Merge pull request #129 from google/gbg/smp-improvements

improve smp compatibility with other OS flows

bumble/smp.py

@@ -518,13 +518,15 @@ class PairingDelegate:
     async def confirm(self) -> bool:
         return True
 
-    async def compare_numbers(self, _number: int, _digits: int = 6) -> bool:
+    # pylint: disable-next=unused-argument
+    async def compare_numbers(self, number: int, digits: int) -> bool:
         return True
 
     async def get_number(self) -> int:
         return 0
 
-    async def display_number(self, _number: int, _digits: int = 6) -> None:
+    # pylint: disable-next=unused-argument
+    async def display_number(self, number: int, digits: int) -> None:
         pass
 
     async def key_distribution_response(
@@ -661,7 +663,8 @@ class Session:
         self.peer_expected_distributions = []
         self.dh_key = None
         self.confirm_value = None
-        self.passkey = 0
+        self.passkey = None
+        self.passkey_ready = asyncio.Event()
         self.passkey_step = 0
         self.passkey_display = False
         self.pairing_method = 0
@@ -839,6 +842,7 @@ class Session:
         # Generate random Passkey/PIN code
         self.passkey = secrets.randbelow(1000000)
         logger.debug(f'Pairing PIN CODE: {self.passkey:06}')
+        self.passkey_ready.set()
 
         # The value of TK is computed from the PIN code
         if not self.sc:
@@ -859,6 +863,8 @@ class Session:
                 self.tk = passkey.to_bytes(16, byteorder='little')
                 logger.debug(f'TK from passkey = {self.tk.hex()}')
 
+            self.passkey_ready.set()
+
             if next_steps is not None:
                 next_steps()
 
@@ -910,17 +916,29 @@ class Session:
         logger.debug(f'generated random: {self.r.hex()}')
 
         if self.sc:
-            if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
-                z = 0
-            elif self.pairing_method == self.PASSKEY:
-                z = 0x80 + ((self.passkey >> self.passkey_step) & 1)
-            else:
-                return
 
-            if self.is_initiator:
-                confirm_value = crypto.f4(self.pka, self.pkb, self.r, bytes([z]))
-            else:
-                confirm_value = crypto.f4(self.pkb, self.pka, self.r, bytes([z]))
+            async def next_steps():
+                if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
+                    z = 0
+                elif self.pairing_method == self.PASSKEY:
+                    # We need a passkey
+                    await self.passkey_ready.wait()
+
+                    z = 0x80 + ((self.passkey >> self.passkey_step) & 1)
+                else:
+                    return
+
+                if self.is_initiator:
+                    confirm_value = crypto.f4(self.pka, self.pkb, self.r, bytes([z]))
+                else:
+                    confirm_value = crypto.f4(self.pkb, self.pka, self.r, bytes([z]))
+
+                self.send_command(
+                    SMP_Pairing_Confirm_Command(confirm_value=confirm_value)
+                )
+
+            # Perform the next steps asynchronously in case we need to wait for input
+            self.connection.abort_on('disconnection', next_steps())
         else:
             confirm_value = crypto.c1(
                 self.tk,
@@ -933,7 +951,7 @@ class Session:
                 self.ra,
             )
 
-        self.send_command(SMP_Pairing_Confirm_Command(confirm_value=confirm_value))
+            self.send_command(SMP_Pairing_Confirm_Command(confirm_value=confirm_value))
 
     def send_pairing_random_command(self):
         self.send_command(SMP_Pairing_Random_Command(random_value=self.r))
@@ -1364,8 +1382,8 @@ class Session:
 
         # Start phase 2
         if self.sc:
-            if self.pairing_method == self.PASSKEY and self.passkey_display:
-                self.display_passkey()
+            if self.pairing_method == self.PASSKEY:
+                self.display_or_input_passkey()
 
             self.send_public_key_command()
         else:
@@ -1426,18 +1444,22 @@ class Session:
         else:
             srand = self.r
             mrand = command.random_value
-        stk = crypto.s1(self.tk, srand, mrand)
-        logger.debug(f'STK = {stk.hex()}')
+        self.stk = crypto.s1(self.tk, srand, mrand)
+        logger.debug(f'STK = {self.stk.hex()}')
 
         # Generate LTK
         self.ltk = crypto.r()
 
         if self.is_initiator:
-            self.start_encryption(stk)
+            self.start_encryption(self.stk)
         else:
             self.send_pairing_random_command()
 
     def on_smp_pairing_random_command_secure_connections(self, command):
+        if self.pairing_method == self.PASSKEY and self.passkey is None:
+            logger.warning('no passkey entered, ignoring command')
+            return
+
         # pylint: disable=too-many-return-statements
         if self.is_initiator:
             if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
@@ -1565,17 +1587,13 @@ class Session:
         logger.debug(f'DH key: {self.dh_key.hex()}')
 
         if self.is_initiator:
-            if self.pairing_method == self.PASSKEY:
-                if self.passkey_display:
-                    self.send_pairing_confirm_command()
-                else:
-                    self.input_passkey(self.send_pairing_confirm_command)
+            self.send_pairing_confirm_command()
         else:
-            # Send our public key back to the initiator
             if self.pairing_method == self.PASSKEY:
-                self.display_or_input_passkey(self.send_public_key_command)
-            else:
-                self.send_public_key_command()
+                self.display_or_input_passkey()
+
+            # Send our public key back to the initiator
+            self.send_public_key_command()
 
             if self.pairing_method in (self.JUST_WORKS, self.NUMERIC_COMPARISON):
                 # We can now send the confirmation value