-----------Magic Slate 20/40-----------
A 4am crack                  2017-02-11
---------------------------------------

Name: Magic Slate 20-/40-column
Version: 1.02
Genre: productivity
Year: 1984
Credits: Donna Stanger, Paul Elseth,
  Jim Kulzer, Simon Lie
Publisher: Sunburst Communications
Platform: Apple ][+ or later
Media: single-sided 5.25-inch floppy
OS: custom
Previous cracks: none
Similar cracks:
  #1003 Magic Slate 20 v1.3

                   ~

               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.1.0


   NAME           TYPE  BLKS  MODIFIED

   MS              SYS    24  <NO DATE>
   MS.EDIT20       BIN    50  <NO DATE>
   MS.EDIT40       BIN    51  <NO DATE>
   MS.PRINT40      BIN    37  <NO DATE>
   MS.UTILS40      BIN    26  <NO DATE>
   MS.CONFIG       BIN     3  <NO DATE>

BLOCKS FREE:64    USED:216   TOTAL:280

PRESS [RETURN]

                 --^--

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.1.0/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   $03/$09-$85   $04/$0A-$1D
$17/$0E-$30


             PRESS [RETURN]

                 --^--

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

- T04,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.)

- T17,S0E is similarly unsuspicious.

That leaves T03,S09. 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 $5B:

                 --v--

T03,S09
----------- DISASSEMBLY MODE ----------
; save flags
005B:08             PHP

; prevent interrupts
005C:78             SEI

; not sure what this does
005D:A5 43          LDA   $43
005F:29 7F          AND   #$7F
0061:85 07          STA   $07
0063:A9 00          LDA   #$00
0065:85 46          STA   $46
0067:85 47          STA   $47
0069:85 44          STA   $44
006B:A9 60          LDA   #$60
006D:85 45          STA   $45
006F:A9 01          LDA   #$01
0071:85 42          STA   $42
0073:20 00 08       JSR   $0800
0076:A9 08          LDA   #$08
0078:85 46          STA   $46
007A:A9 00          LDA   #$00
007C:85 47          STA   $47
007E:85 42          STA   $42
0080:20 00 08       JSR   $0800

; turn on drive motor manually
0083:A6 07          LDX   $07
0085:BD 89 C0       LDA   $C089,X
0088:BD 8E C0       LDA   $C08E,X

; set up Death Counter
008B:A0 00          LDY   #$00
008D:84 08          STY   $08
008F:C8             INY
0090:D0 04          BNE   $0096
0092:E6 08          INC   $08

; if Death Counter hits 0, fail
0094:F0 1F          BEQ   $00B5

; match nibble sequence "D5 BE EC"
0096:BD 8C C0       LDA   $C08C,X
0099:10 FB          BPL   $0096
009B:C9 D5          CMP   #$D5
009D:D0 F0          BNE   $008F
009F:BD 8C C0       LDA   $C08C,X
00A2:10 FB          BPL   $009F
00A4:C9 BE          CMP   #$BE
00A6:D0 F3          BNE   $009B
00A8:BD 8C C0       LDA   $C08C,X
00AB:10 FB          BPL   $00A8
00AD:C9 EC          CMP   #$EC
00AF:D0 EA          BNE   $009B

; restore flags, clear carry, and exit
00B1:28             PLP
00B2:18             CLC
00B3:90 02          BCC   $00B7

; restore flags, set carry, and exit
00B5:28             PLP
00B6:38             SEC

; turn off drive motor on the way out
00B7:BD 88 C0       LDA   $C088,X
00BA: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
$B5 to match the success path at offset
$B1, the caller will always think the
protection check succeeded. In other
words, change the "SEC" to a "CLC".

T03,S07,$B6: 38 -> 18

Quod erat liberandum.

                   ~

              Usage Notes


Hold <Ctrl-C> on boot to enter the
configuration menu. You can setup your
printer and switch between 20 and 40
column editing mode.

---------------------------------------
A 4am crack                    No. 1009
------------------EOF------------------