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230 lines
6.6 KiB
ReStructuredText
230 lines
6.6 KiB
ReStructuredText
Digital TV Conditional Access Interface (CI API)
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================================================
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.. note::
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This documentation is outdated.
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This document describes the usage of the high level CI API as
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in accordance to the Linux DVB API. This is a not a documentation for the,
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existing low level CI API.
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.. note::
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For the Twinhan/Twinhan clones, the dst_ca module handles the CI
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hardware handling.This module is loaded automatically if a CI
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(Common Interface, that holds the CAM (Conditional Access Module)
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is detected.
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ca_zap
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~~~~~~
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A userspace application, like ``ca_zap`` is required to handle encrypted
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MPEG-TS streams.
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The ``ca_zap`` userland application is in charge of sending the
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descrambling related information to the Conditional Access Module (CAM).
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This application requires the following to function properly as of now.
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a) Tune to a valid channel, with szap.
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eg: $ szap -c channels.conf -r "TMC" -x
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b) a channels.conf containing a valid PMT PID
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eg: TMC:11996:h:0:27500:278:512:650:321
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here 278 is a valid PMT PID. the rest of the values are the
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same ones that szap uses.
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c) after running a szap, you have to run ca_zap, for the
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descrambler to function,
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eg: $ ca_zap channels.conf "TMC"
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d) Hopefully enjoy your favourite subscribed channel as you do with
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a FTA card.
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.. note::
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Currently ca_zap, and dst_test, both are meant for demonstration
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purposes only, they can become full fledged applications if necessary.
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Cards that fall in this category
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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At present the cards that fall in this category are the Twinhan and its
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clones, these cards are available as VVMER, Tomato, Hercules, Orange and
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so on.
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CI modules that are supported
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The CI module support is largely dependent upon the firmware on the cards
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Some cards do support almost all of the available CI modules. There is
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nothing much that can be done in order to make additional CI modules
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working with these cards.
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Modules that have been tested by this driver at present are
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(1) Irdeto 1 and 2 from SCM
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(2) Viaccess from SCM
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(3) Dragoncam
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The High level CI API
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~~~~~~~~~~~~~~~~~~~~~
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For the programmer
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^^^^^^^^^^^^^^^^^^
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With the High Level CI approach any new card with almost any random
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architecture can be implemented with this style, the definitions
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inside the switch statement can be easily adapted for any card, thereby
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eliminating the need for any additional ioctls.
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The disadvantage is that the driver/hardware has to manage the rest. For
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the application programmer it would be as simple as sending/receiving an
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array to/from the CI ioctls as defined in the Linux DVB API. No changes
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have been made in the API to accommodate this feature.
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Why the need for another CI interface?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This is one of the most commonly asked question. Well a nice question.
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Strictly speaking this is not a new interface.
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The CI interface is defined in the DVB API in ca.h as:
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.. code-block:: c
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typedef struct ca_slot_info {
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int num; /* slot number */
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int type; /* CA interface this slot supports */
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#define CA_CI 1 /* CI high level interface */
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#define CA_CI_LINK 2 /* CI link layer level interface */
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#define CA_CI_PHYS 4 /* CI physical layer level interface */
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#define CA_DESCR 8 /* built-in descrambler */
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#define CA_SC 128 /* simple smart card interface */
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unsigned int flags;
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#define CA_CI_MODULE_PRESENT 1 /* module (or card) inserted */
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#define CA_CI_MODULE_READY 2
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} ca_slot_info_t;
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This CI interface follows the CI high level interface, which is not
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implemented by most applications. Hence this area is revisited.
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This CI interface is quite different in the case that it tries to
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accommodate all other CI based devices, that fall into the other categories.
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This means that this CI interface handles the EN50221 style tags in the
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Application layer only and no session management is taken care of by the
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application. The driver/hardware will take care of all that.
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This interface is purely an EN50221 interface exchanging APDU's. This
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means that no session management, link layer or a transport layer do
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exist in this case in the application to driver communication. It is
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as simple as that. The driver/hardware has to take care of that.
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With this High Level CI interface, the interface can be defined with the
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regular ioctls.
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All these ioctls are also valid for the High level CI interface
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#define CA_RESET _IO('o', 128)
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#define CA_GET_CAP _IOR('o', 129, ca_caps_t)
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#define CA_GET_SLOT_INFO _IOR('o', 130, ca_slot_info_t)
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#define CA_GET_DESCR_INFO _IOR('o', 131, ca_descr_info_t)
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#define CA_GET_MSG _IOR('o', 132, ca_msg_t)
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#define CA_SEND_MSG _IOW('o', 133, ca_msg_t)
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#define CA_SET_DESCR _IOW('o', 134, ca_descr_t)
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On querying the device, the device yields information thus:
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.. code-block:: none
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CA_GET_SLOT_INFO
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----------------------------
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Command = [info]
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APP: Number=[1]
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APP: Type=[1]
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APP: flags=[1]
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APP: CI High level interface
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APP: CA/CI Module Present
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CA_GET_CAP
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----------------------------
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Command = [caps]
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APP: Slots=[1]
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APP: Type=[1]
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APP: Descrambler keys=[16]
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APP: Type=[1]
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CA_SEND_MSG
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----------------------------
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Descriptors(Program Level)=[ 09 06 06 04 05 50 ff f1]
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Found CA descriptor @ program level
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(20) ES type=[2] ES pid=[201] ES length =[0 (0x0)]
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(25) ES type=[4] ES pid=[301] ES length =[0 (0x0)]
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ca_message length is 25 (0x19) bytes
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EN50221 CA MSG=[ 9f 80 32 19 03 01 2d d1 f0 08 01 09 06 06 04 05 50 ff f1 02 e0 c9 00 00 04 e1 2d 00 00]
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Not all ioctl's are implemented in the driver from the API, the other
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features of the hardware that cannot be implemented by the API are achieved
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using the CA_GET_MSG and CA_SEND_MSG ioctls. An EN50221 style wrapper is
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used to exchange the data to maintain compatibility with other hardware.
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.. code-block:: c
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/* a message to/from a CI-CAM */
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typedef struct ca_msg {
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unsigned int index;
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unsigned int type;
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unsigned int length;
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unsigned char msg[256];
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} ca_msg_t;
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The flow of data can be described thus,
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.. code-block:: none
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App (User)
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-----
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parse
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v
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en50221 APDU (package)
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--------------------------------------
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| | | High Level CI driver
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| v |
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| en50221 APDU (unpackage) |
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| | |
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| sanity checks |
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| do (H/W dep) |
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--------------------------------------
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| Hardware
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v
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The High Level CI interface uses the EN50221 DVB standard, following a
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standard ensures futureproofness.
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