#!/usr/bin/env bash
# Ripped from syzkaller create-image

# create-image.sh creates a minimal Debian Linux image suitable for syzkaller.

set -eux

# Create a minimal Debian distribution in a directory.
PREINSTALL_PKGS=build-essential,openssh-server,sudo,curl,tar,time,debian-ports-archive-keyring
# Variables affected by options
ARCH=$(uname -m)
RELEASE=bullseye
SEEK=2047
PERF=false

# Display help function
display_help() {
    echo "Usage: $0 [option...] " >&2
    echo
    echo "   -a, --arch                 Set architecture"
    echo "   -d, --distribution         Set on which debian distribution to create"
    echo "   -s, --seek                 Image size (MB), default 2048 (2G)"
    echo "   -h, --help                 Display help message"
    echo
}

while true; do
    if [ $# -eq 0 ];then
    echo $#
    break
    fi
    case "$1" in
        -h | --help)
            display_help
            exit 0
            ;;
        -a | --arch)
        ARCH=$2
            shift 2
            ;;
        -d | --distribution)
        RELEASE=$2
            shift 2
            ;;
        -s | --seek)
        SEEK=$(($2 - 1))
            shift 2
            ;;
        -*)
            echo "Error: Unknown option: $1" >&2
            exit 1
            ;;
        *)  # No more options
            break
            ;;
    esac
done

# Handle cases where qemu and Debian use different arch names
case "$ARCH" in
    ppc64le)
        DEBARCH=ppc64el
        ;;
    aarch64)
        DEBARCH=arm64
        ;;
    arm)
        DEBARCH=armel
        ;;
    x86_64)
        DEBARCH=amd64
        ;;
    *)
        DEBARCH=$ARCH
        ;;
esac

# Foreign architecture

FOREIGN=false
if [ $ARCH != $(uname -m) ]; then
    # i386 on an x86_64 host is exempted, as we can run i386 binaries natively
    if [ $ARCH != "i386" -o $(uname -m) != "x86_64" ]; then
        FOREIGN=true
    fi
fi

if [ $FOREIGN = "true" ]; then
    # Check for according qemu static binary
    if ! which qemu-$ARCH-static; then
        echo "Please install qemu static binary for architecture $ARCH (package 'qemu-user-static' on Debian/Ubuntu/Fedora)"
        exit 1
    fi
    # Check for according binfmt entry
    if [ ! -r /proc/sys/fs/binfmt_misc/qemu-$ARCH ]; then
        echo "binfmt entry /proc/sys/fs/binfmt_misc/qemu-$ARCH does not exist"
        exit 1
    fi
fi

DIR=$RELEASE
sudo rm -rf $DIR
sudo mkdir -p $DIR
sudo chmod 0755 $DIR

# 1. debootstrap stage

DEBOOTSTRAP_PARAMS="--arch=$DEBARCH --include=$PREINSTALL_PKGS --components=main,contrib,non-free,non-free-firmware $RELEASE $DIR"
if [ $FOREIGN = "true" ]; then
    DEBOOTSTRAP_PARAMS="--foreign $DEBOOTSTRAP_PARAMS"
fi

# riscv64 is hosted in the debian-ports repository
# debian-ports doesn't include non-free, so we exclude firmware-atheros
if [ $DEBARCH == "riscv64" ]; then
    DEBOOTSTRAP_PARAMS="--keyring /usr/share/keyrings/debian-ports-archive-keyring.gpg --exclude firmware-atheros $DEBOOTSTRAP_PARAMS http://deb.debian.org/debian-ports"
fi

# debootstrap may fail for EoL Debian releases
RET=0
sudo --preserve-env=http_proxy,https_proxy,ftp_proxy,no_proxy debootstrap $DEBOOTSTRAP_PARAMS || RET=$?

if [ $RET != 0 ] && [ $DEBARCH != "riscv64" ]; then
    # Try running debootstrap again using the Debian archive
    DEBOOTSTRAP_PARAMS="--keyring /usr/share/keyrings/debian-archive-removed-keys.gpg $DEBOOTSTRAP_PARAMS https://archive.debian.org/debian-archive/debian/"
    sudo --preserve-env=http_proxy,https_proxy,ftp_proxy,no_proxy debootstrap $DEBOOTSTRAP_PARAMS
fi

# 2. debootstrap stage: only necessary if target != host architecture

if [ $FOREIGN = "true" ]; then
    sudo cp $(which qemu-$ARCH-static) $DIR/$(which qemu-$ARCH-static)
    sudo chroot $DIR /bin/bash -c "/debootstrap/debootstrap --second-stage"
fi

# Set some defaults and enable promtless ssh to the machine for root.
sudo sed -i '/^root/ { s/:x:/::/ }' $DIR/etc/passwd
echo 'T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100' | sudo tee -a $DIR/etc/inittab
printf '\nauto eth0\niface eth0 inet dhcp\n' | sudo tee -a $DIR/etc/network/interfaces
echo '/dev/root / ext4 defaults 0 0' | sudo tee -a $DIR/etc/fstab
echo 'debugfs /sys/kernel/debug debugfs defaults 0 0' | sudo tee -a $DIR/etc/fstab
echo 'securityfs /sys/kernel/security securityfs defaults 0 0' | sudo tee -a $DIR/etc/fstab
echo 'configfs /sys/kernel/config/ configfs defaults 0 0' | sudo tee -a $DIR/etc/fstab
echo 'binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc defaults 0 0' | sudo tee -a $DIR/etc/fstab
echo -en "127.0.0.1\tlocalhost\n" | sudo tee $DIR/etc/hosts
echo "nameserver 8.8.8.8" | sudo tee -a $DIR/etc/resolv.conf
echo "cor-tribunal" | sudo tee $DIR/etc/hostname
ssh-keygen -f $RELEASE.id_rsa -t rsa -N ''
sudo mkdir -p $DIR/root/.ssh/
cat $RELEASE.id_rsa.pub | sudo tee $DIR/root/.ssh/authorized_keys

# challenge specific setup
sudo git clone https://github.com/cifsd-team/ksmbd-tools.git $DIR/ksmbd-tools
sudo chroot $DIR /bin/bash -c 'apt update && apt install -y pkgconf autoconf dh-autoreconf automake libtool make gawk libnl-genl-3-dev libglib2.0-dev'
sudo chroot $DIR /bin/bash -c 'cd ksmbd-tools && ./autogen.sh && ./configure --with-rundir=/run && make && make install'
sudo chroot $DIR /bin/bash -c "mkdir -vp CompanyShare && chmod 777 CompanyShare && ksmbd.addshare --add --option 'path=/CompanyShare' --option 'read only = no' CompanyShare"
sudo chroot $DIR /bin/bash -c "ksmbd.adduser --add fossboss --password=fossboss"
sudo chroot $DIR /bin/bash -c "adduser --shell /bin/bash --home /home/fossboss --gecos --disabled-password fossboss"
sudo chroot $DIR /bin/bash -c "ksmbd.addshare --update --option 'force user = fossboss' --option 'force fossboss' CompanyShare"
sudo chroot $DIR /bin/bash -c "systemctl enable ksmbd.service"
sudo chroot $DIR /bin/bash -c "apt install -y netcat-traditional"
sudo rm $DIR/root/.bash_history

for x in $(sudo find $DIR/); do sudo touch -t 0606060606 $x || true; done

# Build a disk image
dd if=/dev/zero of=$RELEASE.img bs=1M seek=$SEEK count=1
sudo mkfs.ext4 -F $RELEASE.img
sudo mkdir -p /mnt/$DIR
sudo mount -o loop $RELEASE.img /mnt/$DIR
sudo cp -a $DIR/. /mnt/$DIR/.
sudo umount /mnt/$DIR
qemu-img convert -f raw -O qcow2 $RELEASE.img $RELEASE-temp.qcow2
rm $RELEASE.img
sudo virt-sparsify $RELEASE-temp.qcow2 $RELEASE.qcow2
rm $RELEASE-temp.qcow2