-----------Math Class Level 5---------- A 4am crack 2015-08-21 --------------------------------------- Name: Math Class Level 5: Advanced Multiplication and Division Genre: educational Year: 1989 Credits: - design by Peggy Brennan, Bonnie Brook, Lawrence Comella - programming by Thomas Whiting - graphics by Peggy Brennan - sound by Steven Martin Publisher: Troll Associates Media: single-sided 5.25-inch floppy OS: DOS 3.3 Previous cracks: none Identical cracks: Design Your Own Home: Architectural Design (no. 379) Design Your Own Home: Landscape Design (no. 341) Dividing Fractions (no. 338) Subtracting Mixed Fractions (no. 326) Peter Rabbit Reading (no. 289) Write It Right (no. 216) Understanding Maps and Globes (no. 215) Seasons (no. 214) In the Days of Knights and Castles (no. 213) Library Skills (no. 212) Fun with Verbs (no. 211) Cause and Effect (no. 207) Fraction Tutorial (no. 194) ~ Chapter 0 In Which Various Automated Tools Fail In Interesting Ways COPYA immediate disk read error Locksmith Fast Disk Backup unable to read any track EDD 4 bit copy (no sync, no count) no errors, but copy grinds on boot Copy ][+ nibble editor modified address epilogue "AF FF FF" odd-numbered tracks (1, 3, 5...) also have a modified address prologue ("D4 AA 96") --v-- COPY ][ PLUS BIT COPY PROGRAM 8.4 (C) 1982-9 CENTRAL POINT SOFTWARE, INC. --------------------------------------- TRACK: 03 START: 38FC LENGTH: 1803 ^^ 38C0: F9 F9 9B E9 E7 E7 E5 E5 VIEW 38C8: D6 F7 D3 A6 96 E5 E5 DC 38D0: B5 ED CD D3 9A A6 9F AC 38D8: DE AA EB FF FF FF FF FF 38E0: EB AB FF BF EB D4 AA 96 <-38E5 ^^^^^^^^ address prologue 38E8: FF FE AB AB AE AE FA FB 38F0: AF FF FF FC FF FF FF FF ^^^^^^^^ address epilogue 38F8: FF FF FF FF D5 AA AD 97 ^^^^^^^^ data prologue 3900: 9B AC AB B5 BD AE 9D 97 --------------------------------------- A TO ANALYZE DATA ESC TO QUIT ? FOR HELP SCREEN / CHANGE PARMS Q FOR NEXT TRACK SPACE TO RE-READ --^-- Disk Fixer ["O" -> "Input/Output Control"] set Address Epilogue to "AF FF FF" -> even-numbered tracks readable T00 looks like a DOS 3.3 RWTS set Address Prologue to "D4 AA 96" -> odd-numbered tracks also readable T01 readable. Also T03, T05, T07... T11 looks like a DOS 3.3 disk catalog T01,S09 -> startup program is "M" Why didn't COPYA work? modified prologue and epilogue Why didn't Locksmith FDB work? modified prologue and epilogue Why didn't my EDD copy work? I don't know. Maybe a nibble check during boot? Next steps: 1. capture RWTS with AUTOTRACE 2. convert disk to standard format with Advanced Demuffin 3. patch RWTS to read demuffin'd disk 4. find the nibble check & bypass it 5. declare victory(*) (*) Take a nap. ~ Chapter 1 In Which We Stop And Smell The RWTS [S6,D1=original disk] [S6,D2=blank disk] [S5,D1=my work disk] ]PR#5 ... CAPTURING BOOT0 ...reboots slot 6... ...reboots slot 5... SAVING BOOT0 /!\ BOOT0 JUMPS TO $08F0 CAPTURING BOOT1 ...reboots slot 6... ...reboots slot 5... SAVING BOOT1 SAVING RWTS ]BLOAD BOOT0,A$800 ]CALL -151 *801L . . all normal until... . 084A- 4C F0 08 JMP $08F0 *8F0L 08F0- A9 AA LDA #$AA 08F2- 85 31 STA $31 08F4- A9 00 LDA #$00 08F6- 8D F1 B6 STA $B6F1 08F9- 4C 00 B7 JMP $B700 I've seen this before. The RWTS uses zero page $31 to check the second byte of the address (or data (or both)) prologue (or epilogue (or both)). *BLOAD RWTS,A$2800 *FE89G FE93G ; disconnect DOS *B800<2800.2FFFM ; move RWTS into place *B944L ; routine to read address prologue B944- A0 FC LDY #$FC B946- 84 26 STY $26 B948- C8 INY B949- D0 04 BNE $B94F B94B- E6 26 INC $26 B94D- F0 F3 BEQ $B942 B94F- BD 8C C0 LDA $C08C,X B952- 10 FB BPL $B94F ; find prologue nibble #1 B954- 4A LSR B955- C9 6A CMP #$6A B957- D0 EF BNE $B948 B959- BD 8C C0 LDA $C08C,X B95C- 10 FB BPL $B959 ; find #2 B95E- C5 31 CMP $31 <-- ! B960- D0 F2 BNE $B954 B962- A0 03 LDY #$03 B964- BD 8C C0 LDA $C08C,X B967- 10 FB BPL $B964 ; find #3 B969- C9 96 CMP #$96 B96B- D0 E7 BNE $B954 Well this just answers a whole slew of questions at once. The code to find prologue nibble #1 explains how this disk can read its odd-numbered tracks (with non-standard address prologue "D4 AA 96"). Normal address prologue byte 1 is $D5. In binary: $D5 = 1101 0101 After LSR: 0110 1010 = $6A Odd-numbered tracks use $D4 instead. In binary: $D4 = 1101 0100 After LSR: 0110 1010 = $6A So this code will match either prologue and work on both odd and even tracks. Furthermore, RWTS code is time-critical between reading the last bit of one nibble and reading the first bit of the next. If it's too fast or too slow, it will get out of phase (because the disk spins independently of the CPU). Compare DOS 3.3 (cycle count in margin) B94F- BD 8C C0 LDA $C08C,X B952- 10 FB BPL $B94F B954- C9 D5 CMP #$D5 | 2 B956- D0 F0 BNE $B948 | 2 * B958- EA NOP | 2 B959- BD 8C C0 LDA $C08C,X B95C- 10 FB BPL $B959 (*) on the time-critical path, this branch is not taken, so always 2 ...and this disk's RWTS: B94F- BD 8C C0 LDA $C08C,X B952- 10 FB BPL $B94F B954- 4A LSR | 2 B955- C9 6A CMP #$6A | 2 B957- D0 EF BNE $B948 | 2 * B959- BD 8C C0 LDA $C08C,X B95C- 10 FB BPL $B959 Despite being more "flexible" (matching $D5 or $D4), this disk's RWTS uses the same number of bytes of code and runs in the same number of cycles. Nice. Furthermore, look at this code to match nibble #2 of the address prologue: *B959L B959- BD 8C C0 LDA $C08C,X B95C- 10 FB BPL $B959 B95E- C5 31 CMP $31 <-- ! B960- D0 F2 BNE $B954 There's zero page $31, initialized at $BB00 during boot. Solution: an IOB module that Advanced Demuffin calls before calling the original disk's RWTS. (Read the docs on my work disk.) ~ Chapter 2 In Which We Attempt To Use The Original Disk As A Weapon Against Itself *C500G ... ]CALL -151 ]BLOAD ADVANCED DEMUFFIN 1.5 ; standard Advanced Demuffin setup ; (unchanged) 1400- 4A LSR 1401- 8D 22 0F STA $0F22 1404- 8C 23 0F STY $0F23 1407- 8E 27 0F STX $0F27 140A- A9 01 LDA #$01 140C- 8D 20 0F STA $0F20 140F- 8D 2A 0F STA $0F2A ; initialize zero page used by the RWTS 1412- A9 AA LDA #$AA 1414- 85 31 STA $31 ; call RWTS 1416- A9 0F LDA #$0F 1418- A0 1E LDY #$1E 141A- 4C 00 BD JMP $BD00 *BSAVE IOB $31,A$1400,L$FB *BRUN ADVANCED DEMUFFIN 1.5 ["5" to switch to slot 5] ["R" to load a new RWTS module] --> At $B8, load "RWTS" from drive 1 [press "I" to load a new IOB module] --> load "IOB $31" from drive 1 ["6" to switch to slot 6] ["C" to convert disk] --v-- ADVANCED DEMUFFIN 1.5 (C) 1983, 2014 ORIGINAL BY THE STACK UPDATES BY 4AM =======PRESS ANY KEY TO CONTINUE======= TRK:................................... +.5: 0123456789ABCDEF0123456789ABCDEF012 SC0:................................... SC1:................................... SC2:................................... SC3:................................... SC4:................................... SC5:................................... SC6:................................... SC7:................................... SC8:................................... SC9:................................... SCA:................................... SCB:................................... SCC:................................... SCD:................................... SCE:................................... SCF:................................... ======================================= 16SC $00,$00-$22,$0F BY1.0 S6,D1->S6,D2 --^-- ]PR#5 ... ]CATALOG,S6,D1 C1983 DSR^C#254 033 FREE B 007 D B 021 TITLE B 002 O.TGEN B 009 FONT B 002 PSD B 005 TROLL B 014 M B 007 MNNU B 009 HD1 B 015 M1.1 B 012 LAB1 B 013 SCR0 A 004 HELLO B 008 S1B B 010 S1A B 014 M1.2B B 014 M1.2C B 008 M1.2 B 007 S1C B 008 SMK B 006 SCR2 B 003 BAR B 004 NUMS B 014 M2.1 B 005 M2.1B B 009 CALC B 014 M2.2 B 007 SCR3 B 005 M2.2B B 019 MULT B 017 DIV B 017 MENU B 004 AVER B 010 M3.1 B 014 M1.3 B 014 M2.3 B 008 M2.3B B 002 BOTTLE B 014 M4.1 B 005 M4.1B B 015 M4.2 B 005 M4.2B B 002 SCR4 B 020 FRAC B 007 CRED B 007 QUIT B 005 H.M B 005 H.1 B 005 H.2 B 005 H.3 B 005 H.4 B 002 Q ]BRUN M ...works... [S6,D1=demuffin'd copy] ]PR#6 ...works... Wait, what? ~ Chapter 3 In Which We Angrily Investigate Why We Suddenly Have A Working Copy [S6,D1=mysteriously working copy] [S5,D1=my work disk] ]PR#5 ]BLOAD RWTS,A$2800 ]CALL -151 *FE89G FE93G *B800<2800.2FFFM *B944L . . all weirdness accounted for, until... . ; find epilogue byte #1 B98B- BD 8C C0 LDA $C08C,X B98E- 10 FB BPL $B98B B990- C9 DE CMP #$DE ; if found $DE, immediately exit with ; a "success" status (clear carry bit) B992- F0 0A BEQ $B99E ; if not $DE, do... this thing B994- 48 PHA B995- 68 PLA B996- BD 8C C0 LDA $C08C,X ; Note: no BPL loop here! It only reads ; the data latch once. B999- C9 08 CMP #$08 B99B- B0 A5 BCS $B942 B99D- EA NOP B99E- 18 CLC B99F- 60 RTS It's looking for a timing bit after the first epilogue byte. It doesn't even care what the first epilogue byte was, as long as it wasn't $DE. This RWTS will accept two different address prologues, "D5 AA 96" or "D4 AA 96". It will also accept two different address epilogues, "DE" or anything- other-than-DE-followed-by-a-timing-bit. Why didn't the EDD copy work? EDD preserved the original prologue epilogue but not the timing bits. The prologue checker (at $B944) finds "D5 AA 96" (even-numbered tracks) or "D4 AA 96" (odd-numbered tracks). But the epilogue checker's first compare (at $B98B) didn't match because the first epilogue byte was still the original value ($AF), and its second compare (at $B999) didn't match because there was no timing bit after the first byte. There was never any separate nibble check; the structure of the disk itself is designed to foil nibble copiers. Why did the demuffin'd copy work? Advanced Demuffin wrote out the data from each sector onto a standard disk that uses "D5 AA 96" prologue and "DE AA EB" epilogue. The RWTS always matches "D5 AA 96" and doesn't care that it never sees a "D4 AA 96" for a prologue. The epilogue checker always matches "DE" and never checks the timing bit. Thus, no RWTS patches are necessary. Quod erat liberandum. --------------------------------------- A 4am crack No. 412 ------------------EOF------------------