Python script to monitor the Windows registry and ensure that Outlook email encryption by default stays off

outlook-disable-encryption.py

import ctypes, ctypes.wintypes

advapi32 = ctypes.windll.advapi32

# LSTATUS RegOpenKeyExA(HKEY hKey, LPCSTR lpSubKey, DWORD ulOptions, REGSAM samDesired, PHKEY phkResult)
RegOpenKeyExA = advapi32.RegOpenKeyExA
RegOpenKeyExA.argtypes = (ctypes.wintypes.HKEY, ctypes.wintypes.LPCSTR, ctypes.wintypes.DWORD, ctypes.wintypes.DWORD, ctypes.wintypes.PHKEY)

# LSTATUS RegCloseKey(HKEY hKey)
RegCloseKey = advapi32.RegCloseKey
RegCloseKey.argtypes = (ctypes.wintypes.HKEY, )

# LSTATUS RegSetKeyValueA(HKEY hKey, LPCSTR lpSubKey, LPCSTR lpValueName, DWORD dwType, LPCVOID lpData, DWORD cbData)
RegSetKeyValueA = advapi32.RegSetKeyValueA
RegSetKeyValueA.argtypes = (ctypes.wintypes.HKEY, ctypes.wintypes.LPCSTR, ctypes.wintypes.LPCSTR, ctypes.wintypes.DWORD, ctypes.wintypes.LPCVOID, ctypes.wintypes.DWORD)

# LSTATUS RegNotifyChangeKeyValue(HKEY hKey, BOOL bWatchSubtree, DWORD dwNotifyFilter, HANDLE hEvent, BOOL fAsynchronous)
RegNotifyChangeKeyValue = advapi32.RegNotifyChangeKeyValue
RegNotifyChangeKeyValue.argtypes = (ctypes.wintypes.HKEY, ctypes.wintypes.BOOL, ctypes.wintypes.DWORD, ctypes.wintypes.HANDLE, ctypes.wintypes.BOOL)

HKEY_CURRENT_USER = ctypes.wintypes.HKEY(0x80000001)
KEY_NOTIFY = 0x0010
REG_NOTIFY_CHANGE_LAST_SET = 0x00000004
REG_DWORD = 4

def wait_for_change(hkey, subpath):
    hdl = ctypes.wintypes.HKEY()
    res = RegOpenKeyExA(hkey, subpath, 0, KEY_NOTIFY, hdl)
    if res != 0:
        raise RuntimeError('RegOpenKeyExA failed, error {}'.format(res))
    res = RegNotifyChangeKeyValue(hdl, False, REG_NOTIFY_CHANGE_LAST_SET, None, False)
    if res != 0:
        raise RuntimeError('RegNotifyChangeKeyValue failed, error {}'.format(res))
    RegCloseKey(hdl)

def set_key_value(hkey, subpath, valuename, value):
    val = ctypes.wintypes.DWORD(value)
    res = RegSetKeyValueA(hkey, subpath, valuename, REG_DWORD, ctypes.addressof(val), ctypes.sizeof(val))
    if res != 0:
        raise RuntimeError('RegSetKeyValueA failed, error {}'.format(res))

if __name__ == '__main__':
    import sys
    verbose = len(sys.argv) > 1 and sys.argv[1] == '-v'
    if verbose:
        print('note that the application cannot respond to Ctrl+C while waiting')

    # [HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security]
    # "InitEncrypt"=dword:00000002

    HKEY = HKEY_CURRENT_USER
    SUBPATH = br'Software\Microsoft\Office\16.0\Outlook\Security'
    VALUENAME = b'InitEncrypt'
    VALUE = 2

    while True:
        if verbose:
            print('waiting for change in {}'.format(SUBPATH))
        wait_for_change(HKEY, SUBPATH)
        if verbose:
            print('{} changed'.format(SUBPATH))
        set_key_value(HKEY, SUBPATH, VALUENAME, VALUE)
        if verbose:
            print("{} {} reset".format(SUBPATH, VALUENAME))