PostgreSQL instance encryption
==============================

If the instance (cluster) encryption is enabled, data (including WAL) is
encrypted before it's stored to disk. Conversely, decryption is the first
thing to happen when the data is read from disk into memory.


Installation
------------

1. openssl library is used to perform the actual encryption. Therefore you
need to make sure that you have openssl installed.

2. Run the configure script and (besides other options) pass --with-openssl to
it.

3. make install


Create encrypted instance
-------------------------

In order to encrypt / decrypt data, the PostgreSQL processes need an
encryption key.  You need to provide the server either with the actual key or
with a password from which the key will be derived.

The initdb utility accepts command line option -K, whose argument is a command
that returns the key or the password. Depending on your choice, the expected
output of the command is

encryption_key=<your key>

(The key length is 64 bytes and it's expected in hexadecimal format, hence 128
hexadecimal digits.)

or

encryption_password=<your password>

Whichever kind of credentials you prefer, simply run initdb with the -K
option, and that's it. For example:

initdb -K /data/my_pwd_command.sh -D data_encrypted

The command should now appear in your postgresql.conf file (see the variable
encryption_key_command) so you don't have to pass it again when starting the
instance.

If you passed encryption password (as opposed the encryption key), it's
recommended to generate the key as well. While the PostgreSQL server (backend)
accepts either kind of credentials, the front-end utilities (pg_waldump,
pg_resetwal, pg_rewind, etc.) only accept the encryption key.

To derive the key, run the pg_keysetup utility and pass your data directory to
it. The utility reads the password from standard input and writes the key to
the standard output. For example:

echo <encryption password> | pg_keysetup -D data_encrypted

Once you have a command that returns this key (with the "encryption_key="
prefix as explained above), you can set it as the value of the
encryption_key_command configuration variable or use it to run the front-end
commands. For example:

pg_waldump -K /data/my_key_command.sh -p data_encrypted/pg_wal/ 000000010000000000000001

CAUTION! Different key is derived if you run pg_keysetup on a different data
directory, even if the password is identical.


Startup
-------

Since the key command is in postgresql.conf, there's nothing special about the
instance startup. Once you have your instance running, the first thing you
should do is to connect and check the "data_encryption" variable:

    SHOW data_encryption;
     data_encryption
    -----------------
     on
    (1 row)

The "on" value indicates that encryption of your new instance was successfully
enabled.