Windows Registry access for Python script

Question

I'm working on a Python 3.7 script that eventually will be a CLI program like reg.exe is. I'm aiming to include the ability to add, delete and query keys and subkeys. At this point, I can create a new Key and iterate through all keys within the specific path however; once I try to write a value to the new key I made, I get a WinError 5 - Access denied.

Is there a way I can include in the script a way to have access to write to the registry?

I'm still a beginner with Python and programming, I've had a look at documents but I cant figure this one out.

Any help will be greatly appreciated. My code soo far:

import winreg

reg_connection = winreg.ConnectRegistry(None, winreg.HKEY_CURRENT_USER)

reg_key = winreg.OpenKey(reg_connection, r"SOFTWARE\Microsoft\\")

winreg.CreateKey(reg_key, "New Key")

for key in range(3000):
    try:
        show_sub_keys = winreg.EnumKey(reg_key, key)
        print(show_sub_keys)
    except WindosError:
        break

new_key_value = winreg.OpenKey(reg_connection, r"SOFTWARE\Microsoft\New Key")
winreg.SetValueEx(new_key_value, "New Value",0,winreg.REG_SZ, "This Value")
winreg.CloseKey(new_key_value)

Don't use ConnectRegistry just to access the local registry. It maps a predefined key handle (i.e. HKEY_LOCAL_MACHINE, HKEY_USERS, or HKEY_PERFORMANCE_DATA) to an RPC handle for remote registry access. HKEY_CURRENT_USER is a predefined-handle that by default maps to a handle for the current user's registry key, "\Registry\User\<User SID String>". This is meaningless for remote access (no user profile is loaded), so it's not supported. — Eryk Sun
– Eryk Sun, Commented Dec 9, 2018 at 4:01

zett42 · Accepted Answer · 2018-12-08 20:42:00Z

1

new_key_value = winreg.OpenKey(reg_connection, r"SOFTWARE\Microsoft\New Key")

Here you do not specify an argument for the optional access parameter, so the call passes the default value of KEY_READ. Hence you can only read from the key, but not write.

You should pass an argument for the access parameter, that specifies the permissions you need:

new_key_value = winreg.OpenKey(reg_connection, r"SOFTWARE\Microsoft\New Key", 0, 
                               winreg.KEY_SET_VALUE)

For further details, see the winreg reference.

answered Dec 8, 2018 at 20:42

zett42

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5 Comments

Eryk Sun Over a year ago

zett42 Over a year ago

@eryksun In the case of this question, only KEY_SET_VALUE is required. Requesting more access than needed would violate the principle of least privilege. In particular, the DACL of a key may grant you permissions to write individual values, but prevents you from creating sub keys, in which case requesting KEY_WRITE would fail.

Eryk Sun Over a year ago

winreg.CreateKey(reg_key, "New Key")... really?

Atreyu Over a year ago

Thanks for the help on this one :) because im new to this, its a bit confusing at first, but I understand now what seems to be the better way from these suggestions. Thanks everyone. I'll review the Winreg library again until i understand it better.

Atreyu Over a year ago

If I need further help with the program, is it best to ask it here as its already the topic or does that need to be asked elsewhere?

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