PowerShell Universal Authentication Example Supporting Multiple Domains

authentication.ps1

Set-PSUAuthenticationMethod -Type "Form" -ScriptBlock {
param(
	[PSCredential]$Credential
)

Add-Type -AssemblyName System.DirectoryServices.AccountManagement
	
# is this a UPN?
if ( $Credential.UserName.IndexOf('@') -gt -1 ) {

	# juggle back and forth from SID to get NTAccount format
	$NTAccountName = ([System.Security.Principal.NTAccount]$Credential.UserName).Translate([System.Security.Principal.SecurityIdentifier]).Translate([System.Security.Principal.NTAccount]).Value

} elseif ( $Credential.UserName.IndexOf('\') -gt -1 ) {

	# already NTAccount format
	$NTAccountName = $Credential.UserName

} else {

	# someone didn't enter their domain...
	$NTAccountName = "NETBIOSDOMAIN\" + $Credential.GetNetworkCredential().UserName

}

# split domain and username
$DomainName, $UserName = $NTAccountName.Split('\',2)
	
# perform auth with AD
$PrincipalContext = New-Object System.DirectoryServices.AccountManagement.PrincipalContext( 'Domain', $DomainName )
$Authenticated = $PrincipalContext.ValidateCredentials( $UserName, $Credential.GetNetworkCredential().Password, 'Negotiate, Sealing' )
	
if ( $Authenticated ) {

	# discover the user principal, needed for the user DN
	$UserPrincipal = [System.DirectoryServices.AccountManagement.UserPrincipal]::FindByIdentity($PrincipalContext, [System.DirectoryServices.AccountManagement.IdentityType]::SamAccountName, $NTAccountName )

	# get the user's domain
	$UserDomainContext = [System.DirectoryServices.ActiveDirectory.DirectoryContext]::new( 'Domain', $DomainName, $Credential.UserName, $Credential.GetNetworkCredential().Password )
	$UserDomain = [System.DirectoryServices.ActiveDirectory.Domain]::GetDomain( $UserDomainContext )

	# get the computer's domain
	$ComputerDomain = [System.DirectoryServices.ActiveDirectory.Domain]::GetComputerDomain()

	# hold all the user groups
	[System.Collections.Generic.List[hashtable]]$Groups = @()

	# get groups from user's domain
	[adsisearcher]::new( $UserDomain.GetDirectoryEntry(), "(&(objectCategory=group)(objectClass=group)(member:1.2.840.113556.1.4.1941:=$($UserPrincipal.DistinguishedName)))", @('name') ).FindAll().ForEach({

		$Groups.Add(@{
			Type = 'Group'
			Value = $_.Properties['name'][0]
			Issuer = $UserDomain.Name
		})
	
	})

	# get groups from the computer's domain (if different)
	if ( $UserDomain.Name -ne $ComputerDomain.Name ) {

		# lookup the user's foreign security principal in the computer's domain
		$ForeignSecurityPrincipal = [adsisearcher]::new( $ComputerDomain.GetDirectoryEntry(), "(&(objectCategory=foreignSecurityPrincipal)(objectClass=foreignSecurityPrincipal)(name=$($UserPrincipal.Sid)))", @('distinguishedName') ).FindOne().Properties['distinguishedName'][0]
	
		# find all the group memberships
		[adsisearcher]::new( $ComputerDomain.GetDirectoryEntry(), "(&(objectCategory=group)(objectClass=group)(member:1.2.840.113556.1.4.1941:=$ForeignSecurityPrincipal))", @('name') ).FindAll().ForEach({
	
			$Groups.Add(@{
				Type = 'Group'
				Value = $_.Properties['name'][0]
				Issuer = $ComputerDomain.Name
			})
	
		})
	
	}
		
	New-PSUAuthenticationResult -Success -UserName $UserPrincipal.UserPrincipalName -Claims {
		$Groups | ForEach-Object { New-PSUAuthorizationClaim @_ }
	}
	
} else {

	New-PSUAuthenticationResult -ErrorMessage 'Bad username or password'

}
}