Integerüberlauf bei MD5-Berechnung

[BasilBavaria]

Hai!

Immer wenn es mal schnell gehen muß ...

Hab hier folgende MD5.pas gefunden und ins Programm eingebunden:

Code:

// -----------------------------------------------------------------------------------------------
//
//                                 MD5 Message-Digest for Delphi 4
//
//                                 Delphi 4 Unit implementing the
//                      RSA Data Security, Inc. MD5 Message-Digest Algorithm
//
//                          Implementation of Ronald L. Rivest's RFC 1321
//
//                      Copyright © 1997-1999 Medienagentur Fichtner & Meyer
//                                  Written by Matthias Fichtner
//
// -----------------------------------------------------------------------------------------------
//               See RFC 1321 for RSA Data Security's copyright and license notice!
// -----------------------------------------------------------------------------------------------
//
//     14-Jun-97  mf  Implemented MD5 according to RFC 1321                           RFC 1321
//     16-Jun-97  mf  Initial release of the compiled unit (no source code)           RFC 1321
//     28-Feb-99  mf  Added MD5Match function for comparing two digests               RFC 1321
//     13-Sep-99  mf  Reworked the entire unit                                        RFC 1321
//     17-Sep-99  mf  Reworked the "Test Driver" project                              RFC 1321
//     19-Sep-99  mf  Release of sources for MD5 unit and "Test Driver" project       RFC 1321
//
// -----------------------------------------------------------------------------------------------
//                   The latest release of md5.pas will always be available from
//                  the distribution site at: http://www.fichtner.net/delphi/md5/
// -----------------------------------------------------------------------------------------------
//                       Please send questions, bug reports and suggestions
//                      regarding this code to: [e-mail]
// -----------------------------------------------------------------------------------------------
//                        This code is provided "as is" without express or
//                     implied warranty of any kind. Use it at your own risk.
// -----------------------------------------------------------------------------------------------

unit md5;

// -----------------------------------------------------------------------------------------------
INTERFACE
// -----------------------------------------------------------------------------------------------

uses
   Windows;

type
   MD5Count = array[0..1] of DWORD;
   MD5State = array[0..3] of DWORD;
   MD5Block = array[0..15] of DWORD;
   MD5CBits = array[0..7] of byte;
   MD5Digest = array[0..15] of byte;
   MD5Buffer = array[0..63] of byte;
   MD5Context = record
      State: MD5State;
      Count: MD5Count;
      Buffer: MD5Buffer;
   end;

procedure MD5Init(var Context: MD5Context);
procedure MD5Update(var Context: MD5Context; Input: pChar; Length: longword);
procedure MD5Final(var Context: MD5Context; var Digest: MD5Digest);

function MD5String(M: string): MD5Digest;
function MD5File(N: string): MD5Digest;
function MD5Print(D: MD5Digest): string;

function MD5Match(D1, D2: MD5Digest): boolean;

// -----------------------------------------------------------------------------------------------
IMPLEMENTATION
// -----------------------------------------------------------------------------------------------

var
   PADDING: MD5Buffer = (
      $80, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00,
      $00, $00, $00, $00, $00, $00, $00, $00
   );

function F(x, y, z: DWORD): DWORD;
begin
   Result := (x and y) or ((not x) and z);
end;

function G(x, y, z: DWORD): DWORD;
begin
   Result := (x and z) or (y and (not z));
end;

function H(x, y, z: DWORD): DWORD;
begin
   Result := x xor y xor z;
end;

function I(x, y, z: DWORD): DWORD;
begin
   Result := y xor (x or (not z));
end;

procedure rot(var x: DWORD; n: BYTE);
begin
   x := (x shl n) or (x shr (32 - n));
end;

procedure FF(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
   inc(a, F(b, c, d) + x + ac);
   rot(a, s);
   inc(a, b);
end;

procedure GG(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
   inc(a, G(b, c, d) + x + ac);
   rot(a, s);
   inc(a, b);
end;

procedure HH(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
   inc(a, H(b, c, d) + x + ac);
   rot(a, s);
   inc(a, b);
end;

procedure II(var a: DWORD; b, c, d, x: DWORD; s: BYTE; ac: DWORD);
begin
   inc(a, I(b, c, d) + x + ac);
   rot(a, s);
   inc(a, b);
end;

// -----------------------------------------------------------------------------------------------

// Encode Count bytes at Source into (Count / 4) DWORDs at Target
procedure Encode(Source, Target: pointer; Count: longword);
var
   S: PByte;
   T: PDWORD;
   I: longword;
begin
   S := Source;
   T := Target;
   for I := 1 to Count div 4 do begin
      T^ := S^;
      inc(S);
      T^ := T^ or (S^ shl 8);
      inc(S);
      T^ := T^ or (S^ shl 16);
      inc(S);
      T^ := T^ or (S^ shl 24);
      inc(S);
      inc(T);
   end;
end;

// Decode Count DWORDs at Source into (Count * 4) Bytes at Target
procedure Decode(Source, Target: pointer; Count: longword);
var
   S: PDWORD;
   T: PByte;
   I: longword;
begin
   S := Source;
   T := Target;
   for I := 1 to Count do begin
      T^ := S^ and $ff;
      inc(T);
      T^ := (S^ shr 8) and $ff;
      inc(T);
      T^ := (S^ shr 16) and $ff;
      inc(T);
      T^ := (S^ shr 24) and $ff;
      inc(T);
      inc(S);
   end;
end;

// Transform State according to first 64 bytes at Buffer
procedure Transform(Buffer: pointer; var State: MD5State);
var
   a, b, c, d: DWORD;
   Block: MD5Block;
begin
   Encode(Buffer, @Block, 64);
   a := State[0];
   b := State[1];
   c := State[2];
   d := State[3];
   FF (a, b, c, d, Block[ 0],  7, $d76aa478);
   FF (d, a, b, c, Block[ 1], 12, $e8c7b756);
   FF (c, d, a, b, Block[ 2], 17, $242070db);
   FF (b, c, d, a, Block[ 3], 22, $c1bdceee);
   FF (a, b, c, d, Block[ 4],  7, $f57c0faf);
   FF (d, a, b, c, Block[ 5], 12, $4787c62a);
   FF (c, d, a, b, Block[ 6], 17, $a8304613);
   FF (b, c, d, a, Block[ 7], 22, $fd469501);
   FF (a, b, c, d, Block[ 8],  7, $698098d8);
   FF (d, a, b, c, Block[ 9], 12, $8b44f7af);
   FF (c, d, a, b, Block[10], 17, $ffff5bb1);
   FF (b, c, d, a, Block[11], 22, $895cd7be);
   FF (a, b, c, d, Block[12],  7, $6b901122);
   FF (d, a, b, c, Block[13], 12, $fd987193);
   FF (c, d, a, b, Block[14], 17, $a679438e);
   FF (b, c, d, a, Block[15], 22, $49b40821);
   GG (a, b, c, d, Block[ 1],  5, $f61e2562);
   GG (d, a, b, c, Block[ 6],  9, $c040b340);
   GG (c, d, a, b, Block[11], 14, $265e5a51);
   GG (b, c, d, a, Block[ 0], 20, $e9b6c7aa);
   GG (a, b, c, d, Block[ 5],  5, $d62f105d);
   GG (d, a, b, c, Block[10],  9,  $2441453);
   GG (c, d, a, b, Block[15], 14, $d8a1e681);
   GG (b, c, d, a, Block[ 4], 20, $e7d3fbc8);
   GG (a, b, c, d, Block[ 9],  5, $21e1cde6);
   GG (d, a, b, c, Block[14],  9, $c33707d6);
   GG (c, d, a, b, Block[ 3], 14, $f4d50d87);
   GG (b, c, d, a, Block[ 8], 20, $455a14ed);
   GG (a, b, c, d, Block[13],  5, $a9e3e905);
   GG (d, a, b, c, Block[ 2],  9, $fcefa3f8);
   GG (c, d, a, b, Block[ 7], 14, $676f02d9);
   GG (b, c, d, a, Block[12], 20, $8d2a4c8a);
   HH (a, b, c, d, Block[ 5],  4, $fffa3942);
   HH (d, a, b, c, Block[ 8], 11, $8771f681);
   HH (c, d, a, b, Block[11], 16, $6d9d6122);
   HH (b, c, d, a, Block[14], 23, $fde5380c);
   HH (a, b, c, d, Block[ 1],  4, $a4beea44);
   HH (d, a, b, c, Block[ 4], 11, $4bdecfa9);
   HH (c, d, a, b, Block[ 7], 16, $f6bb4b60);
   HH (b, c, d, a, Block[10], 23, $bebfbc70);
   HH (a, b, c, d, Block[13],  4, $289b7ec6);
   HH (d, a, b, c, Block[ 0], 11, $eaa127fa);
   HH (c, d, a, b, Block[ 3], 16, $d4ef3085);
   HH (b, c, d, a, Block[ 6], 23,  $4881d05);
   HH (a, b, c, d, Block[ 9],  4, $d9d4d039);
   HH (d, a, b, c, Block[12], 11, $e6db99e5);
   HH (c, d, a, b, Block[15], 16, $1fa27cf8);
   HH (b, c, d, a, Block[ 2], 23, $c4ac5665);
   II (a, b, c, d, Block[ 0],  6, $f4292244);
   II (d, a, b, c, Block[ 7], 10, $432aff97);
   II (c, d, a, b, Block[14], 15, $ab9423a7);
   II (b, c, d, a, Block[ 5], 21, $fc93a039);
   II (a, b, c, d, Block[12],  6, $655b59c3);
   II (d, a, b, c, Block[ 3], 10, $8f0ccc92);
   II (c, d, a, b, Block[10], 15, $ffeff47d);
   II (b, c, d, a, Block[ 1], 21, $85845dd1);
   II (a, b, c, d, Block[ 8],  6, $6fa87e4f);
   II (d, a, b, c, Block[15], 10, $fe2ce6e0);
   II (c, d, a, b, Block[ 6], 15, $a3014314);
   II (b, c, d, a, Block[13], 21, $4e0811a1);
   II (a, b, c, d, Block[ 4],  6, $f7537e82);
   II (d, a, b, c, Block[11], 10, $bd3af235);
   II (c, d, a, b, Block[ 2], 15, $2ad7d2bb);
   II (b, c, d, a, Block[ 9], 21, $eb86d391);
   inc(State[0], a);
   inc(State[1], b);
   inc(State[2], c);
   inc(State[3], d);
end;

// -----------------------------------------------------------------------------------------------

// Initialize given Context
procedure MD5Init(var Context: MD5Context);
begin
   with Context do begin
      State[0] := $67452301;
      State[1] := $efcdab89;
      State[2] := $98badcfe;
      State[3] := $10325476;
      Count[0] := 0;
      Count[1] := 0;
      ZeroMemory(@Buffer, SizeOf(MD5Buffer));
   end;
end;

// Update given Context to include Length bytes of Input
procedure MD5Update(var Context: MD5Context; Input: pChar; Length: longword);
var
   Index: longword;
   PartLen: longword;
   I: longword;
begin
   with Context do begin
      Index := (Count[0] shr 3) and $3f;
      inc(Count[0], Length shl 3);
      if Count[0] < (Length shl 3) then inc(Count[1]);
      inc(Count[1], Length shr 29);
   end;
   PartLen := 64 - Index;
   if Length >= PartLen then begin
      CopyMemory(@Context.Buffer[Index], Input, PartLen);
      Transform(@Context.Buffer, Context.State);
      I := PartLen;
      while I + 63 < Length do begin
         Transform(@Input[I], Context.State);
         inc(I, 64);
      end;
      Index := 0;
   end else I := 0;
   CopyMemory(@Context.Buffer[Index], @Input[I], Length - I);
end;

// Finalize given Context, create Digest and zeroize Context
procedure MD5Final(var Context: MD5Context; var Digest: MD5Digest);
var
   Bits: MD5CBits;
   Index: longword;
   PadLen: longword;
begin
   Decode(@Context.Count, @Bits, 2);
   Index := (Context.Count[0] shr 3) and $3f;
   if Index < 56 then PadLen := 56 - Index else PadLen := 120 - Index;
   MD5Update(Context, @PADDING, PadLen);
   MD5Update(Context, @Bits, 8);
   Decode(@Context.State, @Digest, 4);
   ZeroMemory(@Context, SizeOf(MD5Context));
end;

// -----------------------------------------------------------------------------------------------

// Create digest of given Message
function MD5String(M: string): MD5Digest;
var
   Context: MD5Context;
begin
   MD5Init(Context);
   MD5Update(Context, pChar(M), length(M));
   MD5Final(Context, Result);
end;

// Create digest of file with given Name
function MD5File(N: string): MD5Digest;
var
   FileHandle: THandle;
   MapHandle: THandle;
   ViewPointer: pointer;
   Context: MD5Context;
begin
   MD5Init(Context);
   FileHandle := CreateFile(pChar(N), GENERIC_READ, FILE_SHARE_READ or FILE_SHARE_WRITE,
      nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL or FILE_FLAG_SEQUENTIAL_SCAN, 0);
   if FileHandle <> INVALID_HANDLE_VALUE then try
      MapHandle := CreateFileMapping(FileHandle, nil, PAGE_READONLY, 0, 0, nil);
      if MapHandle <> 0 then try
         ViewPointer := MapViewOfFile(MapHandle, FILE_MAP_READ, 0, 0, 0);
         if ViewPointer <> nil then try
            MD5Update(Context, ViewPointer, GetFileSize(FileHandle, nil));
         finally
            UnmapViewOfFile(ViewPointer);
         end;
      finally
         CloseHandle(MapHandle);
      end;
   finally
      CloseHandle(FileHandle);
   end;
   MD5Final(Context, Result);
end;

// Create hex representation of given Digest
function MD5Print(D: MD5Digest): string;
var
   I: byte;
const
   Digits: array[0..15] of char =
      ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
begin
   Result := '';
   for I := 0 to 15 do Result := Result + Digits[(D[I] shr 4) and $0f] + Digits[D[I] and $0f];
end;

// -----------------------------------------------------------------------------------------------

// Compare two Digests
function MD5Match(D1, D2: MD5Digest): boolean;
var
   I: byte;
begin
   I := 0;
   Result := TRUE;
   while Result and (I < 16) do begin
      Result := D1[I] = D2[I];
      inc(I);
   end;
end;

end.

Wenn ich einen Hash ermittel will, bringt das Programm eine Exception "Integerüberlauf" und bricht ab.
Der Fehler passiert bei der Verarbeitung MD5Final vermutlich im Bereich der procedure FF.

Aufherufen wird der MD5-Zweig wie folgt:

Code:

schluessel := 'basil';
memo1.Lines.Add('MD5Hash für PW : ' + schluessel);
memo1.Lines.Add(MD5Print(MD5String(schluessel)));

Hat schon mal jemand ein gleichartiges Problem gehabt und wie gelöst? Ich komm da nicht weiter ...

Danke