1. Counter Strike Download Unblocked

One night while playing Counter Strike: Condition Zero (CZ), I decided to take a break and challenge myself to find an exploitable bug in the old engine known as GoldSrc. Condition Zero, Half-Life 1, and CS 1.6 all run on the GoldSrc engine, which was created by Valve and is based upon the original Quake engine.What makes Counter Strike an interesting target is that it relies on a game lobby for players to find and select servers to play on. Upon connecting to the server, the game client will automatically download any required resources (maps, textures, sounds, etc.).Once all of the resources have been downloaded, they have to be loaded and parsed from disk into memory. Only then will the client begin receiving commands and entity updates from the server.This automatic resource fetching looked like the ticket to a remotely exploitable vulnerability via a local file.The vulnerability discussed in this article has been disclosed to Valve Security and the.I would like to extend my thanks to the Valve Security team and specifically to Alfred Reynolds who was my liaison during the disclosure process. The whole process, from initial email to fix, lasted less than 30 days. I certainly look forward to disclosing to Valve in the future. Finding CrashesMy approach to finding bugs was to use the.Essentially I gathered a bunch of existing BSP map files for my corpus and then used them as seeds to my fuzzing engine.

This will corrupt them and then feed them back in to the program (CZ) to be parsed while being watched for any crashes. If a crash is found, it is recorded and stored for later triage and classification.I figured that highly complex file formats such as.BSP would map quite well to low-level memcpy operations in the engine.

It’s even possible that stored sizes of data structures in the BSP file will be less validated than most file formats.I had a few false starts to this project when selecting a fuzzer to use. FirstI tried under Cygwin, but thisproved to be completely broken for crash detection. Next I triedwhich I was unable to get towork due to some binary incompatibilities and possible Windows 10 issues. Thisled to a multi-day rabbit hole of building DynamicRIO from source andrebuilding WinAFL against it. In the end I gave up trying to get a coveragebased fuzzer to work and went instead with the solid.This proved to be an excellent choice due to its easy configuration file anddeep integration with Microsoft debugging tools, including WinDBG.

Counter Strike Download Unblocked

I also had some relevant experience with the frameworkthrough fuzzing VLC when it used to be called Failure Observation Engine (FOE).BFF is a simple “dumb” fuzzer, meaning it merely corrupts bytes in the file andwrites it back out. It has no knowledge of the BSP file format or of the targetit is fuzzing. This is great for quick setup, but for more complex formats,code coverage of the parsing code may be limited. For shallow bugs, dumbfuzzing will not have much of an issue finding them.With this fuzzer in mind, I went about exploring instrumentation on the GoldSrc engine. When running a game on this engine, the executable hl.exe boots, loads common engine resources, and then loads a game specific DLL (known as a client DLL or cldll) which drives the engine via a proxy API. This API and the associated utilities are the primary SDK interface that many game modders deal with. Technically Counter Strike 1.6 ( cstrike) and Condition Zero ( czero) are both considered “mods” as they merely use the proxy API for gameplay.

When running a mod like CZ, the engine command line looks like: hl.exe -game czero $OTHERARGS. In order to quickly iterate through map files, I looked up the command line flags for starting the engine with CZ and to load a map upon start. This is the command line I used:C:Program Files (x86)SteamsteamappscommonHalf-Lifehl.exe -game czero -dev -window -console +svlan 1 +map MAPNAMEwhere -window makes it so I can fuzz and browse the web at the same time, svlan 1 makes a local-only server, and map immediately changes the map on login.With the ability to programmatically run the engine, I installed BFF, Debugging Tools for Windows, and then started configuring BFF. BFF installs to C:BFF by default and has the concept of a fuzzing campaign. I started a new one for CZ and then edited the bff.yaml configuration file: campaign: id: counter strike czero keepheisenbugs: False usebuttonclicker: False target: program: C:UsersMyName.babuncygwinbinbash.exe cmdlinetemplate: $PROGRAM -c 'C:/BFF/mover.sh' $SEEDFILE 'C:/Program Files (x86)/Steam/steamapps/common/Half-Life/hl.exe' -game czero -dev -window -console +svlan 1 +map aimfuzz' NUL. Directories: seedfiledir: seedfilesbsp workingdir: fuzzdir resultsdir: results.

Fuzzer: fuzzer: bytemut fuzzzipcontainer: FalseEverything except program, cmdlinetemplate, and seedfiledir are the defaults. Notice that this cmdline isn’t just running hl.exe. This is because I ran into problems getting the corrupted BSP file to be read by the engine. GoldSrc has a dedicated, per-mod resource directory and will not load resources based on an absolute path. Hence, I made a bash script under Cygwin to first move the generated BSP file to the resource directory as aimfuzz.bsp.

It’s a simple three-liner, it gets the job done, and doesn’t affect crash detection due to exec.