Getting information about PostgreSQL SSL connections

PostgreSQL can, as many other products, use SSL to secure client/server communications. It can be configured to be optional or required, to require a client certificate, or even to use the SSL client certificate to log in. However, the DBA tools are currently a bit lacking in this regard. In particular, there is no way for a DBA to see what SSL parameters are in force (or indeed if SSL is enabled at all) for an already existing connection.

There are multiple ways to see the status of a specific connection (such as the libpq PQgetssl() function, the psql startup message or the sslinfo module. Unfortunately all these methods have one thing in common - they are only available to the process making the connection to the database, not to a DBA inspecting the system from the outside.

9.4 will make it a little bit better, because log_connections now include SSL information when the user connects, similar to:

LOG:  connection authorized: user=mha database=postgres SSL enabled (protocol=TLSv1.1, cipher=ECDHE-RSA-AES256-SHA)

But this can still be a bit of a pain to figure out for existing connectioons of course.

To deal with this problem, I've written a small PostgreSQL extension called pg_sslstatus. When loaded using shared_preload_libraries it will keep track of the SSL status for each connection, and expose it through a system view named pg_sslstatus like this:

postgres=# SELECT * FROM pg_sslstatus;
  pid  | ssl | bits | compression | version |        cipher        |                         clientdn                         
-------+-----+------+-------------+---------+----------------------+----------------------------------------------------------
 27286 | t   |  256 | f           | TLSv1   | ECDHE-RSA-AES256-SHA | 
 26682 | t   |  256 | t           | TLSv1   | ECDHE-RSA-AES256-SHA | /C=AU/ST=Some-State/O=Internet Widgits Pty Ltd/CN=magnus
 26693 | f   |      |             |         |                      | 
(3 rows)

It will include one row for each connection, and can then be joined with either pg_stat_activity or pg_stat_replication to view the SSL data in a bigger context:

postgres=# SELECT datname, usename, client_addr, ssl, cipher FROM pg_stat_activity INNER JOIN pg_sslstatus ON pg_stat_activity.pid=pg_sslstatus.pid;
 datname  | usename | client_addr | ssl |        cipher        
----------+---------+-------------+-----+----------------------
 postgres | mha     | 127.0.0.1   | t   | ECDHE-RSA-AES256-SHA
 postgres | mha     |             | f   | 
 pgweb    | pgweb   |             | f   | 
(2 rows)

The extension is available from my github account today for existing version of PostgreSQL, under the standard PostgreSQL license. My plan is to work on having a similar view included in PostgreSQL 9.5 by default, but it's unfortunately too late to include it in 9.4 at this point.

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