-------------Magic Slate 40------------
A 4am crack                  2017-08-25
---------------------------------------

Name: Magic Slate 40-column
Version: 1.4
Genre: productivity
Year: 1987
Credits: Donna Stanger, Paul Elseth
Publisher: Sunburst Communications
Platform: Apple ][+ or later
Media: single-sided 5.25-inch floppy
OS: custom
Previous cracks: none
Similar cracks:
  #1005 Magic Slate 80 v1.4

                   ~

               Chapter 0
 In Which Various Automated Tools Fail
          In Interesting Ways


COPYA
  fails on first pass

Locksmith Fast Disk Backup
  unable to read track $01

EDD 4 bit copy (no sync, no count)
  works

Copy ][+
  disk presents a ProDOS catalog

                 --v--

CATALOG DISK            SLOT 6  DRIVE 1
/MAGIC.SLATE.40


   NAME           TYPE  BLKS  MODIFIED

   MS              SYS    32  16-JUL-87
   MS.CONFIG       BIN     3  <NO DATE>
   MS.EDIT40       SYS    53  03-SEP-87
   MS.PRINT40      SYS    45  07-JUL-87
   MS.UTILS40      SYS    28  19-OCT-87

BLOCKS FREE:104   USED:176   TOTAL:280

                 --^--

Copy ][+ nibble editor
  T01 has no structure at all, no data,
  just sync bytes and scattered nibbles

                 --v--

   COPY ][ PLUS BIT COPY PROGRAM 8.4
(C) 1982-9 CENTRAL POINT SOFTWARE, INC.
---------------------------------------

TRACK: 01  START: 1800  LENGTH: 3DFF

4CF8: FF FF FF FF FF FF FF FF   VIEW
4D00: FF FF FF FF FF FF FF FF
4D08: FF FF E4 FF FF FF FF FF
4D10: FF B9 FF FF FF FF FF E4
4D18: FF FF FF FF FF D5 BE EC  <-4D1D
4D20: F4 F4 F4 F4 F4 F4 FF FF
4D28: FF FF FF FF FF FF FF FF
4D30: FF FF FF D2 D2 D2 FF FF  FIND:
4D38: FF FF FF FF FF FF FF FF  D5

---------------------------------------

  A  TO ANALYZE DATA  ESC TO QUIT

  ?  FOR HELP SCREEN  /  CHANGE PARMS

  Q  FOR NEXT TRACK   SPACE TO RE-READ


                 --^--

Disk Fixer
  T00 has standard ProDOS bootloader
  and disk catalog (see Copy ][+ above)
  but the disk does not sound or look
  like ProDOS when it boots.
  No way to read T01.

Why didn't COPYA work?
  Track $01 is missing/unreadable

Why didn't Locksmith FDB work?
  probably a runtime check that ensures
  that track $01 is missing/unreadable

EDD worked. What does that tell us?
  No half or quarter tracks, because I
  didn't even try to copy those. There
  is definitely a run-time protection
  check of some kind, but it's probably
  just checking that track $01 is
  unreadable.

Next steps:

  1. Search disk for common elements of
     a run-time protection check
  2. If that fails, trace the boot
  3. If that fails, I dunno, go feed
     the ducks or something

                   ~

               Chapter 1
        In Which We Get Lucky,
     To The Detriment Of The Ducks


On the theory that some code on disk is
trying to access track $01, and thus
noticing if it's unexpectedly readable,
let's enumerate some of the ways that
could happen:

- Reading a file that is mapped to the
  unreadable track $01. Copy II+ "disk
  map" shows there are no files mapped
  to track $01, so let's rule that out.
  In fact, the first file suspiciously
  skips over the track altogether:

                 --v--

DISK MAP                SLOT 6  DRIVE 1
/MAGIC.SLATE.40/MS

   TRACK           1               2
   0123456789ABCDEF0123456789ABCDEF012

S0 ..****.............................
EE ..****.............................
CD ..****.............................
TC ..****.............................
OB ..****.............................
RA ..****.............................
 9 ..****.............................
 8 ..****.............................
 7 ..****.............................
 6 ..****.............................
 5 ..****.............................
 4 ..****.............................
 3 ..****.............................
 2 ..****.............................
 1 *.***..............................
 F *.***..............................

   USE ARROW KEYS TO MAP OTHER FILES

                 --^--

- Issuing a ProDOS MLI "raw block read"
  and checking the return code. This is
  a popular technique under ProDOS,
  partly because it can be adapted to
  work on 3.5-inch and 5.25-inch disks.
  But I'm not sure if this disk is
  really full ProDOS or if it just uses
  the ProDOS disk structure for
  convenience. At any rate, a sector
  search for "20 00 BF" (a JSR to the
  standard ProDOS MLI entry point)
  yields precisely zero results, so...

- Manually seeking to the track and
  looking for a nibble sequence. There
  is no explicit support for "seeking
  to a particular track" unless you're
  calling ProDOS internals. Without
  calling into ProDOS, this technique
  would require low-level disk access
  (turning on the drive and hitting the
  right stepper motors and whatnot).
  Here are some possibilities:

  "BD 89 C0" (LDA $C089,X)   ; drive on
  "AD E9 C0" (LDA $C0E9)     ; drive on
  "BD 80 C0" (LDA $C080,X)   ; stepper

And lo! A search for "BD 89 C0" yields
several results.

                 --v--

------------- DISK SEARCH -------------

$00/$0E-$A7   $02/$0D-$53   $05/$0A-$76
$13/$07-$2F

                 --^--

- T00,S0E is part of PRODOS (although I
 think it's called "MS" on this disk).

- T05,S0A appears to be legitimate RWTS
  code of some sort. (The existence of
  "LDA $C08A,X" nearly is a strong
  indication of legitimacy; RWTS code
  needs to deal with both drives, but
  copy protection routines rarely work
  on anything but drive 1.)

- T13,S07 is similarly unsuspicious.

That leaves T02,S0D. And that is a
different kettle of nibbles altogether.

                   ~

               Chapter 2
     A Different Kettle of Nibbles


The routine containing "LDA $C089,X"
appears to start at offset $3B:

                 --v--

T02,S0D
----------- DISASSEMBLY MODE ----------
; save flags
003B:08             PHP

; prevent interrupts
003C:78             SEI

; not sure what this does
003D:84 46          STY   $46
003F:84 47          STY   $47
0041:20 00 08       JSR   $0800
0044:A9 08          LDA   #$08
0046:85 46          STA   $46
0048:A9 00          LDA   #$00
004A:85 47          STA   $47
004C:85 42          STA   $42
004E:20 00 08       JSR   $0800

; turn on drive motor manually
0051:A6 07          LDX   $07
0053:BD 89 C0       LDA   $C089,X
0056:BD 8E C0       LDA   $C08E,X

; set up Death Counter
0059:A0 00          LDY   #$00
005B:84 08          STY   $08
005D:C8             INY
005E:D0 04          BNE   $0064
0060:E6 08          INC   $08

; if Death Counter hits 0, fail
0062:F0 1F          BEQ   $0083

; match nibble sequence "D5 BE EC"
0064:BD 8C C0       LDA   $C08C,X
0067:10 FB          BPL   $0064
0069:C9 D5          CMP   #$D5
006B:D0 F0          BNE   $005D
006D:BD 8C C0       LDA   $C08C,X
0070:10 FB          BPL   $006D
0072:C9 BE          CMP   #$BE
0074:D0 F3          BNE   $0069
0076:BD 8C C0       LDA   $C08C,X
0079:10 FB          BPL   $0076
007B:C9 EC          CMP   #$EC
007D:D0 EA          BNE   $0069

; restore flags, clear carry, and exit
007F:28             PLP
0080:18             CLC
0081:90 02          BCC   $0085

; restore flags, set carry, and exit
0083:28             PLP
0084:38             SEC

; turn off drive motor on the way out
0085:BD 88 C0       LDA   $C088,X
0088:60             RTS

                 --^--

Pretty straightforward. We're looking
for a non-standard nibble sequence that
doesn't normally exist. But it does
exist on track $01 -- I saw it earlier
in the Copy II Plus nibble editor. The
caller expects the carry flag to be
clear on success or set on failure
(like DOS and ProDOS conventions).

If I change the failure path at offset
$83 to match the success path at offset
$7F, the caller will always think the
protection check succeeded. In other
words, change the "SEC" to a "CLC".

T02,S0D,$84: 38 -> 18

Quod erat liberandum.

---------------------------------------
A 4am crack                    No. 1384
------------------EOF------------------