X2Go Server with PostgreSQL database backend

Note: This wiki page explains how you can configure X2Go with PostgreSQL as database backend. However, for small setups, this is unneccessary. If you have one standalone X2Go server and only a small number of users, then you can use the SQLite database backend (which is the default after installation of the x2goserver package). The PostgreSQL backend is recommended for sites that run more than one X2Go Server (X2Go multi-node farms) and/or a large number of users.

With X2Go Server v3.0.99.0 the whole session database backend code had been fully rewritten due to a serious security issue that had been brought up by Morty, Reinhard and Arw. Sind then, the sudo command is no longer required by x2goserver to neither contact the SQLite database (installation default) nor the PostgreSQL database. Since v3.0.99.x PostgreSQL views and rules are used to restrict users from modifying or accessing data of other users.

For accessing the X2Go/PostgreSQL database X2Go Server uses the Perl DBI package.

• configure PostgreSQL server to enable TCP connections from your X2Go Server host
• configure PostgreSQL server for md5 authentication for users from X2Go Server in

/etc/postgresql/(version)/main/pg_hba.conf

Example:

# IPv4 local connections:

host    all         all         127.0.0.1/32          md5

You must create a database user which can create databases and users for X2Go database administration. You can also use the postgres user to do this job.

You must save the password of this user in the file

/etc/x2go/x2gosql/passwords/pgadmin

Only root should have access to this file. It will be used only for database and user creation, you may/should delete it after these tasks are done. You can set a new password using this command on your PostgreSQL server:

$ su postgres -c "psql"
psql (8.4.8)

You are using psql, the command-line interface to PostgreSQL.
Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

postgres=# alter user postgres encrypted password '<secret-password>';
ALTER ROLE
postgres=# \q

#postgres or sqlite
backend=postgres

[postgres]
host=localhost
port=5432

#database admin (must have permissions to create databases and users)
dbadmin=postgres

#disable: SSL connections are never used
#allow: try non-SSL, then SSL
#prefer: try SSL, then non-SSL
#require: connect only with SSL
#default - prefer
ssl=prefer

$ /usr/lib/x2go/script/x2godbadmin --help
X2Go SQL admin interface. Use it to create the X2Go session database and insert or
remove users or groups in X2Go session database.

Usage:
x2godbadmin --createdb
x2godbadmin --listusers
x2godbadmin --adduser|rmuser <UNIX user>
x2godbadmin --addgroup|rmgroup <UNIX group>

$ x2godbadmin --createdb

You can add UNIX users or groups to database using commands
$ x2godbadmin --adduser example

<code>
$ x2godbadmin --addgroup x2gousers

After that step users of the posix group x2gousers can create X2Go sessions. Of course, any other group could be used here, as well.

In hopefully rare cases it may become necessary to fix the X2Go session database via standard PostgreSQL tools (e.g. psql). This should not happen and please please please report the issue as a bug against the x2goserver X2Go component. However, if you are in the unlucky situation of having to fix up the session DB, then the below lines may render useful to you.

In case it becomes necessary to edit the X2Go session database on the PostgreSQL server by hand, connect to the DB with this command:

$ psql --user x2godbuser --password -h localhost --dbname x2go_sessions

As password use the password found in /etc/x2go/x2gosql/passwords/x2goadmin.

After successful login, the psql PostgreSQL client shows these lines:

ts-01:~ # psql --user x2godbuser --password -h localhost --dbname x2go_sessions
Password for user x2godbuser: <hidden>
Welcome to psql <version>, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

x2go_sessions=>

The database has five tables:

x2go_sessions=> \dt
             List of relations
 Schema |     Name      | Type  |  Owner   
--------+---------------+-------+----------
 public | messages      | table | postgres
 public | mounts        | table | postgres
 public | sessions      | table | postgres
 public | used_ports    | table | postgres
 public | user_messages | table | postgres
(5 rows)

Three of them are important for session management: sessions, used_ports, mounts.

Furthermore, the database defined four views:

x2go_sessions=> \dv
            List of relations
 Schema |     Name      | Type |  Owner   
--------+---------------+------+----------
 public | mounts_view   | view | postgres
 public | ports_view    | view | postgres
 public | servers_view  | view | postgres
 public | sessions_view | view | postgres
(4 rows)

x2go_sessions=> 

If you want to show the content of a table or view, evoke this SQL command:

x2go_sessions=> select * from used_ports;
    server    |              session_id               |   creator_id    | port  
--------------+---------------------------------------+-----------------+-------
 ts-01 | mike-57-1379961697_stRTERMINAL_dp24 | x2gouser_mike | 30019
 ts-01 | mike-57-1379961697_stRTERMINAL_dp24 | x2gouser_mike | 30018
 ts-01 | mike-57-1379961697_stRTERMINAL_dp24 | x2gouser_mike | 30020
(3 rows)

If you want to remove these entries (because they are there but they by some reason should not be there), use this command set:

x2go_sessions=> delete from used_ports where port=30020;
DELETE 1

… or …

x2go_sessions=> delete from used_ports where session_id=mike-57-1379961697_stRTERMINAL_dp24;
DELETE 3

For further input on manipulating PostgreSQL database via the psql client tool, see the PostgreSQL reference.