Bluetooth mouse - Windows and Ubuntu dual boot.

bt_mouse.py

r"""
Bluetooth mouse - Windows and Ubuntu dual boot.
[ more info on my blog here https://wp.me/p1u8Xj-ib ]

Ordinarily, if you pair a Bluetooth mouse in Linux,
then boot into a Windows partition, you'll need to
pair the mouse again in Windows for it to work. As a
consequence, the pairing will be lost in Linux. You'll
have to pair again when you switch partition to get it
to work. This is not sustainable!

To get it to work across both partitions once and for
all, you need to export some of the pairing data from
the registry of the Windows partition, manipulate the
data a little, then import it into the relevant
Bluetooth config file in Linux.

There are quite a few guides out there on how to do
this - I tried a few and none of them quite worked for
me, though they did help me to put this solution
together.

In this instance, I used a Microsoft Bluetooth Mouse,
pairing with an Inateck Bluetooth USB dongle. The
operating systems were Windows 10 and Ubuntu 18.04.

Step 1 - pair the mouse in the Linux partition
Step 2 - pair the mouse in the Windows partition
Step 3 - using regedit running as administrator in
         Windows, browse to

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BTHPORT\Parameters\Keys

Step 4 - change the permissions on the registry key
         to give yourself read access
Step 5 - press f5 to refresh the view
Step 6 - this should reveal a key with an 'adapter
         address' as its name, and a similar-looking
         'remote device address' sub-key
Step 7 - you'll hopefully see some values called LTK,
         KeyLength, EDIV and ERand
Step 8 - fill those values in in the section below,
         replacing the example values:
"""

LTK = "f3,c4,b6,43,51,70,8d,6a,ff,45,81,e4,4c,99,75,e4"
KeyLength = "00000010"
EDIV = "0000b333"
ERand = "e6,5f,88,bc,cc,09,0b,32"

"""
Step 9 - run this Python code, and it'll generate the
         corresponding values that you'll need in Linux
Step 10 - boot into Linux, and substitute the generated
          values into the 'info' file in
          /var/lib/bluetooth/<adapter address>/<remote device address>
Step 11 - rename the <remote device address> folder to
          match the remote device address shown in the
          Windows registry
Step 12 - reboot, or restart the bluetooth service
          ('# service bluetooth restart')
          [I found it could take a couple of minutes for
          the mouse to show as connected]
Step 13 - mouse!
Step 14 - once you have it working, it's probably a good
          idea to go back and set the Windows registry
          permissions back to how they were originally

"""

# Calculate 'Key' value
Key = "".join(LTK.split(",")).upper()
print("Key={}".format(Key))

# Calculate 'EncSize' value
EncSize = int(KeyLength, 16)  # Convert hex to decimal
print("EncSize={}".format(EncSize))

# Calculate EDiv value
EDiv = int(EDIV, 16)  # Convert hex to decimal
print("EDiv={}".format(EDiv))

# Calculate Rand value
ERand_list = ERand.split(",")
ERand_list.reverse()  # Reverse order of hex pairs
ERand_rev_hex = "".join(ERand_list)
Rand = int(ERand_rev_hex, 16)  # Convert hex to decimal
print("Rand={}".format(Rand))