Copyright 2001-2008 gemalto
Author: Jean-Daniel Aussel, mailto:jean-daniel.aussel@gemalto.com
This file is part of pyscard.
pyscard is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
pyscard is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along
with pyscard; if not, write to the Free Software Foundation, Inc., 51 Franklin
St, Fifth Floor, Boston, MA 02110-1301 USA
The pyscard smartcard library is a framework for building smart card aware applications in Python. The smartcard module is built on top of the PCSC API Python wrapper module.
pyscard supports Windows 2000 and XP by using the Microsoft Smart Card Base components, and linux by using PCSC-lite.
We will see in this section some variations on how to send APDU commands to a smart card.
In the reader-centric approach, we open a connection with a card thru a smart card reader, and send APDU commands to the card using the connection:
>>>
from smartcard.System import readers
>>> from smartcard.util import toHexString
>>>
>>> r=readers()
>>> print r
['SchlumbergerSema Reflex USB v.2 0', 'Utimaco CardManUSB 0']
>>> connection = r[0].createConnection()
>>> connection.connect()
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>> data, sw1, sw2 = connection.transmit( SELECT + DF_TELECOM )
>>> print "%x %x" % (sw1, sw2)
9f 1a
>>>
The list of available readers is retrieved with the readers() function. We create a connection with the first reader (index 0 for reader 1, 1 for reader 2, ...) with the r[0].createConnection() call and connect to the card with the connect() method of the connection. We can then send APDU commands to the card with the transmit() method.
Scripts written with the reader centric approach however have the following drawbacks:
Most of these issues are solved with the card-centric approach
In the card-centric approach, we create a request for a specific type of card and wait until a card matching the request is inserted. Once a matching card is introduced, a connection to the card is automatically created and we can send APDU commands to the card using this connection.
The following scripts requests a card with a known ATR:
>>>
from smartcard.CardType import ATRCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString, toBytes
>>>
>>> cardtype = ATRCardType( toBytes( "3B 16 94 20 02 01 00 00
0D" ) )
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>> print toHexString( cardservice.connection.getATR() )
3B 16 94 20 02 01 00 00 0D
>>>
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>> data, sw1, sw2 = cardservice.connection.transmit( SELECT + DF_TELECOM
)
>>> print "%x %x" % (sw1, sw2)
9f 1a
>>>
To request a card with a know ATR, you must first create an ATRCardType object with the desired ATR:
>>>
cardtype = ATRCardType( toBytes( "3B 16 94 20 02 01 00 00 0D" ) )
And then create a CardRequest for this card type. In the sample, we request a time-out of 1 second.
>>>
cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
The waitforcard() will either return with a card service or a time-out. The card service connection attribute can be used thereafter to transmit APDU commands to the card, as with the reader centric approach.
>>>
cardservice.connection.connect()
>>> print toHexString( cardservice.connection.getATR() )
If necessary, the reader used for the connection can be accessed thru the CardConnection object:
>>>
print cardservice.connection.getReader()
SchlumbergerSema Reflex USB v.2 0
The ATRCardType also supports masks:
>>>
from smartcard.CardType import ATRCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString, toBytes
>>>
>>> cardtype = ATRCardType( toBytes( "3B 15 94 20 02 01
00 00 0F" ), toBytes( "00 00 FF FF FF FF FF FF 00" ) )
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>> print toHexString( cardservice.connection.getATR() )
3B 16 94 20 02 01 00 00 0D
Other CardTypes are available, and new CardTypes can be created, as described below.
The AnyCardType is useful for requesting any card in any reader:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>> print toHexString( cardservice.connection.getATR() )
3B 16 94 20 02 01 00 00 0D
>>> print cardservice.connection.getReader()
SchlumbergerSema Reflex USB v.2 0
Custom CardTypes can be created, e.g. a card type that checks the ATR and the historical bytes of the card. To create a custom CardType, deriver your CardType class from the the CardType base class (or any other CardType) and override the matches() method. For exemple to create a DCCardType that will match cards with the direct convention (first byte of ATR to 0x3b):
>>>
from smartcard.CardType import CardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString
>>>
>>> class DCCardType(CardType):
... def matches( self, atr, reader=None ):
... return atr[0]==0x3B
...
>>> cardtype = DCCardType()
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>> print toHexString( cardservice.connection.getATR() )
3B 16 94 20 02 01 00 00 0D
>>> print cardservice.connection.getReader()
SchlumbergerSema Reflex USB v.2 0
>>>
Scripts written with the card-centric approach fixes the problems of the reader-centric approach:
Scripts written with the card-centric approach have however the following drawbacks:
By defaults, the connect() method of the CardConnection object.will try to connect using either the T=0 or T=1 protocol. To force a connection protocol, you can pass the required protocol to the connect() method.
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardConnection import CardConnection
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect( CardConnection.T1_protocol )
>>> print toHexString( cardservice.connection.getATR() )
3B 16 94 20 02 01 00 00 0D
>>> print cardservice.connection.getReader()
SchlumbergerSema Reflex USB v.2 0
Alternatively, you can specify the required protocol in the CardConnection transmit() method:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardConnection import CardConnection
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString, toBytes
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>>
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>> apdu = SELECT+DF_TELECOM
>>> print 'sending ' + toHexString(apdu)
sending A0 A4 00 00 02 7F 10
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu, CardConnection.T1_protocol
)
>>> print 'response: ', response, ' status words: ', "%x %x"
% (sw1, sw2)
response: [] status words: 9f 1a
>>>
>>> if sw1 == 0x9F:
... GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
... apdu = GET_RESPONSE + [sw2]
... print 'sending ' + toHexString(apdu)
... response, sw1, sw2 = cardservice.connection.transmit(
apdu )
... print 'response: ', toHexString(response), ' status
words: ', "%x %x" % (sw1, sw2)
...
sending A0 C0 00 00 1A
response: 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A
00 01 00 00 status words: 90 0
>>>
In the object-centric approach, we associate a high-level object with a set of smart cards supported by the object. For example we associate a javacard loader class with a set of javacard smart cards. We create a request for the specific object, and wait until a card supported by the object is inserted. Once a card supported by the object is inserted, we perform the required function by calling the objec methods.
To be written...
A straightforward way of tracing command and response APDUs is to insert print statements around the transmit() method calls:
>>>
from smartcard.CardType import ATRCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString, toBytes
>>>
>>> cardtype = ATRCardType( toBytes( "3B 16 94 20 02 01 00 00
0D" ) )
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>>
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>> apdu = SELECT+DF_TELECOM
>>> print 'sending ' + toHexString(apdu)
sending A0 A4 00 00 02 7F 10
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu )
>>> print 'response: ', response, ' status words: ', "%x %x"
% (sw1, sw2)
response: [] status words: 9f 1a
>>>
>>> if sw1 == 0x9F:
... GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
... apdu = GET_RESPONSE + [sw2]
... print 'sending ' + toHexString(apdu)
... response, sw1, sw2 = cardservice.connection.transmit(
apdu )
... print 'response: ', toHexString(response), ' status
words: ', "%x %x" % (sw1, sw2)
...
sending A0 C0 00 00 1A
response: 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A
00 01 00 00 status words: 90 0
>>>
Scripts written this way are quite difficult to read, because there are more tracing statements than actual apdu transmits..
A small improvement in visibility would be to replace the print instructions by functions, e.g.:
>>>
from smartcard.CardType import ATRCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString, toBytes
>>>
>>> cardtype = ATRCardType( toBytes( "3B 16 94 20 02 01 00 00
0D" ) )
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>>
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>> def trace_command(apdu):
... print 'sending ' + toHexString(apdu)
...
>>> def trace_response( response, sw1, sw2 ):
... if None==response: response=[]
... print 'response: ', toHexString(response), ' status
words: ', "%x %x" % (sw1, sw2)
...
>>> apdu = SELECT+DF_TELECOM
>>> trace_command(apdu)
sending A0 A4 00 00 02 7F 10
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu )
>>> trace_response( response, sw1, sw2 )
response: status words: 9f 1a
>>>
>>> if sw1 == 0x9F:
... GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
... apdu = GET_RESPONSE + [sw2]
... trace_command(apdu)
... response, sw1, sw2 = cardservice.connection.transmit(
apdu )
... trace_response( response, sw1, sw2 )
...
sending A0 C0 00 00 1A
response: 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A
00 01 00 00 status words: 90 0
>>>
The prefered solution is to implement a card connection observer, and register the observer with the card connection. The card connection will then notify the observer when card connection events occur (e.g. connection, disconnection, apdu command or apdu response). This is illustrated in the following script:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.CardConnectionObserver import ConsoleCardConnectionObserver
>>>
>>> GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=10, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> observer=ConsoleCardConnectionObserver()
>>> cardservice.connection.addObserver( observer )
>>>
>>> cardservice.connection.connect()
connecting to SchlumbergerSema Reflex USB v.2 0
>>>
>>> apdu = SELECT+DF_TELECOM
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu )
> A0 A4 00 00 02 7F 10
< [] 9F 1A
>>> if sw1 == 0x9F:
... apdu = GET_RESPONSE + [sw2]
... response, sw1, sw2 = cardservice.connection.transmit(
apdu )
... else:
... print 'no DF_TELECOM'
...
> A0 C0 00 00 1A
< 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A 00 01
00 00 90 0
>>>
In this script, a ConsoleCardConnectionObserver is attached to the card service connection once the watiforcard() call returns.
>>>
observer=ConsoleCardConnectionObserver()
>>> cardservice.connection.addObserver( observer )
On card connection events (connect, disconnect, transmit command apdu, receive response apdu), the card connection notifies its obersers with a CarConnectionEvent including the event type and the event data. The ConsoleCardConnectionObserver is a simple observer that will print on the console the card connection events. The class definition is the following:
class ConsoleCardConnectionObserver(
CardConnectionObserver ):
def update( self, cardconnection, ccevent ):
if
'connect'==ccevent.type:
print
'connecting to ' + cardconnection.getReader()
elif
'disconnect'==ccevent.type:
print
'disconnecting from ' + cardconnection.getReader()
elif
'command'==ccevent.type:
print
'> ', toHexString( ccevent.args[0] )
elif
'response'==ccevent.type:
if []==ccevent.args[0]:
print
'< [] ', "%-2X %-2X" % tuple(ccevent.args[-2:])
else:
print '< ', toHexString(ccevent.args[0]),
"%-2X %-2X" % tuple(ccevent.args[-2:])
The console card connection observer is thus printing the connect, disconnect, command and response apdu events:
>>>
cardservice.connection.connect()
connecting to SchlumbergerSema Reflex USB v.2 0
>>>
>>> apdu = SELECT+DF_TELECOM
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu )
> A0 A4 00 00 02 7F 10
< [] 9F 1A
>>> if sw1 == 0x9F:
... apdu = GET_RESPONSE + [sw2]
... response, sw1, sw2 = cardservice.connection.transmit(
apdu )
... else:
... print 'no DF_TELECOM'
...
> A0 C0 00 00 1A
< 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A 00 01
00 00 90 0
A card connection observer's update methode is called upon card connection event, with the connection and the connection event as parameters. The CardConnectionEvent class definition is the following:
class CardConnectionEvent:
"""Base class for card connection events.
This event is notified by CardConnection objects.
type:
'connect', 'disconnect', 'command', 'response'
args: None for 'connect' or 'disconnect'
command APDU byte list for 'command'
[response data, sw1, sw2] for 'response'
type: 'connect' args:"""
def __init__( self, type, args=None):
self.type=type
self.args=args
You can write your own card connection observer, for example to perform fancy output in a wxWindows frame, or apdu interpretation. The following scripts defines a small SELECT and GET RESPONSE apdu interpreter:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.CardConnectionObserver import CardConnectionObserver
>>> from smartcard.util import toHexString
>>>
>>> from string import replace
>>>
>>> class TracerAndSELECTInterpreter( CardConnectionObserver ):
... def update( self, cardconnection, ccevent ):
... if 'connect'==ccevent.type:
... print
'connecting to ' + cardconnection.getReader()
... elif 'disconnect'==ccevent.type:
... print
'disconnecting from ' + cardconnection.getReader()
... elif 'command'==ccevent.type:
... str=toHexString(ccevent.args[0])
... str
= replace( str , "A0 A4 00 00 02", "SELECT" )
... str
= replace( str , "A0 C0 00 00", "GET RESPONSE" )
... print
'> ', str
... elif 'response'==ccevent.type:
... if
[]==ccevent.args[0]:
... print
'< [] ', "%-2X %-2X" % tuple(ccevent.args[-2:])
... else:
... print
'< ', toHexString(ccevent.args[0]), "%-2X %-2X" % tuple(ccevent.args[-2:])
...
>>>
>>> GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=10, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> observer=TracerAndSELECTInterpreter()
>>> cardservice.connection.addObserver( observer )
>>>
>>> cardservice.connection.connect()
connecting to SchlumbergerSema Reflex USB v.2 0
>>>
>>> apdu = SELECT+DF_TELECOM
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu )
> SELECT 7F 10
< [] 9F 1A
>>> if sw1 == 0x9F:
... apdu = GET_RESPONSE + [sw2]
... response, sw1, sw2 = cardservice.connection.transmit(
apdu )
... else:
... print 'no DF_TELECOM'
...
> GET RESPONSE 1A
< 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A 00 01
00 00 90 0
>>>
Errors can and do happen when sending APDUs to smart cards. This discussion discusses possible strategies to check and report APDU transmission errors.
As for APDU tracing, a straightforward way of checking for errors in response APDUs during the execution of scripts is to insert testt statements after the transmit() method calls:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.CardConnectionObserver import ConsoleCardConnectionObserver
>>>
>>> GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=10, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> observer=ConsoleCardConnectionObserver()
>>> cardservice.connection.addObserver( observer )
>>>
>>> cardservice.connection.connect()
connecting to Utimaco CardManUSB 0
>>>
>>> apdu = SELECT+DF_TELECOM
>>> response, sw1, sw2 = cardservice.connection.transmit( apdu )
> A0 A4 00 00 02 7F 10
< [] 6E 0
>>>
>>> if sw1 in range(0x61, 0x6f):
... print "Error: sw1: %x sw2: %x" % (sw1, sw2)
...
Error: sw1: 6e sw2: 0
>>> if sw1 == 0x9F:
... apdu = GET_RESPONSE + [sw2]
... response, sw1, sw2 = cardservice.connection.transmit( apdu )
...
>>> cardservice.connection.disconnect()
disconnecting from Utimaco CardManUSB 0
>>>
Scripts written this way are quite difficult to read, because there are more error detection statements than actual apdu transmits.
An improvement in visibility is to wrap the transmit instruction inside a function mytransmit, e.g.:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.CardConnectionObserver import ConsoleCardConnectionObserver
>>>
>>> def mytransmit( connection, apdu ):
... response, sw1, sw2 = connection.transmit( apdu )
... if sw1 in range(0x61, 0x6f):
... print "Error: sw1: %x sw2: %x" % (sw1, sw2)
... return response, sw1, sw2
...
>>>
>>> GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
>>> SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
>>> DF_TELECOM = [0x7F, 0x10]
>>>
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=10, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> observer=ConsoleCardConnectionObserver()
>>> cardservice.connection.addObserver( observer )
>>>
>>> cardservice.connection.connect()
connecting to Utimaco CardManUSB 0
>>>
>>> apdu = SELECT+DF_TELECOM
>>> response, sw1, sw2 = mytransmit( cardservice.connection, apdu )
> A0 A4 00 00 02 7F 10
< [] 6E 0
Error: sw1: 6e sw2: 0
>>>
>>> if sw1 == 0x9F:
... apdu = GET_RESPONSE + [sw2]
... response, sw1, sw2 = mytransmit( cardservice.connection, apdu )
...
>>> cardservice.connection.disconnect()
disconnecting from Utimaco CardManUSB 0
>>>
The prefered solution is for testing errors is to use smarcard.sw.ErrorChecker, as described in the following section.
Status word errors can occur from different sources. The ISO7816-4 standards defines status words for sw1 in the range 0x62 to 0x6F and some values of sw2, except for 0x66 which is reserved for security related issues. The ISO7816-8 standards define other status words, e.g. sw1=0x68 and sw2=0x83 or 0x84 for command chaining errors. Other standards, like Open Platform, define additional status words error, e.g. sw1=0x94 and sw2=0x84.
The prefered strategy for status word error checking is based around individual error checkers (smartcard.sw.ErrorChecker) that can be chained into an error checking chain (smartcars.sw.ErrorCheckingChain).
An error checker is a class deriving from ErrorChecker that checks for recognized sw1, sw2 error conditions when called, and raises an exception when finding such condition. This is illustrated in the following sample:
>>>
from smartcard.sw.ISO7816_4ErrorChecker import ISO7816_4ErrorChecker
>>>
>>> errorchecker=ISO7816_4ErrorChecker()
>>> errorchecker( [], 0x90, 0x00 )
>>> errorchecker( [], 0x6A, 0x80 )
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ISO7816_4ErrorChecker.py",
line 137, in __call__
raise exception( data, sw1, sw2, message )
smartcard.sw.SWExceptions.CheckingErrorException: 'Status word exception: checking
error - Incorrect parameters in the data field!'
>>>
The first call to error checker does not raise an exception, since 90 00 does not report any error. The second calls however raises a CheckingErrorException.
Error checkers can be chained into error checking chain. Each checker in the chain is called until an error condition is met, in which case an exception is raised. This is illustrated in the following sample:
>>>
from smartcard.sw.ISO7816_4ErrorChecker import ISO7816_4ErrorChecker
>>> from smartcard.sw.ISO7816_8ErrorChecker import ISO7816_8ErrorChecker
>>> from smartcard.sw.ISO7816_9ErrorChecker import ISO7816_9ErrorChecker
>>>
>>> from smartcard.sw.ErrorCheckingChain import ErrorCheckingChain
>>>
>>> errorchain = []
>>> errorchain=[ ErrorCheckingChain( errorchain, ISO7816_9ErrorChecker()
),
... ErrorCheckingChain( errorchain, ISO7816_8ErrorChecker() ),
... ErrorCheckingChain( errorchain, ISO7816_4ErrorChecker() ) ]
>>>
>>> errorchain[0]( [], 0x90, 0x00 )
>>> errorchain[0]( [], 0x6A, 0x8a )
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ErrorCheckingChain.py",
line 60,
in __call__
self.strategy( data, sw1, sw2 )
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ISO7816_9ErrorChecker.py",
line 74, in __call__
raise exception( data, sw1, sw2, message )
smartcard.sw.SWExceptions.CheckingErrorException: 'Status word exception: checking
error - DF name already exists!'
>>>
In this sample, an error checking chain is created that will check first for iso 7816-9 errors, then iso7816-8 errors, and finally iso7816-4 errors.
The first call to the error chain does not raise an exception, since 90 00 does not report any error. The second calls however raises a CheckingErrorException, caused by the iso7816-9 error checker.
You can filter undesired exceptions in a chain by adding a filtered exception to the error checking chain:
>>>
from smartcard.sw.ISO7816_4ErrorChecker import ISO7816_4ErrorChecker
>>> from smartcard.sw.ISO7816_8ErrorChecker import ISO7816_8ErrorChecker
>>> from smartcard.sw.ISO7816_9ErrorChecker import ISO7816_9ErrorChecker
>>>
>>> from smartcard.sw.ErrorCheckingChain import ErrorCheckingChain
>>>
>>> errorchain = []
>>> errorchain=[ ErrorCheckingChain( errorchain, ISO7816_9ErrorChecker()
),
... ErrorCheckingChain( errorchain, ISO7816_8ErrorChecker() ),
... ErrorCheckingChain( errorchain, ISO7816_4ErrorChecker() ) ]
>>>
>>>
>>> errorchain[0]( [], 0x90, 0x00 )
>>> errorchain[0]( [], 0x62, 0x00 )
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ErrorCheckingChain.py",
line 72, in __call__
return self.next()( data, sw1, sw2 )
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ErrorCheckingChain.py",
line 72, in __call__
return self.next()( data, sw1, sw2 )
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ErrorCheckingChain.py",
line 60, in __call__
self.strategy( data, sw1, sw2 )
File "D:\projects\pyscard-install\factory\python\lib\site-packages\smartcard\sw\ISO7816_4ErrorChecker.py",
line 137, in __call__
raise exception( data, sw1, sw2, message )
smartcard.sw.SWExceptions.WarningProcessingException: 'Status word exception:
warning processing - Response padded/ More APDU commands expected!'
>>>
>>> from smartcard.sw.SWExceptions import WarningProcessingException
>>>
>>> errorchain[0].addFilterException( WarningProcessingException )
>>> errorchain[0]( [], 0x62, 0x00 )
>>>
The first call to the error chain with sw1 sw2 = 62 00 raises a WarningProcessingException.
>>>
errorchain[0]( [], 0x62, 0x00 )
Traceback (most recent call last):
...
After adding a filter for WarningProcessingException, the second call to the error chain with sw1 sw2 = 62 00 does not raise any exception:
>>>
from smartcard.sw.SWExceptions import WarningProcessingException
>>>
>>> errorchain[0].addFilterException( WarningProcessingException )
>>> errorchain[0]( [], 0x62, 0x00 )
>>>
To detect APDU response errors during transmission, simply set the error checking chain of the connection used for transmission:
from smartcard.CardType
import AnyCardType
from smartcard.CardRequest import CardRequest
from smartcard.CardConnectionObserver import ConsoleCardConnectionObserver
from smartcard.sw.ErrorCheckingChain
import ErrorCheckingChain
from smartcard.sw.ISO7816_4ErrorChecker import ISO7816_4ErrorChecker
from smartcard.sw.ISO7816_8ErrorChecker import ISO7816_8ErrorChecker
from smartcard.sw.SWExceptions import SWException, WarningProcessingException
# request
any card
cardtype = AnyCardType()
cardrequest = CardRequest( timeout=10, cardType=cardtype )
cardservice = cardrequest.waitforcard()
# our error
checking chain
errorchain=[]
errorchain=[ ErrorCheckingChain( errorchain, ISO7816_8ErrorChecker() ),
ErrorCheckingChain(
errorchain, ISO7816_4ErrorChecker() ) ]
cardservice.connection.setErrorCheckingChain( errorchain )
# a console
tracer
observer=ConsoleCardConnectionObserver()
cardservice.connection.addObserver( observer )
# send a few
apdus; exceptions will occur upon errors
cardservice.connection.connect()
try:
SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02]
DF_TELECOM = [0x7F, 0x10]
apdu = SELECT+DF_TELECOM
response, sw1, sw2 = cardservice.connection.transmit(
apdu )
if sw1 == 0x9F:
GET_RESPONSE = [0XA0, 0XC0,
00, 00 ]
apdu = GET_RESPONSE + [sw2]
response, sw1, sw2 = cardservice.connection.transmit(
apdu )
except SWException, e:
print str(e)
Executing the previous script on a SIM card will cause an output similar to:
connecting
to SchlumbergerSema Reflex USB v.2 0
> A0 A4 00 00 02 7F 10
< [] 9F 1A
> A0 C0 00 00 1A
< 00 00 00 00 7F 10 02 00 00 00 00 00 0D 13 00 0A 04 00 83 8A 83 8A 00 01
00 00 90 0
disconnecting from SchlumbergerSema Reflex USB v.2 0
disconnecting from SchlumbergerSema Reflex USB v.2 0
whereas executing the script on a non-SIM card will result in:
connecting
to Utimaco CardManUSB 0
> A0 A4 00 00 02 7F 10
< [] 6E 0
'Status word exception: checking error - Class (CLA) not supported!'
disconnecting from Utimaco CardManUSB 0
disconnecting from Utimaco CardManUSB 0
To implement an error checking chain, create an ErrorCheckingChain object with the desired error checking strategies, and set this chain object as the card connection error checking chain. The card connection will use the chain for error checking upon reception of a response apdu:
Implementing a custom error checker requires implementing a sub-class of ErrorChecker, and overriding the __call__ method. The following error checker raises a SecurityRelatedException exception when sw1=0x66 and sw2=0x00:
from smartcard.sw.ErrorChecker
import ErrorChecker
from smartcard.sw.SWExceptions import SecurityRelatedException
class MyErrorChecker(
ErrorChecker ):
def __call__( self, data, sw1, sw2 ):
if 0x66==sw1 and 0x00==sw2:
raise
SecurityRelatedException( data, sw1, sw2 )
Custom checkers can be used standalone, as in the following sample, or chained to other error checkers:
from smartcard.CardType
import AnyCardType
from smartcard.CardRequest import CardRequest
from smartcard.sw.ErrorCheckingChain
import ErrorCheckingChain
from smartcard.sw.ErrorChecker import ErrorChecker
from smartcard.sw.SWExceptions import SecurityRelatedException
class MyErrorChecker(
ErrorChecker ):
def __call__( self, data, sw1, sw2 ):
if 0x66==sw1 and 0x00==sw2:
raise
SecurityRelatedException( data, sw1, sw2 )
# request
any card
cardtype = AnyCardType()
cardrequest = CardRequest( timeout=10, cardType=cardtype )
cardservice = cardrequest.waitforcard()
# our error
checking chain
errorchain=[]
errorchain=[ ErrorCheckingChain( [], MyErrorChecker() ) ]
cardservice.connection.setErrorCheckingChain( errorchain )
# send a few
apdus; exceptions will occur upon errors
cardservice.connection.connect()
SELECT = [0xA0,
0xA4, 0x00, 0x00, 0x02]
DF_TELECOM = [0x7F, 0x10]
apdu = SELECT+DF_TELECOM
response, sw1, sw2 = cardservice.connection.transmit( apdu )
if sw1 == 0x9F:
GET_RESPONSE = [0XA0, 0XC0, 00, 00 ]
apdu = GET_RESPONSE + [sw2]
response, sw1, sw2 = cardservice.connection.transmit(
apdu )
The easiest way to retrieve the list of smartcard readers is the smartcard.System.readers() function:
>>>
import smartcard.System
>>> print smartcard.System.readers()
['Schlumberger e-gate 0', 'SchlumbergerSema Reflex USB v.2 0', 'Utimaco CardManUSB
0']
>>>
Reader group management is only available on Windows, since PCSC-lite does not currently supports reader groups management.
Readers can be organized in reader groups. To retrieve the smartcard reader groups, use readergroups():
>>>
import smartcard.System
>>> print smartcard.System.readergroups()
['SCard$DefaultReaders']
>>>
The readergroups() object has all the list attributes. To add a reader group, simply use the + operator, e.g.:
>>>
from smartcard.System import readergroups
>>> g=readergroups()
>>> print g
['SCard$DefaultReaders']
>>> g+='Biometric$Readers'
>>> print g
['SCard$DefaultReaders', 'Biometric$Readers']
>>>
You can also use the append and insert methods, as well as the + operator, e.g.:
>>>
from smartcard.System import readergroups
>>> g=readergroups()
>>> print g
['SCard$DefaultReaders']
>>> g=g+['Biometric$Readers','Pinpad$Readers']
>>> print g
['SCard$DefaultReaders', 'Biometric$Readers', 'Pinpad$Readers']
>>>
or
>>>
from smartcard.System import readergroups
>>> g=readergroups()
>>> print g
['SCard$DefaultReaders']
>>> g.append('Biometric$Readers')
>>> g.insert(1,'Pinpad$Readers')
>>> print g
['SCard$DefaultReaders', 'Pinpad$Readers', 'Biometric$Readers']
>>>
Smartcard reader groups are not persistent until a reader as been added to the group. To add a reader to a reader group, use addreadertogroups():
>>>
from smartcard.System import readergroups, addreadertogroups, readers
>>> g=readergroups()
>>> g+='USB$Readers'
>>> addreadertogroups( 'Schlumberger e-gate 0', 'USB$Readers' )
>>> readers( 'USB$Readers')
['Schlumberger e-gate 0']
>>>
To remove a reader group, all list operators are available to manage reader groups, including pop() or remove():
>>>
from smartcard.System import readergroups, addreadertogroups, readers
>>> g=readergroups()
>>> g+='USB$Readers'
>>> print g
['SCard$DefaultReaders', 'USB$Readers']
>>> g.pop(1)
'USB$Readers'
>>> g
['SCard$DefaultReaders']
>>>
or
>>>
from smartcard.System import readergroups, addreadertogroups, readers
>>> g=readergroups()
>>> g+='USB$Readers'
>>> print g
['SCard$DefaultReaders', 'USB$Readers']
>>> readergroups().remove('USB$Readers')
>>> readergroups()
['SCard$DefaultReaders']
>>>
You can monitor the insertion or removal of readers using the ReaderObserver interface.
To monitor reader insertion, create a ReaderObserver object that implements an update() method that will be called upon reader/insertion removal. The following sample code implements a ReaderObserver that simply prints the inserted/removed readers on the standard output:
from smartcard.ReaderMonitoring import ReaderObserver class printobserver( ReaderObserver ): """A simple reader observer that is notified when readers are added/removed from the system and prints the list of readers """ def update( self, observable, (addedreaders, removedreaders) ): print "Added readers", addedreaders print "Removed readers", removedreaders
To monitor reader insertion/removal, simply add the observer to the ReaderMonitor:
from sys import stdin, exc_info from time import sleep from smartcard.ReaderMonitoring import ReaderMonitor, ReaderObserver try: print "Add or remove a smartcard reader to the system." print "This program will exit in 10 seconds" print "" readermonitor = ReaderMonitor() readerobserver = printobserver() readermonitor.addObserver( readerobserver ) sleep(10) # don't forget to remove observer, or the # monitor will poll forever... readermonitor.deleteObserver(readerobserver) print 'press Enter to continue' stdin.readline() except error: print exc_info()[0], ': ', exc_info()[1]
You can monitor the insertion or removal of cards using the CardObserver interface.
To monitor card insertion and removal, create a CardObserver object that implements an update() method that will be called upon card insertion/removal. The following sample code implements a CardObserver that simply prints the inserted/removed cards on the standard output, named printobserver. To monitor card insertion/removal, simply add the card observer to the CardMonitor: :
from smartcard.CardMonitoring import CardMonitor, CardObserver from smartcard.util import * # a simple card observer that prints inserted/removed cards class printobserver( CardObserver ): """A simple card observer that is notified when cards are inserted/removed from the system and prints the list of cards """ def update( self, observable, (addedcards, removedcards) ): for card in addedcards: print "+Inserted: ", toHexString( card.atr ) for card in removedcards: print "-Removed: ", toHexString( card.atr ) try: print "Insert or remove a smartcard in the system." print "This program will exit in 10 seconds" print "" cardmonitor = CardMonitor() cardobserver = printobserver() cardmonitor.addObserver( cardobserver )
The update method of the CardObserver receives two lists of Cards objects, the recently added cards and the recently removed cards. A connection can be created to each Card object of the added card list for sending APDUS.
The following sample code implements a CardObserver class named transmitobserver, that connects to inserted cards and transmit an APDU, in our case SELECT DF_TELECOM:
# a card observer that connects to new cards and performs a transaction, e.g. SELECT DF_TELECOM class transmitobserver( CardObserver ): """A card observer that is notified when cards are inserted/removed from the system, connects to cards and SELECT DF_TELECOM """ def __init__( self ): self.cards=[] def update( self, observable, (addedcards, removedcards) ): for card in addedcards: if card not in self.cards: self.cards+=[card] print "+Inserted: ", toHexString( card.atr ) card.connection = card.createConnection() card.connection.connect() response, sw1, sw2 = card.connection.transmit( SELECT_DF_TELECOM ) print "%.2x %.2x" % (sw1, sw2) for card in removedcards: print "-Removed: ", toHexString( card.atr ) if card in self.cards: self.cards.remove( card )
To monitor card insertion, connect to inserted cards and send the APDU, create an instance of transmitobserver and add it to the CardMonitor: :
from time import sleep print "Insert or remove a smartcard in the system." print "This program will exit in 100 seconds" print "" cardmonitor = CardMonitor() cardobserver = transmitobserver() cardmonitor.addObserver( cardobserver ) sleep(100)
Connecting to a card and sending APDUs is done thru a CardConnection object. CardConnection objects are created using a CardRequest, or by the CardMonitoring.
A successful CardRequest returns a CardService matching the requested card service for the card, or a PassThruCardService if no specific card service was required:
>>>
from smartcard.CardType import AnyCardType
>>> from smartcard.CardRequest import CardRequest
>>> from smartcard.util import toHexString
>>>
>>> cardtype = AnyCardType()
>>> cardrequest = CardRequest( timeout=1, cardType=cardtype )
>>> cardservice = cardrequest.waitforcard()
>>>
>>> cardservice.connection.connect()
>>> print toHexString( cardservice.connection.getATR() )
3B 16 94 20 02 01 00 00 0D
>>> print cardservice.connection.getReader()
SchlumbergerSema Reflex USB v.2 0
Each CardService has a connection attribute, which is a CardConnection for the card.
The update method of a CardObserver receives a tuple with a list of connected cards and a list of removed cards. To create a CardConnection from a card object, use the createConnection() method of the desired card:
class myobserver( CardObserver ): def update( self, observable, (addedcards, removedcards) ): for card in addedcards: print "+Inserted: ", toHexString( card.atr ) card.connection = card.createConnection() card.connection.connect() response, sw1, sw2 = card.connection.transmit( SELECT_DF_TELECOM ) print "%.2x %.2x" % (sw1, sw2)
A CardConnectionDecorator modifies the behaviour of a CardConnection object. For example, the following CardConnectionDecorator overwrites the CardConnection getATR() method:
class FakeATRConnection( CardConnectionDecorator ): '''This decorator changes the fist byte of the ATR.''' def __init__( self, cardconnection ): CardConnectionDecorator.__init__( self, cardconnection ) def getATR( self ): """Replace first BYTE of ATR by 3F""" atr = CardConnectionDecorator.getATR( self ) return [ 0x3f ] + atr [1:]
To apply the decorator, just construct the decorator around the CardConnection instance to wrap and use the decorator in place of the card connection object:
# request any card type cardtype = AnyCardType() cardrequest = CardRequest( timeout=1.5, cardType=cardtype ) cardservice = cardrequest.waitforcard() # attach the console tracer observer=ConsoleCardConnectionObserver() cardservice.connection.addObserver( observer ) # attach our decorator cardservice.connection = FakeATRConnection( cardservice.connection ) # connect to the card and perform a few transmits cardservice.connection.connect() print 'ATR', toHexString( cardservice.connection.getATR() )
Decorators can be nested. For example to nest a FakeATRConnection with a SecureChannelConnection, use the following construction:
# attach our decorator FakeATRConnection( SecureChannelConnection( cardservice.connection ) ) # connect to the card and perform a few transmits cardservice.connection.connect() print 'ATR', toHexString( cardservice.connection.getATR() )
The ExclusiveConnectCardConnection object performs an exclusive connection to the card, i.e. no other thread or process will be able to connect to the card. With PCSC readers, this is done by performing a SCardConnect with the SCARD_SHARE_EXCLUSIVE attribute.
from smartcard.CardType import AnyCardType from smartcard.CardRequest import CardRequest from smartcard.CardConnection import CardConnection from smartcard.util import toHexString from smartcard.ExclusiveConnectCardConnection import ExclusiveConnectCardConnection # request any card type cardtype = AnyCardType() cardrequest = CardRequest( timeout=5, cardType=cardtype ) cardservice = cardrequest.waitforcard() # attach our decorator cardservice.connection = ExclusiveConnectCardConnection( cardservice.connection ) # connect to the card and perform a few transmits cardservice.connection.connect() print 'ATR', toHexString( cardservice.connection.getATR() )
The ExclusiveTransmitCardConnection performs an exclusive transaction to the card, i.e. a series of transmit that cannot be interupted by other threads' transmits. To do so, include the desired transmits between an lock() and unlock() method call on the ExclusiveTransmitCardConnection:
from smartcard.CardType import AnyCardType from smartcard.CardRequest import CardRequest from smartcard.CardConnectionObserver import ConsoleCardConnectionObserver from smartcard.CardConnection import CardConnection from smartcard.util import toHexString from smartcard.ExclusiveTransmitCardConnection import ExclusiveTransmitCardConnection # define the apdus used in this script GET_RESPONSE = [0XA0, 0XC0, 00, 00 ] SELECT = [0xA0, 0xA4, 0x00, 0x00, 0x02] DF_TELECOM = [0x7F, 0x10] # request any card type cardtype = AnyCardType() cardrequest = CardRequest( timeout=5, cardType=cardtype ) cardservice = cardrequest.waitforcard() # attach the console tracer observer=ConsoleCardConnectionObserver() cardservice.connection.addObserver( observer ) # attach our decorator cardservice.connection = ExclusiveTransmitCardConnection( cardservice.connection ) # connect to the card and perform a few transmits cardservice.connection.connect() print 'ATR', toHexString( cardservice.connection.getATR() ) try: # lock for initiating transaction cardservice.connection.lock() apdu = SELECT+DF_TELECOM response, sw1, sw2 = cardservice.connection.transmit( apdu ) if sw1 == 0x9F: apdu = GET_RESPONSE + [sw2] response, sw1, sw2 = cardservice.connection.transmit( apdu ) finally: # unlock connection at the end of the transaction cardservice.connection.unlock()
Another sample of application of CardConnection decorators is to implement secure channel. The following sample is a template CardConnection decorator for secure channel, where each command APDU is cyphered and each response APDU is uncyphered:
class SecureChannelConnection( CardConnectionDecorator ): '''This decorator is a mockup of secure channel connection. It merely pretends to cypher/uncypher upon apdu transmission.''' def __init__( self, cardconnection ): CardConnectionDecorator.__init__( self, cardconnection ) def cypher( self, bytes ): '''Cypher mock-up; you would include the secure channel logics here.''' print 'cyphering', toHexString( bytes ) return bytes def uncypher( self, data ): '''Uncypher mock-up; you would include the secure channel logics here.''' print 'uncyphering', toHexString( data ) return data def transmit( self, bytes, protocol=CardConnection.T0_protocol ): """Cypher/uncypher APDUs before transmission""" cypheredbytes = self.cypher( bytes ) data, sw1, sw2 = CardConnectionDecorator.transmit( self, cypheredbytes, protocol ) if []!=data: data = self.uncypher( data ) return data, sw1, sw2
Version 2.1, February 1999
Copyright (C) 1991, 1999 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
[This is the first released version of the Lesser GPL. It also counts
as the successor of the GNU Library Public License, version 2, hence
the version number 2.1.]
Preamble
The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public Licenses are intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users.
This license, the Lesser General Public License, applies to some specially designated software packages--typically libraries--of the Free Software Foundation and other authors who decide to use it. You can use it too, but we suggest you first think carefully about whether this license or the ordinary General Public License is the better strategy to use in any particular case, based on the explanations below.
When we speak of free software, we are referring to freedom of use, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish); that you receive source code or can get it if you want it; that you can change the software and use pieces of it in new free programs; and that you are informed that you can do these things.
To protect your rights, we need to make restrictions that forbid distributors to deny you these rights or to ask you to surrender these rights. These restrictions translate to certain responsibilities for you if you distribute copies of the library or if you modify it.
For example, if you distribute copies of the library, whether gratis or for a fee, you must give the recipients all the rights that we gave you. You must make sure that they, too, receive or can get the source code. If you link other code with the library, you must provide complete object files to the recipients, so that they can relink them with the library after making changes to the library and recompiling it. And you must show them these terms so they know their rights.
We protect your rights with a two-step method: (1) we copyright the library, and (2) we offer you this license, which gives you legal permission to copy, distribute and/or modify the library.
To protect each distributor, we want to make it very clear that there is no warranty for the free library. Also, if the library is modified by someone else and passed on, the recipients should know that what they have is not the original version, so that the original author's reputation will not be affected by problems that might be introduced by others.
Finally, software patents pose a constant threat to the existence of any free program. We wish to make sure that a company cannot effectively restrict the users of a free program by obtaining a restrictive license from a patent holder. Therefore, we insist that any patent license obtained for a version of the library must be consistent with the full freedom of use specified in this license.
Most GNU software, including some libraries, is covered by the ordinary GNU General Public License. This license, the GNU Lesser General Public License, applies to certain designated libraries, and is quite different from the ordinary General Public License. We use this license for certain libraries in order to permit linking those libraries into non-free programs.
When a program is linked with a library, whether statically or using a shared library, the combination of the two is legally speaking a combined work, a derivative of the original library. The ordinary General Public License therefore permits such linking only if the entire combination fits its criteria of freedom. The Lesser General Public License permits more lax criteria for linking other code with the library.
We call this license the "Lesser" General Public License because it does Less to protect the user's freedom than the ordinary General Public License. It also provides other free software developers Less of an advantage over competing non-free programs. These disadvantages are the reason we use the ordinary General Public License for many libraries. However, the Lesser license provides advantages in certain special circumstances.
For example, on rare occasions, there may be a special need to encourage the widest possible use of a certain library, so that it becomes a de-facto standard. To achieve this, non-free programs must be allowed to use the library. A more frequent case is that a free library does the same job as widely used non-free libraries. In this case, there is little to gain by limiting the free library to free software only, so we use the Lesser General Public License.
In other cases, permission to use a particular library in non-free programs enables a greater number of people to use a large body of free software. For example, permission to use the GNU C Library in non-free programs enables many more people to use the whole GNU operating system, as well as its variant, the GNU/Linux operating system.
Although the Lesser General Public License is Less protective of the users' freedom, it does ensure that the user of a program that is linked with the Library has the freedom and the wherewithal to run that program using a modified version of the Library.
The precise terms and conditions for copying, distribution and modification follow. Pay close attention to the difference between a "work based on the library" and a "work that uses the library". The former contains code derived from the library, whereas the latter must be combined with the library in order to run.
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License Agreement applies to any software library or other program which contains a notice placed by the copyright holder or other authorized party saying it may be distributed under the terms of this Lesser General Public License (also called "this License"). Each licensee is addressed as "you".
A "library" means a collection of software functions and/or data prepared so as to be conveniently linked with application programs (which use some of those functions and data) to form executables.
The "Library", below, refers to any such software library or work which has been distributed under these terms. A "work based on the Library" means either the Library or any derivative work under copyright law: that is to say, a work containing the Library or a portion of it, either verbatim or with modifications and/or translated straightforwardly into another language. (Hereinafter, translation is included without limitation in the term "modification".)
"Source code" for a work means the preferred form of the work for making modifications to it. For a library, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the library.
Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running a program using the Library is not restricted, and output from such a program is covered only if its contents constitute a work based on the Library (independent of the use of the Library in a tool for writing it). Whether that is true depends on what the Library does and what the program that uses the Library does.
1. You may copy and distribute verbatim copies of the Library's complete source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and distribute a copy of this License along with the Library.
You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.
2. You may modify your copy or copies of the Library or any portion of it, thus forming a work based on the Library, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
* a) The modified work must itself be a software library.
* b) You must cause the files modified to carry prominent notices stating that
you changed the files and the date of any change.
* c) You must cause the whole of the work to be licensed at no charge to all
third parties under the terms of this License.
* d) If a facility in the modified Library refers to a function or a table of
data to be supplied by an application program that uses the facility, other
than as an argument passed when the facility is invoked, then you must make
a good faith effort to ensure that, in the event an application does not supply
such function or table, the facility still operates, and performs whatever part
of its purpose remains meaningful.
(For example, a function in a library to compute square roots has a purpose that is entirely well-defined independent of the application. Therefore, Subsection 2d requires that any application-supplied function or table used by this function must be optional: if the application does not supply it, the square root function must still compute square roots.)
These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Library, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Library, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.
Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Library.
In addition, mere aggregation of another work not based on the Library with the Library (or with a work based on the Library) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.
3. You may opt to apply the terms of the ordinary GNU General Public License instead of this License to a given copy of the Library. To do this, you must alter all the notices that refer to this License, so that they refer to the ordinary GNU General Public License, version 2, instead of to this License. (If a newer version than version 2 of the ordinary GNU General Public License has appeared, then you can specify that version instead if you wish.) Do not make any other change in these notices.
Once this change is made in a given copy, it is irreversible for that copy, so the ordinary GNU General Public License applies to all subsequent copies and derivative works made from that copy.
This option is useful when you wish to copy part of the code of the Library into a program that is not a library.
4. You may copy and distribute the Library (or a portion or derivative of it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange.
If distribution of object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place satisfies the requirement to distribute the source code, even though third parties are not compelled to copy the source along with the object code.
5. A program that contains no derivative of any portion of the Library, but is designed to work with the Library by being compiled or linked with it, is called a "work that uses the Library". Such a work, in isolation, is not a derivative work of the Library, and therefore falls outside the scope of this License.
However, linking a "work that uses the Library" with the Library creates an executable that is a derivative of the Library (because it contains portions of the Library), rather than a "work that uses the library". The executable is therefore covered by this License. Section 6 states terms for distribution of such executables.
When a "work that uses the Library" uses material from a header file that is part of the Library, the object code for the work may be a derivative work of the Library even though the source code is not. Whether this is true is especially significant if the work can be linked without the Library, or if the work is itself a library. The threshold for this to be true is not precisely defined by law.
If such an object file uses only numerical parameters, data structure layouts and accessors, and small macros and small inline functions (ten lines or less in length), then the use of the object file is unrestricted, regardless of whether it is legally a derivative work. (Executables containing this object code plus portions of the Library will still fall under Section 6.)
Otherwise, if the work is a derivative of the Library, you may distribute the object code for the work under the terms of Section 6. Any executables containing that work also fall under Section 6, whether or not they are linked directly with the Library itself.
6. As an exception to the Sections above, you may also combine or link a "work that uses the Library" with the Library to produce a work containing portions of the Library, and distribute that work under terms of your choice, provided that the terms permit modification of the work for the customer's own use and reverse engineering for debugging such modifications.
You must give prominent notice with each copy of the work that the Library is used in it and that the Library and its use are covered by this License. You must supply a copy of this License. If the work during execution displays copyright notices, you must include the copyright notice for the Library among them, as well as a reference directing the user to the copy of this License. Also, you must do one of these things:
* a) Accompany the work with the complete corresponding machine-readable source
code for the Library including whatever changes were used in the work (which
must be distributed under Sections 1 and 2 above); and, if the work is an executable
linked with the Library, with the complete machine-readable "work that
uses the Library", as object code and/or source code, so that the user
can modify the Library and then relink to produce a modified executable containing
the modified Library. (It is understood that the user who changes the contents
of definitions files in the Library will not necessarily be able to recompile
the application to use the modified definitions.)
* b) Use a suitable shared library mechanism for linking with the Library. A
suitable mechanism is one that (1) uses at run time a copy of the library already
present on the user's computer system, rather than copying library functions
into the executable, and (2) will operate properly with a modified version of
the library, if the user installs one, as long as the modified version is interface-compatible
with the version that the work was made with.
* c) Accompany the work with a written offer, valid for at least three years,
to give the same user the materials specified in Subsection 6a, above, for a
charge no more than the cost of performing this distribution.
* d) If distribution of the work is made by offering access to copy from a designated
place, offer equivalent access to copy the above specified materials from the
same place.
* e) Verify that the user has already received a copy of these materials or
that you have already sent this user a copy.
For an executable, the required form of the "work that uses the Library" must include any data and utility programs needed for reproducing the executable from it. However, as a special exception, the materials to be distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.
It may happen that this requirement contradicts the license restrictions of other proprietary libraries that do not normally accompany the operating system. Such a contradiction means you cannot use both them and the Library together in an executable that you distribute.
7. You may place library facilities that are a work based on the Library side-by-side in a single library together with other library facilities not covered by this License, and distribute such a combined library, provided that the separate distribution of the work based on the Library and of the other library facilities is otherwise permitted, and provided that you do these two things:
* a) Accompany the combined library with a copy of the same work based on
the Library, uncombined with any other library facilities. This must be distributed
under the terms of the Sections above.
* b) Give prominent notice with the combined library of the fact that part of
it is a work based on the Library, and explaining where to find the accompanying
uncombined form of the same work.
8. You may not copy, modify, sublicense, link with, or distribute the Library except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, link with, or distribute the Library is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
9. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Library or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Library (or any work based on the Library), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Library or works based on it.
10. Each time you redistribute the Library (or any work based on the Library), the recipient automatically receives a license from the original licensor to copy, distribute, link with or modify the Library subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties with this License.
11. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Library at all. For example, if a patent license would not permit royalty-free redistribution of the Library by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Library.
If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply, and the section as a whole is intended to apply in other circumstances.
It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.
This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.
12. If the distribution and/or use of the Library is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Library under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.
13. The Free Software Foundation may publish revised and/or new versions of the Lesser General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Library specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Library does not specify a license version number, you may choose any version ever published by the Free Software Foundation.
14. If you wish to incorporate parts of the Library into other free programs whose distribution conditions are incompatible with these, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.
NO WARRANTY
15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE LIBRARY "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY IS WITH YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.