Introduce GlobalPlatform SCP02 implementation

This implementation of GlobalPlatform SCP02 currently only supports
C-MAC and C-ENC, but no R-MAC or R-ENC yet.

The patch also introduces the notion of having a SCP instance associated
with a SimCardCommands instance.  No code is using this yet, it will be
introduced in a separate patch.

Change-Id: I56020382b9dfe8ba0f7c1c9f71eb1a9746bc5a27

pySim/secure_channel.py

@@ -0,0 +1,37 @@
+# Generic code related to Secure Channel processing
+#
+# (C) 2023-2024 by Harald Welte <laforge@osmocom.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import abc
+from pySim.utils import b2h, h2b, ResTuple, Hexstr
+
+class SecureChannel(abc.ABC):
+    @abc.abstractmethod
+    def wrap_cmd_apdu(self, apdu: bytes) -> bytes:
+        """Wrap Command APDU according to specific Secure Channel Protocol."""
+        pass
+
+    @abc.abstractmethod
+    def unwrap_rsp_apdu(self, sw: bytes, rsp_apdu: bytes) -> bytes:
+        """UnWrap Response-APDU according to specific Secure Channel Protocol."""
+        pass
+
+    def send_apdu_wrapper(self, send_fn: callable, pdu: Hexstr, *args, **kwargs) -> ResTuple:
+        """Wrapper function to wrap command APDU and unwrap repsonse APDU around send_apdu callable."""
+        pdu_wrapped = b2h(self.wrap_cmd_apdu(h2b(pdu)))
+        res, sw = send_fn(pdu_wrapped, *args, **kwargs)
+        res_unwrapped = b2h(self.unwrap_rsp_apdu(h2b(sw), h2b(res)))
+        return res_unwrapped, sw