docker-mailserver/rspamd.md at e58dd1b95b3552ea850dad6b2ef0b87f8a9bae78

14 KiB

Raw Blame History

title
Security \| Rspamd

!!! warning "The current state of Rspamd integration into DMS"

Recent pull requests have stabilized integration of Rspamd to a point that we encourage users to test the feature. We are confident that there are no major bugs in our integration that make using Rspamd infeasible. Please note that there may still be (breaking) changes ahead as integration is still work in progress!

We expect to stabilize this feature with version `v12.1.0`.

About

Rspamd is a "fast, free and open-source spam filtering system". DMS integrates Rspamd like any other service. We provide a very simple but easy to maintain setup of Rspamd.

If you want to have a look at the default configuration files for Rspamd that DMS packs, navigate to target/rspamd/ inside the repository. Please consult the section "The Default Configuration" section down below for a written overview.

!!! note "AMD64 vs ARM64"

We are currently doing a best-effort installation of Rspamd for ARM64 (from the Debian backports repository for Debian 11). The current version difference is two minor versions (AMD64 is at version 3.4, ARM64 at 3.2 \[13th Feb 2023\]).

Maintainers noticed only few differences, some of them with a big impact though. For those running Rspamd on ARM64, we recommend [disabling](#with-the-help-of-a-custom-file) the [DKIM signing module][dkim-signing-module] if you don't use it.

The following environment variables are related to Rspamd:

The Default Configuration

Mode of Operation

The proxy worker operates in self-scan mode. This simplifies the setup as we do not require a normal worker. You can easily change this though by overriding the configuration by DMS.

DMS does not set a default password for the controller worker. You may want to do that yourself. In setups where you already have an authentication provider in front of the Rspamd webpage, you may want to set the secure_ip option to "0.0.0.0/0" for the controller worker to disable password authentication inside Rspamd completely.

Persistence with Redis

When Rspamd is enabled, we implicitly also start an instance of Redis in the container. Redis is configured to persist it's data via RDB snapshots to disk in the directory /var/lib/redis (which is a symbolic link to /var/mail-state/lib-redis/ when ONE_DIR=1 and a volume is mounted to /var/mail-state/). With the volume mount the snapshot will restore the Redis data across container restarts, and provide a way to keep backup.

Redis uses /etc/redis/redis.conf for configuration. We adjust this file when enabling the internal Redis service. If you have an external instance of Redis to use, the internal Redis service can be opt-out via setting the ENV ENABLE_RSPAMD_REDIS=0 (link also details required changes to the DMS rspamd config).

Modules

You can find a list of all Rspamd modules on their website.

Disabled By Default

DMS disables certain modules (clickhouse, elastic, greylist, neural, reputation, spamassassin, url_redirector, metric_exporter) by default. We believe these are not required in a standard setup, and they would otherwise needlessly use system resources.

Anti-Virus (ClamAV)

You can choose to enable ClamAV, and Rspamd will then use it to check for viruses. Just set the environment variable ENABLE_CLAMAV=1.

RBLs (Realtime Blacklists) / DNSBLs (DNS-based Blacklists)

The RBL module is enabled by default. As a consequence, Rspamd will perform DNS lookups to a variety of blacklists. Whether an RBL or a DNSBL is queried depends on where the domain name was obtained: RBL servers are queried with IP addresses extracted from message headers, DNSBL server are queried with domains and IP addresses extracted from the message body [source].

!!! danger "Rspamd and DNS Block Lists"

When the RBL module is enabled, Rspamd will do a variety of DNS requests to (amongst other things) DNSBLs. There are a variety of issues involved when using DNSBLs. Rspamd will try to mitigate some of them by properly evaluating all return codes. This evaluation is a best effort though, so if the DNSBL operators change or add return codes, it may take a while for Rspamd to adjust as well.

If you want to use DNSBLs, **try to use your own DNS resolver** and make sure it is set up correctly, i.e. it should be a non-public & **recursive** resolver. Otherwise, you might not be able ([see this Spamhaus post](https://www.spamhaus.org/faq/section/DNSBL%20Usage#365)) to make use of the block lists.

Providing Custom Settings & Overriding Settings

Manually

DMS brings sane default settings for Rspamd. They are located at /etc/rspamd/local.d/ inside the container (or target/rspamd/local.d/ in the repository). If you want to change these settings and / or provide your own settings, you can

place files at /etc/rspamd/override.d/ which will override Rspamd settings and DMS settings
(re-)place files at /etc/rspamd/local.d/ to override DMS settings and merge them with Rspamd settings

!!! warning "Clashing Overrides"

Note that when also [using the `rspamd-commands` file](#with-the-help-of-a-custom-file), files in `override.d` may be overwritten in case you adjust them manually and with the help of the file.

With the Help of a Custom File

DMS provides the ability to do simple adjustments to Rspamd modules with the help of a single file. Just place a file called rspamd-modules.conf into the directory docker-data/dms/config/ (which translates to /tmp/docker-mailserver/ in the container). If this file is present, DMS will evaluate it. The structure is very simple. Each line in the file looks like this:

COMMAND ARGUMENT1 ARGUMENT2 ARGUMENT3

where COMMAND can be:

disable-module: disables the module with name ARGUMENT1
enable-module: explicitly enables the module with name ARGUMENT1
set-option-for-module: sets the value for option ARGUMENT2 to ARGUMENT3 inside module ARGUMENT1
set-option-for-controller: set the value of option ARGUMENT1 to ARGUMENT2 for the controller worker
set-option-for-proxy: set the value of option ARGUMENT1 to ARGUMENT2 for the proxy worker
set-common-option: set the option ARGUMENT1 that defines basic Rspamd behaviour to value ARGUMENT2
add-line: this will add the complete line after ARGUMENT1 (with all characters) to the file /etc/rspamd/override.d/<ARGUMENT1>

!!! example "An Example Is Shown Down Below"

!!! note "File Names & Extensions"

For command 1 - 3, we append the `.conf` suffix to the module name to get the correct file name automatically. For commands 4 - 6, the file name is fixed (you don't even need to provide it). For command 7, you will need to provide the whole file name (including the suffix) yourself!

You can also have comments (the line starts with #) and blank lines in rspamd-modules.conf - they are properly handled and not evaluated.

!!! tip "Adjusting Modules This Way"

These simple commands are meant to give users the ability to _easily_ alter modules and their options. As a consequence, they are not powerful enough to enable multi-line adjustments. If you need to do something more complex, we advise to do that [manually](#manually)!

Examples & Advanced Configuration

A Very Basic Configuration

You want to start using Rspamd? Rspamd is disabled by default, so you need to set the following environment variables:

ENABLE_RSPAMD=1
ENABLE_OPENDKIM=0
ENABLE_OPENDMARC=0
ENABLE_AMAVIS=0
ENABLE_SPAMASSASSIN=0

This will enable Rspamd and disable services you don't need when using Rspamd. Note that with this setup, the default DKIM signing that DMS provides does not work (as it is disabled)! To solve this issue, look at this subsection.

Adjusting and Extending The Very Basic Configuration

Rspamd is running, but you want or need to adjust it?

Say you want to be able to easily look at the frontend Rspamd provides on port 11334 (default) without the need to enter a password (maybe because you already provide authorization and authentication). You will need to adjust the controller worker: create a file called rspamd-modules.conf and add the line set-option-for-controller secure_ip "0.0.0.0/0". Place the file rspamd-modules.conf inside the directory on the host you mount to /tmp/docker-mailserver/ inside the container (in our documentation, we use docker-data/dms/config on the host for this purpose). And you're done! Note: this disables authentication on the website - make sure you know what you're doing!
You additionally want to enable the auto-spam-learning for the Bayes module? No problem, just add another line to rspamd-modules.conf that looks like this: set-option-for-module classifier-bayes autolearn true.
But the chartable module gets on your nerves? Just disable it by adding another line: disable-module chartable .

DKIM Signing

By default, DMS offers no option to generate and configure signing e-mails with DKIM. This is because the parsing would be difficult. But don't worry: the process is relatively straightforward nevertheless. The official Rspamd documentation for the DKIM signing module is pretty good. Basically, you need to

exec into the container
Run a command similar to rspamadm dkim_keygen -s 'woosh' -b 2048 -d example.com -k example.private > example.txt, adjusted to your needs
Make sure to then persists the files example.private and example.txt (created in step 2) in the container (for example with a Docker bind mount)
Create a configuration for the DKIM signing module, i.e. a file called dkim_signing.conf that you mount to /etc/rspamd/local.d/ or /etc/rspamd/override.d/. We provide example configurations down below. We recommend mounting this file into the container as well (as described here); do not use rspamd-modules.conf for this purpose.

??? example "DKIM Signing Module Configuration Examples"

A simple configuration could look like this:

```cf
# documentation: https://rspamd.com/doc/modules/dkim_signing.html

enabled = true;

sign_authenticated = true;
sign_local = true;

use_domain = "header";
use_redis = false; # don't change unless Redis also provides the DKIM keys
use_esld = true;
check_pubkey = true;

domain {
    example.com {
        path = "/path/to/example.private";
        selector = "woosh";
    }
}
```

If you have multiple domains and you want to sign with the modern ED25519 elliptic curve but also with RSA (you will likely want to have RSA as a fallback!):

```cf
# documentation: https://rspamd.com/doc/modules/dkim_signing.html

enabled = true;

sign_authenticated = true;
sign_local = true;

use_domain = "header";
use_redis = false; # don't change unless Redis also provides the DKIM keys
use_esld = true;
check_pubkey = true;

domain {
    example.com {
        selectors [
            {
                path = "/path/to/com.example.rsa.private";
                selector = "dkim-rsa";
            },
            {
              path = /path/to/com.example.ed25519.private";
              selector = "dkim-ed25519";
            }
      ]
    }
    example.org {
        selectors [
            {
                path = "/path/to/org.example.rsa.private";
                selector = "dkim-rsa";
            },
            {
              path = "/path/to/org.example.ed25519.private";
              selector = "dkim-ed25519";
            }
        ]
    }
}
```

Abusix Integration

This subsection gives information about the integration of Abusix, "a set of blocklists that work as an additional email security layer for your existing mail environment". The setup is straight-forward and well documented:

Create an account
Retrieve your API key
Navigate to the "Getting Started" documentation for Rspamd and follow the steps described there
Make sure to change <APIKEY> to your private API key

We recommend mounting the files directly into the container, as they are rather big and not manageable with the modules script. If mounted to the correct location, Rspamd will automatically pick them up.

While Abusix can be integrated into Postfix, Postscreen and a multitude of other software, we recommend integrating Abusix only into a single piece of software running in your mail server - everything else would be excessive and wasting queries. Moreover, we recommend the integration into suitable filtering software and not Postfix itself, as software like Postscreen or Rspamd can properly evaluate the return codes and other configuration.

14 KiB Raw Blame History