Use DerParse instead of AsnParse

DerToEccSign.pas

procedure DerToEccSign(const algo: TCryptAsymAlgo; const sign_der: RawByteString;
  var sign: RawUtf8);
const
  DER_SEQUENCE = #$30;
  CAA_ECCBYTES: array[TCryptAsymAlgo] of Integer = (
    32, // caaES256
    48, // caaES384
    66, // caaES512
    32, // caaES256K
    0,  // caaRS256
    0,  // caaRS384
    0,  // caaRS512
    0,  // caaPS256
    0,  // caaPS384
    0,  // caaPS512
    32); // caaEdDSA
var
  derlen: Cardinal;
  der: PByteArray;
  eccbytes: Integer;
  buf: array [0..131] of AnsiChar;
  len: Integer;
begin
  if algo = caaEdDSA then
  begin
    sign := BinToBase64uri(pointer(sign_der), length(sign_der));
    exit;
  end;
  derlen := length(sign_der);
  der := PByteArray(sign_der);
  if (derlen < 50) or
     (der[0] <> ord(DER_SEQUENCE)) or
     (der[1] > derlen - 2) then
    exit;
  eccbytes := CAA_ECCBYTES[algo];
  if der[1] and $80 <> 0 then
  begin
    // 2-byte length
    assert((der[1] and $7f) = 1);
    len := der[2];
    if DerParse(DerParse(@der[3], @buf[0], eccbytes),
        @buf[eccbytes], eccbytes) <> PAnsiChar(@der[len + 3]) then
      exit;
  end
  else
  begin
    len := der[1];
    if DerParse(DerParse(@der[2], @buf[0], eccbytes),
        @buf[eccbytes], eccbytes) <> PAnsiChar(@der[len + 2]) then
      exit;
  end;
  sign := BinToBase64uri(@buf[0], eccbytes * 2);
end;