I'm in the process of writing an application in C++ on Linux. The goal is to have it load dynamically linked libraries at run-time and to provide all the services that the libraries require. The main aim is to have it act as a black box where code loaded at run-time can not break out and damage the rest of the system.
I've never done anything like this before and am a little lost of the best method to take. If I load all the dynamically linked libraries under a special process and then use something like SELinux to limit the ability for the central daemon to do anything outside of its requirements would that seem like a reasonable solution?
The reason I ask is that I want to allow people to load code into this container application that then handles all the server side stuff for them, so things such as security, permissions, networking, logging etc are all provided with a simple, clean and cross platform API regardless of the version of UNIX that the container is running on.
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I am running a Java minecraft server on my Linux server. I have been asked to install some mods (e.g. data packs) on the server which appear to contain Java code written by a third party other than Mojang.
Is this Java code restricted in what it can do, or can it run any arbitrary code it likes (e.g. read /etc/passwd, open TCP ports, claim huge amounts of memory, etc.)?
In other words, how risky are minecraft mods containing Java code?
This is a very good question. I actually was wondering that too. I have spent a bit of time looking at the binaries of minecraft and the minecraft server spigot. I assume we both use the Java Edition.
First of all, the Java code, once you run it on a host, can do anything. The only mechanism that can prevent that and protect the user from the developer in Java, is the security manager. Once you turn on the security manager (which is an opt-in mechanism) you have the ability to define a set of rules that Java will obey like e.g. it will not write into directories you don't allow it too.
So the question is: is minecraft using the security manager per default. I am 99% sure it does not. No one is using the security manager because it is a pain to configure it right and things stop working every time you get it wrong (you know that an applications uses the security manager because you face problems with policy misconfiguration every now and then).
Running minecraft is made by running an exe. I would not now where to turn the security manager on even if I would like too. There is a bit of hope with the spigot server. You can install the security manager with -Djava.security.manager and input your policy with -Djava.security.policy==my.policy. But getting the policy right will be pain. I will try to look into it though when I have a free week or so.
Minecraft mods can act with the full permissions of the user running Minecraft. If you don't trust the author of a mod, then there's basically two approaches to safely use it:
Audit the source code yourself, and then compile the mod yourself so you know it matches the binary
Run Minecraft in a sandbox such as a VM, or as a heavily restricted user.
I read over internet "containers wrap up a piece of software in a complete filesystem that contains everything it needs to run: code, runtime, system tools, system libraries – anything you can install on a server".
I also read that linux containers cannot run on windows.
The benifits of containers stated "Containers run as an isolated process in userspace on the host operating system."
I don't understand if the containers are not platform independent what we are actually achieving out it?
1) Anyhow all the applications on a linux box should run as an isolated process in their userspace.
2) If containers only contain app code + runtimes + tools + libraries. They can be shipped together. What conatiners are getting here?
Posting the comment as answer::
If containers only contain app code + runtimes + tools + libraries.
They can be shipped together. What conatiners are getting here?
Suppose there is an enterprise with thousands of employees and all of them work on Visual Studio C++. Now, the administrator can create a container with the installed (only C++ components) and configured VS, and deploy that container to all employees. The employees can instantly start working without bothering about installation and configuration of the application. Again, if the employee somehow corrupts the application, they only need to download the container again and they are good to go.
Sandboxing
Security
Maintenance
Mobility
Backup
Many more to go.
Are container platform independent?
IMHO, I don't think so, as they rely on the system calls. Though, I am open to other concepts if anybody knows better on this topic.
Even only considering one platform, containers have their advantages; just not perhaps the ones you need right now. :-) Containers help in administration/maintenance of complex IT systems. With containers you can easily isolate applications, their configuration, and their users, to achieve:
Better security (if someone breaks in, damage is usually limited to one container)
Better safety (if something breaks, or e.g. you make an error, only applications in a given container will be victim to this)
Easier management (containers can be started/stopped separately, can be transferred to another hosts (granted: host with the same OS; in case of Linux containers the host must also be Linux))
Easier testing (you can create and dispose-off containers at will, anytime)
Lighter backup (you can backup just the container; not the whole host)
Some form of increasing availaibility (by proper pre-configuration and automatic switching a container over to another host you can be up and running quicker in case of the primary host failure)
...just to name the first advantages coming to mind.
I want to create a application that contains a feature that allows users to submit code and the server will compile and run it, similar to Ideone & Spoj. How do I do this securely in a scalable manner?
Partial Solutions I'm aware of:
IDEA 1 - 3rd Party Services
The Sphere Engine. However this costs a LOT of money!
I'm not aware of any open source application I can run on my server to achieve this, or a cheaper alternative. Please correct me if i'm wrong.
IDEA 2 - VM
This would be the next most sensible choice. However, I'm unsure how to implement it. For example let's say I created a VM and started to run the user's code. This would restrict damage on MY system, but not the damage on the VM, which other users would have to use. Does that mean I have to create a new VM each and every time I want to compile and run user's code (which clearly is not scalable - correct me if I'm wrong.
Having not set up a thing, I assumed that services like TravisCI (which compiles code and runs it under test cases you provide), have a base virtual machine image, which boots up and processes your code. The next user to come along gets a separate VM booted from the same base image, your changes aren't stored.
So inside the VM, the user code can do whatever. All of its effects, except stuff written to the console will be erased at the end of the time limit.
I would like to create something like "file honeypot" on Windows OS.
The problem I would like to answer is this:
I need to detect that file is accessed (Malware wants to read file to send it over internet) so I can react to it. But I do not know how exacly tackle this thing.
I can periodically test file - Do not like this sollution. Would like some event driven without need to bother processor every few ms. But could work if file is huge enought so it cannot be read between checks.
I could exclusively open file myselve and somehow detect if file is accessed. But I have no idea how to do this thing.
Any idea about how to resolve this issue effectively? Maybe creating specialized driver could help but I have little experience in this.
Thanks
Tracking (and possibly preventing) filesystem access on Windows is accomplished using filesystem filter drivers. But you must be aware that kernel-mode code (rootkits etc) can bypass the filter driver stack and send the request directly to the filesystem. In this case only the filesystem driver itself can log or intercept access.
I'm going to assume that what you're writing is a relatively simple honeypot. The integrity of the system on which you're running has not been compromised, there is no rootkit or filter driver installation by malware and there is no process running that can implement avoidance or anti-avoidance measures.
The most likely scenario I can think of is that a server process running on the computer is subject to some kind of external control which would allow files containing sensitive data to be read remotely. It could be a web server, a mail server, an FTP server or something else but I assume nothing else on the computer has been compromised. And the task at hand is to watch particular files and see if anything is reading them.
With these assumptions a file system watcher will not help. It can monitor parts of the system for the creation of new files or modification or deletion of existing ones, but as far as I know it cannot monitor for read only access.
The only event-driven mechanism I am aware of is a filter driver. This is a specialised piece of driver software that can be inserted into the driver chain and monitor access to files. With the constraints above, it is a reliable solution to the problem at the cost of being quite hard to write.
If a polling mechanism is sufficient then I can see two avenues. One is to try to lock the file exclusively, which will fail if it is open. This is easy, but slow.
The other is to monitor the open file handles. I know it can be done because I know programs that do it, but I can't tell you how without some research.
If my assumptions are wrong, please edit your question and provide additional information.
For reasons beyond the scope of this post, I want to run external (user submitted) code similar to the computer language benchmark game. Obviously this needs to be done in a restricted environment. Here are my restriction requirements:
Can only read/write to current working directory (will be large tempdir)
No external access (internet, etc)
Anything else I probably don't care about (e.g., processor/memory usage, etc).
I myself have several restrictions. A solution which uses standard *nix functionality (specifically RHEL 5.x) would be preferred, as then I could use our cluster for the backend. It is also difficult to get software installed there, so something in the base distribution would be optimal.
Now, the questions:
Can this even be done with externally compiled binaries? It seems like it could be possible, but also like it could just be hopeless.
What about if we force the code itself to be submitted, and compile it ourselves. Does that make the problem easier or harder?
Should I just give up on home directory protection, and use a VM/rollback? What about blocking external communication (isn't the VM usually talked to over a bridged LAN connection?)
Something I missed?
Possibly useful ideas:
rssh. Doesn't help with compiled code though
Using a VM with rollback after code finishes (can network be configured so there is a local bridge but no WAN bridge?). Doesn't work on cluster.
I would examine and evaluate both a VM and a special SELinux context.
I don't think you'll be able to do what you need with simple file system protection because you won't be able to prevent access to syscalls which will allow access to the network etc. You can probably use AppArmor to do what you need though. That uses the kernel and virtualizes the foreign binary.