SecureString.pas

{******************************************************************************}
{*  ISecureString                                                             *}
{*                                                                            *}
{*  Created by Stefan van As <dutchdelphidude@gmail.com>                      *}
{*                                                                            *}
{*  DISCLAIMER                                                                *}
{*                                                                            *}
{*  This software is provided 'as is' with no explicit or implied warranties  *}
{*  in respect of its properties, including, but not limited to, correctness  *}
{*  and/or fitness for purpose.                                               *}
{******************************************************************************}

unit SecureString;

interface

type
  ISecureString = interface
    function Data: string;
    function Length: Integer;
  end;

function NewSecureString(const S: string): ISecureString;

implementation

uses
  Windows;

{ TSecureString }

type
  TSecureString = class(TInterfacedObject, ISecureString)
  strict private
    FData: string;
  public
    constructor Create(const Value: string);
    destructor Destroy; override;
    function Data: string;
    function Length: Integer;
  end;

constructor TSecureString.Create(const Value: string);
begin
  inherited Create;
  SetString(FData, PChar(Value), System.Length(Value));
end;

destructor TSecureString.Destroy;
var
  I: Integer;
begin
  if System.Length(FData) > 0 then
  begin
    I := PInteger(PByte(FData) - 8)^;
    if (I > -1) and (I < 2) then
      ZeroMemory(Pointer(FData), System.Length(FData) * SizeOf(Char));
  end;
  inherited Destroy;
end;

function TSecureString.Data: string;
begin
  Result := FData;
end;

function TSecureString.Length: Integer;
begin
  Result := System.Length(FData);
end;

function NewSecureString(const S: string): ISecureString;
var
  I: Integer;
begin
  Result := TSecureString.Create(S);
  if System.Length(S) > 0 then
  begin
    I := PInteger(PByte(S) - 8)^;
    if (I > -1) and (I < 2) then
      ZeroMemory(Pointer(S), System.Length(S) * SizeOf(Char));
  end;
end;

end.