Byte order and TLbBigInt

[1one-w01f]

Hi,

I am trying to use the RSA module to do some signature verification, and I found that the byte order of TLbBigInt to be kind of funny.

If I do this to load pubkey.der which was generated using OpenSSL,

pubKey := TLbRSAKey.Create(aks1024);
pubKey.LoadFromFile('pubkey.der');

then the modular exponentiation seems to be wrong. Somehow I had to reverse the byte order of the modulus to make it working.

However, even if the modular exponentiation works, the signature verification cannot succeed, because at line 688 of LbRSA.pas, the byte orders of SHA1Digest1 and SHA1Digest2 are reverse of each other (I checked the Local Variables by using adding a breakpoint there), and thus Result will be False.

Any thoughts on this?

[1one-w01f]

If it'd help, here's the source code I used to do the testing. I used Delphi 10.3 Community Edition, and got LockBox installed through the GetIt Package Manager, in case it matters.

program Project2;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils, LbRSA, LbAsym, LbBigInt, LbUtils, System.Classes, LbConst;

var
  i: integer;

  pubKey: TLbRSAKey;
  privKey: TLbRSAKey;

  ssa: TLbRSASSA;

  sig: TRSASignatureBlock;
  revsig: TRSASignatureBlock;

  sighexstr: String;

  result: Boolean;

  n: array[0..cBytes1024-1] of Byte = ($bf,$1a,$f5,$1e,$6a,$7b,$5d,$93,$29,$8e,$f9,$e8,$59,$1d,$01,$e4,$c6,$5b,$3f,$60,$00,$16,$00,$73,$fa,$01,$94,$fa,$24,$09,$70,$27,$fc,$5d,$18,$8f,$69,$53,$c3,$77,$47,$c6,$65,$1c,$32,$ca,$f4,$4e,$9f,$54,$97,$06,$fd,$c2,$54,$eb,$0a,$36,$66,$36,$29,$8d,$9d,$b8,$1d,$17,$82,$76,$7b,$07,$db,$87,$a1,$9d,$a9,$1e,$f2,$0e,$d7,$05,$13,$ed,$90,$df,$f1,$a2,$7d,$dc,$02,$0c,$cb,$ce,$b3,$d1,$14,$25,$b7,$43,$a7,$33,$99,
  $6d,$a2,$6d,$6f,$bb,$78,$3b,$e0,$b7,$3f,$a3,$9c,$fe,$eb,$94,$fa,$df,$8c,$35,$36,$44,$b1,$ad,$67,$99,$ce,$9f);
  n_rev: array[0..cBytes1024-1] of Byte;

  e: array[0..0] of Byte = ($03);

begin

  // let's reverse the modulus n
  for i := 0 to cBytes1024-1 do
    n_rev[cBytes1024-1-i] := n[i];

  pubKey := TLbRSAKey.Create(aks1024);
//  pubKey.LoadFromFile('pubkey.der');
  pubKey.Modulus.CopyBuffer(n_rev, cBytes1024);
  pubKey.Exponent.CopyBuffer(e, 1);
  Writeln('pubkey loaded');

  ssa := TlbRSASSA.Create(nil);
  ssa.PublicKey.Assign(pubKey);
  Writeln('pubkey.n = ' + ssa.PublicKey.ModulusAsString);
  Writeln('pubkey.e = ' + ssa.PublicKey.ExponentAsString);

  ssa.HashMethod := hmSHA1;

  sighexstr := '024f9b63004472a035bf6d7dd77247f45b3df6e1d0860ea91000fcba21616bb95a06c128df0c2dda0bec4c7efb559b6cb020e675ef836fb468780905efc8c296' +
'95b03df88d870b84c80e851fcbad53f28c20fda9f1ec8d2a8ffd6648717140fe779c0de58704941fae9f3ac0cf4f6b3f080dd4725ac13fe2d240752f280b671b' ;
  HexToBin(PChar(sighexstr), @sig, length(sig));

  // now let's reverse sig as well ...
  for i := 0 to cBytes1024-1 do
    revsig[cBytes1024-1-i] := sig[i];

  ssa.Signature.CopyBuffer(revsig, length(revsig));


  result := ssa.VerifyString('hello world!');
  Writeln(result);


  Readln(Input);
end.

[romankassebaum]

I have absolutely no idea. It would be nice if you could fix this.