V-72977

control "V-72977" do
  title "PostgreSQL must generate audit records when unsuccessful attempts to
  add privileges/permissions occur."
  desc  "Failed attempts to change the permissions, privileges, and roles
  granted to users and roles must be tracked. Without an audit trail,
  unauthorized attempts to elevate or restrict privileges could go undetected.
  In an SQL environment, adding permissions is typically done via the GRANT
  command, or, in the negative, the REVOKE command.
  To aid in diagnosis, it is necessary to keep track of failed attempts in
  addition to the successful ones."
  impact 0.5
  tag "severity": "medium"
  tag "gtitle": "SRG-APP-000495-DB-000327"
  tag "gid": "V-72977"
  tag "rid": "SV-87629r1_rule"
  tag "stig_id": "PGS9-00-006900"
  tag "cci": "CCI-000172"
  tag "nist": ["AU-12 c", "Rev_4"]
  tag "check": "First, as the database administrator (shown here as
  \"postgres\"), create a role 'bob' and a test table by running the following
  SQL:
  $ sudo su - postgres
  $ psql -c \"CREATE ROLE bob; CREATE TABLE test(id INT)\"
  Next, set current role to bob and attempt to modify privileges:
  $ psql -c \"SET ROLE bob; GRANT ALL PRIVILEGES ON test TO bob;\"
  Now, as the database administrator (shown here as \"postgres\"), verify the
  unsuccessful attempt was logged:
  $ sudo su - postgres
  $ cat ${PGDATA?}/pg_log/<latest_log>
  2016-07-14 18:12:23.208 EDT postgres postgres ERROR: permission denied for
  relation test
  2016-07-14 18:12:23.208 EDT postgres postgres STATEMENT: GRANT ALL PRIVILEGES
  ON test TO bob;
  If audit logs are not generated when unsuccessful attempts to add
  privileges/permissions occur, this is a finding."
  tag "fix": "Configure PostgreSQL to produce audit records when unsuccessful
  attempts to add privileges occur.
  All denials are logged by default if logging is enabled. To ensure that
  logging is enabled, review supplementary stdout APPENDIX-C for instructions
  on enabling logging."

  sql = postgres_session(PG_DBA, PG_DBA_PASSWORD, PG_HOST)
  log_directory_query = sql.query('SHOW log_directory;', [PG_DB])
  log_directory = log_directory_query.output
  current_log_command = "ls -1t #{log_directory}/*.pg_log | head -1"
  current_log = command(current_log_command).stdout.strip
  control = File.basename(__FILE__, File.extname(__FILE__))
  message = "starting tests for #{control}"
  message_sql = "DO language plpgsql $$ BEGIN "\
    "RAISE LOG '#{message}'; END $$;"
  start = Time.now.strftime('%Y-%m-%d %H:%M')
  get_logs = "sed -nre '/#{start}.*LOG:\\s+#{message}/,$p' #{current_log}"

  setup = 'CREATE ROLE bob; CREATE TABLE test(id INT);'
  set_role = 'SET ROLE bob;'
  teardown = 'DROP TABLE test; DROP ROLE bob;'
  grant = "#{set_role} GRANT ALL PRIVILEGES ON test TO bob;"
  error = 'permission denied for relation test'

  sql.query(message_sql, [PG_DB])
  sql.query(setup, [PG_DB])
  sql.query(grant, [PG_DB])
  sql.query(teardown, [PG_DB])

  describe command(get_logs) do
    its('stdout') { should match /ERROR:\s+#{error}/ }
    its('stdout') { should match /STATEMENT:\s+#{grant}/ }
  end
end