Olive.Random/Olive.Random.URandom.pas

{********************************************************}
{                                                        }
{   Olive BBS                                            }
{                                                        }
{   Copyleft (ↄ) 2020 Olive BBS                          }
{                                                        }
{   This file is part of Olive BBS                       }
{                                                        }
{   Olive BBS is free software: you can redistribute it  }
{   and/or modify it under the terms of the GNU General  }
{   Public License as published by the Free Software     }
{   Foundation, either version 3 of the License, or      }
{   (at your option) any later version.                  }
{                                                        }
{   Olive BBS is distributed in the hope that it will    }
{   be useful, but WITHOUT ANY WARRANTY; without even    }
{   the implied warranty of MERCHANTABILITY or FITNESS   }
{   FOR A PARTICULAR PURPOSE.  See the GNU General       }
{   Public License for more details.                     }
{                                                        }
{   You should have received a copy of the GNU General   }
{   Public License along with Olive BBS.  If not, see    }
{   <http://www.gnu.org/licenses/>.                      }
{                                                        }
{********************************************************}
{        ___                   ___    ___                }
{       (   ).-.              (   )  (   )               }
{   .--. | |( __)___  ___ .--. | |.-. | |.-.     .--.    }
{  /    \| |(''"(   )(   /    \| /   \| /   \  /  _  \   }
{ |  .-. | | | | | |  | |  .-. |  .-. |  .-. |. .' `. ;  }
{ | |  | | | | | | |  | |  | | | |  | | |  | || '   | |  }
{ | |  | | | | | | |  | |  |/  | |  | | |  | |_\_`.(___) }
{ | |  | | | | | | |  | |  ' _.| |  | | |  | (   ). '.   }
{ | '  | | | | | ' '  ; |  .'.-| '  | | '  | || |  `\ |  }
{ '  `-' | | | |  \ `' /'  `-' ' `-' ;' `-' ; ; '._,' '  }
{  `.__.(___(___)  '_.'  `.__.' `.__.  `.__.   '.___.'   }
{                                                        }
{********************************************************}

{$mode objfpc}{$H+}
Unit Olive.Random.URandom;

interface

uses
  CTypes,
  Objects,
  Classes,
  SysUtils,
  Olive.Random.RandomInterface;

const
  {$IF DEFINED(CPU64)} SYS_getrandom = 318;
  {$ELSEIF DEFINED(CPU32)} SYS_getrandom = 355;
  {$ELSE} SYS_getrandom = 278; {$ENDIF}
  GRND_DEFAULT = $0000;

type
  PCChar = ^CChar;
  PURandom = ^URandom;
  URandom = class (RandomTrait, RandomInterface)
    private
      function GetSystemBytes(var RandomByteBuffer : TBytes; NBytes : SizeUint) : CInt;
    public
      function GetBytes(NBytes : SizeUInt) : TBytes;
      function GetString(NBytes : SizeUInt) : AnsiString;
  end;

function syscall(NRGetRandom : CInt) : CInt;cdecl;varargs;external 'c' name 'syscall';

implementation

function URandom.GetSystemBytes(var RandomByteBuffer : TBytes; NBytes : SizeUint) : CInt;
var
  RandomCharBuffer : PCChar;
  Return : CInt;
begin
  GetMem(RandomCharBuffer, NBytes);
  Return := syscall(SYS_getrandom, @RandomCharBuffer^, NBytes, GRND_DEFAULT);
  Move(RandomCharBuffer[0], RandomByteBuffer[0], NBytes);
  FreeMem(RandomCharBuffer);
  Result := Return;
end;

function URandom.GetBytes(NBytes : SizeUInt) : TBytes;
var
  RandomBuffer : AnsiString;
begin
  SetLength(Result, NBytes);
  SetLength(RandomBuffer, NBytes);
  RandomBuffer := GetString(NBytes);
  Move(RandomBuffer[1], Result[0], NBytes);
end;

function URandom.GetString(NBytes : SizeUInt) : AnsiString;
var
  Buffer : TFileStream;
  RandomByteBuffer : TBytes;
  ReadBytes : SizeUInt;
  SysBytesRead : CInt;
begin
  SetLength(RandomByteBuffer, (NBytes*2));
  SetLength(Result, NBytes);
  SysBytesRead := GetSystemBytes(RandomByteBuffer, (NBytes*2));
  if (SysBytesRead <> (NBytes*2)) then
    begin
      if FileExists('/dev/urandom') then
        begin
          Buffer := TFileStream.Create('/dev/urandom', fmOpenRead);
          Buffer.Position := 0;
          ReadBytes := 0;
          while ReadBytes <= (NBytes*2) do
            begin
              Buffer.Read(RandomByteBuffer[ReadBytes], SizeOf(RandomByteBuffer));
              Inc(ReadBytes);
            end;
          Buffer.Free;
        end
        else if (not FileExists('/dev/udrandom')) then
        begin
            RandomByteBuffer := MTRandomBytes((NBytes*2));
        end else
        begin
          raise Exception.Create('All methods to aquire random bytes failed.')
            at get_caller_addr(get_frame), get_caller_frame(get_frame);
        end;
    end;
  Move(RandomByteBuffer[0], Result[1], NBytes);
end;

end.