-----------Decimals Practice----------- A 4am crack 2016-01-14 --------------------------------------- Name: Decimals Practice Genre: educational Year: 1982 Publisher: Control Data Corporation Media: single-sided 5.25-inch disk OS: DOS 3.3 Previous cracks: none Similar cracks: #501 Speed Reader II #492 Fractions Practice #431 Gertrude's Secrets v1.0 #395 Algebra Volume 3 v1.2 ~ 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 hangs on boot with the drive motor on Copy ][+ nibble editor all tracks use standard prologues (address: D5 AA 96, data: D5 AA AD) but modified epilogues (address: FF FF FF, data: FF FF FF) Disk Fixer ["O" -> "Input/Output Control"] set Address Epilogue to "FF FF FF" set Data Epilogue to "FF FF FF" Success! All tracks readable! T00 -> looks like a DOS 3.3 RWTS T11 -> DOS 3.3 disk catalog T01,S09 -> startup program is "HELLO" Why didn't COPYA work? modified epilogue bytes (every track) Why didn't Locksmith FDB work? modified epilogue bytes (every track) Why didn't my EDD copy work? probably a nibble check during boot Next steps: 1. capture RWTS with AUTOTRACE 2. convert disk to standard format with Advanced Demuffin 3. find nibble check and bypass it ~ Chapter 1 In Which We Attempt To Use The Original Disk As A Weapon Against Itself [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 ($BBFE) CAPTURING BOOT1 ...reboots slot 6... ...reboots slot 5... SAVING BOOT1 SAVING RWTS ]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 ["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:R.................................. +.5: 0123456789ABCDEF0123456789ABCDEF012 SC0:................................... SC1:................................... SC2:................................... SC3:................................... SC4:................................... SC5:................................... SC6:................................... SC7:................................... SC8:................................... SC9:................................... SCA:R.................................. SCB:................................... SCC:................................... SCD:................................... SCE:................................... SCF:................................... ======================================= 16SC $00,$00-$22,$0F BY1.0 S6,D1->S6,D2 --^-- Hmm. Even the disk's own RWTS can't read T00,S0A. I'm hoping that part of the copy protection and not a bad disk. ]PR#5 ]CATALOG,S6,D2 C1983 DSR^C#254 309 FREE *A 003 HELLO *B 002 LOMEM: *B 026 DARTS.GEN *B 017 RUNTIME *B 022 DDARTS.TITLE.OBJ *B 007 BALLOON.SHP *B 003 DARTS.SHP *B 024 DDARTS.P1.OBJ *B 066 DDARTS.P2.OBJ *B 002 NAME.SHP ]RUN HELLO ...crashes... [S6,D1=demuffin'd copy] ]PR#6 ...hangs... But it's _progress_. ~ Chapter 2 In Which We Run Into An Old Friend Who Disapproves Of Our Hobbies And Actively Tries To Block Us So Not Really That Good Of A Friend ]PR#5 ... ]BLOAD BOOT0,A$800 ]CALL -151 *801L . . . 084A- 6C FE BB JMP ($BBFE) Hmm. *BLOAD BOOT1,A$2600 *FE89G FE93G ; disconnect DOS *B600<2600.2FFFM ; move RWTS into place *BBFE.BBFF BBFE- 00 BB *BB00L ; Ah, I recognize this routine already. ; It was used by several different ; publishers, and it apparently had ; tweakable options. Turning off an ; option would generate code that makes ; no sense at first glance. ; First, set the RUN flag so that, even ; if I manage to break out to a BASIC ; prompt, any command will act like RUN BB00- A9 FF LDA #$FF BB02- 85 D6 STA $D6 ; Some disks have a "LDA $C08E,X" here ; to require that the disk be write- ; protected. With the option off, it's ; just an unconditional jump. BB07- A9 FF LDA #$FF BB09- EA NOP BB0A- 30 05 BMI $BB11 ;[always skipped] ;BB0C- A2 B1 LDX #$B1 ;BB0E- 4C F0 BB JMP $BBF0 ; Some disks check the low-level reset ; vector (I think this was protection ; against "boot inspectors" like Watson ; that installed themselves in the ; language card and left it active ; during boot). This disk changes the ; CMP to an "LDA #$00", making this ; another unconditional jump. BB11- AD FD FF LDA $FFFD BB14- A9 00 LDA #$00 BB16- F0 05 BEQ $BB1D ;[always skipped] ;BB18- A2 B2 LDX #$B2 ;BB1A- 4C F0 BB JMP $BBF0 BB1D- BD 8C C0 LDA $C08C,X ; Set the first character of the input ; buffer to null. This can be checked ; later to ensure that an attacker (me) ; hasn't interrupted the boot and been ; typing things. BB20- A9 00 LDA #$00 BB22- 8D 00 02 STA $0200 ; look for a magic nibble sequence on ; track 0 BB25- BD 8C C0 LDA $C08C,X BB28- 10 FB BPL $BB25 BB2A- C9 EB CMP #$EB BB2C- D0 F7 BNE $BB25 BB2E- BD 8C C0 LDA $C08C,X BB31- 10 FB BPL $BB2E BB33- C9 D5 CMP #$D5 BB35- D0 EE BNE $BB25 BB37- BD 8C C0 LDA $C08C,X BB3A- 10 FB BPL $BB37 BB3C- C9 AA CMP #$AA BB3E- D0 E5 BNE $BB25 ; wipe most of memory ($0800..$95FF) ; although, ironically, not the part ; I'm using for boot tracing BB40- A9 4C LDA #$4C BB42- A0 00 LDY #$00 BB44- 99 00 95 STA $9500,Y BB47- 88 DEY BB48- D0 FA BNE $BB44 BB4A- CE 46 BB DEC $BB46 BB4D- AD 46 BB LDA $BB46 BB50- C9 07 CMP #$07 BB52- D0 EC BNE $BB40 ; fiddle with the RWTS to ignore ; epilogue bytes BB54- A9 18 LDA #$18 BB56- 8D 42 B9 STA $B942 ; sector $0A BB59- A9 0A LDA #$0A BB5B- 8D ED B7 STA $B7ED BB5E- D0 05 BNE $BB65 ...[some zeroes used for data later]... ; track $00 BB65- A9 00 LDA #$00 BB67- 8D EC B7 STA $B7EC ; into $4000 BB6A- 8D F0 B7 STA $B7F0 BB6D- A9 40 LDA #$40 BB6F- 8D F1 B7 STA $B7F1 ; read command BB72- A9 01 LDA #$01 BB74- 8D F4 B7 STA $B7F4 ; set up rest of RWTS table BB77- 8D F8 B7 STA $B7F8 BB7A- 8D EA B7 STA $B7EA BB7D- 8E E9 B7 STX $B7E9 BB80- 8E F7 B7 STX $B7F7 ; more RWTS fiddling, so sector reads ; save raw nibble data in $6C00 range BB83- A0 6C LDY #$6C BB85- 8C 10 B9 STY $B910 BB88- 8C CE B8 STY $B8CE BB8B- 8C D2 B8 STY $B8D2 BB8E- 88 DEY BB8F- 8C 21 B9 STY $B921 ; a sector read, with modified RWTS BB92- 20 E7 BB JSR $BBE7 ; copy the raw nibble data elsewhere BB95- A0 55 LDY #$55 BB97- B9 00 6C LDA $6C00,Y BB9A- 99 00 5C STA $5C00,Y BB9D- 88 DEY BB9E- 10 F7 BPL $BB97 BBA0- AD 02 6B LDA $6B02 BBA3- 85 06 STA $06 ; another sector read BBA5- 20 E7 BB JSR $BBE7 BBA8- AD 02 6B LDA $6B02 BBAB- 85 07 STA $07 ; and another BBAD- 20 E7 BB JSR $BBE7 BBB0- AD 02 6B LDA $6B02 BBB3- 85 08 STA $08 ; compare this read's nibble data to ; the previous read's nibble data BBB5- A0 55 LDY #$55 BBB7- B9 00 6C LDA $6C00,Y BBBA- D9 00 5C CMP $5C00,Y ; fail if anything doesn't match BBBD- D0 2F BNE $BBEE BBBF- 88 DEY BBC0- 10 F5 BPL $BBB7 ; more comparisons of the side effects ; generated by the modified RWTS BBC2- A5 06 LDA $06 BBC4- C5 07 CMP $07 BBC6- D0 04 BNE $BBCC BBC8- C5 08 CMP $08 BBCA- F0 17 BEQ $BBE3 ; success path is here -- ; first, restore the RWTS code BBCC- A9 38 LDA #$38 BBCE- 8D 42 B9 STA $B942 BBD1- A0 BC LDY #$BC BBD3- 8C 10 B9 STY $B910 BBD6- 8C CE B8 STY $B8CE BBD9- 8C D2 B8 STY $B8D2 BBDC- 88 DEY BBDD- 8C 21 B9 STY $B921 ; then continue with boot1 as normal BBE0- 4C 00 B7 JMP $B700 BBE3- 4C 54 BB JMP $BB54 ... BBE7- A9 B7 LDA #$B7 BBE9- A0 E8 LDY #$E8 BBEB- 4C B5 B7 JMP $B7B5 ; failure path from comparison at $BBBD BBEE- A2 B3 LDX #$B3 ; general failure path is here -- ; clear screen, show text screen, write ; error code, and jump to The Badlands BBF0- 20 58 FC JSR $FC58 BBF3- 20 2D FF JSR $FF2D BBF6- 8E 03 04 STX $0403 BBF9- 4C 5B B7 JMP $B75B I'm guessing my non-working copy never got as far as wiping main memory, since the search for the nibble sequence is unconditional and neverending. That explains the behavior I saw -- it spun forever with the drive motor on, and it never got off track 0. The important takeaway here is that there don't appear to be any long-term side effects of this copy protection. If it succeeds, it restores everything that it modified (in the RWTS code), then it just jumps to $B700 to start the boot1 phase. But that's it; nothing else seems to rely on some magic number that it pulls from the raw nibbles or anything. It doesn't decrypt anything. It doesn't even clear the carry flag. ~ Chapter 3 In Which We Remove All Traces Of Copy Protection Using An Automated Tool That I Wrote For Just Such An Occasion [S6,D1=demuffin'd copy] [S5,D1=my work disk] ]PR#5 ... ]BRUN PDP ; fix epilogue byte checking in RWTS T00,S03,$91 change FF to DE T00,S03,$9B change FF to AA T00,S03,$35 change FF to DE T00,S03,$3F change FF to AA T00,S02,$9E change FF to DE T00,S02,$A3 change FF to AA T00,S02,$A8 change FF to EB ; neutralize RWTS swappers (called when ; the program needs to switch between ; reading the protected program disk ; and the unprotected data disk -- I ; don't think this disk uses any data ; disks, but the protection is generic) T00,S04,$69 change A9 to 60 T00,S04,$7D change A9 to 60 ; bypass nibble check after boot0 T00,S00,$4B change FEBB to FD08 ; fix nibble tables (ooh, I didn't see ; these in my investigation -- hooray ; for automation) T00,S04,$29 change AA to 96 T00,S04,$AA change 00 to AA Quod erat liberandum. ~ Compatibility Notes The original disk crashes at $08B8 on an enhanced //e or later, for reasons unrelated to copy protection. I looked into it briefly -- there's a bug in the machine ID detection in DARTS.GEN, similar to one I saw in Microzine 1 -- but fixing that bug just uncovered another, and I gave up. --------------------------------------- A 4am crack No. 572 ------------------EOF------------------