Add documentation for before queue filtering

[pmg-docs.git] / pmgconfig.adoc

[[chapter_pmgconfig]]
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pmgconfig(1)
============
:pmg-toplevel:

NAME
----

pmgconfig - Proxmox Mail Gateway Configuration Management Toolkit


SYNOPSIS
--------

include::pmgconfig.1-synopsis.adoc[]


DESCRIPTION
-----------
endif::manvolnum[]
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Configuration Management
========================
:pmg-toplevel:
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{pmg} is usually configured using the web-based Graphical User
Interface (GUI), but it is also possible to directly edit the
configuration files, use the REST API over 'https'
or the command line tool `pmgsh`.

The command line tool `pmgconfig` is used to simplify some common
configuration tasks, i.e. to generate cerificates and to rewrite
service configuration files.

NOTE: We use a Postgres database to store mail filter rules and
statistic data. See chapter xref:chapter_pmgdb[Database Management]
for more information.


Configuration files overview
----------------------------

`/etc/network/interfaces`::

Network setup. We never modify this files directly. Instead, we write
changes to `/etc/network/interfaces.new`. When you reboot, we rename
the file to `/etc/network/interfaces`, so any changes gets activated
on the next reboot.

`/etc/resolv.conf`::

DNS search domain and nameserver setup.

`/etc/hostname`::

The system's host name.

`/etc/hosts`::

Static table lookup for hostnames.

`/etc/pmg/pmg.conf`::

Stores common administration options, i.e. the spam and mail proxy setup.

`/etc/pmg/cluster.conf`::

The cluster setup.

`/etc/pmg/domains`::

The list of relay domains.

`/etc/pmg/dkim/domains`::

The list of domains for outbound DKIM signing.

`/etc/pmg/fetchmailrc`::

Fetchmail configuration (POP3 and IMAP setup).

`/etc/pmg/ldap.conf`::

LDAP configuration.

`/etc/pmg/mynetworks`::

List of local (trusted) networks.

`/etc/pmg/subscription`::

Stores your subscription key and status.

`/etc/pmg/tls_policy`::

TLS policy for outbound connections.

`/etc/pmg/transports`::

Message delivery transport setup.

`/etc/pmg/user.conf`::

GUI user configuration.

`/etc/mail/spamassassin/custom.cf`::

Custom {spamassassin} setup.

`/etc/mail/spamassassin/pmg-scores.cf`::

Custom {spamassassin} rule scores.

Keys and Certificates
---------------------

`/etc/pmg/pmg-api.pem`::

Key and certificate (combined) used be the HTTPs server (API).

`/etc/pmg/pmg-authkey.key`::

Privat key use to generate authentication tickets.

`/etc/pmg/pmg-authkey.pub`::

Public key use to verify authentication tickets.

`/etc/pmg/pmg-csrf.key`::

Internally used to generate CSRF tokens.

`/etc/pmg/pmg-tls.pem`::

Key and certificate (combined) to encrypt mail traffic (TLS).

`/etc/pmg/dkim/<selector>.private`::

Key for DKIM signing mails with selector '<selector>'.


Service Configuration Templates
-------------------------------

{pmg} uses various services to implement mail filtering, for example
the {postfix} Mail Transport Agent (MTA), the {clamav} antivirus
engine and the Apache {spamassassin} project. Those services use
separate configuration files, so we need to rewrite those files when
configuration is changed.

We use a template based approach to generate those files. The {tts} is
a well known, fast and flexible template processing system. You can
find the default templates in `/var/lib/pmg/templates/`. Please do not
modify them directly, because your modification would get lost on the
next update. Instead, copy the template you wish to change to
`/etc/pmg/templates/`, then apply your changes there.

Templates can access any configuration setting, and you can use the
`pmgconfig dump` command to get a list of all variable names:

----
# pmgconfig dump
...
dns.domain = yourdomain.tld
dns.hostname = pmg
ipconfig.int_ip = 192.168.2.127
pmg.admin.advfilter = 1
...
----

The same tool is used to force regeneration of all template based
configuration files. You need to run that after modifying a template,
or when you directly edit configuration files

----
# pmgconfig sync --restart 1
----

The above command also restarts services if the underlying configuration
files are changed. Please note that this is automatically done when
you change the configuration using the GUI or API.

NOTE: Modified templates from `/etc/pmg/templates/` are automatically
synced from the master node to all cluster members.


[[pmgconfig_systemconfig]]
System Configuration
--------------------

Network and Time
~~~~~~~~~~~~~~~~

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Normally the network and time is already configured when you visit the
GUI. The installer asks for those settings and sets up the correct
values.

The default setup uses a single Ethernet adapter and static IP
assignment. The configuration is stored at '/etc/network/interfaces',
and the actual network setup is done the standard Debian way using
package 'ifupdown'.

.Example network setup '/etc/network/interfaces'
----
source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

auto ens18
iface ens18 inet static
        address  192.168.2.127
        netmask  255.255.240.0
        gateway  192.168.2.1
----

.DNS recommendations

Many tests to detect SPAM mails use DNS queries, so it is important to
have a fast and reliable DNS server. We also query some public
available DNS Blacklists. Most of them apply rate limits for clients,
so they simply will not work if you use a public DNS server (because
they are usually blocked). We recommend to use your own DNS server,
which need to be configured in 'recursive' mode.


Options
~~~~~~~

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Those settings are saved to subsection 'admin' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.admin-conf-opts.adoc[]


Mail Proxy Configuration
------------------------

[[pmgconfig_mailproxy_relaying]]
Relaying
~~~~~~~~

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Those settings are saved to subsection 'mail' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.mail-relaying-conf-opts.adoc[]

[[pmgconfig_mailproxy_relay_domains]]
Relay Domains
~~~~~~~~~~~~~

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List of relayed mail domains, i.e. what destination domains this
system will relay mail to. The system will reject incoming mails to
other domains.


[[pmgconfig_mailproxy_ports]]
Ports
~~~~~

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Those settings are saved to subsection 'mail' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.mail-ports-conf-opts.adoc[]


[[pmgconfig_mailproxy_options]]
Options
~~~~~~~

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Those settings are saved to subsection 'mail' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.mail-options-conf-opts.adoc[]


[[pmgconfig_mailproxy_before_after_queue]]
Before and After Queue scanning
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Scanning email can happen at two different stages of mail-processing:

* During the SMTP Session after the complete message has been received (after
  the 'DATA' command), known as 'before queue filtering'.

* After intially accepting the mail and putting it on a queue for further
  processing, known as 'after queue filtering'.

The former has the advantage that the system can reject a mail (by sending a
permanent reject code '554'), and leave the task of notifying the original
sender to the other mailserver. This is of particular advantage if the
processed mail is a spam message or contains a virus and has a forged
sender-address. Sending out a notification in this situation leads so-called
'backscatter' mail, which might cause your server to get listed as spamming on
RBLs.

The latter has the advantage of providing faster delivery of mails for the
sending servers, since queueing mails is much faster than analyzing it for
spam and viruses.

If a mail is addressed to multiple recipients (e.g. when multiple addresses are
subscribed to the same mailinglist) the situation is more complicated: Your
mailserver can only reject or accept the mail for all recipients, after having
received the complete message, while your rule setup might accept the mail for
part of the recipients and reject it for others. This can be due to a
complicated rule setup, or if your users use the 'User White- and Blacklist'
feature.

If the resulting action of the rule system is the same for all recipients {pmg}
responds accordingly if configured for before queue filtering (sending '554'
for a blocked mail and '250' for an accepted or quarantined mail). If some
mailboxes accept the mail and some reject it the system has to accept the mail.

Whether {pmg} notifies the sender that delivery failed for some recipients by
sending a non-delivery report, depends on the 'ndr_on_block' setting in
'/etc/pmg/pmg.conf'. If enabled an NDR is sent. Keeping it disabled prevents
NDRs being sent to the (possibly forged) sender and thus minimizes the chance
of getting your IP listed on a RBL. However in certain environments it can be
unacceptable not to inform the sender about a rejected mail.

The setting has the same effect if after queue filtering is configured, with
the exception that an NDR is always sent out, even if all recipients block the
mail, since the mail already got accepted before being analyzed.

The details of integrating the mail proxy with {postfix} in both setups are
explained in {postfix_beforequeue} and {postfix_afterqueue} respectively.

NOTE: Since before queue filtering is currently incompatible with the
'Tracking Center' you need to enable it by manually
editing '/etc/pmg/pmg.conf'.


[[pmgconfig_mailproxy_transports]]
Transports
~~~~~~~~~~

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You can use {pmg} to send e-mails to different internal
e-mail servers. For example you can send e-mails addressed to
domain.com to your first e-mail server, and e-mails addressed to
subdomain.domain.com to a second one.

You can add the IP addresses, hostname and SMTP ports and mail domains (or
just single email addresses) of your additional e-mail servers.


[[pmgconfig_mailproxy_networks]]
Networks
~~~~~~~~

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You can add additional internal (trusted) IP networks or hosts.
All hosts in this list are allowed to relay.

NOTE: Hosts in the same subnet with Proxmox can relay by default and
it’s not needed to add them in this list.


[[pmgconfig_mailproxy_tls]]
TLS
~~~

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Transport Layer Security (TLS) provides certificate-based
authentication and encrypted sessions. An encrypted session protects
the information that is transmitted with SMTP mail. When you activate
TLS, {pmg} automatically generates a new self signed
certificate for you (`/etc/pmg/pmg-tls.pem`).

{pmg} uses opportunistic TLS encryption by default. The SMTP transaction is
encrypted if the 'STARTTLS' ESMTP feature is supported by the remote
server.  Otherwise, messages are sent in the clear.
You can set a different TLS policy per desitination domain, should you for
example need to prevent e-mail delivery without encryption, or to work around
a broken 'STARTTLS' ESMTP implementation. See {postfix_tls_readme} for details
on the supported policies.

Enable TLS logging::

To get additional information about SMTP TLS activity you can enable
TLS logging. That way information about TLS sessions and used
certificate’s is logged via syslog.

Add TLS received header::

Set this option to include information about the protocol and cipher
used as well as the client and issuer CommonName into the "Received:"
message header.

Those settings are saved to subsection 'mail' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.mail-tls-conf-opts.adoc[]


[[pmgconfig_mailproxy_dkim]]
DKIM Signing
~~~~~~~~~~~~

DomainKeys Identified Mail (DKIM) Signatures (see {dkim_rfc}) is a method to
cryptographically authenticate a mail as originating from a particular domain.
Before sending the mail a hash over certain header fields and the body is
computed, signed with a private key and added in the `DKIM-Signature` header of
the mail. The 'selector' (a short identifier chosen by you, used to identify
which system and private key were used for signing) is also included in the
`DKIM-Signature` header.

The verification is done by the receiver: The public key is fetched
via DNS TXT lookup for `yourselector._domainkey.yourdomain.example` and used
for verifying the hash. You can publish multiple selectors for your domain,
each use by a system which sends e-mail from your domain, without the need to
share the private key.

{pmg} verifies DKIM Signatures for inbound mail in the Spam Filter by default.

Additionally it supports conditionally signing outbound mail if configured.
It uses one private key and selector per PMG deployment (all nodes in a cluster
use the same key). The key has a minimal size of 1024 bits and rsa-sha256 is
used as signing algorithm.

The headers included in the signature are taken from the list of
`Mail::DKIM::Signer`. Additionally `Content-Type` (if present), `From`, `To`,
`CC`, `Reply-To` and `Subject` get oversigned.

You can either sign all mails received on the internal port using the domain of
the envelope sender address or create a list of domains, for which e-mails
should be signed, defaulting to the list of relay domains.


Enable DKIM Signing::

Controls whether outbound mail should get DKIM signed.

Selector::

The selector used for signing the mail. The private key used for signing is
saved under `/etc/pmg/dkim/yourselector.private`. You can display the DNS TXT
record which you need to add to all domains signed by {pmg} by clicking on the
'View DNS Record' Button.

Sign all Outgoing Mail::

Controls whether all outbound mail should get signed or only mails from domains
listed in `/etc/pmg/dkim/domains` if it exists and `/etc/pmg/domains` otherwise.

Those settings are saved to subsection 'admin' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.admin-dkim-conf-opts.adoc[]


Whitelist
~~~~~~~~~

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All SMTP checks are disabled for those entries (e. g. Greylisting,
SPF, RBL, ...)

NOTE: If you use a backup MX server (e.g. your ISP offers this service
for you) you should always add those servers here.


[[pmgconfig_spamdetector]]
Spam Detector Configuration
---------------------------

Options
~~~~~~~

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{pmg} uses a wide variety of local and network tests to identify spam
signatures. This makes it harder for spammers to identify one aspect
which they can craft their messages to work around the spam filter.

Every single e-mail will be analyzed and gets a spam score
assigned. The system attempts to optimize the efficiency of the rules
that are run in terms of minimizing the number of false positives and
false negatives.

include::pmg.spam-conf-opts.adoc[]


[[pmgconfig_spamdetector_quarantine]]
Quarantine
~~~~~~~~~~

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Proxmox analyses all incoming e-mail messages and decides for each
e-mail if its ham or spam (or virus). Good e-mails are delivered to
the inbox and spam messages can be moved into the spam quarantine.

The system can be configured to send daily reports to inform users
about the personal spam messages received the last day. That report is
only sent if there are new messages in the quarantine.

Some options are only available in the config file `/etc/pmg/pmg.conf`,
and not in the webinterface.

include::pmg.spamquar-conf-opts.adoc[]


[[pmgconfig_clamav]]
Virus Detector Configuration
----------------------------

[[pmgconfig_clamav_options]]
Options
~~~~~~~

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All mails are automatically passed to the included virus detector
({clamav}). The default setting are considered safe, so it is usually
not required to change them.

{clamav} related settings are saved to subsection 'clamav' in `/etc/pmg/pmg.conf`,
using the following configuration keys:

include::pmg.clamav-conf-opts.adoc[]

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Please note that the virus signature database it automatically
updated. But you can see the database status on the GUI, and you can
trigger manual updates there.


[[pmgconfig_clamav_quarantine]]
Quarantine
~~~~~~~~~~

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Indentified virus mails are automatically moved to the virus
quarantine. The administartor can view those mails using the GUI, or
deliver them in case of false positives. {pmg} does not notify
individual users about received virus mails.

Virus quarantine related settings are saved to subsection 'virusquar'
in `/etc/pmg/pmg.conf`, using the following configuration keys:

include::pmg.virusquar-conf-opts.adoc[]


Custom SpamAssassin configuration
---------------------------------

This is only for advanced users. {spamassassin}'s rules and their associated
scores get updated regularly and are trained on a huge corpus, which gets
classified by experts. In most cases adding a rule for matching a particular
keyword is the wrong approach, leading to many false positives. Usually bad
detection rates are better addressed by properly setting up DNS than by adding
a custom rule - watch out for matches to 'URIBL_BLOCKED' in the logs or
spam-headers - see the {spamassassin_dnsbl}.

To add or change the Proxmox {spamassassin} configuration please login to the
console via SSH. Change to the `/etc/mail/spamassassin/` directory. In this
directory there are several files (`init.pre`, `local.cf`, ...) - do not change
them, as they will be overwritten by any {spamassassin} rule update.

To add your special configuration, you have to create a new file and name it
`custom.cf` (in this directory), then add your configuration there. Make sure
to use the correct {spamassassin} syntax, and test with

----
# spamassassin -D --lint
----

If you run a cluster, the `custom.cf` file is synchronized from the
master node to all cluster members automatically.


[[pmgconfig_custom_check]]
Custom Check Interface
----------------------

For use cases which are not handled by the {pmg} Virus Detector and
{spamassassin} configuration, advanced users can create a custom check
executable which, if enabled will be called before the Virus Detector and before
passing an e-mail through the Rule System. The custom check API is kept as
simple as possible, while still providing a great deal of control over the
treatment of an e-mail. Its input is passed via two CLI arguments:

* the 'api-version' (currently `v1`) - for potential future change of the
  invocation

* the 'queue-file-name' - a filename, which contains the complete e-mail as
  rfc822/eml file

The expected output need to be printed on STDOUT and consists of two lines:

* the 'api-version' (currently 'v1') - see above

* one of the following 3 results:
** 'OK' - e-mail is ok
** 'VIRUS: <virusdescription>' - e-mail is treated as if it contained a virus
    (the virusdescription is logged and added to the e-mail's headers)
** 'SCORE: <number>' - <number> is added (negative numbers are also possible)
    to the e-mail's spamscore

The check is run with a 5 minute timeout - if it is exceeded the check
executable is killed and the e-mail is treated as OK.

All output written to STDERR by the check is written with priority 'err' to the
journal/mail.log.

A simple sample script following the API (and yielding a random result) for
reference:

----
#!/bin/sh

echo "called with $*" 1>&2

if [ "$#" -ne 2 ]; then
  echo "usage: $0 APIVERSION QUEUEFILENAME" 1>&2
  exit 1
fi

apiver="$1"
shift

if [ "$apiver" != "v1" ]; then
  echo "wrong APIVERSION: $apiver" 1>&2
  exit 2
fi

queue_file="$1"

echo "v1"

choice=$(shuf -i 0-3 -n1)

case "$choice" in
  0)
    echo OK
    ;;
  1)
    echo SCORE: 4
    ;;
  2)
    echo VIRUS: Random Virus
    ;;
  3) #timeout-test
    for i in $(seq 1 7); do
      echo "custom checking mail: $queue_file - minute $i" 1>&2
      sleep 60
    done
    ;;
esac

exit 0
----

The custom check needs to be enabled in the admin section of `/etc/pmg/pmg.conf`

----
section: admin
    custom_check 1
----

The location of the custom check executable can also be set there with the key
`custom_check_path` and defaults to `/usr/local/bin/pmg-custom-check`.


User Management
---------------

User management in {pmg} consists of three types of users/accounts:


[[pmgconfig_localuser]]
Local Users
~~~~~~~~~~~

image::images/screenshot/pmg-gui-local-user-config.png[]

Local users are used to manage and audit {pmg}. Those users can login on the
management web interface.

There are three roles:

* Administrator
+
Is allowed to manage settings of {pmg}, except some tasks like
network configuration and upgrading.

* Quarantine manager
+
Is allowed to manage quarantines, blacklists and whitelists, but not other
settings. Has no right to view any other data.

* Auditor
+
With this role, the user is only allowed to view data and configuration, but
not to edit it.

In addition there is always the 'root' user, which is used to perform special
system administrator tasks, such as updgrading a host or changing the
network configuration.

NOTE: Only pam users are able to login via the webconsole and ssh, which the
users created with the web interface are not. Those users are created for
{pmg} administration only.

Local user related settings are saved in `/etc/pmg/user.conf`.

For details of the fields see xref:pmg_user_configuration_file[user.conf]

[[pmgconfig_ldap]]
LDAP/Active Directory
~~~~~~~~~~~~~~~~~~~~~

image::images/screenshot/pmg-gui-ldap-user-config.png[]

You can specify multiple LDAP/Active Directory profiles, so that you can
create rules matching those users and groups.

Creating a profile requires (at least) the following:

* profile name
* protocol (LDAP or LDAPS; LDAPS is recommended)
* at least one server
* a user and password (if your server does not support anonymous binds)

All other fields should work with the defaults for most setups, but can be
used to customize the queries.

The settings are saved to `/etc/pmg/ldap.conf`. Details for the options
can be found here: xref:pmg_ldap_configuration_file[ldap.conf]

Bind user
^^^^^^^^^

It is highly recommended that the user which you use for connecting to the
LDAP server only has the permission to query the server. For LDAP servers
(for example OpenLDAP or FreeIPA), the username has to be of a format like
'uid=username,cn=users,cn=accounts,dc=domain' , where the specific fields are
depending on your setup. For Active Directory servers, the format should be
like 'username@domain' or 'domain\username'.

Sync
^^^^

{pmg} synchronizes the relevant user and group info periodically, so that
that information is available in a fast manner, even when the LDAP/AD server
is temporarily not accessible.

After a successfull sync, the groups and users should be visible on the web
interface. After that, you can create rules targeting LDAP users and groups.


[[pmgconfig_fetchmail]]
Fetchmail
~~~~~~~~~

image::images/screenshot/pmg-gui-fetchmail-config.png[]

Fetchmail is utility for polling and forwarding e-mails. You can define
e-mail accounts, which will then be fetched and forwarded to the e-mail
address you defined.

You have to add an entry for each account/target combination you want to
fetch and forward. Those will then be regularly polled and forwarded,
according to your configuration.

The API and web interface offer following configuration options:

include::fetchmail.conf.5-opts.adoc[]


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