micropython · andrewleech · Jul 23, 2021 · Aug 17, 2021 · Aug 17, 2021 · Aug 17, 2021
diff --git a/micropython/bluetooth/aioble/aioble/device.py b/micropython/bluetooth/aioble/aioble/device.py
@@ -262,7 +262,7 @@ def is_connected(self):
     def timeout(self, timeout_ms):
         return DeviceTimeout(self, timeout_ms)
 
-    async def exchange_mtu(self, mtu=None):
+    async def exchange_mtu(self, mtu=None, timeout_ms=1000):
         if not self.is_connected():
             raise ValueError("Not connected")
 
@@ -271,7 +271,8 @@ async def exchange_mtu(self, mtu=None):
 
         self._mtu_event = self._mtu_event or asyncio.ThreadSafeFlag()
         ble.gattc_exchange_mtu(self._conn_handle)
-        await self._mtu_event.wait()
+        with self.timeout(timeout_ms):
+            await self._mtu_event.wait()
         return self.mtu
 
     # Wait for a connection on an L2CAP connection-oriented-channel.

diff --git a/micropython/bluetooth/aioble/aioble/security.py b/micropython/bluetooth/aioble/aioble/security.py
@@ -4,6 +4,7 @@
 from micropython import const, schedule
 import uasyncio as asyncio
 import binascii
+import ustruct
 import json
 
 from .core import log_info, log_warn, ble, register_irq_handler
@@ -26,10 +27,14 @@
 
 _DEFAULT_PATH = "ble_secrets.json"
 
-_secrets = {}
+# Maintain list of known keys, newest at the top.
+_secrets = []
 _modified = False
 _path = None
 
+connected_sec = None
+gatt_svc = None
+
 
 # Must call this before stack startup.
 def load_secrets(path=None):
@@ -40,13 +45,14 @@ def load_secrets(path=None):
     _path = path or _path or _DEFAULT_PATH
 
     # Reset old secrets.
-    _secrets = {}
+    _secrets = []
     try:
         with open(_path, "r") as f:
             entries = json.load(f)
-            for sec_type, key, value in entries:
+            for sec_type, key, value, *digest in entries:
+                digest = digest[0] or None
                 # Decode bytes from hex.
-                _secrets[sec_type, binascii.a2b_base64(key)] = binascii.a2b_base64(value)
+                _secrets.append(((sec_type, binascii.a2b_base64(key)), binascii.a2b_base64(value), digest))
     except:
         log_warn("No secrets available")
 
@@ -65,15 +71,15 @@ def _save_secrets(arg=None):
         # Convert bytes to hex strings (otherwise JSON will treat them like
         # strings).
         json_secrets = [
-            (sec_type, binascii.b2a_base64(key), binascii.b2a_base64(value))
-            for (sec_type, key), value in _secrets.items()
+            (sec_type, binascii.b2a_base64(key), binascii.b2a_base64(value), digest)
+            for (sec_type, key), value, digest in _secrets
         ]
         json.dump(json_secrets, f)
         _modified = False
 
 
 def _security_irq(event, data):
-    global _modified
+    global _modified, connected_sec, gatt_svc
 
     if event == _IRQ_ENCRYPTION_UPDATE:
         # Connection has updated (usually due to pairing).
@@ -88,6 +94,19 @@ def _security_irq(event, data):
             if encrypted and connection._pair_event:
                 connection._pair_event.set()
 
+            if bonded and \
+                    None not in (gatt_svc, connected_sec) and \
+                    connected_sec[2] != gatt_svc.hexdigest:
+                gatt_svc.send_changed(connection)
+
+                # Update the hash in the database
+                _secrets.remove(connected_sec)
+                updated_sec = connected_sec[:-1] + (gatt_svc.hexdigest,)
+                _secrets.insert(0, updated_sec)
+                # Queue up a save (don't synchronously write to flash).
+                _modified = True
+                schedule(_save_secrets, None)
+
     elif event == _IRQ_SET_SECRET:
         sec_type, key, value = data
         key = sec_type, bytes(key)
@@ -97,13 +116,15 @@ def _security_irq(event, data):
 
         if value is None:
             # Delete secret.
-            if key not in _secrets:
-                return False
+            for to_delete in [
+                entry for entry in _secrets if entry[0] == key
+            ]:
+                _secrets.remove(to_delete)
 
-            del _secrets[key]
         else:
             # Save secret.
-            _secrets[key] = value
+            current_digest = gatt_svc.hexdigest if gatt_svc else None
+            _secrets.insert(0, (key, value, current_digest))
 
         # Queue up a save (don't synchronously write to flash).
         _modified = True
@@ -119,7 +140,7 @@ def _security_irq(event, data):
         if key is None:
             # Return the index'th secret of this type.
             i = 0
-            for (t, _key), value in _secrets.items():
+            for (t, _key), value, digest in _secrets:
                 if t == sec_type:
                     if i == index:
                         return value
@@ -128,7 +149,11 @@ def _security_irq(event, data):
         else:
             # Return the secret for this key (or None).
             key = sec_type, bytes(key)
-            return _secrets.get(key, None)
+
+            for k, v, d in _secrets:
+                if k == key:
+                    return v
+            return None
 
     elif event == _IRQ_PASSKEY_ACTION:
         conn_handle, action, passkey = data

diff --git a/micropython/bluetooth/aioble/aioble/server.py b/micropython/bluetooth/aioble/aioble/server.py
@@ -83,11 +83,15 @@ def read(self):
             return ble.gatts_read(self._value_handle)
 
     # Write value to local db.
-    def write(self, data):
+    def write(self, data, send_update=False):
         if self._value_handle is None:
             self._initial = data
         else:
-            ble.gatts_write(self._value_handle, data)
+            if send_update:
+                # Send_update arg only added in 1.17, don't pass this arg unless required.
+                ble.gatts_write(self._value_handle, data, True)
+            else:
+                ble.gatts_write(self._value_handle, data)
 
     # Wait for a write on this characteristic.
     # Returns the device that did the write.
@@ -186,10 +190,11 @@ def _indicate_done(conn_handle, value_handle, status):
                     # Timeout.
                     return
                 # See TODO in __init__ to support multiple concurrent indications.
-                assert connection == characteristic._indicate_connection
-                characteristic._indicate_status = status
-                characteristic._indicate_event.set()
-
+                if connection == characteristic._indicate_connection:
+                    characteristic._indicate_status = status
+                    characteristic._indicate_event.set()
+                else:
+                    log_warn("Received indication for unexpected connection")
 
 class BufferedCharacteristic(Characteristic):
     def __init__(self, service, uuid, max_len=20, append=False):
@@ -223,9 +228,13 @@ def __init__(self, characteristic, uuid, read=False, write=False, initial=None):
 
 # Turn the Service/Characteristic/Descriptor classes into a registration tuple
 # and then extract their value handles.
-def register_services(*services):
+def register_services(*services, include_gatt_svc=True):
     ensure_active()
     _registered_characteristics.clear()
+    if include_gatt_svc:
+        from .services.generic_attribute_service import GenericAttributeService
+        gatt_svc = GenericAttributeService(services)
+        services = (gatt_svc,) + services
     handles = ble.gatts_register_services(tuple(s._tuple() for s in services))
     for i in range(len(services)):
         service_handles = handles[i]

diff --git a/micropython/bluetooth/aioble/aioble/services/__init__.py b/micropython/bluetooth/aioble/aioble/services/__init__.py
diff --git a/micropython/bluetooth/aioble/aioble/services/generic_attribute_service.py b/micropython/bluetooth/aioble/aioble/services/generic_attribute_service.py
@@ -0,0 +1,75 @@
+# -*- coding: utf-8 -*-
+#
+#   @file
+#   @brief: Bluetooth Generic Attribute Service
+#
+# Copyright (c) 2021, Planet Innovation
+# 436 Elgar Road, Box Hill, 3128, VIC, Australia
+# Phone: +61 3 9945 7510
+#
+# The copyright to the computer program(s) herein is the property of
+# Planet Innovation, Australia.
+# The program(s) may be used and/or copied only with the written permission
+# of Planet Innovation or in accordance with the terms and conditions
+# stipulated in the agreement/contract under which the program(s) have been
+# supplied.
+#
+
+import ustruct
+import bluetooth
+from aioble import Service, Characteristic, security
+from aioble.core import ble, log_info
+from hashlib import md5
+from ubinascii import hexlify
+try:
+    from utyping import *
+except:
+    pass
+
+
+class GenericAttributeService(Service):
+    # Generic Attribute service UUID
+    SERVICE_UUID = bluetooth.UUID(0x1801)
+
+    # Service Changed Characteristic
+    UUID_SERVICE_CHANGED = bluetooth.UUID(0x2A05)
+    # Database Hash Characteristic (New in BLE 5.1)
+    UUID_DATABASE_HASH = bluetooth.UUID(0x2B2A)
+
+    def __init__(self, services: Tuple[Service]):
+
+        super().__init__(self.SERVICE_UUID)
+
+        # Database hash is typically a 128bit AES-CMAC value, however
+        # is generally only monitored for change as an opaque value.
+        # MD5 is also 128 bit, faster and builtin
+        hasher = md5()
+        for service in services:
+            for char in service.characteristics:
+                hasher.update(char.uuid)
+                hasher.update(str(char.flags))
+        self.digest = hasher.digest()
+        self.hexdigest = hexlify(self.digest).decode()
+        log_info("BLE: DB Hash=", self.hexdigest)
+        security.current_digest = self.hexdigest
+        security.gatt_svc = self
+
+        self.SERVICE_CHANGED = Characteristic(
+            service=self,
+            uuid=self.UUID_SERVICE_CHANGED,
+            read=True,
+            indicate=True,
+            initial=''
+        )
+
+        self.DATABASE_HASH = Characteristic(
+            service=self,
+            uuid=self.UUID_DATABASE_HASH,
+            read=True,
+            initial=self.digest
+        )
+
+    def send_changed(self, connection, start=0, end=0xFFFF):
+        self.SERVICE_CHANGED.write(ustruct.pack('!HH', start, end))
+        log_info("Indicate Service Changed")
+        ble.gatts_indicate(connection._conn_handle, self.SERVICE_CHANGED._value_handle)