control "V-73051" do
  title "PostgreSQL must automatically terminate a user session after
organization-defined conditions or trigger events requiring session disconnect."
  desc  "This addresses the termination of user-initiated logical sessions in
contrast to the termination of network connections that are associated with
communications sessions (i.e., network disconnect). A logical session (for local,
network, and remote access) is initiated whenever a user (or process acting on
behalf of a user) accesses an organizational information system. Such user sessions
can be terminated (and thus terminate user access) without terminating network
sessions.

Session termination ends all processes associated with a user's logical session
except those batch processes/jobs that are specifically created by the user (i.e.,
session owner) to continue after the session is terminated.

Conditions or trigger events requiring automatic session termination can include,
for example, organization-defined periods of user inactivity, targeted responses to
certain types of incidents, and time-of-day restrictions on information system use.

This capability is typically reserved for specific cases where the system owner,
data owner, or organization requires additional assurance."
  impact 0.5
  tag "severity": "medium"
  tag "gtitle": "SRG-APP-000295-DB-000305"
  tag "gid": "V-73051"
  tag "rid": "SV-87703r1_rule"
  tag "stig_id": "PGS9-00-011600"
  tag "cci": "CCI-002361"
  tag "nist": ["AC-12", "Rev_4"]
  tag "check": "Review system documentation to obtain the organization's definition
of circumstances requiring automatic session termination. If the documentation
explicitly states that such termination is not required or is prohibited, this is
not a finding.

If the documentation requires automatic session termination, but PostgreSQL is not
configured accordingly, this is a finding."
  tag "fix": "Configure PostgreSQL to automatically terminate a user session after
organization-defined conditions or trigger events requiring session termination.

Examples follow.

### Change a role to nologin and disconnect the user

ALTER ROLE '<username>' NOLOGIN;
SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE username='<username>';

### Disconnecting users during a specific time range
See supplementary content APPENDIX-A for a bash script for this example.

The script found in APPENDIX-A using the -l command can disable all users with
rolcanlogin=t from logging in. The script keeps track of who it disables in a
.restore_login file. After the specified time is over, the same script can be run
with the -r command to restore all login connections.

This script would be added to a cron job:

# lock at 5 am every day of the week, month, year at the 0 minute mark.
0 5 * * * postgres /var/lib/pgsql/no_login.sh -d postgres -l
# restore at 5 pm every day of the week, month, year at the 0 minute mark.
0 17 * * * postgres /var/lib/pgsql/no_login.sh -d postgres -r"

  only_if { false }

end