Magic Alias Mail Forwarding (1/2)

software email haraka

How to create a dynamic alias for your mail ?

Forwarding any email account for your domain name's to your personal email

Have you either been in the situation (recently) that you personal email was disclosed because some website was hacked ?

Wouldn't be cool to have a fwd.facebook@mydomain.com email and use that when registering on Facebook ?

Even better if you did not have to setup such email account on your mail client ?

The solution I'm disclosing here allows you to use any email in the form fwd.*xxx*@domain.com to forward to a single email account transparently, without any prior configuration when creating a new email account.

It's sweet, simple and a lot more useful, because now, you'll know what website sells your email address to the spammer, what website was hacked and never said so and so on.

Ok, let's give the recipe now.

Ingredients

  1. You need a domain name from where you can control the DNS zone. Typically, you want to be able to add or define the MX part of the domain
  2. You need a linux based server (either a cloud instance, or a dedicated server connected to Internet directly)
  3. Instructions below are for a debian Stretch based distribution (should probably work as well for ubuntu), and this will need some tweaking for other distributions for the package name

What we will do

We will set up Haraka mail SMTP server who's in charge of accepting only email for your domain, using a specific format for the user part of the email, and forward it to your personal email's. Then we'll update the DNS records so that other will be able to send you emails to your domain's fresh server Finally, we'll ensure that this mail server is not a relay.

Conventions used in this tutorial

  • IP is your public IP address. If it's IPv4, it's in the format a.b.c.d (for example: 134.23.24.54), if it's IPv6 it's in the format [abc:def::234]
  • domain.com is your domain name. I expect you already have some DNS rules that links your domain to your's server IP address (so you have a domain.com A IN IPrule in your zone). Typically, if you do ping domain.com from anywhere, it should answer with your IP.
  • your@email your personal (private) email address
  • /home/you replace by the path to your home folder
  • Command starting with $ should be typed as regular user, and command starting with # should be typed as root. You don't need to type the dollar or hash sign. Please notice that you should be very careful with commands run as root (double check before validating them)

Let's get started!

Installing prerequisite

Haraka needs nodeJS for its core. So let's install it first:

$ sudo su
# curl -sL https://deb.nodesource.com/setup_10.x | bash -
# apt-get install -y nodejs gcc g++ make swaks

Then, because you might have versioning issue in the future, it's a good idea to load a node versioning manager:

$ curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.34.0/install.sh | bash
$ export NVM_DIR="$HOME/.nvm"
$ [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"  # This loads nvm
$ [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"  # This loads nvm bash_completion

We'll need nodejs LTS version:

$ nvm install v10.15.0

Then install Haraka (beware the uppercase here):

$ npm install -g Haraka

This should give some warning but no errors. Ensure everything is working by typing $ haraka -h

This should give this answer:

$ haraka -h
Haraka.js — A Node.js Email Server project
Usage: haraka [options] [path]
Options:
    -v, --version       Outputs version number
    -h, --help          Outputs this help message
    -h NAME             Shows help for NAME
    -c, --configs       Path to your config directory
    -i, --install       Copies the default configs to a specified dir
    -l, --list          List the plugins bundled with Haraka
    -p, --plugin        Generate a new plugin with the given name
    -f, --force         Force overwriting of old files
    --qlist             List the outbound queue
    --qstat             Get statistics on the outbound queue
    --qunstick          Unstick (force delivery) for a given domain
    -o, --order         Show all registered plugins and their run order
    -t PLUGIN           Plugin test mode
    --------------- PLUGIN TEST MODE OPTIONS (all optional) --------------
    --ip IP             IP address to use
    --helo HELO         HELO to use
    --ehlo EHLO         EHLO to use
    --envfrom FROM      MAIL FROM to use
    --envfrom TO        RCPT TO(s) to use
    --message FILE      Message file to use
    --dump-mime         Dump the MIME structure and body text
    --dump-stream       Dump the MessageStream to stdout
    --skip-deny         Continue running hooks after DENY/DENYSOFT
    --set-relay         Set connection.relaying

Then, we need to install it definitively so it can be run as root (don't worry, it'll decay to a no-priviledge user afterward).

$ sudo ln -sf /home/you/.nvm/versions/node/v10.15.0/bin/haraka /usr/bin/haraka
$ sudo mkdir /var/lib/haraka
$ sudo haraka -i /var/lib/haraka

Haraka's config and queue will be stored in /var/lib/haraka and will run as unpriviledged user smtp. Let's create such user and group:

$ sudo addgroup smtp
$ sudo adduser --system --no-create-home --disabled-password --disabled-login smtp --ingroup smtp

Then, we'll need some specific plugin here for the forwarding called rcpt_to.alias_forword (yes, the name is wrong):

$ cd /home/you/.nvm/versions/node/v10.15.0/lib/node_modules/Haraka/plugins
$ wget https://raw.githubusercontent.com/guoyiang/haraka-alias-forward/master/plugins/rcpt_to.alias_forword.js
$ cd ../config
$ wget https://raw.githubusercontent.com/guoyiang/haraka-alias-forward/master/config/rcpt_to.alias_forword

Configuring the mail server

Unlike other email servers (with those complex term like MTA, MDA, MSA, LDA, etc...), this server is not in charge of keeping (queueing) emails. You don't care about spam filtering here, or antivirus and so on. This work will be done by your usual email provider.

Typically Haraka architecture is based on plugins. For each selected plugin, you must provide a configuration. In this example, I'm running with the minimum set of plugins for the task (you are free to add more later on, but start simple, test and then improve, not the opposite).

The plugins we are using are the following (type the commands below):

$ sudo mv /var/lib/haraka/config/plugins /var/lib/haraka/config/plugins.old
$ sudo su
# echo -e "syslog\ndnsbl\nhelo.checks\nrcpt_to.alias_forword\ndata.headers\nqueue/discard\nlimit" /var/lib/haraka/config/plugins
# nano /var/lib/haraka/config/rcpt_to.alias_forword

This last command should have opened an editor, where you'll enter this (replacing domain by your domain name and your@email by your personal email:

{
    "accept_when_match" : true,
    "discard_income_mail" : true,
    "alias": {
          "domain": [
            {
                "local_name": "fwd.*",
                "forward_to": "your@email"
            }]
    }
}

If you want to also accept regular mail, you can add non wildcard rules in the domain section like this:

{
    "local_name" : "info",
    "forward_to": "your@email"
}

This will accept info@domain and forward to your@email and also info-whatever@domain but not something@domain.

Configure the server with $ sudo nano /var/lib/haraka/smtp.iniand enter this (replacing IP by your server's IP address):

listen=IP:25,IP:587,[IPv6]:25,[IPv6]:587
public_ip=IP

user=smtp
group=smtp

daemonize=true
daemon_log_file=/var/log/haraka.log
daemon_pid_file=/var/run/haraka.pid

spool_dir=/var/spool/haraka
spool_after=524288

Then test the server is working:

$ sudo kill `cat /var/run/haraka.pid`; sudo rm /var/run/haraka.pid; sudo haraka -c /var/lib/haraka

If the server is working, you shouldn't get a message saying "server shutting down" Please notice that the configuration above listen on TLS (secure) port. In this tutorial, I'm not explaining how to get a certificate for your domain and how to run the TLS plugin. If Haraka complains, remove the port 587 from the config above. It will be a good idea to set up TLS later, since at least to a man in the middle, the email will transit ciphered on the internet

Telling others about your new mail server

We now need to set up the MX record in your DNS zone. Typically, when someone wants to send a mail to @some.com, she'll query the DNS record typed MX of the domain some.com. This will redirect to a server address and she'll then connect on this address and port 25 (SMTP) or 587 (ESMTP) to deliver the mail.

On our side, we'll simply need to tell we have a SMTP server listening on our server by adding a DNS record. Provided you already have domain. 3600 IN A IP the number is not that important, you'll need to add (replacing domain by your domain name, beware of the final dot that's required):

domain. 3600    IN  MX  10 domain.

If I'm talking chinese here, you'll need to go to your registrar website, that's usually where you can edit your domain's DNS zone record. So for example, let's I have the domain bob.com on my server located at 1.1.1.1, then I should get the following record in the end:

bob.com. 3600 IN A 1.1.1.1
bob.com. 3600 IN MX 10 bob.com.

Testing you can send email now

Now that the server is started and the domain zone is ready, it's time to test. Try to send an email either via command line (through swaks) or your email program to bob@domain. You should get a notice that it's rejected (if not, double check the configuration above)

Then try to send a mail to fwd.test@domain and magically, it should appear in your personal mailbox few seconds later.

If everything is working correctly, we'll need to finalize the installation.

Finalizing

First, we'll only allow smtp user to read/write to the haraka working folder and create a systemd service so the mail server is started on boot. Use your favorite editor to create the file /lib/systemd/system/haraka.service as root that should contain:

[Unit]
Description=Haraka MTA
After=syslog.target network.target remote-fs.target nss-lookup.target

[Service]
Type=forking
PIDFile=/var/run/haraka.pid
ExecStart=/usr/bin/haraka -c /var/lib/haraka
KillMode=process
PrivateTmp=true

[Install]
WantedBy=multi-user.target

Then run these commands:

$ sudo chown smtp:smtp -R /var/lib/haraka
$ sudo chmod 0660 -R /var/lib/haraka
$ sudo systemctl enable haraka
$ sudo kill `cat /var/run/haraka.pid`; sudo rm /var/run/haraka.pid
$ sudo systemctl start haraka

Conclusion

Provided you're using a password manager (you should), then now, whenever you browse and need to create an account on any website, you'll give the following email fwd.websitename@domain and a generated password that you'll save in your password manager.

Please notice however that you can't reply to these emails (unless you create the identity in your mail client, but this is a bit painful), so this is mainly used for website that never expect to receive emails like (shopping website, newsletter, etc...)

Next, whenever you'll receive spam, you'll see in the header what website sold your contact or just get hacked. It's then up to you to replicate ;-)

Update: Please see the updated steps required for 100% delivery with new SMTP server's policy in 2020.

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