Kopierschutz

[Peter666]

Ich habe mich vorhin mal hingesetzt und angefangen einen alten Assemblersource für einen Junk Code Generator zu erstellen. Herausgekommen ist folgendes..

Code:

unit UJunkit;
interface
const
  ETG_MOVRR = $00000001;
  ETG_MOVRC = $00000002;
  ETG_MOVSXZX = $00000004;
  ETG_XCHG = $00000008;
  ETG_LEA = $00000010;
  ETG_TTTRR = $00000020;
  ETG_TTTRC = $00000040;
  ETG_INCDEC = $00000080;
  ETG_NOTNEG = $00000100;
  ETG_TESTRR = $00000200;
  ETG_TESTRC = $00000400;
  ETG_IMUL = $00000800;
  ETG_SHIFT = $00001000;
  ETG_SHxD = $00002000;
  ETG_BSWAP = $00004000;
  ETG_XADD = $00008000;
  ETG_BSx = $00010000;
  ETG_BTx = $00020000;
  ETG_JMPS = $00040000;
  ETG_SEG = $00080000;
  ETG_REP = $00100000;
  ETG_ALL = $001FFFFF;
  ETG_DEFAULT = ETG_TTTRC; // used if no cmds specified

  REG_EAX = $00000001;
  REG_ECX = $00000002;
  REG_EDX = $00000004;
  REG_EBX = $00000008;
  REG_ESP = $00000010;
  REG_EBP = $00000020;
  REG_ESI = $00000040;
  REG_EDI = $00000080;
  REG_ALL = (not REG_ESP) and $FF;
  REG_DEFAULT = REG_EAX; // used if no regs specified

procedure Junk(user_param, cmd_avail, regsrcavail,
  regdstavail: DWORD; out osizeptr: DWORD; ncmds, bufsize: DWORD;
  buf: Pointer);

implementation

type
  TRandomFunc = function(userdata, range: DWORD): DWORD; cdecl;

  TETG_Engine = procedure(
    user_param: DWORD; // user-parameter
    cmd_avail: DWORD; // set of ETG_xxx
    regsrcavail: DWORD; // set of REG_xxx
    regdstavail: DWORD; // set of REG_xxx
    out osizeptr: DWORD; // ptr to generated bufsize
    ncmds: DWORD; // max number of commands
    bufsize: DWORD; // max size of buffer
    buf: Pointer; // ptr to output buffer
    Random: TRandomFunc
    ); cdecl;

const
  ETG_bin: array[0..1139] of byte = (
    $C8, $50, $00, $00, $60, $8B, $7D, $24,
    $FC, $81, $65, $10, $EF, $00, $00, $00,
    $75, $07, $C7, $45, $10, $01, $00, $00,
    $00, $81, $65, $14, $EF, $00, $00, $00,
    $75, $07, $C7, $45, $14, $01, $00, $00,
    $00, $81, $65, $0C, $FF, $FF, $1F, $00,
    $75, $07, $C7, $45, $0C, $40, $00, $00,
    $00, $8B, $C7, $2B, $45, $24, $8B, $4D,
    $18, $89, $01, $83, $C0, $10, $3B, $45,
    $20, $73, $0C, $FF, $4D, $1C, $7C, $07,
    $E8, $05, $00, $00, $00, $EB, $E2, $61,
    $C9, $C3, $C7, $45, $FC, $01, $00, $00,
    $00, $C7, $45, $F8, $08, $00, $00, $00,
    $E8, $E4, $03, $00, $00, $89, $45, $C8,
    $C1, $E0, $03, $89, $45, $C4, $E8, $D1,
    $03, $00, $00, $89, $45, $C0, $C1, $E0,
    $03, $89, $45, $BC, $8B, $45, $14, $23,
    $45, $10, $A9, $0F, $00, $00, $00, $74,
    $13, $B8, $02, $00, $00, $00, $E8, $93,
    $03, $00, $00, $89, $45, $FC, $C1, $E0,
    $03, $89, $45, $F8, $B8, $02, $00, $00,
    $00, $E8, $80, $03, $00, $00, $89, $45,
    $DC, $D1, $E0, $89, $45, $D8, $C1, $E0,
    $02, $89, $45, $D4, $B8, $04, $00, $00,
    $00, $E8, $68, $03, $00, $00, $C1, $E0,
    $03, $89, $45, $D0, $E8, $70, $03, $00,
    $00, $C1, $E0, $03, $89, $45, $CC, $E8,
    $70, $03, $00, $00, $89, $45, $F4, $C1,
    $E0, $03, $89, $45, $E4, $E8, $62, $03,
    $00, $00, $89, $45, $EC, $E8, $5F, $03,
    $00, $00, $89, $45, $F0, $C1, $E0, $03,
    $89, $45, $E0, $E8, $51, $03, $00, $00,
    $89, $45, $E8, $E8, $4E, $03, $00, $00,
    $89, $45, $B8, $C1, $E0, $03, $89, $45,
    $B4, $E8, $40, $03, $00, $00, $89, $45,
    $B0, $B8, $1F, $00, $00, $00, $E8, $0B,
    $03, $00, $00, $96, $46, $8B, $55, $0C,
    $8B, $45, $FC, $D1, $EA, $73, $0E, $4E,
    $0F, $84, $27, $01, $00, $00, $4E, $0F,
    $84, $2D, $01, $00, $00, $D1, $EA, $73,
    $0E, $4E, $0F, $84, $2F, $01, $00, $00,
    $4E, $0F, $84, $36, $01, $00, $00, $D1,
    $EA, $73, $07, $4E, $0F, $84, $32, $01,
    $00, $00, $D1, $EA, $73, $07, $4E, $0F,
    $84, $47, $01, $00, $00, $D1, $EA, $73,
    $07, $4E, $0F, $84, $41, $01, $00, $00,
    $D1, $EA, $73, $0E, $4E, $0F, $84, $44,
    $01, $00, $00, $4E, $0F, $84, $45, $01,
    $00, $00, $D1, $EA, $73, $0E, $4E, $0F,
    $84, $42, $01, $00, $00, $4E, $0F, $84,
    $4C, $01, $00, $00, $D1, $EA, $73, $0E,
    $4E, $0F, $84, $59, $01, $00, $00, $4E,
    $0F, $84, $5F, $01, $00, $00, $D1, $EA,
    $73, $07, $4E, $0F, $84, $5E, $01, $00,
    $00, $D1, $EA, $73, $07, $4E, $0F, $84,
    $60, $01, $00, $00, $D1, $EA, $73, $07,
    $4E, $0F, $84, $62, $01, $00, $00, $D1,
    $EA, $73, $0E, $4E, $0F, $84, $65, $01,
    $00, $00, $4E, $0F, $84, $6E, $01, $00,
    $00, $D1, $EA, $73, $0E, $4E, $0F, $84,
    $70, $01, $00, $00, $4E, $0F, $84, $79,
    $01, $00, $00, $D1, $EA, $73, $0E, $4E,
    $0F, $84, $7F, $01, $00, $00, $4E, $0F,
    $84, $97, $01, $00, $00, $D1, $EA, $73,
    $07, $4E, $0F, $84, $A4, $01, $00, $00,
    $D1, $EA, $73, $07, $4E, $0F, $84, $A0,
    $01, $00, $00, $D1, $EA, $73, $07, $4E,
    $0F, $84, $A3, $01, $00, $00, $D1, $EA,
    $73, $0E, $4E, $0F, $84, $A6, $01, $00,
    $00, $4E, $0F, $84, $B0, $01, $00, $00,
    $D1, $EA, $73, $07, $4E, $0F, $84, $B0,
    $01, $00, $00, $D1, $EA, $73, $0E, $4E,
    $0F, $84, $B7, $01, $00, $00, $4E, $0F,
    $84, $B7, $01, $00, $00, $D1, $EA, $73,
    $07, $4E, $0F, $84, $B3, $01, $00, $00,
    $E9, $BC, $FE, $FF, $FF, $0C, $88, $AA,
    $B0, $C0, $0B, $45, $E4, $0B, $45, $F0,
    $AA, $C3, $0C, $8A, $AA, $B0, $C0, $0B,
    $45, $E0, $0B, $45, $F4, $AA, $C3, $B0,
    $B0, $0B, $45, $F8, $0B, $45, $F0, $AA,
    $E9, $8D, $01, $00, $00, $0C, $C6, $AA,
    $B0, $C0, $EB, $F0, $B0, $0F, $AA, $B0,
    $B6, $0B, $45, $FC, $0B, $45, $D4, $AA,
    $B0, $C0, $0B, $45, $C4, $EB, $D3, $0C,
    $86, $AA, $B0, $C0, $0B, $45, $E0, $0B,
    $45, $E8, $AA, $C3, $0C, $86, $AA, $EB,
    $F1, $B0, $8D, $AA, $B0, $05, $0B, $45,
    $C4, $AA, $E9, $59, $01, $00, $00, $0C,
    $00, $0B, $45, $CC, $AA, $EB, $99, $0C,
    $02, $0B, $45, $CC, $AA, $EB, $9E, $0C,
    $80, $AA, $B0, $C0, $0B, $45, $CC, $0B,
    $45, $F0, $AA, $E9, $32, $01, $00, $00,
    $F7, $45, $14, $01, $00, $00, $00, $0F,
    $84, $2C, $FE, $FF, $FF, $0C, $04, $0B,
    $45, $CC, $AA, $E9, $1A, $01, $00, $00,
    $0C, $FE, $AA, $B0, $C0, $0B, $45, $D4,
    $E9, $60, $FF, $FF, $FF, $B0, $40, $0B,
    $45, $D4, $0B, $45, $C8, $AA, $C3, $0C,
    $F6, $AA, $B0, $D0, $0B, $45, $D4, $E9,
    $49, $FF, $FF, $FF, $0C, $84, $AA, $B0,
    $C0, $0B, $45, $B4, $0B, $45, $B0, $AA,
    $C3, $0C, $F6, $AA, $B0, $C0, $0B, $45,
    $B8, $AA, $E9, $DB, $00, $00, $00, $B0,
    $0F, $AA, $B0, $AF, $AA, $B0, $C0, $0B,
    $45, $C4, $0B, $45, $C0, $AA, $C3, $B0,
    $69, $AA, $E8, $EE, $FF, $FF, $FF, $E9,
    $C4, $00, $00, $00, $0C, $D0, $0B, $45,
    $D8, $AA, $B0, $C0, $0B, $45, $CC, $0B,
    $45, $F0, $AA, $C3, $0C, $C0, $AA, $B0,
    $C0, $0B, $45, $CC, $0B, $45, $F0, $AA,
    $E9, $AD, $00, $00, $00, $B0, $0F, $AA,
    $B0, $A4, $0B, $45, $D4, $AA, $B0, $C0,
    $E8, $05, $00, $00, $00, $E9, $98, $00,
    $00, $00, $B0, $C0, $0B, $45, $BC, $0B,
    $45, $C8, $AA, $C3, $F7, $45, $10, $02,
    $00, $00, $00, $0F, $84, $78, $FD, $FF,
    $FF, $B0, $0F, $AA, $B0, $A5, $0B, $45,
    $D4, $AA, $EB, $DE, $B0, $0F, $AA, $B0,
    $C8, $EB, $DC, $B0, $0F, $AA, $B0, $C0,
    $0B, $45, $FC, $AA, $E9, $E1, $FE, $FF,
    $FF, $B0, $0F, $AA, $B0, $BC, $0B, $45,
    $DC, $AA, $E9, $6E, $FF, $FF, $FF, $B0,
    $0F, $AA, $B0, $BA, $AA, $B0, $E0, $0B,
    $45, $D0, $0B, $45, $C8, $AA, $EB, $42,
    $B0, $0F, $AA, $B0, $A3, $0B, $45, $D0,
    $AA, $EB, $9F, $66, $B8, $EB, $01, $66,
    $AB, $B8, $00, $01, $00, $00, $E8, $33,
    $00, $00, $00, $AA, $C3, $B0, $26, $0B,
    $45, $D0, $AA, $C3, $B0, $64, $0B, $45,
    $DC, $AA, $C3, $B0, $F2, $0B, $45, $DC,
    $AA, $C3, $83, $7D, $FC, $00, $74, $0A,
    $E8, $00, $00, $00, $00, $E8, $00, $00,
    $00, $00, $B8, $00, $01, $00, $00, $E8,
    $02, $00, $00, $00, $AA, $C3, $60, $50,
    $FF, $75, $08, $FF, $55, $28, $83, $C4,
    $08, $89, $44, $24, $1C, $61, $0B, $C0,
    $C3, $B8, $08, $00, $00, $00, $E8, $E3,
    $FF, $FF, $FF, $C3, $8B, $55, $10, $EB,
    $0D, $8B, $55, $14, $EB, $08, $8B, $55,
    $10, $0B, $55, $14, $EB, $00, $E8, $DE,
    $FF, $FF, $FF, $8B, $C8, $83, $7D, $FC,
    $00, $75, $03, $83, $E1, $03, $0F, $A3,
    $CA, $73, $EB, $C3);

var randseed: DWORD;

function MyRandom(userdata, range: DWORD): DWORD; cdecl;
begin
  if range = 0 then result := 0 else
  begin
    randseed := randseed * 214013 + 2531011;
    result := randseed mod range;
  end;
end;

procedure Junk(user_param, cmd_avail, regsrcavail,
  regdstavail: DWORD; out osizeptr: DWORD; ncmds, bufsize: DWORD;
  buf: Pointer);
begin
  randseed := GetTickCount;
  TETG_Engine(@ETG_bin)(user_param, cmd_avail, regsrcavail, regdstavail,
    osizeptr, ncmds, bufsize, buf, MyRandom);
  PAnsiChar(buf)[osizeptr] := #$C3; {ret} inc(osizeptr);
end;

Ich war ehrlich gesagt etwas Faul und habe nicht den Assemblercode (Quelle: ETG 2.00 engine) übersetzt, sondern nur das beiliegende C Beispiel umgesetzt.
Soweit erstellt die Anwendung recht praktischen Datenmüll, wenn ich das wie folgt aufrufe
var
buf: Array[0..2000] of byte;

Junk(
0,
ETG_ALL,
REG_ALL,
REG_EAX or REG_EBX,
bufsize,
1000,
sizeof(buf),
@buf);

Damit man den Code via call auch aufrufen kann, sollte am Ende des Puffers, also bei buf[bufsize] noch ein $C3 (ret) gepackt werden.
Mein Problem ist jedoch folgendes: Wenn ich innerhalb meiner Anwendung etwas wie folgt mache:

db $90,$90...$90

und mit meinem Patchtool in der Exe die Nops durch den Junkcode ersetze, müsste ich doch die Register vorher und hinterher manuell wiederherstellen, oder? Ein einfaches Pusha, popa reicht jedoch in dem Fall nicht. Hat da jemand eventuell eine Idee?

Peter

[Assarbad]

Zitat von Peter666:

Damit man den Code via call auch aufrufen kann, sollte am Ende des Puffers, also bei buf[bufsize] noch ein $C3 (ret) gepackt werden.
Mein Problem ist jedoch folgendes: Wenn ich innerhalb meiner Anwendung etwas wie folgt mache:

db $90,$90...$90

und mit meinem Patchtool in der Exe die Nops durch den Junkcode ersetze, müsste ich doch die Register vorher und hinterher manuell wiederherstellen, oder? Ein einfaches Pusha, popa reicht jedoch in dem Fall nicht. Hat da jemand eventuell eine Idee?

Was soll das bringen? Das ist doch dann sehr leicht durchschaubar. Da kann man direkt ein Python oder IDC-Skript für IDA schreiben und es filtern. Selbst ohne Filtern kann ich mir den Stackpointer ja anzeigen lassen.

PUSHA und POPA werden übrigens in "echtem Code" (also von Compilern) eher selten eingesetzt, würden also geradezu herausstehen.

[Peter666]

Ja, schon klar aber so ein Garbage code in bestimmte Funktionen gebaut, erschwehrt das Lesen im Debugger ungemein.

[OldGrumpy]

Ja aber nur so lange bis man via Script den Junk ausgefiltert hat. Wer halbwegs oft mit obfuskiertem Code zu tun hat, macht das aus dem Handgelenk, irgendwann bekommt man auch ein Auge für Junkcode und sieht sehr schnell was Sache ist.