88 lines
2.8 KiB
Python
88 lines
2.8 KiB
Python
from platypush.backend import Backend
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from platypush.message.event.scard import SmartCardDetectedEvent, SmartCardRemovedEvent
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class ScardBackend(Backend):
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"""
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Generic backend to read smart cards and NFC tags and trigger an event
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whenever a device is detected.
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Extend this backend to implement more advanced communication with custom
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smart cards.
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"""
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def __init__(self, atr=None, *args, **kwargs):
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"""
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:param atr: If set, the backend will trigger events only for card(s)
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with the specified ATR(s). It can be either an ATR string
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(space-separated hex octects) or a list of ATR strings. Default:
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none (any card will be detected).
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"""
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from smartcard.CardType import AnyCardType, ATRCardType
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super().__init__(*args, **kwargs)
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self.ATRs = []
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if atr:
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if isinstance(atr, str):
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self.ATRs = [atr]
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elif isinstance(atr, list):
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self.ATRs = atr
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else:
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raise RuntimeError(
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f"Unsupported ATR: \"{atr}\" - type: {type(atr)}, "
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+ "supported types: string, list"
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)
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self.cardtype = ATRCardType(*[self._to_bytes(atr) for atr in self.ATRs])
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else:
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self.cardtype = AnyCardType()
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@staticmethod
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def _to_bytes(data) -> bytes:
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if isinstance(data, str):
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data = data.encode()
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return data
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def run(self):
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from smartcard.CardRequest import CardRequest
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from smartcard.Exceptions import NoCardException, CardConnectionException
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from smartcard.util import toHexString
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super().run()
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self.logger.info(
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'Initialized smart card reader backend - ATR filter: {}'.format(self.ATRs)
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)
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prev_atr = None
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reader = None
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while not self.should_stop():
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try:
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cardrequest = CardRequest(timeout=None, cardType=self.cardtype)
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cardservice = cardrequest.waitforcard()
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cardservice.connection.connect()
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reader = cardservice.connection.getReader()
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atr = toHexString(cardservice.connection.getATR())
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if atr != prev_atr:
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self.logger.info(
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'Smart card detected on reader {}, ATR: {}'.format(reader, atr)
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)
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self.bus.post(SmartCardDetectedEvent(atr=atr, reader=reader))
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prev_atr = atr
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except Exception as e:
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if isinstance(e, (NoCardException, CardConnectionException)):
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self.bus.post(SmartCardRemovedEvent(atr=prev_atr, reader=reader))
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else:
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self.logger.exception(e)
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prev_atr = None
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# vim:sw=4:ts=4:et:
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