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transport: change APDU format paradigm

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Unfortunately we have mixed up the concept of TPDUs and APDUs in
earlier versions of pySim-shell. This lead to problems with
detecteding the APDU case properly (see also ISO/IEC 7816-3) and
also prevented us from adding support for T=1.

This problem has been fixed long time ago and all APDUs sent from
the pySim-shell code should be well formed and valid according to
ISO/IEC 7816-3.

To ensure that we continue to format APDUs correctly as APDUs (and
not TPDUs) we have added a mechanism to the LinkBase class that
would either raise an exception or print a warning if someone
mistakenly tries to send an APDU that is really a TPDU. Whether a
warning is printed or an exception is raised is controlled via the
apdu_strict member in the LinkBase class, which is false (print
warning only) by default.

The reason why we have implemneted the mechanism this way was
because we wanted to ensure that existing APDU scripts (pySim-shell
apdu command) keep working, even though when those scripts uses
APDUs which are formally invalid.

Sending a TPDU instead of an APDU via a T=0 link will still work
in almost all cases. This is also the reason why this problem
slipped through unnoticed for long time. However, there may still
be subtile problems araising from this practice. The root of the
problem is that it is impossible to distinguish between APDU case
3 and 4 when a TPDU instead of an APDU is sent. However in order
to handle a case 4 APDU correctly we must be able to distinguish
the APDU case correctly to handle the case correctly.
ETSI TS 102 221, section 7.3.1.1.4, clause 4 is very clear about
the fact that not (only) the status word (e.g. 61xx) but the
APDU case is what matters.

To complete the logic in LinkBaseTpdu and to maintain compatibility
(older APDU scripts), we must still be able to switch between the
'apdu_strict' mode and the non-strict mode. However, it makes sense
to do this on a per-api-call basis instead globally via a class
property.

At the same time we will limit the effect of pySim-shell's
apdu_strict setable to the apdu command only. By doing so, the
bahviour of the apdu command is not altered. Users will still
have to enable the 'strict' mode explicitly. At the same time
all the internal functionality of pySim-shell will always use
the 'strict' mode.

Related: OS#6970
Change-Id: I9a531a825def318b28bf58291d811cf119003fab
This commit is contained in:
Philipp Maier
2026-03-19 12:10:09 +01:00
parent 0634f77308
commit 35384b1c96
3 changed files with 24 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
pySim-shell.py
View File

@@ -136,8 +136,7 @@ Online manual available at https://downloads.osmocom.org/docs/pysim/master/html/
self.add_settable(Settable2Compat('apdu_trace', bool, 'Trace and display APDUs exchanged with card', self,
onchange_cb=self._onchange_apdu_trace))
self.add_settable(Settable2Compat('apdu_strict', bool,
'Enforce APDU responses according to ISO/IEC 7816-3, table 12', self,
onchange_cb=self._onchange_apdu_strict))
'Strictly apply APDU format according to ISO/IEC 7816-3, table 12', self))
self.add_settable(Settable2Compat('verbose', bool,
'Enable/disable verbose logging', self,
onchange_cb=self._onchange_verbose))
@@ -218,13 +217,6 @@ Online manual available at https://downloads.osmocom.org/docs/pysim/master/html/
else:
self.card._scc._tp.apdu_tracer = None
def _onchange_apdu_strict(self, param_name, old, new):
if self.card:
if new == True:
self.card._scc._tp.apdu_strict = True
else:
self.card._scc._tp.apdu_strict = False
def _onchange_verbose(self, param_name, old, new):
PySimLogger.set_verbose(new)
if new == True:
@@ -295,9 +287,9 @@ Online manual available at https://downloads.osmocom.org/docs/pysim/master/html/
# can be executed without the presence of a runtime state (self.rs) object. However, this also means that
# self.lchan is also not present (see method equip).
if opts.raw or self.lchan is None:
data, sw = self.card._scc.send_apdu(opts.APDU, apply_lchan = False)
data, sw = self.card._scc.send_apdu(opts.APDU, apply_lchan = False, apdu_strict = self.apdu_strict)
else:
data, sw = self.lchan.scc.send_apdu(opts.APDU, apply_lchan = False)
data, sw = self.lchan.scc.send_apdu(opts.APDU, apply_lchan = False, apdu_strict = self.apdu_strict)
if data:
self.poutput("SW: %s, RESP: %s" % (sw, data))
else:

23
pySim/commands.py
View File

@@ -87,7 +87,7 @@ class SimCardCommands:
else:
return 255
def send_apdu(self, pdu: Hexstr, apply_lchan:bool = True) -> ResTuple:
def send_apdu(self, pdu: Hexstr, apply_lchan:bool = True, apdu_strict: bool = True) -> ResTuple:
"""Sends an APDU and auto fetch response data
Args:
@@ -101,11 +101,12 @@ class SimCardCommands:
if apply_lchan:
pdu = cla_with_lchan(pdu[0:2], self.lchan_nr) + pdu[2:]
if self.scp:
return self.scp.send_apdu_wrapper(self._tp.send_apdu, pdu)
return self.scp.send_apdu_wrapper(self._tp.send_apdu, pdu, apdu_strict = apdu_strict)
else:
return self._tp.send_apdu(pdu)
return self._tp.send_apdu(pdu, apdu_strict = apdu_strict)
def send_apdu_checksw(self, pdu: Hexstr, sw: SwMatchstr = "9000", apply_lchan:bool = True) -> ResTuple:
def send_apdu_checksw(self, pdu: Hexstr, sw: SwMatchstr = "9000", apply_lchan:bool = True,
apdu_strict: bool = True) -> ResTuple:
"""Sends an APDU and check returned SW
Args:
@@ -121,12 +122,13 @@ class SimCardCommands:
if apply_lchan:
pdu = cla_with_lchan(pdu[0:2], self.lchan_nr) + pdu[2:]
if self.scp:
return self.scp.send_apdu_wrapper(self._tp.send_apdu_checksw, pdu, sw)
return self.scp.send_apdu_wrapper(self._tp.send_apdu_checksw, pdu, sw, apdu_strict = apdu_strict)
else:
return self._tp.send_apdu_checksw(pdu, sw)
return self._tp.send_apdu_checksw(pdu, sw, apdu_strict = apdu_strict)
def send_apdu_constr(self, cla: Hexstr, ins: Hexstr, p1: Hexstr, p2: Hexstr, cmd_constr: Construct,
cmd_data: Hexstr, resp_constr: Construct, apply_lchan:bool = True) -> Tuple[dict, SwHexstr]:
cmd_data: Hexstr, resp_constr: Construct, apply_lchan:bool = True,
apdu_strict: bool = True) -> Tuple[dict, SwHexstr]:
"""Build and sends an APDU using a 'construct' definition; parses response.
Args:
@@ -145,7 +147,7 @@ class SimCardCommands:
lc = i2h([len(cmd)]) if cmd_data else ''
le = '00' if resp_constr else ''
pdu = ''.join([cla, ins, p1, p2, lc, b2h(cmd), le])
(data, sw) = self.send_apdu(pdu, apply_lchan = apply_lchan)
(data, sw) = self.send_apdu(pdu, apply_lchan = apply_lchan, apdu_strict = apdu_strict)
if data:
# filter the resulting dict to avoid '_io' members inside
rsp = filter_dict(resp_constr.parse(h2b(data)))
@@ -155,7 +157,8 @@ class SimCardCommands:
def send_apdu_constr_checksw(self, cla: Hexstr, ins: Hexstr, p1: Hexstr, p2: Hexstr,
cmd_constr: Construct, cmd_data: Hexstr, resp_constr: Construct,
sw_exp: SwMatchstr="9000", apply_lchan:bool = True) -> Tuple[dict, SwHexstr]:
sw_exp: SwMatchstr="9000", apply_lchan:bool = True,
apdu_strict: bool = True) -> Tuple[dict, SwHexstr]:
"""Build and sends an APDU using a 'construct' definition; parses response.
Args:
@@ -171,7 +174,7 @@ class SimCardCommands:
Tuple of (decoded_data, sw)
"""
(rsp, sw) = self.send_apdu_constr(cla, ins, p1, p2, cmd_constr, cmd_data, resp_constr,
apply_lchan = apply_lchan)
apply_lchan = apply_lchan, apdu_strict = apdu_strict)
if not sw_match(sw, sw_exp):
raise SwMatchError(sw, sw_exp.lower(), self._tp.sw_interpreter)
return (rsp, sw)

15
pySim/transport/__init__.py
View File

@@ -90,7 +90,6 @@ class LinkBase(abc.ABC):
self.sw_interpreter = sw_interpreter
self.apdu_tracer = apdu_tracer
self.proactive_handler = proactive_handler
self.apdu_strict = False
@abc.abstractmethod
def __str__(self) -> str:
@@ -141,11 +140,12 @@ class LinkBase(abc.ABC):
self.apdu_tracer.trace_reset()
return self._reset_card()
def send_apdu(self, apdu: Hexstr) -> ResTuple:
def send_apdu(self, apdu: Hexstr, apdu_strict: bool = True) -> ResTuple:
"""Sends an APDU with minimal processing
Args:
apdu : string of hexadecimal characters (ex. "A0A40000023F00", must comply to ISO/IEC 7816-3, section 12.1)
apdu_strict : strictly apply APDU format according to ISO/IEC 7816-3, table 12
Returns:
tuple(data, sw), where
data : string (in hex) of returned data (ex. "074F4EFFFF")
@@ -174,26 +174,27 @@ class LinkBase(abc.ABC):
if len(data) > 0 and (case == 3 or case == 1):
exeption_str = 'received unexpected response data, incorrect APDU-case ' + \
'(%d, should be %d, missing Le field?)!' % (case, case + 1)
if self.apdu_strict:
if apdu_strict:
raise ValueError(exeption_str)
else:
log.warning(exeption_str)
return (data, sw)
def send_apdu_checksw(self, apdu: Hexstr, sw: SwMatchstr = "9000") -> ResTuple:
def send_apdu_checksw(self, apdu: Hexstr, sw: SwMatchstr = "9000", apdu_strict: bool = True) -> ResTuple:
"""Sends an APDU and check returned SW
Args:
apdu : string of hexadecimal characters (ex. "A0A40000023F00", must comply to ISO/IEC 7816-3, section 12.1)
sw : string of 4 hexadecimal characters (ex. "9000"). The user may mask out certain
digits using a '?' to add some ambiguity if needed.
sw : string of 4 hexadecimal characters (ex. "9000"). The user may mask out certain digits using a '?'
to add some ambiguity if needed.
apdu_strict : strictly apply APDU format according to ISO/IEC 7816-3, table 12
Returns:
tuple(data, sw), where
data : string (in hex) of returned data (ex. "074F4EFFFF")
sw : string (in hex) of status word (ex. "9000")
"""
rv = self.send_apdu(apdu)
rv = self.send_apdu(apdu, apdu_strict)
last_sw = rv[1]
while sw == '9000' and sw_match(last_sw, '91xx'):