Converting AD UserAccountControl Attribute Values

UserAccountControl is one of the most important attributes of user and computer accounts in Active Directory. This attribute determines the status of the account in the AD domain: whether the account is active or locked, whether the option of password change at the next logon is enabled, whether users can change their passwords, etc. However, not all administrators are fully aware of how and for what purpose UserAccountControl attribute is used in AD.

Open the properties of any AD account in the Active Directory Users and Computers (ADUC) console and go to the Account tab. Please, pay attention to the group of user attributes in the Account Options section. Here you can see the following options:

• User must change password at next logon;
• User cannot change password;
• Password never expires;
• Store password using reversible encryption (not safe);
• Account is disabled;
• Smart card is required for interactive logon;
• Account is sensitive and cannot be delegated;
• Use Kerberos DES encryption types for this account;
• This account supports Kerberos AES 128/256 bit encryption;
• Do not require Kerberos Preauthentication.

Each of these user account attributes is essentially a bit value that can be in the state 1 (True) or 0 (False). However, these values are not stored as separate AD attributes, the UserAccountControl attribute is used instead.

UserAccountControl as an Active Directory Attribute

The total value of all options specified above is kept in the value of UserAccountControl attribute, i. e. instead of storing all these options in different attributes, a single Active Directory attribute is used. UserAccountControl is a bit mask with every bit being a separate flag and having a different value (enabled or disabled). So depending on the enabled account options a user will have different UserAccountControl attribute values. You can see the current value of the attribute in the corresponding Attribute Editor tab or using Get-ADUser cmdlet in PowerShell:

get-aduser jkelly -properties *|select name,UserAccountControl | ft

In this example the value of the attribute is 0x10202 (decimal value is 66050). What do these numbers mean?

The table of available flags of AD accounts is given below. Each flag corresponds to a certain UserAccountControl bit, and UserAccountControl value equals to the sum of all flags.

For example, there is a regular account for which the requirement to change the password is disabled. The userAccountControl value is calculated as follows:

NORMAL_ACCOUNT (512) + DONT_EXPIRE_PASSWORD (65536) = 66048

So the value of userAccountControl from my example (66050) was obtained as follows:

NORMAL_ACCOUNT (512) + DONT_EXPIRE_PASSWORD (65536) + ACCOUNTDISABLE (2) = 66050

A locked user account has 514 as a userAccountControl value:

(NORMAL_ACCOUNT (512)+ ACCOUNTDISABLE (2) = 514

Default UserAccountControl values for typical domain objects:

1. A regular AD user: 0x200 (512);
2. A domain controller: 0x82000 (532480);
3. A workstation/server: 0x1000 (4096).

Using some filters, you can select from the AD objects with a certain useraccountcontrol value. For example, to display all active (normal) accounts:

Get-ADUser -Properties * -ldapFilter "(useraccountcontrol=512)"

Display the list of all locked accounts:

Get-ADUser -Properties * -ldapFilter "(useraccountcontrol=514)"

The list of accounts with a non-expiring password oprions:

Get-ADUser -Properties * -ldapFilter "(useraccountcontrol=66048)"

You can sum the necessary bits from the table and select AD objects using these commands:

$UserAccountControl_hex= 0x10000 + 0x0080 + 0x200000
Get-ADUser -Filter {UserAccountControl -band$UserAccountControl_hex}

PowerShell script to decode UserAccountControl value

To make it more convenient, I want to have a tool to automatically converts the value of UserAccountControl bit mask into human-transparent form. Let’s try to write a simple PowerShell function that takes the decimal value of UserAccountControl attribute and returns the list of enabled options of the account. Since UserAccountControl is a bit mask, you can assign a text description to each bit.

I wrote this PowerShell function DecodeUserAccountControl to convert UserAccountControl value into a readable piece of information:

Function DecodeUserAccountControl ([int]$UAC)
{
$UACPropertyFlags = @(
"SCRIPT",
"ACCOUNTDISABLE",
"RESERVED",
"HOMEDIR_REQUIRED",
"LOCKOUT",
"PASSWD_NOTREQD",
"PASSWD_CANT_CHANGE",
"ENCRYPTED_TEXT_PWD_ALLOWED",
"TEMP_DUPLICATE_ACCOUNT",
"NORMAL_ACCOUNT",
"RESERVED",
"INTERDOMAIN_TRUST_ACCOUNT",
"WORKSTATION_TRUST_ACCOUNT",
"SERVER_TRUST_ACCOUNT",
"RESERVED",
"RESERVED",
"DONT_EXPIRE_PASSWORD",
"MNS_LOGON_ACCOUNT",
"SMARTCARD_REQUIRED",
"TRUSTED_FOR_DELEGATION",
"NOT_DELEGATED",
"USE_DES_KEY_ONLY",
"DONT_REQ_PREAUTH",
"PASSWORD_EXPIRED",
"TRUSTED_TO_AUTH_FOR_DELEGATION",
"RESERVED",
"PARTIAL_SECRETS_ACCOUNT"
"RESERVED"
"RESERVED"
"RESERVED"
"RESERVED"
"RESERVED"
)
$Attributes = ""
1..($UACPropertyFlags.Length) | Where-Object {$UAC -bAnd [math]::Pow(2,$_)} | ForEach-Object {If ($Attributes.Length -EQ 0) {$Attributes = $UACPropertyFlags[$_]} Else {$Attributes = $Attributes + " | " + $UACPropertyFlags[$_]}}
Return $Attributes
}

Let’s check what value 66050 of UserAccountControl means:

DecodeUserAccountControl 66050

As you can see, the script has returned that the following attributes are enabled for this user:

ACCOUNTDISABLE | NORMAL_ACCOUNT | DONT_EXPIRE_PASSWORD

The same script can be used to decode the UserAccountControl values on the fly when getting the information about AD accounts in the convenient form using Get-AdUser or Get-ADComputer cmdlets, for example:

get-aduser ms-pam -properties *|select @{n='UsrAcCtrl';e={DecodeUserAccountControl($_.userAccountControl)}}

ACCOUNTDISABLE | NORMAL_ACCOUNT | DONT_EXPIRE_PASSWORD

get-adcomputer rome-dc01 -properties *|select @{n='UsrAcCtrl';e={DecodeUserAccountControl($_.userAccountControl)}}

SERVER_TRUST_ACCOUNT | TRUSTED_FOR_DELEGATION