laforge has submitted this change. ( https://gerrit.osmocom.org/c/pysim/+/42441?usp=email )

Change subject: transport: change APDU format paradigm ......................................................................

transport: change APDU format paradigm

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, since pySim-shell, pySim-prog and pySim-read internally use proper APDUs, we may enable the 'apdu_strict' mode by default.

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 --- M pySim-shell.py M pySim/transport/__init__.py 2 files changed, 12 insertions(+), 11 deletions(-)

Approvals: laforge: Looks good to me, approved Jenkins Builder: Verified

diff --git a/pySim-shell.py b/pySim-shell.py index 50deea2..2bfc720 100755 --- a/pySim-shell.py +++ b/pySim-shell.py @@ -136,8 +136,7 @@ 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 @@ 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: @@ -281,7 +273,7 @@ apdu_cmd_parser.add_argument('--expect-sw', help='expect a specified status word', type=str, default=None) apdu_cmd_parser.add_argument('--expect-response-regex', help='match response against regex', type=str, default=None) apdu_cmd_parser.add_argument('--raw', help='Bypass the logical channel (and secure channel)', action='store_true') - apdu_cmd_parser.add_argument('APDU', type=is_hexstr, help='APDU as hex string') + apdu_cmd_parser.add_argument('APDU', type=is_hexstr, help='APDU as hex string (see also: ISO/IEC 7816-3, section 12.1')

@cmd2.with_argparser(apdu_cmd_parser) def do_apdu(self, opts): @@ -290,14 +282,23 @@ tracked. Depending on the raw APDU sent, pySim-shell may not continue to work as expected if you e.g. select a different file."""

+ if not hasattr(self, 'apdu_strict_warning_displayed') and self.apdu_strict is False: + self.poutput("Warning: The default for the setable parameter `apdu_strict` will be changed from") + self.poutput(" `False` to `True` in future pySim-shell releases. In case you are using") + self.poutput(" the `apdu` command from a script that still mixes APDUs with TPDUs, consider") + self.poutput(" fixing or adding a `set apdu_strict false` line at the beginning.") + self.apdu_strict_warning_displayed = True; + # When sending raw APDUs we access the scc object through _scc member of the card object. It should also be # noted that the apdu command plays an exceptional role since it is the only card accessing command that # 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). + self.card._scc._tp.apdu_strict = self.apdu_strict if opts.raw or self.lchan is None: data, sw = self.card._scc.send_apdu(opts.APDU, apply_lchan = False) else: data, sw = self.lchan.scc.send_apdu(opts.APDU, apply_lchan = False) + self.card._scc._tp.apdu_strict = True if data: self.poutput("SW: %s, RESP: %s" % (sw, data)) else: diff --git a/pySim/transport/__init__.py b/pySim/transport/__init__.py index f19790c..6833a90 100644 --- a/pySim/transport/__init__.py +++ b/pySim/transport/__init__.py @@ -90,7 +90,7 @@ self.sw_interpreter = sw_interpreter self.apdu_tracer = apdu_tracer self.proactive_handler = proactive_handler - self.apdu_strict = False + self.apdu_strict = True

@abc.abstractmethod def __str__(self) -> str: