- att.py: raise core.InvalidPacketError instead of generic ValueError
- smp.py: raise core.InvalidPacketError instead of generic ValueError
- hfp.py: add MAX_BUFFER_SIZE class constant (64KB)
- hfp.py: drop incoming data when it would overflow buffer instead of
truncating, preserving existing partial-packet state
Per review comments on PR #912 by @zxzxwu.
Add length checks in from_bytes() for ATT and SMP protocol parsers
to prevent IndexError crashes from empty PDUs sent by remote Bluetooth
devices. Also add buffer size limit and UTF-8 error handling in HFP
protocol to prevent memory exhaustion and decode crashes.
- bumble/att.py: validate PDU is non-empty before accessing pdu[0]
- bumble/smp.py: validate PDU is non-empty before accessing pdu[0]
- bumble/hfp.py: limit buffer to 64KB, handle invalid UTF-8 gracefully
These issues can be triggered by a remote Bluetooth device sending
malformed packets, causing denial of service on the host.
Bluetooth spec @ Vol 3, Part F - 3.4.6.3 Table 3.36 shows that the
ATT_EXECUTE_WRITE_REQ PDU contains the parameter 'Flags' with size 1
octet, which allows to cancel all prepared writes (0x00) or to
immediately write all pending prepared values (0x01).
* 'permission' instead of 'permissions'
* Also added a more user friendly error message when Attribute.string_to_permissions fails
```
TypeError: Attribute::permissions error:
Expected a string containing any of the keys, seperated by commas: READABLE,WRITEABLE,READ_REQUIRES_ENCRYPTION,WRITE_REQUIRES_ENCRYPTION,READ_REQUIRES_AUTHENTICATION,WRITE_REQUIRES_AUTHENTICATION,READ_REQUIRES_AUTHORIZATION,WRITE_REQUIRES_AUTHORIZATION
Got: 1
```
```
Exception: Error parsing Device Config's GATT Services. The key 'permission' must be renamed to 'permissions'
```
before:
```
File "/home/alanrosenthal/code/fitbit/bumble/bumble/gatt.py", line 572, in __str__
f'Descriptor(handle=0x{self.handle:04X}, '
File "/home/alanrosenthal/code/fitbit/bumble/bumble/att.py", line 756, in read_value
self.permissions & self.READ_REQUIRES_ENCRYPTION
TypeError: unsupported operand type(s) for &: 'str' and 'int'
```
