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Discussione: [X360 Reversing] Chapter 1: CB_B patches

  1. #1
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    [X360 Reversing] Chapter 1: CB_B patches


    << Previuos Chapter <<

    Chapter 1: CB_B patches



    Before you start reading: executables and patches are written in Assembly (O RLY?).
    If you don’t know what ASM is and/or hardware basics you can stop your reading here, sorry.


    Let’s take our disassembled CB_B 9188 (we’re working on a Trinity, do you remember?) and start looking the related patch file.
    Oh, as you probably noticed all instructions have fixed length. This is very helpful!



    Patch #1

    00 00 4D F4 00 00 00 01 60 00 00 00
    That’s pretty easy! It replaces whatever’s at 0x4DF4 with 0x60000000 (opcode for nop).
    But what’s at 0x4DF4? CB LDV (fuseline 02).
    The first check compares the position (counting from left) of the rightmost F in fuseline 02
    with data stored at 0x3B1 (sequence byte), and if it doesn’t match it jumps to the second check (otherwise it’ll continue boot).
    We patch that jump with a nop.


    Patch #2

    00 00 4F 50 00 00 00 03 60 00 00 00 60 00 00 00 60 00 00 00
    Three nops starting from 0x4F50, cut off error 0xA3 (haven’t found info about it nor tried to reverse what is).


    Patch #3

    00 00 56 60 00 00 00 01 38 60 00 00
    Replaces call to XeCryptMemDiff (that checks CD hash) with li r3,0.
    This because next instruction checks for r3 (which should be XeCryptMemDiff’s return value) comparing it with 0.
    If they’re equal boot continues.



    >> Next Chapter >>

    Credits:
    xeBuild Team
    Free60
    RGLoader
    Ultima modifica di DrSchottky; 12-10-2015 alle 13:25

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  3. #2
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    Ultima modifica di DrSchottky; 08-10-2015 alle 22:29

  4. #3
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    is there an imagebuild application made with delphi or an open source for it , like J-runner

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    Citazione Originariamente Scritto da sky19 Visualizza Messaggio
    is there an imagebuild application made with delphi or an open source for it , like J-runner
    The original build.py

  6. #5
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    where can i find it ? , also is there some tutorials , couldn't find a regular tuto

  7. #6
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    Tutorial for what?
    You can find the script in gligli's github repo.

  8. #7
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    Tutorial for X360 Reversing NAND image , cause i want to learn anything related to xbox 360 if you have any lessons

  9. #8
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    Citazione Originariamente Scritto da sky19 Visualizza Messaggio
    Tutorial for X360 Reversing NAND image , cause i want to learn anything related to xbox 360 if you have any lessons
    Free60 is a massive source of information, you can start reading there.

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