PowerShell function for testing passwords against HIBP Pwned Password database

Test-PwnedPassword.ps1

function Test-PwnedPassword {
	[CmdletBinding()]
	param ( 
		[Parameter()]
		[System.Security.SecureString]
		$Password = ( Read-Host -Prompt "Enter a password to test" -AsSecureString ),
		
		[Parameter()]
		[switch]
		$Detailed
	)

	$dummyCredential = New-Object -TypeName 'System.Management.Automation.PSCredential' -ArgumentList 'PwnedPasswordTest', $Password;

	$enc = [System.Text.Encoding]::UTF8;
	$sha1 = new-object -TypeName 'System.Security.Cryptography.SHA1CryptoServiceProvider';

	$hashstring = [system.bitconverter]::ToString($sha1.ComputeHash($enc.GetBytes($dummyCredential.GetNetworkCredential().Password))).Replace('-','');

	$uri = ( "https://api.pwnedpasswords.com/range/{0}" -f $hashstring.Substring(0,5) );
	$re = ( "^{0}\:(\d+)" -f $hashstring.Substring(5) );

	Write-Verbose ( "URI: {0}" -f $uri );

	[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12;
	$response = invoke-webrequest -Uri $uri;

	if ( $response.StatusCode -eq 200 ) {
		
		$out = [PSCustomObject]@{
			'Pwned' = $false;
			'Message' = 'Good news — no pwnage found!';
		}

		( $response.Content -split "`n" ) -match $re |
		ForEach-Object {
			if ( $_ -match $re ) {
				$out.Pwned = $true;
				$out.Message = ( 'Oh no - pwned! This password has been seen {0} times in public data breaches, and should not be used.' -f $matches[1] );
			}
		}

		if ( $Detailed.IsPresent ) {
			$out;
		} 
		else {
			$out.Pwned;
		}
	} 
	else {
		Write-Error ( "HTTP Status Code {0}" -f $response.StatusCode );
	}

<#
.SYNOPSIS
Test a provided password against the Have I Been Pwned? Pwned Passwords database.

.DESCRIPTION
Test a provided password against the Have I Been Pwned? Pwned Passwords database using REST API.

.PARAMETER Password
SecureString object containing password to be tested.
If not provided, will be prompted.

.PARAMETER Detailed
Provide detailed information about result.

.OUTPUTS
If -Detailed is not specified, a simple $true or $false is returned, indicating whether or not the password has been pwned.
If -Detailed is specified, an object is returned with two properties:
* Pwned: $true or $false
* Message: Message describing result

.EXAMPLE
$passwordToTest = ConvertTo-SecureString -String 'Pass@word' -AsPlainText -Force
Test-PwnedPassword -Password $passwordToTest

.LINK
https://www.troyhunt.com/ive-just-launched-pwned-passwords-version-2/


.NOTES
2019-03-07 jesse.kozloski     knocked this together after reading https://www.troyhunt.com/ive-just-launched-pwned-passwords-version-2/
                              seemed like a fun little project.
#>

}