cert_len,
-                                   VCardKey *key[],
-                                   int cert_count);
-      The vcard is the value returned from vcard_new. The type is the
-      card type emulator that this card should presented to the guest as.
-      The flags are card type emulator specific options. The certs,
-      cert_len, and keys are all arrays of length cert_count. These are the
-      the same of the parameters xxxx_card_init() accepts.
-   Finally the card is associated with it's reader by the call:
-            VReaderStatus vreader_insert_card(VReader *vreader, VCard *vcard);
-      This function, like vreader_add_reader, will take care of any event
-      notification for the card insert.
-    VCardEmulError vcard_emul_force_card_remove(VReader *vreader);
-  Force a card that is present to appear to be removed to the guest, even if
-  that card is a physical card and is present.
-    VCardEmulError vcard_emul_force_card_insert(VReader *reader);
-  Force a card that has been removed by vcard_emul_force_card_remove to be
-  reinserted from the point of view of the guest. This will only work if the
-  card is physically present (which is always true fro a soft card).
-     void vcard_emul_get_atr(Vcard *card, unsigned char *atr, int *atr_len);
-  Return the virtual ATR for the card. By convention this should be the value
-  VCARD_ATR_PREFIX(size) followed by several ascii bytes related to this
-  particular emulator. For instance the NSS emulator returns
-  {VCARD_ATR_PREFIX(3), 'N', 'S', 'S' }. Do ot return more data then *atr_len;
-     void vcard_emul_reset(VCard *card, VCardPower power)
-   Set the state of 'card' to the current power level and reset its internal
-   state (logout, etc).
-List of files and their function:
-README - This file
-card_7816.c - emulate basic 7816 functionality. Parse APDUs.
-card_7816.h - apdu and response services definitions.
-card_7816t.h - 7816 specific structures, types and definitions.
-event.c - event handling code.
-event.h - event handling services definitions.
-eventt.h - event handling structures and types
-vcard.c - handle common virtual card services like creation, destruction, and
-          applet management.
-vcard.h - common virtual card services function definitions.
-vcardt.h - comon virtual card types
-vreader.c - common virtual reader services.
-vreader.h - common virtual reader services definitions.
-vreadert.h - comon virtual reader types.
-vcard_emul_type.c - manage the card type emulators.
-vcard_emul_type.h - definitions for card type emulators.
-cac.c - card type emulator for CAC cards
-vcard_emul.h - virtual card emulator service definitions.
-vcard_emul_nss.c - virtual card emulator implementation for nss.
-vscclient.c - socket connection to guest qemu usb driver.
-vscard_common.h - common header with the guest qemu usb driver.
-mutex.h - header file for machine independent mutexes.
-link_test.c - static test to make sure all the symbols are properly defined.