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• Approaches To Modifying Game Resource Files

  16 août 2016, par Multimedia Mike — Game Hacking

  I have been assisting The Translator in the translation of another mid-1990s adventure game. This one isn’t quite as multimedia-heavy as the last title, and the challenges are a bit different. I wanted to compose this post in order to describe my thought process and mental model in approaching this problem. Hopefully, this will help some others understand my approach since what I’m doing here often appears as magic to some of my correspondents.

  High Level Model
  At the highest level, it is valuable to understand the code and the data at play. The code is the game’s engine and the data refers to the collection of resources that comprise the game’s graphics, sound, text, and other assets.

  
  
  Simplistic high-level game engine model
  

  Ideally, we want to change the data in such a way that the original game engine adopts it as its own because it has the same format as the original data. It is very undesirable to have to modify the binary engine executable in any way.

  Modifying The Game Data Directly
  How to modify the data ? If we modify the text strings for the sake of language translation, one approach might be to search for strings within the game data files and change them directly. This model assumes that the text strings are stored in a plain, uncompressed format. Some games might store these strings in a text format which can be easily edited with any text editor. Other games will store them as binary data.
  

  In the latter situation, a game hacker can scan through data files with utilities like Unix ‘strings’ to find the resources with the desired strings. Then, use a hex editor to edit the strings directly. For example, change “Original String”…

  0098F800   00 00 00 00  00 00 00 4F  72 69 67 69  6E 61 6C 20  .......Original 
  0098F810   53 74 72 69  6E 67 00 00  00 00 00 00  00 00 00 00  String..........
  

  …to “Short String” and pad the difference in string lengths using spaces (0x20) :

  0098F800   00 00 00 00  00 00 00 53  68 6F 72 74  20 53 74 72  .......Short Str
  0098F810   69 6E 67 20  20 20 00 00  00 00 00 00  00 00 00 00  ing   ..........
  

  This has some obvious problems. First, translated strings need to be of equal our smaller length compared to the original. What if we want to encode “Much Longer String” ?

  0098F800   00 00 00 00  00 00 00 4D  75 63 68 20  4C 6F 6E 67  .......Much Long
  0098F810   65 72 20 53  74 72 00 00  00 00 00 00  00 00 00 00  er Str..........
  

  It won’t fit. The second problem pertains to character set limitations. If the font in use was only designed for ASCII, it’s going to be inadequate for expressing nearly any other language.

  So a better approach is needed.

  Understanding The Data Structures
  An alternative to the approach outlined above is to understand the game’s resources so they can be modified at a deeper level. Here’s a model to motivate this investigation :

  
  
  Model of the game resource archive format
  

  This is a very common layout for such formats : there is a file header, a sequence of resource blocks, and a trailing index which describes the locations and types of the foregoing blocks.

  What use is understanding the data structures ? In doing so, it becomes possible to write new utilities that disassemble the data into individual pieces, modify the necessary pieces, and then reassemble them into a form that the original game engine likes.

  It’s important to take a careful, experimental approach to this since mistakes can be ruthlessly difficult to debug (unless you relish the thought of debugging the control flow through an opaque DOS executable). Thus, the very first goal in all of this is to create a program that can disassemble and reassemble the resource, thus creating an identical resource file. This diagram illustrates this complex initial process :

  
  
  Rewriting the game resource file
  

  So, yeah, this is one of the most complicated “copy file” operations that I can possibly code. But it forms an important basis, since the next step is to carefully replace one piece at a time.

  
  
  Modifying a specific game resource
  

  This diagram shows a simplistic model of a resource block that contains a series of message strings. The header contains pointers to each of the strings within the block. Instead of copying this particular resource block directly to the new file, a proposed modification utility will intercept it and rewrite the entire thing, writing new strings of arbitrary length and creating an adjusted header which will correctly point to the start of each new string. Thus, translated strings can be longer than the original strings.

  Further Work
  Exploiting this same approach, we can intercept and modify other game resources including fonts, images, and anything else that might need to be translated. I will explore specific examples in a later blog post.

  Followup

  • Translating Return to Ringworld, in which I apply the ideas expressed in this post.

• ffmpeg concat : "Unsafe file name"

  17 août 2016, par sers

  Trying to convert a bunch of mts-files into a big mp4-file :

  stephan@rechenmonster:/mnt/backupsystem/archive2/Videos/20151222/PRIVATE/AVCHD/BDMV$ ~/bin/ffmpeg-git-20160817-64bit-static/ffmpeg -v info -f concat -i <(find STREAM -name '*' -printf "file '$PWD/%p'\n") -deinterlace -r 25 -s hd720 -c:v libx264 -crf 23 -acodec copy -strict -2 ~/tmp/Videos/20151222.mp4
  
  ffmpeg version N-81364-gf85842b-static http://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 5.4.1 (Debian 5.4.1-1) 20160803
  
    configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab --enable-libsoxr --enable-frei0r --enable-libfribidi --disable-indev=sndio --disable-outdev=sndio --enable-librtmp --enable-libmfx --enable-libzimg --cc=gcc-5
  
    libavutil      55. 28.100 / 55. 28.100
  
    libavcodec     57. 53.100 / 57. 53.100
  
    libavformat    57. 46.101 / 57. 46.101
  
    libavdevice    57.  0.102 / 57.  0.102
  
    libavfilter     6. 51.100 /  6. 51.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  1.100 /  2.  1.100
  
    libpostproc    54.  0.100 / 54.  0.100
  
  [concat @ 0x56054a0] Unsafe file name '/mnt/backupsystem/archive2/Videos/20151222/PRIVATE/AVCHD/BDMV/STREAM'
  
  /dev/fd/63: Operation not permitted

  Any ideas what goes wrong here ? What does the term "unsafe file" mean in this context ?

  Thanks,
  Stephan

• Anomalie #3814 : Onglet {Mes articles} erroné en SPIP3.0

  9 août 2016, par Olivier Dutertre

  J’ai effectivement un ensemble de plugins installés, mais j’ai déja pu
  évacuer agenda et inscription 2.5 comme source puisqu’un autre
  internaute à testé avec ces deux plugins et ne reproduis pas.

  Le 09/08/2016 21:01, redmine@spip.org a écrit :

  La demande #3814 a été mise à jour par Pierre KUHN.

  Bonsoir,

  Tu utilises des plugins précis pour avoir ce problème ?

  ---

  Anomalie #3814 : Onglet Mes articles erroné en SPIP3.0
  <https://core.spip.net/issues/3814#change-11946>

  • Auteur : Olivier Dutertre
  • Statut : Nouveau
  • Priorité : Normal
  • Assigné à :
  • Catégorie : base de données
  • Version cible : 3.0
  • Resolution :
  • Navigateur :

  Je rencontre le soucis avec SPIP 3.0.22 reproduis sur deux versions du
  même site (prod et dev). Je n’ai pas eu de réponse sur la liste.
  J’ignore si ici est le bon endroit pour signaler ce genre de problème,
  alors merci de votre bienveillance.

  Dans la partie privée, l’onglet /mes articles/ de la page /articles/
  affiche des information incorrectes, c’est à dire des article qui ne
  sont pas forcément de l’auteur passé en paramètre.

  En explorant avec le mode debug, voila ce que j’ai découvert :

  la boucle telle que prévue initialement est :

  Elle donne le code suivant :

  SELECT articles.id_article, 0 as points, ’’, articles.titre, articles.statut, articles.id_rubrique, articles.titre AS titre_rang, articles.lang, articles.date, articles.id_rubrique, articles.id_article
  FROM info_articles AS `articles`
  INNER JOIN info_evenements AS L2 ON ( L2.id_article = articles.id_article )
  WHERE (L2.id_auteur = 3)
  AND ((articles.statut IN (’prepa’,’publie’,’refuse’,’prepa’)))
  GROUP BY articles.id_article
  ORDER BY articles.date DESC, articles.titre

  Je ne comprends pas la raison du recours à la table événements. et j’y
  vois une raison des résultats aberrant de la boucle

  Si par contre Je modifie la boucle avec une jointure :

  auteurs_liens)id_article ?id_rubrique ?id_mot ?id_auteur ?where ?statut ?recherche ?tri #ENVpar,date,#GETdefaut_tripar titrepagination #ENVnb,10 !lang_select>

  Cela me donne un code plus encourageant :

  SELECT articles.id_article, 0 as points, ’’, articles.titre, articles.statut, articles.id_rubrique, articles.titre AS titre_rang, articles.lang, articles.date, articles.id_rubrique, articles.id_article
  FROM info_articles AS `articles`
  INNER JOIN info_auteurs_liens AS L2 ON ( L2.id_objet = articles.id_article AND L2.objet=’article’)
  WHERE (L2.id_auteur = 3)
  AND ((articles.statut IN (’prepa’,’publie’,’refuse’,’prepa’)))
  GROUP BY articles.id_article
  ORDER BY articles.date DESC, articles.titre

  et surtout le résultat est conforme à mes attentes.

  Quelqu’un pourra-t’il éclaircir la raison de ce mystère ?

  ---

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