mirror of
https://github.com/Grasscutters/mitmproxy.git
synced 2024-11-23 08:11:00 +00:00
128 lines
4.4 KiB
ReStructuredText
128 lines
4.4 KiB
ReStructuredText
.. _gamecenter:
|
|
|
|
Setting highscores on Apple's GameCenter
|
|
========================================
|
|
|
|
The setup
|
|
---------
|
|
|
|
In this tutorial, I'm going to show you how simple it is to creatively
|
|
interfere with Apple Game Center traffic using mitmproxy. To set things up,
|
|
:ref:`install the mitmproxy root certificate <certinstall>`. Then
|
|
start mitmproxy on your desktop, and confige the iPhone to use it as a proxy.
|
|
|
|
|
|
Taking a look at the Game Center traffic
|
|
----------------------------------------
|
|
|
|
Lets take a first look at the Game Center traffic. The game I'll use in this
|
|
tutorial is `Super Mega Worm`_ - a great little retro-apocalyptic sidescroller for the iPhone:
|
|
|
|
.. image:: supermega.png
|
|
:align: center
|
|
|
|
|
|
After finishing a game (take your time), watch the traffic flowing through
|
|
mitmproxy:
|
|
|
|
.. image:: one.png
|
|
:align: center
|
|
|
|
We see a bunch of things we might expect - initialisation, the retrieval of
|
|
leaderboards and so forth. Then, right at the end, there's a POST to this
|
|
tantalising URL:
|
|
|
|
.. code-block:: none
|
|
|
|
https://service.gc.apple.com/WebObjects/GKGameStatsService.woa/wa/submitScore
|
|
|
|
The contents of the submission are particularly interesting:
|
|
|
|
.. code-block:: xml
|
|
|
|
<!--(block|syntax("xml"))-->
|
|
<plist version="1.0">
|
|
<dict>
|
|
<key>scores</key>
|
|
<array>
|
|
<dict>
|
|
<key>category</key>
|
|
<string>SMW_Adv_USA1</string>
|
|
<key>context</key>
|
|
<integer>0</integer>
|
|
<key>score-value</key>
|
|
<integer>0</integer>
|
|
<key>timestamp</key>
|
|
<integer>1363515361321</integer>
|
|
</dict>
|
|
</array>
|
|
</dict>
|
|
</plist>
|
|
<!--(end)-->
|
|
|
|
This is a `property list`_, containing an identifier for the game,
|
|
a score (55, in this case), and a timestamp. Looks pretty simple to mess with.
|
|
|
|
Modifying and replaying the score submission
|
|
--------------------------------------------
|
|
|
|
Lets edit the score submission. First, select it in mitmproxy, then press
|
|
:kbd:`enter` to view it. Make sure you're viewing the request, not the response -
|
|
you can use :kbd:`tab` to flick between the two. Now press :kbd:`e` for edit. You'll
|
|
be prompted for the part of the request you want to change - press :kbd:`r` for
|
|
raw body. Your preferred editor (taken from the EDITOR environment variable) will
|
|
now fire up. Lets bump the score up to something a bit more ambitious:
|
|
|
|
.. code-block:: xml
|
|
|
|
<!--(block|syntax("xml"))-->
|
|
<plist version="1.0">
|
|
<dict>
|
|
<key>scores</key>
|
|
<array>
|
|
<dict>
|
|
<key>category</key>
|
|
<string>SMW_Adv_USA1</string>
|
|
<key>context</key>
|
|
<integer>0</integer>
|
|
<key>score-value</key>
|
|
<integer>2200272667</integer>
|
|
<key>timestamp</key>
|
|
<integer>1363515361321</integer>
|
|
</dict>
|
|
</array>
|
|
</dict>
|
|
</plist>
|
|
<!--(end)-->
|
|
|
|
Save the file and exit your editor.
|
|
|
|
The final step is to replay this modified request. Simply press :kbd:`r` for replay.
|
|
|
|
|
|
The glorious result and some intrigue
|
|
-------------------------------------
|
|
|
|
.. image:: leaderboard.png
|
|
:align: center
|
|
|
|
And that's it - according to the records, I am the greatest Super Mega Worm
|
|
player of all time.
|
|
|
|
There's a curious addendum to this tale. When I first wrote this tutorial, all
|
|
the top competitors' scores were the same: 2,147,483,647 (this is no longer the
|
|
case, beacause there are now so many fellow cheaters using this tutorial). If
|
|
you think that number seems familiar, you're right: it's 2^31-1, the maximum
|
|
value you can fit into a signed 32-bit int. Now let me tell you another
|
|
peculiar thing about Super Mega Worm - at the end of every game, it submits
|
|
your highest previous score to the Game Center, not your current score. This
|
|
means that it stores your highscore somewhere, and I'm guessing that it reads
|
|
that stored score back into a signed integer. So, if you _were_ to cheat by the
|
|
relatively pedestrian means of modifying the saved score on your jailbroken
|
|
phone, then 2^31-1 might well be the maximum score you could get. Then again,
|
|
if the game itself stores its score in a signed 32-bit int, you could get the
|
|
same score through perfect play, effectively beating the game. So, which is it
|
|
in this case? I'll leave that for you to decide.
|
|
|
|
.. _Super Mega Worm: https://itunes.apple.com/us/app/super-mega-worm/id388541990?mt=8
|
|
.. _property list: https://en.wikipedia.org/wiki/Property_list |