Hash.Util.pp

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{   Renegade BBS                                        }

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{   _______                                  __         }
{  |   _   .-----.-----.-----.-----.---.-.--|  .-----.  }
{  |.  l   |  -__|     |  -__|  _  |  _  |  _  |  -__|  }
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{  |:  |   |                 |_____|                    }
{  |::.|:. |                                            }
{  `--- ---'                                            }
{*******************************************************}

unit Hash.Util;
{$codepage utf8}
{$h+}{$mode objfpc}

interface

type
  RTHashUtil = object
    public
      function HashEquals(KnownHash, CheckedHash : ansistring): boolean;static;
  end;

implementation

function RTHashUtil.HashEquals(KnownHash, CheckedHash : ansistring): boolean;
var
  HashCounter,
  ResultStatus : SizeInt;
begin
      ResultStatus := 0;
      if Length(KnownHash) <> Length(CheckedHash) then
        begin
          Result := False;
          Exit;
        end;
      for HashCounter := 1 to Length(KnownHash) do
      begin
        {
          From ext/standard/password.c php_password_verify line 244
          We're using this method instead of = in order to provide
          resistance towards timing attacks. This is a constant time
          equality check that will always check every byte of both
          values.

         }
         ResultStatus := ResultStatus or
         (ord(CheckedHash[HashCounter]) xor
         ord(KnownHash[HashCounter]));

      end;

      Result := (ResultStatus = 0);
end;

end.