Policyd rate limit

Postfix policyd server allowing to limit the number of mails accepted by postfix over several time periods, by sasl usernames and/or ip addresses.

Installation

First, create the user that will run the daemon:

adduser --system --group --home /run/policyd-rate-limit --no-create-home policyd-rate-limit

Since version 0.6.0, the configuration file is written using the yaml, so you need the following package:

• pyyaml (sudo apt-get install python3-yaml on debian like systems)

Depending of the backend storage you planning to use, you may need to install additional packages. (The default settings use the sqlite3 bakends and do not need extra packages).

• mysqldb (sudo apt-get install python3-mysqldb on debian like systems) for the mysql backend.
• psycopg2 (sudo apt-get install python3-psycopg2 on debian like systems) fot the postgresql backend

Install with pip:

sudo pip3 install policyd-rate-limit

or from source code:

sudo make install

This will install the policyd_rate_limit module, the policyd-rate-limit binary, copy the default config to /etc/policyd-rate-limit.conf if the file do not exists, copy an init script to /etc/init.d/policyd-rate-limit and an unit file to /etc/systemd/system/policyd-rate-limit.service.

After the installation, you may need to run sudo systemctl daemon-reload for make the unit file visible by systemd.

You should run policyd-rate-limit --clean on a regular basis to delete old records from the database. It could be wise to put it in a daily cron, for example:

0 0 * * * policyd-rate-limit /usr/local/bin/policyd-rate-limit --clean >/dev/null

Options of the policyd-rate-limit binary

• -h, --help: show the help message and exit
• --clean: clean old records from the database
• --get-config PARAMETER_NAME return the value of a config parameter
• --file CONFIG_PATH, -f CONFIG_PATH: path to a config file

Settings

If the option --file is not specified, policyd-rate-limit try to read its configuration from the following path and choose the first existing file:

• ~/.config/policyd-rate-limit.conf
• ~/.config/policyd-rate-limit.yaml
• /etc/policyd-rate-limit.conf
• /etc/policyd-rate-limit.yaml

The .conf are the old configuration format. It was a python module and should not be used. The .yaml are the new configuration format using the YAML syntax.

• debug: make policyd-rate-limit output logs to stderr. The default is True.
• user: The user policyd-rate-limit will use to drop privileges. The default is "policyd-rate-limit".
• group: The group policyd-rate-limit will use to drop privileges. The defaut is "policyd-rate-limit".
• pidfile: path where the program will try to write its pid to. The default is "/var/run/policyd-rate-limit/policyd-rate-limit.pid". policyd-rate-limit will try to create the parent directory and chown it if it do not exists.
• mysql_config: The config to connect to a mysql server
• pgsql_config: The config to connect to a postgresql server
• sqlite_config: The config to connect to a sqlite3 database.
• backend: Which data backend to use. Possible values are 0 for sqlite3, 1 for mysql and 2 for postgresql. The default is 0, use the sqlite3 backend.
• SOCKET: The socket to bind to. Can be a path to an unix socket or a couple [ip, port]. The default is "/var/spool/postfix/ratelimit/policy". policyd-rate-limit will try to create the parent directory and chown it if it do not exists.
• socket_permission: Permissions on the unix socket (if unix socket used). The default is 0o666.
• limits: A list of couple [number of emails, number of seconds]. If one of the element of the list is exeeded (more than 'number of emails' on 'number of seconds' for an ip address or an sasl username), postfix will return a temporary failure.
• limits_by_id: A dictionary of id -> limit list (see limits). Used to override limits and use custom limits for a particular id. Use an empty list for no limits for a particular id. Ids are sasl usernames or ip addresses. The default is {}.
• limit_by_sasl: Apply limits by sasl usernames. The default is True.
• limit_by_sender: Apply limits by sender addresses if sasl username is not found. The defaut is False.
• limit_by_ip: Apply limits by ip addresses if sasl username and sender address are not found. The default is False.
• limited_networks: A list of ip networks in cidr notation on which limits are applied. An empty list is equal to limit_by_ip = False, put "0.0.0.0/0" and ::/0 for every ip addresses.
• success_action: If not limits are reach, which action postfix should do. The default is "dunno". See http://www.postfix.org/access.5.html for possible actions.
• fail_action: If a limit is reach, which action postfix should do. The default is "defer_if_permit Rate limit reach, retry later".
• db_error_action : If we are unable to to contect the database backend, which action postfix should do. The default is "dunno". See http://www.postfix.org/access.5.html for possible actions. See http://www.postfix.org/access.5.html for possible actions.
• config_file: This parameter is automatically set to the path of the configuration file currently in use. You can call it conjunction with --get-config to known which configuration file is used.
• report: if True, send a report to report_to about users reaching limits each time --clean is called. The default is False.
• report_from: From who to send emails reports. It must be defined when report is True.
• report_to: Address to send emails reports to. It must be defined when report is True. It can be a single email address or a list of email adresses.
• report_subject: Subject of the report email. The default is "policyd-rate-limit report".
• report_limits: List of number of seconds from the limits list for which you want to be reported. The default is [86400].
• report_only_if_needed: Only send a report if some users have reach a reported limit. The default is True.
• smtp_server: The smtp server to use to send emails ["host", port]. The default is ["localhost", 25].
• smtp_starttls: Should we use starttls to send mails ? (you should set this to True if you use smtp_credentials). The default is False.
• smtp_credentials: Should we use credentials to connect to smtp_server ? if yes set ["user", "password"], else null. The default is null.

Postfix settings

For postfix 3.0 and later I recommend using the example below. It ensure that if policyd-rate-limit become unavailable for any reason, postfix will ignore it and keep accepting mail as if the rule was not here. I find it nice has in my opinion, policyd-rate-limit is a "non-critical" policy service.

/etc/postfix/main.cf:

smtpd_recipient_restrictions =
    ...,
    check_policy_service { unix:ratelimit/policy, default_action=DUNNO },
    ...

On previous postfix versions, you must use:

/etc/postfix/main.cf:

smtpd_recipient_restrictions =
    ...,
    check_policy_service unix:ratelimit/policy,
    ...