Cloudera Docs

Preparing for Encryption Using Cloudera Navigator Encrypt

Before you can encrypt data, you must prepare a storage repository to hold the encrypted data and a mount point through which to access the encrypted data. The storage repository and mount point must exist before encrypting data using the navencrypt-move command.

Data stored and retrieved from the repository is encrypted and decrypted transparently.

Cloudera Navigator Encrypt does not support:
  • Encrypting a directory that contains or is contained within a mount point for another service (including Navigator Encrypt and NFS). See Encrypting Data for more information.
  • Encrypting immutable files or directories containing immutable files.
  • Installation or use in chroot environments, including creating chroot environments within an encrypted directory.
  • Encrypting HDFS data files.

Navigator Encrypt Commands

The following table lists the commands used to encrypt data:
Table 1. Navigator Encrypt Commands
Command Description
navencrypt Manage, update, and verify your data.
navencrypt-prepare Prepare your system for encryption by creating mount-points and specifying storage.
navencrypt-prepare --undo Remove a mountpoint that is no longer in use.
navencrypt-move Encrypt/decrypt your data to/from the encrypted file system.
navencrypt-profile Generate process profile information in JSON format.
navencrypt-module-setup Build or rebuild the Navigator Encrypt kernel module.

Preparing for Encryption

To get an in-depth look at the details behind the navencrypt-prepare command, or to use a unique configuration, use the interactive prompt by executing navencrypt-prepare with no options. This launches an interactive console that guides you through the following operations:
  • Creating internal encryption keys
  • Registering internal keys in Navigator Key Trustee
  • Registering mount point in /etc/navencrypt/ztab
  • Mounting current mount point
  • Establishing encryption method (dm-crypt for devices)

Using the console, you can choose how you want your data stored and accessed. Navigator Encrypt offers block-level encryption with dm-crypt, which protects your data by encrypting the entire device. This enables full disk encryption and is optimized for some system configurations. You can use block-level encryption with logical devices such as a loop device.

See Block-Level Encryption with dm-crypt for more information.

To prepare for encryption, you must specify a location to store the encrypted data and a mount point through which to access the data. The storage location and mount point must be created before encrypting data.

Block-Level Encryption with dm-crypt

When choosing block-level encryption in the interactive console, you must specify two parameters:
  1. The first parameter is the block device that you want to store the encrypted file system in. Because this device stores all of the encrypted data, it must be as large as or larger than the target data. The device must exist and be empty. Supported storage devices are:
    • Physical block devices (for example, a disk device)
    • Virtual block devices (for example, a block device created by LVM)
    • Loop devices (see Block-Level Encryption with a Loop Device for instructions on creating a loop device)
  2. The second parameter is the mount point for the encrypted file system. This is the location where you can access the encrypted data stored in the first parameter. The mount point must already exist. It is not created by the navencrypt-prepare command.

The entire device in the first parameter is used for encrypted data.

After specifying these two parameters and following the interactive console (discussed further in Preparing for Encryption), you are ready to encrypt your data.

The syntax for the prepare command is as follows:
sudo navencrypt-prepare <device_name> <mount_point>
When specifying the mount point path, do not use a trailing / in the path names. The mount point directory must exist prior to running the navencrypt-prepare command.
For RHEL 7, run the following command after the navencrypt-prepare command completes:
sudo systemctl start navencrypt-mount
The following example shows successful output from a navencrypt-prepare command using dm-crypt for block-level encryption:
$ sudo /usr/sbin/navencrypt-prepare urandom /mnt/dm_encrypted
Type MASTER passphrase:
Encryption Type:  dmCrypt (LUKS)
Cipher:        aes
Key Size:  256
Random Interface: /dev/urandom
Filesystem:    ext4
Verifying MASTER key against Navigator Key Trustee (wait a moment) ... OK
Generation Encryption Keys with /dev/urandom       ... OK
Preparing dmCrypt device (--use-urandom)               ... OK
Creating ext4 filesystem                               ... OK
Registering Encryption Keys (wait a moment)        ... OK
Mounting /dev/sda1                                    ... OK
After you have successfully prepared a client for encryption, you can encrypt and decrypt data using the commands described in Encrypting and Decrypting Data Using Cloudera Navigator Encrypt.

Block-Level Encryption with a Loop Device

A block-level encrypted device can be a physical device or a storage space treated as a device.

To configure a loop device, use the dd command to create a storage space:
sudo dd if=/dev/zero of=/dmcrypt/storage bs=1G count=500

The dd command above creates a 500 GB file. Modify the bs and count values to generate the required file size.

After generating the file, run losetup -f to view unused loop devices. Use the available loop device with the navencrypt-prepare -d command, demonstrated below.

Specifically for loop devices, the -d parameter enables Navigator Encrypt to manage the loop device association. You no longer need to use the losetup command to associate the file with the loop device, and the loop device is automatically prepared at boot. For RHEL 7-compatible OS, you must run the following commands to ensure that a loop device is available at boot:
sudo bash -c 'echo "loop" > /etc/modules-load.d/loop.conf'
sudo bash -c 'echo "options loop max_loop=8" > /etc/modprobe.d/loop_options.conf'

The data storage directory name (/dmcrypt/storage in the previous example) must contain only alphanumeric characters, spaces, hyphens (-), or underscores (_). Other special characters are not supported.

The following example shows the output from a successful command:
$ losetup -f
/dev/loop0
$ sudo navencrypt-prepare -d /dmcrypt/storage /dev/loop0 /dmcrypt/mountpoint
Type MASTER passphrase:

Encryption Type:  dmCrypt (LUKS)
Cipher:           aes
Key Size:         256
Random Interface: OpenSSL
Filesystem:       ext4
Options:

Verifying MASTER key against KeyTrustee (wait a moment)   ... OK
Generation Encryption Keys with OpenSSL                   ... OK
Assigning '/dev/loop0'->'/dmcrypt/storage'                ... OK
Preparing dmCrypt device                                  ... OK
Creating ext4 filesystem                                  ... OK
Registering Encryption Keys (wait a moment)               ... OK
Mounting /dev/loop0                                       ... OK
For upgraded Navigator Encrypt clients that already use loop devices, you can enable Navigator Encrypt to manage the loop device file association (instead of configuring the system to run the losetup command at boot) by adding the nav_datastore option to the entry in /etc/navencrypt/ztab. For example:
# <target mount-dir>        <source device>      <type>    <options>
/dmcrypt/mountpoint     /dev/loop0      luks    key=keytrustee,nav_datastore='/dmcrypt/storage'

After you have created the loop device, continue with the instructions in Block-Level Encryption with dm-crypt.

Navigator Encrypt and Device UUIDs

Navigator Encrypt has always prepared and identified devices simply using a device name, such as /dev/sdb1 or /dev/loop0. However, we know that using a device name or label could lead to a conflict and impact system operations.

Navigator Encrypt also supports preparing devices using a UUID, in addition to device name. This UUID is simply a symbolic link to the actual device, and is created when preparing a device with Navigator Encrypt during a navencrypt-prepare operation.

The advantage of using a device UUID is that if a device’s name changes, the UUID associated with that device does not change. To ensure that Navigator Encrypt recognizes devices even when the device name changes, enter the command:

navencrypt-prepare --use-uuid /dev/sda1 /mountpoint
To unprepare (ensure the device UUID is included), enter either of the following commands:
navencrypt-prepare --undo-force /dev/disk/by-uuid/3a602a15-11f7-46ac-ae98-0a51e1b25cf9
navencrypt-prepare --undo /dev/disk/by-uuid/3a602a15-11f7-46ac-ae98-0a51e1b25cf9

Pass-through Mount Options for navencrypt-prepare

Navigator Encrypt 3.5 and higher provides the ability to specify options to pass to the mount command that is executed during /etc/init.d/navencrypt-mount start (systemctl start navencrypt-mount on RHEL 7). These options are specified with the -o option when preparing a mountpoint with the navencrypt-prepare command.

The following shows an example navencrypt-prepare command output when passing mount options with the -o option:
$ sudo navencrypt-prepare -o discard,resize /mnt/t2 /mnt/t2
Type MASTER passphrase:

Encryption Type:  dmCrypt (LUKS)
Cipher:           aes
Key Size:         256
Random Interface: OpenSSL
Filesystem:       ext4
Options:          discard,resize

Verifying MASTER key against Navigator Key Trustee(wait a moment)     ... OK
Generation Encryption Keys with OpenSSL                               ... OK
Registering Encryption Keys (wait a moment)                           ... OK
Mounting /mnt/t2                                                      ... OK
You can verify the results by viewing the /etc/navencrypt/ztab file:
$ cat /etc/navencrypt/ztab
/mnt/t2 /mnt/t2 dmcrypt key=keytrustee,cipher=aes,keysize=256,discard,resize

Options can be added or removed to existing mount points prepared with versions of Navigator Encrypt prior to 3.5 by editing the /etc/navencrypt/ztab file and adding the comma-separated options (no spaces) to the end of each line as seen in the previous example above.

To see the mounted file systems and options, run mount:
$ mount
/mnt/t2 on /mnt/t2 type dmcrypt (rw,dmcrypt_sig=6de3db1e87077adb,ecryptfs_unlink_sigs,noauto,\
dmcrypt_cipher=aes,dmcrypt_key_bytes=32,discard,resize)

For a list of available mount options, see the man pages for cryptsetup and dmCrypt respectively.