PostgreSQL has native support for using SSL connections to encrypt client/server communications for increased security. This requires that OpenSSL is installed on both client and server systems and that support in PostgreSQL is enabled at build time (see Chapter 14, Installation Instructions).
With SSL support compiled in, the
PostgreSQL server can be started with
SSL enabled by setting the parameter
ssl to on
in
postgresql.conf
. When
starting in SSL mode, the server will look for the
files server.key
and server.crt
in the
data directory, which must contain the server private key
and certificate, respectively. These files must be set up correctly
before an SSL-enabled server can start. If the private key is
protected with a passphrase, the server will prompt for the
passphrase and will not start until it has been entered.
The server will listen for both standard and SSL
connections on the same TCP port, and will negotiate with any
connecting client on whether to use SSL. By default,
this is at the client's option; see Section 20.1, “The pg_hba.conf
file” about how to set up the server to
require use of SSL for some or all connections.
For details on how to create your server private key and certificate, refer to the OpenSSL documentation. A self-signed certificate can be used for testing, but a certificate signed by a certificate authority (CA) (either one of the global CAs or a local one) should be used in production so the client can verify the server's identity. To create a quick self-signed certificate, use the following OpenSSL command:
openssl req -new -text -out server.req
Fill out the information that openssl
asks for. Make sure
that you enter the local host name as “Common Name”; the challenge
password can be left blank. The program will generate a key that is
passphrase protected; it will not accept a passphrase that is less
than four characters long. To remove the passphrase (as you must if
you want automatic start-up of the server), run the commands
openssl rsa -in privkey.pem -out server.key rm privkey.pem
Enter the old passphrase to unlock the existing key. Now do
openssl req -x509 -in server.req -text -key server.key -out server.crt chmod og-rwx server.key
to turn the certificate into a self-signed certificate and to copy the key and certificate to where the server will look for them.
If verification of client certificates is required, place the
certificates of the CA(s) you wish to check for in
the file root.crt
in the data directory. When
present, a client certificate will be requested from the client
during SSL connection startup, and it must have been signed by one of the
certificates present in root.crt
. Certificate
Revocation List (CRL) entries are also checked if the file
root.crl
exists.
When the root.crt
file is not present, client
certificates will not be requested or checked. In this mode, SSL
provides communication security but not authentication.
The files server.key
, server.crt
,
root.crt
, and root.crl
are only examined during server start; so you must restart
the server to make changes in them take effect.