From a06021d296621694d353eb91c5ffa8187a8f9f38 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Diego=20Elio=20Petten=C3=B2?= <flameeyes@flameeyes.com>
Date: Fri, 24 Jan 2020 12:34:45 +0000
Subject: Add a tool to extract a FreeStyle protocol chatter from an usbmon
 capture.

The tool needs https://github.com/Flameeyes/usbmon-tools to work, and is
derived off the extract-hid-chatter tool in that repository, so it's
Apache-2 licensed (unlike the rest of the repository) and shares copyright
with the usbmon-tools authors.

While this does not work correctly for Libre2 traces, it does appear to
work fine with Libre1 systems with text protocol exchanges, and it provides
a starting point.
---
 reversing_tools/abbott/extract_freestyle.py | 109 ++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100755 reversing_tools/abbott/extract_freestyle.py

diff --git a/reversing_tools/abbott/extract_freestyle.py b/reversing_tools/abbott/extract_freestyle.py
new file mode 100755
index 0000000..019b23b
--- /dev/null
+++ b/reversing_tools/abbott/extract_freestyle.py
@@ -0,0 +1,109 @@
+#!/usr/bin/env python3
+#
+# Copyright 2019 The usbmon-tools Authors
+# Copyright 2020 The glucometerutils Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+import logging
+import sys
+
+import usbmon
+import usbmon.chatter
+import usbmon.pcapng
+
+HID_XFER_TYPES = (
+    usbmon.constants.XferType.INTERRUPT,
+    usbmon.constants.XferType.CONTROL,
+)
+
+def main():
+    if sys.version_info < (3, 7):
+        raise Exception(
+            'Unsupported Python version, please use at least Python 3.7.')
+
+    parser = argparse.ArgumentParser()
+
+    parser.add_argument(
+        '--addr_prefix', action='store', type=str, required=True,
+        help=('Prefix match applied to the device address in text format. '
+              'Only packets with source or destination matching this prefix '
+              'will be printed out.'))
+
+    parser.add_argument(
+        '--vlog', action='store', required=False, type=int,
+        help=('Python logging level. See the levels at '
+              'https://docs.python.org/3/library/logging.html#logging-levels'))
+
+    parser.add_argument(
+        'pcap_file', action='store', type=str,
+        help='Path to the pcapng file with the USB capture.')
+
+    args = parser.parse_args()
+
+    logging.basicConfig(level=args.vlog)
+
+    session = usbmon.pcapng.parse_file(args.pcap_file, retag_urbs=False)
+    for first, second in session.in_pairs():
+        # Ignore stray callbacks/errors.
+        if not first.type == usbmon.constants.PacketType.SUBMISSION:
+            continue
+
+        if not first.address.startswith(args.addr_prefix):
+            # No need to check second, they will be linked.
+            continue
+
+        if first.xfer_type == usbmon.constants.XferType.INTERRUPT:
+            pass
+        elif (first.xfer_type == usbmon.constants.XferType.CONTROL and
+              not first.setup_packet or
+              first.setup_packet.type == usbmon.setup.Type.CLASS):
+            pass
+        else:
+            continue
+
+        if first.direction == usbmon.constants.Direction.OUT:
+            packet = first
+        else:
+            packet = second
+
+        if not packet.payload:
+            continue
+
+        assert len(packet.payload) >= 2
+
+        message_length = packet.payload[1]
+
+        # This is the case on Libre 2 (expected encrypted communication), in
+        # which case we ignore the message_length and we keep the whole message
+        # together.
+        if message_length > 62:
+            message_type = 'xx'
+            message = packet.payload
+        else:
+            message_type = f'{packet.payload[0]:02x}'
+            message = packet.payload[2:2+message_length]
+
+        print(usbmon.chatter.dump_bytes(
+            packet.direction,
+            message,
+            prefix=f'[{message_type}]',
+            print_empty=True,
+        ), '\n')
+
+
+if __name__ == "__main__":
+    main()
-- 
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