Merge pull request #60 from EdwinDijkshoorn/PreventRangeCheckException

Prevent range check exception: while the original reporter still didn't provide any test data his changes to prevent this look unsuspicious so I take them now. But test data for this is still welcome!

Author: MHumm

NOTICE.txt

@@ -2,7 +2,7 @@ DEC - Delphi Encryption Compendium
 Version 6.5
 
 Copyright (c) 2018 - 2020 Norman Gallery (ng931884 [at] gmx [dot] de)
-Copyright (c) 2016 - 2022 Markus Humm (markus [dot] humm [at] googlemail [dot] com) (main contact)
+Copyright (c) 2016 - 2023 Markus Humm (markus [dot] humm [at] googlemail [dot] com) (main contact)
 Copyright (c) 2008 - 2019 Frederik A. Winkelsdorf (winkelsdorf [at] gmail [dot] com)
 Copyright (c) 1999 - 2008 Hagen Reddmann (HaReddmann [at] T-Online [dot] de)
 
@@ -27,6 +27,7 @@ Gloegg
 pierangelodalben
 denovosoftware
 alexrayne
+Stevie
 
 Parts of the work loosely based on the works of Wolfgang Erhardt, who is
 unfortunately dead already.

Source/DECCipherModesGCM.pas

@@ -608,7 +608,8 @@ procedure TGCM.DecodeGCM(Source, Dest: TBytes; Size: Integer);
   a_tag := XOR_T128(CalcGaloisHash(DataToAuthenticate, Source, Size), FE_K_Y0);
 
   Setlength(FCalcAuthenticationTag, FCalcAuthenticationTagLength);
-  Move(a_tag[0], FCalcAuthenticationTag[0], FCalcAuthenticationTagLength);
+  if (FCalcAuthenticationTagLength > 0) then
+	Move(a_tag[0], FCalcAuthenticationTag[0], FCalcAuthenticationTagLength);
 
   // Check for correct authentication result is in Done of DECCipherModes
   //  if not IsEqual(FExpectedAuthenticationTag, FCalcAuthenticationTag) then
@@ -646,7 +647,8 @@ procedure TGCM.EncodeGCM(Source, Dest: TBytes; Size: Integer);
 
   AuthTag := XOR_T128(CalcGaloisHash(DataToAuthenticate, Dest, Size), FE_K_Y0);
   Setlength(FCalcAuthenticationTag, FCalcAuthenticationTagLength);
-  Move(AuthTag[0], FCalcAuthenticationTag[0], FCalcAuthenticationTagLength);
+  if (FCalcAuthenticationTagLength > 0) then
+	Move(AuthTag[0], FCalcAuthenticationTag[0], FCalcAuthenticationTagLength);
 end;
 
 function TGCM.EncodeT128(Value: T128): T128;