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dracut-encryptrootfs

Dracut module for encryption of rootfs partition during first boot. The Cryptsetup LUKS implementation is used for crypto.

It is targeted to protect data with encryption for cases when physical access to disk is technically possible.

Workflow

dracut-encryptrootfs does the following to encrypt rootfs partition.

  1. During boot on initramfs aks early user space
    1. copying all rootfs partition content to memory
    2. repartitioning of disk
      1. creating, formatting, labeling label:boot partition
      2. creating, formatting future rootfs partition
    3. generating plain text LUKS key
    4. creating and configuring LUKS volume
    5. copying back rootfs content from memory to LUKS backed partition
    6. encrypting LUKS key and storing it to /boot/luks.key location
  2. During init process
    1. moving all /boot content to label:boot partition where /boot/luks.key is already located
    2. updating /etc/fstab
    3. updating GRUB configuration
    4. updating MBR with re-installing boot loader

Result partition table looks like this

Disk diagram

Installation

Module could be installed from git repo directly. Here is a sample for AWS instance (Centos 7). Make sure that all filesystem content fits in available memory. m3.medium is sufficient for ~2GB of image content.

#!/usr/bin/env bash

# Sample configuration for Centos 7
git clone https://github.com/zaletniy/dracut-encryptrootfs.git
cd dracut-encryptrootfs

yum -y install dropbear cryptsetup

#installing dracut modules
cp -a modules.d/* /usr/lib/dracut/modules.d/
cp encryptrootfs.conf /etc/dracut.conf.d/

#adding public key to config
echo "dropbear_acl=\"ssh-rsa AAAABPAR...e user\"" >> /etc/dracut.conf.d/encryptrootfs.conf
echo "disk=xvda" >> /etc/dracut.conf.d/encryptrootfs.conf
echo "root_partition=xvda1" >> /etc/dracut.conf.d/encryptrootfs.conf
echo "install_debug_deps=true" >> /etc/dracut.conf.d/encryptrootfs.conf
echo "networking_configuration_implementation="dhcp_networking_configuration_centos7.sh"
echo "debug_deps=\"blockdev e2fsck partx partprobe resize2fs tune2fs lsmod env df du md5sum chmod\"" >> /etc/dracut.conf.d/encryptrootfs.conf

#useful for AWS EC2 to update /usr/lib/modules/$(uname -r)/modules.dep
#if image was imported to EC2
depmod -a

#rebuilding of initramfs
dracut -f -v

#installing Systemd service
cp init/dracut-encryptrootfs-final /usr/local/sbin/dracut-encryptrootfs-final
cp init/systemd/encryptrootfs.service /etc/systemd/system/encryptrootfs.service

chmod 664 /etc/systemd/system/encryptrootfs.service
chmod 744 /usr/local/sbin/dracut-encryptrootfs-final

systemctl daemon-reload
systemctl enable encryptrootfs.service

sed -i '/GRUB_CMDLINE_LINUX/d' /etc/default/grub
echo "GRUB_CMDLINE_LINUX=\"ttyS0,115200n8 console=tty0 vconsole.font=latarcyrheb-sun16 vconsole.keymap=us biosdevname=0 plymouth.enable=0 crashkernel=auto rd.neednet=1 ip=dhcp rd.net.dhcp.retry=5 rd.net.timeout.dhcp=60 rd.shell rd.debug log_buf_len=1M\"
" >> /etc/default/grub

sed -i '/GRUB_TIMEOUT/d' /etc/default/grub
echo "GRUB_TIMEOUT=5" >> /etc/default/grub

#debug output
cat /etc/default/grub

grub2-mkconfig -o /boot/grub2/grub.cfg

#debug output
blkid

reboot

Compatibility

Module is compatible with Centos 7 and Centos 6. It uses GRUB, Cryptsetup, systemd and expects MBR partitioning schema.

Key management

The key management logic is pluggable and could be configured with providing corresponding bash implementation naive_keymanagement.sh could be used as example.

Networking configuration

It is expected that LUKS key is never stored in unencrypted way on machine and decrypted with external key management system. So network connectivity is a critical dependency.

Another reason for networking is ability to troubleshoot dracut for headless system where console or VNC is not an option (f.e. AWS EC2).

The networking configuration logic could be customized with providing bash implementation. DHCP implementation dhcp_networking_configuration.sh could be used as sample.

This script will be called until it returns 0 as part of dracut initqueue

AWS KMS integration

To integrate module with AWS Key Management System simple-cloud-encrypt utility could be used.

Troubleshooting

To troubleshoot boot process you can follow all standard documentation with the only difference when you don't have access to machine console you can login via ssh using RSA key configured during module installation.

ssh root@VM_HOST -p 2222, where 2222 - default port

Contributions

Prior to receiving information from any contributor, Symantec requires that all contributors complete, sign, and submit Symantec Personal Contributor Agreement (SPCA). The purpose of the SPCA is to clearly define the terms under which intellectual property has been contributed to the project and thereby allow Symantec to defend the project should there be a legal dispute regarding the software at some future time. A signed SPCA is required to be on file before an individual is given commit privileges to the Symantec open source project. Please note that the privilege to commit to the project is conditional and may be revoked by Symantec.

If you are employed by a corporation, a Symantec Corporate Contributor Agreement (SCCA) is also required before you may contribute to the project. If you are employed by a company, you may have signed an employment agreement that assigns intellectual property ownership in certain of your ideas or code to your company. We require a SCCA to make sure that the intellectual property in your contribution is clearly contributed to the Symantec open source project, even if that intellectual property had previously been assigned by you.

Please complete the SPCA and, if required, the SCCA and return to Symantec at:

Symantec Corporation Legal Department Attention: Product Legal Support Team 350 Ellis Street Mountain View, CA 94043

Please be sure to keep a signed copy for your records.

LICENSE

Copyright 2015 Symantec Corporation.

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License.

You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.