kJudge

kJudge is a kernel-based sandbox for contest management systems. It is intended to safely execute untrusted third-party code. This is achieved by forbidding potentially harmful system calls and specifying time and memory limits on the program to be executed.

Installation

To easily prepare development environment run kernel/setup.sh

1. Change to the kernel/ directory

cd kernel/

2. Download the proper Linux kernel source version (4.14.88 for the moment)

wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.14.88.tar.xz

3. Untar the Linux kernel source archive

tar -xf linux-4.14.88.tar.xz

4. Change to the Linux kernel source directory

cd linux-4.14.88

5. Apply the kjudge kernel patch

patch -p1 < ../kjudge-linux-4.14.88.patch

6. Now you are to build the kernel in any preferred way. If you have no idea how this is done see the Building kernel section

7. After booting to the new kernel verify whether the kernel is patched

uname -r
# output: 4.14.88-kjudge

8. Copy the header file to /usr/include

cp include/kjudge.h /usr/include/kjudge.h

9. (optionally) To run tests change to the tests/ directory and run runTests.py

Usage

TODO

Building kernel

Please note that this is a universal method for building the kernel, but it may not work on some distributions. If so, you are to follow your system specific instructions which unfortunately are not given here.

1. Copy the existing config file

cp -v /boot/config-`uname -r` .config

2. Install required tools for building the kernel

• Debian/Ubuntu Linux

sudo apt-get install build-essential libncurses-dev bison flex libssl-dev libelf-dev

• CentOS/RHEL/Oracle/Scientific Linux

sudo yum groupinstall "Development Tools"
sudo yum install ncurses-devel bison flex elfutils-libelf-devel openssl-devel

• Fedora Linux

sudo dnf group install "Development Tools"
sudo dnf install ncurses-devel bison flex elfutils-libelf-devel openssl-devel

3. Configure the kernel (optional)

make menuconfig

4. Compile the kernel

N=6
make -jN
sudo make modules_install
sudo make install

5. Update grub config (Only for CentOS/RHEL/Oracle/Scientific/Fedora Linux)

sudo grub2-mkconfig -o /boot/grub2/grub.cfg
sudo grubby --set-default /boot/vmlinuz-4.14.88-kjudge
grubby --info=ALL | more
grubby --default-index
grubby --default-kernel

6. Now reboot into the new kernel and verify whether the kernel is patched

uname -r
# output: 4.14.88-kjudge