A follow-up on the last post

I’ve done very little non-hobbyist Unix programming. I’ve been writing code for various Microsoft platforms professionally for over 20 years now. I have a far better understanding of the Unix security model.

How to test if a user is an adminstrator in Python

Note that you can’t just test for membership in the “administrators” group, or your code will fail if you run it in a non-english-speaking country (where “administrators” may be “Administrateurs”).

import ctypes
import ctypes.wintypes

def current_user_is_admin():
    return user_token_is_admin(0)

def user_is_admin(username, password, domain=None):
    """note that username, password, and domain should all be unicode"""

    LOGON32_LOGON_NETWORK = 3
    LOGON32_PROVIDER_DEFAULT = 0
    token = ctypes.wintypes.HANDLE()
    if ctypes.windll.advapi32.LogonUserW(username, domain, password,
            LOGON32_LOGON_NETWORK, LOGON32_PROVIDER_DEFAULT, ctypes.byref(token)) == 0:
        raise Exception("user logon failed")

    try:
        return user_token_is_admin(token)
    finally:
        ctypes.windll.kernel32.CloseHandle(token)
        

def user_token_is_admin(user_token):
    """
    using the win32 api, determine if the user with token user_token has administrator rights

    See MSDN entry here: http://msdn.microsoft.com/en-us/library/aa376389(VS.85).aspx
    """
    class SID_IDENTIFIER_AUTHORITY(ctypes.Structure):
        _fields_ = [
            ("byte0", ctypes.c_byte),
            ("byte1", ctypes.c_byte),
            ("byte2", ctypes.c_byte),
            ("byte3", ctypes.c_byte),
            ("byte4", ctypes.c_byte),
            ("byte5", ctypes.c_byte),
        ]
    nt_authority = SID_IDENTIFIER_AUTHORITY()
    nt_authority.byte5 = 5

    SECURITY_BUILTIN_DOMAIN_RID = 0x20
    DOMAIN_ALIAS_RID_ADMINS = 0x220
    administrators_group = ctypes.c_void_p()
    if ctypes.windll.advapi32.AllocateAndInitializeSid(ctypes.byref(nt_authority), 2,
        SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS,
        0, 0, 0, 0, 0, 0, ctypes.byref(administrators_group)) == 0:
        raise Exception("AllocateAndInitializeSid failed")

    try:
        is_admin = ctypes.wintypes.BOOL()
        if ctypes.windll.advapi32.CheckTokenMembership(
                user_token, administrators_group, ctypes.byref(is_admin)) == 0:
            raise Exception("CheckTokenMembership failed")
        return is_admin.value != 0

    finally:
        ctypes.windll.advapi32.FreeSid(administrators_group)