loader.ps1
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# this is used only to load the module and its attributes function Register-ParameterCache { <# .SYNOPSIS Loads the parameter attributes .DESCRIPTION Once you run this command, or manually import module "ParameterCache" (Import-Module -Name ParameterCache), you have access to the following attributes: [AutoLearn('user')] : caches the values for a parameter in list "user" [AutoComplete('user')] : autocompletes the previously entered values from list "user" [AutoLearnCredential('user')] : same for credentials (to secure storage) [AutocompleteCredential('user')] : same for credentials (from secure storage) .EXAMPLE Register-ParameterCache Call this before using the attributes, or make the module "ParameterCache" a prerequisite for your own modules. .LINK URLs to related sites #> } class AutoLearnAttribute : System.Management.Automation.ArgumentTransformationAttribute { # define path to store hint lists [string]$Path = "$env:temp\hints" # define id to manage multiple hint lists: [string]$Id = 'default' # define prefix character used to delete the hint list [char]$ClearKey = '!' # define parameterless constructor: AutoLearnAttribute() : base() {} # define constructor with parameter for id: AutoLearnAttribute([string]$Id) : base() { $this.Id = $Id } # Transform() is called whenever there is a variable or parameter assignment, and returns the value # that is actually assigned: [object] Transform([System.Management.Automation.EngineIntrinsics]$engineIntrinsics, [object] $inputData) { # make sure the folder with hints exists $exists = Test-Path -Path $this.Path if (!$exists) { $null = New-Item -Path $this.Path -ItemType Directory } # create filename for hint list $filename = '{0}.hint' -f $this.Id $hintPath = Join-Path -Path $this.Path -ChildPath $filename # use a hashtable to keep hint list $hints = @{} # read hint list if it exists $exists = Test-Path -Path $hintPath if ($exists) { Get-Content -Path $hintPath -Encoding Default | # remove leading and trailing blanks ForEach-Object { $_.Trim() } | # remove empty lines Where-Object { ![string]::IsNullOrEmpty($_) } | # add to hashtable ForEach-Object { # value is not used, set it to $true: $hints[$_] = $true } } # does the user input start with the clearing key? if ($inputData.StartsWith($this.ClearKey)) { # remove the prefix: $inputData = $inputData.SubString(1) # clear the hint list: $hints.Clear() } # add new value to hint list if(![string]::IsNullOrWhiteSpace($inputData)) { $hints[$inputData] = $true } # save hints list $hints.Keys | Sort-Object | Set-Content -Path $hintPath -Encoding Default # return the user input (if there was a clearing key at its start, # it is now stripped): return $inputData } } class AutoCompleteAttribute : System.Management.Automation.ArgumentCompleterAttribute { # define path to store hint lists [string]$Path = "$env:temp\hints" # define id to manage multiple hint lists: [string]$Id = 'default' # define parameterless constructor: AutoCompleteAttribute() : base([AutoCompleteAttribute]::_createScriptBlock($this)) {} # define constructor with parameter for id: AutoCompleteAttribute([string]$Id) : base([AutoCompleteAttribute]::_createScriptBlock($this)) { $this.Id = $Id } # create a static helper method that creates the scriptblock that the base constructor needs # this is necessary to be able to access the argument(s) submitted to the constructor # the method needs a reference to the object instance to (later) access its optional parameters: hidden static [ScriptBlock] _createScriptBlock([AutoCompleteAttribute] $instance) { $scriptblock = { # receive information about current state: param($commandName, $parameterName, $wordToComplete, $commandAst, $fakeBoundParameters) # create filename for hint list $filename = '{0}.hint' -f $instance.Id $hintPath = Join-Path -Path $instance.Path -ChildPath $filename # use a hashtable to keep hint list $hints = @{} # read hint list if it exists $exists = Test-Path -Path $hintPath if ($exists) { Get-Content -Path $hintPath -Encoding Default | # remove leading and trailing blanks ForEach-Object { $_.Trim() } | # remove empty lines Where-Object { ![string]::IsNullOrEmpty($_) } | # filter completion items based on existing text: Where-Object { $_.LogName -like "$wordToComplete*" } | # create argument completion results Foreach-Object { [System.Management.Automation.CompletionResult]::new($_, $_, 'ParameterValue', $_) } } }.GetNewClosure() return $scriptblock } } class AutoLearnCredentialAttribute : System.Management.Automation.ArgumentTransformationAttribute { [string]$Path = "$env:temp\hints" [string]$Id = 'default' [char]$ClearKey = '!' AutoLearnCredentialAttribute() : base() {} AutoLearnCredentialAttribute([string]$Id) : base() { $this.Id = $Id } # calculates md5 hash for usernames # hashes are used as keys for the serialized hashtable # declared as "static" because it has no relation to the attribute instance # and is simply a generic helper method: static [string] GetHash([string]$UserName) { $md5 = [System.Security.Cryptography.MD5CryptoServiceProvider]::new() $utf8 = [System.Text.UTF8Encoding]::new() return [System.BitConverter]::ToString($md5.ComputeHash($utf8.GetBytes($UserName.ToLower()))).Replace('-','') } [object] Transform([System.Management.Automation.EngineIntrinsics]$engineIntrinsics, [object] $inputData) { # make sure the folder with hints exists $exists = Test-Path -Path $this.Path if (!$exists) { $null = New-Item -Path $this.Path -ItemType Directory } # create filename for hint list $filename = '{0}.xmlhint' -f $this.Id $hintPath = Join-Path -Path $this.Path -ChildPath $filename # use a hashtable to keep hint list $hints = @{} # read hint list if it exists $exists = Test-Path -Path $hintPath if ($exists) { # hint list is xml data # it is a serialized hashtable and can be # deserialized via Import-CliXml if it exists # result is a hashtable: [System.Collections.Hashtable]$hints = Import-Clixml -Path $hintPath } # if the argument is a string... if ($inputData -is [string]) { # does username start with "!"? [bool]$promptAlways = $inputData.StartsWith($this.ClearKey) # if not,... if (!$promptAlways) { # get the md5 key for the entered username $key = [AutoLearnCredentialAttribute]::GetHash($inputData) # ...check to see if the username has been used before, # and re-use its credential (no need to enter password again) if ($hints.ContainsKey($key)) { # the hashtable contains username and password, so # create a credential from this: # convert username from securestring to plaintext: $BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($hints[$key].UserName) $username = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR) # construct the credential object: $credential = [System.Management.Automation.PSCredential]::new($username, $hints[$key].Password) return $credential } } else { # ...else, remove the "!" at the beginning and prompt # again for the password (this way, passwords can be updated) $inputData = $inputData.SubString(1) # delete the cached credentials $hints.Clear() } # ask for a credential: $cred = $engineIntrinsics.Host.UI.PromptForCredential("Enter password", "Please enter user account and password", $inputData, "") # get the md5 key for the entered username $key = [AutoLearnCredentialAttribute]::GetHash($cred.UserName) # add username and password to the hashtable: $hints[$key] = @{ # save username as securestring to make sure it gets encrypted too: UserName = $cred.UserName | ConvertTo-SecureString -AsPlainText -Force Password = $cred.Password } # update the hashtable and write it to file # passwords are automatically safely encrypted: $hints | Export-Clixml -Path $hintPath # return the credential: return $cred } # if a credential was submitted... elseif ($inputData -is [PSCredential]) { # get the encrypted key for the entered username $key = [AutoLearnCredentialAttribute]::GetHash($inputData.UserName) # save it to the hashtable: $hints[$key] = @{ UserName = $inputData.UserName | ConvertTo-SecureString -AsPlainText -Force Password = $inputData.Password } # update the hashtable and write it to file: $hints | Export-Clixml -Path $hintPath # return the credential: return $inputData } throw [System.InvalidOperationException]::new('Unexpected error.') } } class AutocompleteCredentialAttribute : System.Management.Automation.ArgumentCompleterAttribute { [string]$Path = "$env:temp\hints" [string]$Id = 'default' AutocompleteCredentialAttribute() : base([AutocompleteCredentialAttribute]::_createScriptBlock($this)) {} AutocompleteCredentialAttribute([string]$Id) : base([AutocompleteCredentialAttribute]::_createScriptBlock($this)) { $this.Id = $Id } hidden static [ScriptBlock] _createScriptBlock([AutocompleteCredentialAttribute] $instance) { $scriptblock = { param($commandName, $parameterName, $wordToComplete, $commandAst, $fakeBoundParameters) $filename = '{0}.xmlhint' -f $instance.Id $hintPath = Join-Path -Path $instance.Path -ChildPath $filename $exists = Test-Path -Path $hintPath if ($exists) { # read serialized hint hashtable if it exists... [System.Collections.Hashtable]$hints = Import-Clixml -Path $hintPath # hint the sorted list of cached user names # take the serialized hashtables. We can no longer use the hashtable keys # because they are just MD5 hashes: $hints.Values | ForEach-Object { # decrypt encrypted username $BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($_.UserName) [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR) } | Where-Object { $_ } | # ...that still match the current user input: Where-Object { $_.LogName -like "$wordToComplete*" } | Sort-Object | # return completion results: Foreach-Object { [System.Management.Automation.CompletionResult]::new($_, $_, 'ParameterValue', $_) } } }.GetNewClosure() return $scriptblock } } |