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Reversing a DirectX Game Part 3

This is WIP
DISCLAIMER: The information provided here is for educational purposes only.


Reconnaissance

Looking at calls to CreateFile, this is one of the first files to be accessed. Next the data.pak gets accessed. File mapping object is anonymous.
 

"Data\XmlFiles\resources.xml" is:
<?xml version = "1.0" encoding = "UTF-8"?>
<!-- Copyright (c)2004 Lesta Studio -->

<root>
    <!-- Пути для ресурсов. -->
    <object name = "Resources">
       
        <object name = "VFS">
            <object name = "vfs1">
                <string name = "Type" value = "filesystem"/>
                <string name = "Path" value = "Data"/>
                <boolean name = "Recursive" value = "true"/>
            </object>
           

            <object name = "vfsPakFiles">
                <string name = "Type" value = "sma2"/>
                <string name = "Path" value = "data"/>
                <string name = "Mask" value = "*.pak"/>
                <boolean name = "Recursive" value = "true"/>
            </object>

            <object name = "z">
                <string name = "Type" value = "filesystem"/>
                <string name = "Path" value = "Patch"/>
                <boolean name = "Recursive" value = "true"/>
            </object>
            <object name = "z2">
                <string name = "Type" value = "sma2"/>
                <string name = "Path" value = "Patch"/>
                <string name = "Mask" value = "*.pak"/>
                <boolean name = "Recursive" value = "true"/>
            </object>

        </object>
    </object>

       
</root>
The Russian text is "Paths for resources".

Data.pak gets read here.


In the last tutorial I showed you how I looked at the 3D models being used by the game using PIX. Now it was time to look at what files the game was using. Games tend to bundle all their files into archives. These are archives tend to be big and 9th Company had one file that stood out: 9th Company\Data\data.pak. This file is 1.32 GB and when opened with a hex editor has a bunch of file names at the top of the file and a bunch of data at the bottom of the file. I searched for DXT (DDS texture) and the hex array "89 50 4E 47 0D 0A 1A 0A" (png) in the pack file and saw many occurring instances. Great! The files are not compressed or encrypted. Aside from games using standard packing formats, it does not get any easier than this.

From this point, it was a matter of experimenting to try to figure out the structure of the header. I looked for the length of the file names, file offset, the total number of files, etc. Once I thought I had a pretty good idea, I wrote a simple loop that followed a pattern to determine how many files are in the header. Once I got to 500 files, i thought to look at the beginning of the file again. Scanning over the first few bytes, integer at offset 0x5 seemed to be the only plausible value. And sure enough, looking at the offset after reading, this is where the file description ended and data began. Also, the integer after number of files was an offset where the first file started.


The format looked fairly straight forward.

The header was:
struct {
    char type[] ="SMA";
    int8 type_version;
    int16 unknown;
    int32 total_files;
    int32 file_offset;
    int8 file_name_length;
    char file_name[];
}

The main body had the following repeating structure:
struct {
    int32 file_size;
    int32 unknown;
    int32 file_offset;
    int8 file_name_length;
    char file_name[];
}

I had my script print out the file names and offsets:
SMA 2
Number of files: 2904
Data\Art\Buildings\AminPalace\AminPalace.lm, unknown 0x39046, file size 0x85b9d, offset: 0x262c6
Data\Art\Buildings\AminPalace\AminPalace.xml, unknown 0x3f7, file size 0x946, offset: 0x5f30c
Data\Art\Buildings\Army_Buildings\kazarma.lm, unknown 0x12bfd, file size 0x47883, offset: 0x5f703
Data\Art\Buildings\Army_Buildings\kazarma.xml, unknown 0x3afd, file size 0xf832, offset: 0x72300
......

Using this information, I wrote each file to the disk. Looking at DDS texture file and XML files, it was clear that the files where either ciphered or encrypted in some way. A few of the files were not and the unknown field in those files was zero. At the end of the game manual, it says this:

Zlib, 1995-2002 Jean-loup Gailly & Mark Adler.
Please visit: www.gzip.org/zlib

Looking through the strings in the exe, I found lots of references like these:
007A0B0C=9-Pota.007A0B0C (ASCII "unknown compression method")
007A0AE0=9-Pota.007A0AE0 (ASCII "incorrect header check")
007A0AC4=9-Pota.007A0AC4 (ASCII "unknown header flags set")
007A0AB0=9-Pota.007A0AB0 (ASCII "header crc mismatch")
deflate 1.2.3 Copyright 1995-2005 Jean-loup Gailly
inflate 1.2.3 Copyright 1995-2005 Mark Adler


They are from zlib inflate.c. Using zlib.decompress() on each dumped file yielded an uncompressed file!


import struct
import os
import sys
import errno
import zlib

class File(object):
    def __init__(self, path, offset, size, unk):
        self.path = path
        self.offset = offset
        self.size = size
        self.unk = unk

    def create(self, file_pointer):
        directory = os.path.dirname(self.path)
        try: os.makedirs(directory)
        except OSError, err:
            # Reraise the error unless it's about an already existing directory 
            if err.errno != errno.EEXIST or not os.path.isdir(directory): 
                raise
        if self.size > 0:
            file_pointer.seek(self.offset)
            data = file_pointer.read(self.size)            
            with open(self.path, "wb") as f:
                # decompress
                if self.unk != 0:
                    data = zlib.decompress(data)
                f.write(data)
    


files = []
with open("data.pak", "rb") as f:
    magic, = struct.unpack("3s", f.read(3))
    version, = struct.unpack("<H", f.read(2))
    print magic, version
    if version != 2:
        print "Wrong version detected!"
        sys.exit()

    num_files, = struct.unpack("<I", f.read(4))
    print "Number of files:", num_files

    unknown, = struct.unpack("<I", f.read(4))

    for i in range(0, num_files):
        count, = struct.unpack("B", f.read(1))
        path, = struct.unpack("%is" % count, f.read(count))
        file_size, = struct.unpack("<I", f.read(4))
        unk1, = struct.unpack("<I", f.read(4))
        offset, = struct.unpack("<I", f.read(4))
        # unk1 is not adler32 or crc32
        print "%s, unknown %s, file size %s, offset: %s" % (path,  hex(unk1), hex(file_size), hex(offset))
        
        files.append(File(path, offset, file_size, unk1))


    for fil in files:
        fil.create(f)

Conclusion
Code for this work can be found here https://github.com/sbobovyc/GameTools/tree/master/9rota .

References
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366556%28v=vs.85%29.aspx
http://forums.steampowered.com/forums/showthread.php?t=2554597
http://www.pacificstorm.net/forum/viewtopic.php?t=2942
http://www.pacificstorm.net/forum/viewtopic.php?t=2975
http://www.opensource.apple.com/source/zlib/zlib-23.0.1/zlib/inflate.c
ą
Stan Bobovych,
Sep 3, 2013, 3:05 PM
ą
Stan Bobovych,
Sep 4, 2013, 4:20 PM
ą
Stan Bobovych,
Sep 4, 2013, 3:40 PM
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