Thursday, July 31, 2014

Poor man's IP to to Username, using Powershell & Domain Controller logs

This customer had many offices and needed to get rid of Windows XP machines.
Due to the lack of inventory and computer management, we were unable to know who were the people behind them!
Ping and remote access were shut off from the host so we couldn't gather information via WMI.

But the LastLogonTimeStamp was being updated for these computers which led us to believe they were still in use.
The solution I came up with : if someone was still using these XP machines, they were authenticating against the domain controllers, and a "logon event" was created with the source ip and the username.

Once you load the quick and dirty function called "Get-UserName-for_PC-by-DC-events (silly name sorry), run these 2 commands to get some results

Import-module ActiveDirectory
Get-ADComputer -Filter {Enabled -eq $true -and operatingsystem -like '*xp*'} -Properties IPv4Address | %{Get-UserName-for-PC-by-DC-events -DCname "DC01" -Ip $_.IPv4Address}

7/31/2014 1:18:33 PM  --  john.doe at this address -->  using  Kerberos

A nice enhancement would be to query all domain controllers.
Finally, your mileage may vary depending on how big your security logs are, how often they rotate and how often these XP users log on (you could run a scheduled task)
Function Get-UserName-for-PC-by-DC-events
    $xpathfilter = 'Event[System[EventID=4624] and EventData[Data[@Name="IpAddress"]="'+$ip+'"]]'

    Foreach ($event in get-winevent -ComputerName $DCname -LogName Security -FilterXPath $xpathfilter -MaxEvents 1)
        Write-host $event.TimeCreated " -- " $event.Properties[5].Value "at this address --> " $event.Properties[18].Value " using " $event.Properties[9].Value


Wednesday, July 16, 2014

DCHP server migration from Debian to Windows Server 2008

My customer wanted to migrate DHCP server function from Debian Wheezy 7.50 running ISC-DHCP to Windows Server 2008.
The task can broken in 6 parts

  1. parse dhcpd.conf on the DHCP server (Linux)
  2. import the parsed file to your *new* DHCP server
  3. setup DHCP role on *new*server
  4. run a script on the *new* DHCP server which creates scopes,pools and reservations (Windows) according to the parsed file.
  5. manually rename the scopes to "friendly" names
  6. manually set the server,scope and/or reservation options and scope lease times
Parse dhcpd.conf
get this great AWK parser onto the Debian box
make it executable
chmod +x dhcpparse.awk
parse the file
cat /etc/dhcp/dhcpd.conf | dhcpparse.awk > dhcp-config.txt

Import the parsed file to your Windows Server
have a look at it to remove errors.
Setup DHCP role on Windows Server
skipping this part as it's pretty self explanatory
Run script
You will need this Powershell module , referred to as "Microsoft.DHCP.Powershell.Admin.psm1" in the script. If Window Server is version 2012 R2 , I guess you can use the DHCP server cmdlets from Microsoft instead.
You will also need to make a Powershell module -which is a combination of this function and this function. Just add one function under the other and put the line "export-modulemember IsIpAddressInRange,Get-IPrange". This module is referred as "IPutil.psm1"

Import-Module .\Microsoft.DHCP.Powershell.Admin.psm1

Import-Module .\IPutil.psm1

#Group by line types

$subnets = Select-String -Pattern 'subnet' -Path .\dhcp-config.txt |%{$_.Line}

$pools = Select-String -Pattern 'pool' -Path .\dhcp-config.txt | %{$_.Line}

$hosts = Select-string -Pattern ‘host’ -path  .\dhcp-config.txt |%{$_.Line}

#Create scopes

$scopes = $subnets |%{$l=$_.Split(','); New-DHCPScope -Server $env:COMPUTERNAME -Address $l[1] -SubnetMask $l[2] -Name $l[3]}

foreach ($scope in $scopes)


    # generate all the IP addresses in this scope

    $ips=Get-IPrange -ip $scope.Address -mask $scope.SubnetMask

    # Create pools

    Write-host "Creating pool(s) for " $scope.Address

    foreach ($line in $pools)


        if($ips -contains $line.split(',')[1])


            Add-DhcpIPRange -scope $scope -startaddress $line.split(',')[1] -endaddress $line.split(',')[2]



    # Create reservations

    Write-host "Creating reservation(s) for " $scope.Address

    foreach ($line in $hosts)


        if($ips -contains $line.split(',')[1])


            New-DHCPReservation -scope $scope -IPAddress $line.split(',')[1] -MACAddress $line.split(',')[2] -Description $line.split(',')[4]




Write-host “You should now rename the scopes to friendly names”

Write-host “You should manually set options and lease times"