<# .SYNOPSIS decrypt-file.ps1 [] [] .DESCRIPTION Decrypts the given file .EXAMPLE PS> ./decrypt-file-rules C:\MyFile.txt "123" .NOTES Author: Markus Fleschutz · License: CC0 .LINK https://github.com/fleschutz/PowerShell #> param([string]$Path = "", [string]$Password = "") function DecryptFile { <# .SYNOPSIS Decrypts a file encrypted with Protect-File. .DESCRIPTION Decrypts a file using a provided cryptography key. .PARAMETER FileName File(s) to be decrypted. .PARAMETER Key Cryptography key as a SecureString be used for decryption. .PARAMETER KeyAsPlainText Cryptography key as a String to be used for decryption. .PARAMETER CipherMode Specifies the block cipher mode that was used for encryption. .PARAMETER PaddingMode Specifies the type of padding that was applied when the message data block was shorter than the full number of bytes needed for a cryptographic operation. .PARAMETER Suffix Suffix of the encrypted file to be removed. .PARAMETER RemoveSource Removes the source (encrypted) file after decrypting. .OUTPUTS System.IO.FileInfo. Unprotect-File will return FileInfo with the SourceFile as an added NoteProperty #> [CmdletBinding(DefaultParameterSetName='SecureString')] [OutputType([System.IO.FileInfo[]])] Param( [Parameter(Mandatory=$true, Position=1, ValueFromPipeline=$true, ValueFromPipelineByPropertyName=$true)] [Alias('PSPath','LiteralPath')] [string[]]$FileName, [Parameter(Mandatory=$false, Position=2, ValueFromPipelineByPropertyName=$true)] [ValidateSet('AES','DES','RC2','Rijndael','TripleDES')] [String]$Algorithm = 'AES', [Parameter(Mandatory=$true, Position=3, ValueFromPipelineByPropertyName=$true, ParameterSetName='SecureString')] [System.Security.SecureString]$Key, [Parameter(Mandatory=$true, Position=3, ParameterSetName='PlainText')] [String]$KeyAsPlainText, [Parameter(Mandatory=$false, Position=4, ValueFromPipelineByPropertyName=$true)] [System.Security.Cryptography.CipherMode]$CipherMode = 'CBC', [Parameter(Mandatory=$false, Position=5, ValueFromPipelineByPropertyName=$true)] [System.Security.Cryptography.PaddingMode]$PaddingMode = 'PKCS7', [Parameter(Mandatory=$false, Position=6)] [String]$Suffix, [Parameter()] [Switch]$RemoveSource ) Process { try { if($PSCmdlet.ParameterSetName -eq 'PlainText') { $Key = $KeyAsPlainText | ConvertTo-SecureString -AsPlainText -Force } $BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($Key) $EncryptionKey = [System.Convert]::FromBase64String([System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR)) $Crypto = [System.Security.Cryptography.SymmetricAlgorithm]::Create($Algorithm) $Crypto.Mode = $CipherMode $Crypto.Padding = $PaddingMode $Crypto.KeySize = $EncryptionKey.Length*8 $Crypto.Key = $EncryptionKey } Catch { Write-Error $_ -ErrorAction Stop } if(-not $PSBoundParameters.ContainsKey('Suffix')) { $Suffix = ".$Algorithm" } $Files = Get-Item -LiteralPath $FileName ForEach($File in $Files) { If(-not $File.Name.EndsWith($Suffix)) { Write-Error "$($File.FullName) does not have an extension of '$Suffix'." Continue } $DestinationFile = $File.FullName -replace "$Suffix$" Try { $FileStreamReader = New-Object System.IO.FileStream($File.FullName, [System.IO.FileMode]::Open) $FileStreamWriter = New-Object System.IO.FileStream($DestinationFile, [System.IO.FileMode]::Create) [Byte[]]$LenIV = New-Object Byte[] 4 $FileStreamReader.Seek(0, [System.IO.SeekOrigin]::Begin) | Out-Null $FileStreamReader.Read($LenIV, 0, 3) | Out-Null [Int]$LIV = [System.BitConverter]::ToInt32($LenIV, 0) [Byte[]]$IV = New-Object Byte[] $LIV $FileStreamReader.Seek(4, [System.IO.SeekOrigin]::Begin) | Out-Null $FileStreamReader.Read($IV, 0, $LIV) | Out-Null $Crypto.IV = $IV $Transform = $Crypto.CreateDecryptor() $CryptoStream = New-Object System.Security.Cryptography.CryptoStream($FileStreamWriter, $Transform, [System.Security.Cryptography.CryptoStreamMode]::Write) $FileStreamReader.CopyTo($CryptoStream) $CryptoStream.FlushFinalBlock() $CryptoStream.Close() $FileStreamReader.Close() $FileStreamWriter.Close() if($RemoveSource){Remove-Item $File.FullName} Get-Item $DestinationFile | Add-Member –MemberType NoteProperty –Name SourceFile –Value $File.FullName -PassThru } Catch { Write-Error $_ If($FileStreamWriter) { $FileStreamWriter.Close() Remove-Item -LiteralPath $DestinationFile -Force } Continue } Finally { if($CryptoStream){$CryptoStream.Close()} if($FileStreamReader){$FileStreamReader.Close()} if($FileStreamWriter){$FileStreamWriter.Close()} } } } } try { if ($Path -eq "" ) { $Path = read-host "Enter path to file" } if ($Password -eq "" ) { $Password = read-host "Enter password" } $PasswordBase64 = [System.Convert]::ToBase64String($Password) DecryptFile "$Path" -algorithm AES -keyAsPlainText $PasswordBase64 -removeSource "✔️ Done." exit 0 } catch { "⚠️ Error: $($Error[0]) ($($MyInvocation.MyCommand.Name):$($_.InvocationInfo.ScriptLineNumber))" exit 1 }