Linux Kernel Exploitation

Linux kernel exploitation lab.
Slide: speakerdeck.com/yuawn/kernel-exploitation

Linux kernel exploitation techniques

• ret2user
  • status switch
• modify cr4 register
  • bypass smep
  • bypass smap
• kpti
  • fix cr3 register
  • swapgs_restore_regs_and_return_to_usermode()
• kernel information leak
  • useful kernel structure for UAF
• modprobe_path
• userfaultfd
  • race condition
• setxattr
  • setxattr + userfaultfd
• msg_msg
• signal handler

Prepare files needed to compile kernel module

wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.1.tar.xz
tar Jxvf linux-5.10.1.tar.xz
cp .config linux-5.10.1
cd linux-5.10.1
make menuconfig # load .config
make modules_prepare

Compile linux kernel

sudo apt-get install build-essential libncurses-dev bison flex libssl-dev libelf-dev
wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.1.tar.xz
tar Jxvf linux-5.10.1.tar.xz
cp .config linux-5.10.1
cd linux-5.10.1
make menuconfig # load .config
make -j $(nproc)

busybox

wget https://busybox.net/downloads/busybox-1.32.0.tar.bz2
tar jxvf busybox-1.32.0.tar.bz2
cd busybox-1.32.0
mkdir build
export BUSYBOX_BUILD=$(pwd)/build
make O=$BUSYBOX_BUILD defconfig
make O=$BUSYBOX_BUILD menuconfig # Settings -> Build Options: enable Build static binary (no shared libs)
cd $BUSYBOX_BUILD
make -j 4
make install -j 4

initramfs

mkdir rootfs
cd rootfs
mkdir -pv {bin,sbin,etc,proc,dev,tmp,sys,usr/{bin,sbin}}
cp -r $BUSYBOX_BUILD/_install/* .
vim init # Create init file

• Some files
  • /etc/passwd
  • /home/user
  • /flag