start.sh

#!/bin/bash
USER=${USER:-sftp}
USER_ID=${USER_ID:-1000}
GROUP_ID=${GROUP_ID:-1000}
PASS=${PASS:-c83eDteUDT}

for type in rsa dsa ecdsa ed25519; do
  if ! [ -e "/ssh/ssh_host_${type}_key" ]; then
    echo "/ssh/ssh_host_${type}_key not found, generating..."
    ssh-keygen -f "/ssh/ssh_host_${type}_key" -N '' -t ${type}
  fi

  ln -sf "/ssh/ssh_host_${type}_key" "/etc/ssh/ssh_host_${type}_key"
  ln -sf "/ssh/ssh_host_${type}_key.pub" "/etc/ssh/ssh_host_${type}_key.pub"
done

if (id ${USER}); then
  echo "INFO: User ${USER} already exists"
else
  echo "INFO: User ${USER} does not exists, we create it"
  ENC_PASS=$(perl -e 'print crypt($ARGV[0], "password")' ${PASS})

  GET_USER_BY_ID=$(cat /etc/passwd | grep ${USER_ID} | head -n1 | awk -F: '{ print $1 }')
  deluser ${GET_USER_BY_ID}

  GET_GROUP_BY_ID=$(cat /etc/group | grep ${GROUP_ID} | head -n1 | awk -F: '{ print $1 }')
  delgroup ${GET_GROUP_BY_ID}

  addgroup --gid ${GROUP_ID} sftp-only

  useradd -d /data -m -g sftp-only -p ${ENC_PASS} -u ${USER_ID} -s /bin/false ${USER}
  usermod -aG sftp-only ${USER}

  chown ${USER_ID}:${GROUP_ID} /data/incoming

  if [ ! -e /data/.ssh/authorized_keys ] && [ -n "$PUBKEY" ]; then
    mkdir /data/.ssh
    touch /data/.ssh/authorized_keys
    echo ${PUBKEY} >>/data/.ssh/authorized_keys
  fi
fi

exec /usr/sbin/sshd -D -e