Function to test password complexity

Get-PasswordComplexity.ps1

function Get-PasswordComplexity {
    <#
        .SYNOPSIS
            Testing if a given password is complex

        .DESCRIPTION
            Based on the given SecureString or Credential the function tests if the password used is complex enough.
            The complexity is calculated based on the number of character classes use in the password.
            The classes are lower case letter, upper case letters, numbers and special characters.
            Each class gets a complexity point and the password must include at least 3 classes.
            
            The length requirement defaults to 10, but can be overriden.

            Based on http://tompaps.blogspot.com/2018/01/verify-password-complexity-os.html
            With a few security enhancements in mind and using advanced function.

        .PARAMETER SecurePassword
            The password to be tested as a SecureString

        .PARAMETER Credential
            The credential object which password is going to be tested
        
        .PARAMETER MinPasswordLength
            Optional. Defaults to 10. The minimum length requirement for accepted passwords.
        
        .EXAMPLE 

            $secureString = Read-Host -AsSecureString -Prompt "enter password"
            enter password: ***********
            > Test-PasswordComplexity -SecurePassword $secureString
            > Test-PasswordComplexity -SecurePassword $secureString

            IsValid Length      Complexity ComplexityScore
            ------- ------      ---------- ---------------
            True length - OK complex                  4

        .EXAMPLE 

            $secureStringWeak = Read-Host -AsSecureString -Prompt "enter password"
            enter password: ******
            > Test-PasswordComplexity -SecurePassword $secureStringWeak

            IsValid Length      Complexity  ComplexityScore
            ------- ------      ----------  ---------------
            False length < 10 NOT complex               1

        .LINK
            http://tompaps.blogspot.com/2018/01/verify-password-complexity-os.html
    #>
    [CmdletBinding(
        DefaultParameterSetName = 'SecurePassword'
    )]
    [OutputType('PasswordComplexity')]
    param (
        [Parameter(Mandatory, ParameterSetName = 'SecurePassword')]
        [SecureString]
        $SecurePassword, 

        [Parameter(Mandatory, ParameterSetName = 'Credential')]
        [PSCredential]
        $Credential, 

        [Parameter()]
        [int]
        $MinPasswordLength = 10
    )
    try {
        if ($PSCmdlet.ParameterSetName -eq 'SecurePassword') {
            $passwordString = (New-Object PSCredential "user",$SecurePassword).GetNetworkCredential().Password
        } else {
            $passwordString = $Credential.GetNetworkCredential().Password
        }

        $valid = $true
        # checking the minimal length
        if($passwordString.length -lt $MinPasswordLength){  
            $passwordLength = "length < {0}" -f $MinPasswordLength
            $valid = $false
        } else {
            $passwordLength = "length - OK"  
        }

        $pwComplexity = 0
        # lowercase  
        if($passwordString -cmatch "[a-z]"){  
            $pwComplexity++  
        }  
        
        # uppercase  
        if($passwordString -cmatch "[A-Z]"){  
            $pwComplexity++  
        }  
        
        # digits  
        if($passwordString -cmatch "[0-9]"){  
            $pwComplexity++  
        }  
        
        
        # special character (not alphabetic characters or numbers)  
        if($passwordString -cmatch "[^a-zA-Z0-9]"){  
            $pwComplexity++  
        }  
        
        # if 3 of the criterias      
        if($pwComplexity -ge 3){  
            $complexity = "complex"
        }  
        else{  
            $complexity = "NOT complex"
            $valid = $false
        }  
        
        [PSCustomObject]@{
            IsValid         = $valid
            Length          = $passwordLength
            Complexity      = $complexity
            ComplexityScore = $pwComplexity
            PSTypeName      = 'PasswordComplexity'
        }
    } catch {
        Write-Error -ErrorRecord $_
    }
}

Test-PasswordComplexity.ps1

function Get-PasswordComplexity {
    <#
        .SYNOPSIS
            Testing if a given password is complex

        .DESCRIPTION
            Based on the given SecureString or Credential the function tests if the password used is complex enough.
            The complexity is calculated based on the number of character classes use in the password.
            The classes are lower case letter, upper case letters, numbers and special characters.
            Each class gets a complexity point and the password must include at least 3 classes.
            
            The length requirement defaults to 10, but can be overriden.

            Based on http://tompaps.blogspot.com/2018/01/verify-password-complexity-os.html
            With a few security enhancements in mind and using advanced function.

        .PARAMETER SecurePassword
            The password to be tested as a SecureString

        .PARAMETER Credential
            The credential object which password is going to be tested
        
        .PARAMETER MinPasswordLength
            Optional. Defaults to 10. The minimum length requirement for accepted passwords.
        
        .EXAMPLE 

            $secureString = Read-Host -AsSecureString -Prompt "enter password"
            enter password: ***********
            > Test-PasswordComplexity -SecurePassword $secureString
            > Test-PasswordComplexity -SecurePassword $secureString

            IsValid Length      Complexity ComplexityScore
            ------- ------      ---------- ---------------
            True length - OK complex                  4

        .EXAMPLE 

            $secureStringWeak = Read-Host -AsSecureString -Prompt "enter password"
            enter password: ******
            > Test-PasswordComplexity -SecurePassword $secureStringWeak

            IsValid Length      Complexity  ComplexityScore
            ------- ------      ----------  ---------------
            False length < 10 NOT complex               1

        .LINK
            http://tompaps.blogspot.com/2018/01/verify-password-complexity-os.html
    #>
    [CmdletBinding(
        DefaultParameterSetName = 'SecurePassword'
    )]
    [OutputType('PasswordComplexity')]
    param (
        [Parameter(Mandatory, ParameterSetName = 'SecurePassword')]
        [SecureString]
        $SecurePassword, 

        [Parameter(Mandatory, ParameterSetName = 'Credential')]
        [PSCredential]
        $Credential, 

        [Parameter()]
        [int]
        $MinPasswordLength = 10
    )
    try {
        if ($PSCmdlet.ParameterSetName -eq 'SecurePassword') {
            $passwordString = (New-Object PSCredential "user",$SecurePassword).GetNetworkCredential().Password
        } else {
            $passwordString = $Credential.GetNetworkCredential().Password
        }

        $valid = $true
        # checking the minimal length
        if($passwordString.length -lt $MinPasswordLength){  
            $passwordLength = "length < {0}" -f $MinPasswordLength
            $valid = $false
        } else {
            $passwordLength = "length - OK"  
        }

        $pwComplexity = 0
        # lowercase  
        if($passwordString -cmatch "[a-z]"){  
            $pwComplexity++  
        }  
        
        # uppercase  
        if($passwordString -cmatch "[A-Z]"){  
            $pwComplexity++  
        }  
        
        # digits  
        if($passwordString -cmatch "[0-9]"){  
            $pwComplexity++  
        }  
        
        
        # special character (not alphabetic characters or numbers)  
        if($passwordString -cmatch "[^a-zA-Z0-9]"){  
            $pwComplexity++  
        }  
        
        # if 3 of the criterias      
        if($pwComplexity -ge 3){  
            $complexity = "complex"
        }  
        else{  
            $complexity = "NOT complex"
            $valid = $false
        }  
        
        [PSCustomObject]@{
            IsValid         = $valid
            Length          = $passwordLength
            Complexity      = $complexity
            ComplexityScore = $pwComplexity
            PSTypeName      = 'PasswordComplexity'
        }
    } catch {
        Write-Error -ErrorRecord $_
    }
}