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diff --git a/src/_posts/2021-06-26-selfhosted-email-with-maddy.md b/src/_posts/2021-06-26-selfhosted-email-with-maddy.md new file mode 100644 index 0000000..0ea3491 --- /dev/null +++ b/src/_posts/2021-06-26-selfhosted-email-with-maddy.md @@ -0,0 +1,277 @@ +--- +title: >- + Self-Hosted Email With maddy: A Naive First Attempt +description: >- + How hard could it be? +tags: tech +series: selfhost +--- + +For a _long_ time now I've wanted to get off gmail and host my own email +domains. I've looked into it a few times, but have been discouraged on multiple +fronts: + +* Understanding the protocols underlying email isn't straightforward; it's an + old system, there's a lot of cruft, lots of auxiliary protocols that are now + essentially required, and a lot of different services required to tape it all + together. + +* The services which are required are themselves old, and use operational + patterns that maybe used to make sense but are now pretty freaking cumbersome. + For example, postfix requires something like 3 different system accounts. + +* Deviating from the non-standard route and using something like + [Mail-in-a-box][miab] involves running docker, which I'm trying to avoid. + +So up till now I had let the idea sit, waiting for something better to come +along. + +[maddy][maddy] is, I think, something better. According to the homepage +"\[maddy\] replaces Postfix, Dovecot, OpenDKIM, OpenSPF, OpenDMARC and more with +one daemon with uniform configuration and minimal maintenance cost." Sounds +perfect! The homepage is clean and to the point, it's written in go, and the +docs appear to be reasonably well written. And, to top it all off, it's already +been added to [nixpkgs][nixpkgs]! + +So in this post (and subsequent posts) I'll be documenting my journey into +getting a maddy server running to see how well it works out. + +## Just Do It + +I'm almost 100% sure this won't work, but to start with I'm going to simply get +maddy up and running on my home media server as per the tutorial on its site, +and go from there. + +First there's some global system configuration I need to perform. Ideally maddy +could be completely packaged up and not pollute the rest of the system at all, +and if I was using NixOS I think that would be possible, but as it is I need to +create a user for maddy and ensure it's able to read the TLS certificates that I +manage via [LetsEncrypt][le]. + +```bash +sudo useradd -mrU -s /sbin/nologin -d /var/lib/maddy -c "maddy mail server" maddy +sudo setfacl -R -m u:maddy:rX /etc/letsencrypt/{live,archive} +``` + +The next step is to set up the nix build of the systemd service file. This is a +strategy I've been using recently to nix-ify my services without needing to deal +with nix profiles. The idea is to encode the nix store path to everything +directly into the systemd service file, and install that file normally. In this +case this looks something like: + +``` +pkgs.writeTextFile { + name = "mediocregopher-maddy-service"; + text = '' + [Unit] + Description=mediocregopher maddy + Documentation=man:maddy(1) + Documentation=man:maddy.conf(5) + Documentation=https://maddy.email + After=network.target + + [Service] + Type=notify + NotifyAccess=main + Restart=always + RestartSec=1s + + User=maddy + Group=maddy + + # cd to state directory to make sure any relative paths + # in config will be relative to it unless handled specially. + WorkingDirectory=/mnt/vol1/maddy + ReadWritePaths=/mnt/vol1/maddy + + # ... lots of directives from + # https://github.com/foxcpp/maddy/blob/master/dist/systemd/maddy.service + # that we'll elide here ... + + ExecStart=${pkgs.maddy}/bin/maddy -config ${./maddy.conf} + + ExecReload=/bin/kill -USR1 $MAINPID + ExecReload=/bin/kill -USR2 $MAINPID + + [Install] + WantedBy=multi-user.target + ''; +} +``` + +With the service now testable, it falls on me to actually go through the setup +steps described in the [tutorial][tutorial]. + +## Following The Tutorial + +The first step in the tutorial is setting up of domain names, which I first +perform in cloudflare (where my DNS is hosted) and then reflect into the conf +file. Then I point the `tls file` configuration line at my LetsEncrypt +directory by changing the line to: + +``` +tls file /etc/letsencrypt/live/$(hostname)/fullchain.pem /etc/letsencrypt/live/$(hostname)/privkey.pem +``` + + +maddy can access these files thanks to the `setfacl` command I performed +earlier. + +At this point the server should be effectively configured. However, starting it +via systemd results in this error: + +``` +failed to load /etc/letsencrypt/live/mx.mydomain.com/fullchain.pem and /etc/letsencrypt/live/mx.mydomain.com/privkey.pem +``` + +(For my own security I'm not going to be using the actual email domain in this +post, I'll use `mydomain.com` instead.) + +This makes sense... I use a wildcard domain with LetsEncrypt, so certs for the +`mx` sub-domain specifically won't exist. I need to figure out how to tell maddy +to use the wildcard, or actually create a separate certificate for the `mx` +sub-domain. I'd rather the former, obviously, as it's far less work. + +Luckily, making it use the wildcard isn't too hard, all that is needed is to +change the `tls file` line to: + +``` +tls file /etc/letsencrypt/live/$(primary_domain)/fullchain.pem /etc/letsencrypt/live/$(primary_domain)/privkey.pem +``` + +This works because my `primary_domain` domain is set to the top-level +(`mydomain.com`), which is what the wildcard cert is issued for. + +At this point maddy is up and running, but there's still a slight problem. maddy +appears to be placing all of its state files in `/var/lib/maddy`, even though +I'd like to place them in `/mnt/vol1/maddy`. I had set the `WorkingDirectory` in +the systemd service file to this, but apparently that's not enough. After +digging through the codebase I discover an undocumented directive which can be +added to the conf file: + +``` +state_dir /mnt/vol1/maddy +``` + +Kind of annoying, but at least it works. + +The next step is to fiddle with DNS records some more. I add the SPF, DMARC and +DKIM records to cloudflare as described by the tutorial (what do these do? I +have no fuckin clue). + +I also need to set up MTA-STS (again, not really knowing what that is). The +tutorial says I need to make a file with certain contents available at the URL +`https://mta-sts.mydomain.com/.well-known/mta-sts.txt`. I love it when protocol +has to give up and resort to another one in order to keep itself afloat, it +really inspires confidence. + +Anyway, I set that subdomain up in cloudflare, and add the following to my nginx +configuration: + +``` +server { + listen 80; + server_name mta-sts.mydomain.com; + include include/public_whitelist.conf; + + location / { + return 404; + } + + location /.well-known/mta-sts.txt { + + # Check out openresty if you want to get super useful nginx plugins, like + # the echo module, out-of-the-box. + echo 'mode: enforce'; + echo 'max_age: 604800'; + echo 'mx: mx.mydomain.com'; + } +} +``` + +(Note: my `public_whitelist.conf` only allows cloudflare IPs to access this +sub-domain, which is something I do for all sub-domains which I can put through +cloudflare.) + +Finally, I need to create some actual credentials in maddy with which to send my +email. I do this via the `maddyctl` command-line utility: + +``` +> sudo maddyctl --config maddy.conf creds create 'me@mydomain.com' +Enter password for new user: +> sudo maddyctl --config maddy.conf imap-acct create 'me@mydomain.com' +``` + +## Send It! + +At this point I'm ready to actually test the email sending. I'm going to use +[S-nail][snail] to do so, and after reading through the docs there I put the +following in my `~/.mailrc`: + +``` +set v15-compat +set mta=smtp://me%40mydomain.com:password@localhost:587 smtp-use-starttls +``` + +And attempt the following `mailx` command to send an email from my new mail +server: + +``` +> echo 'Hello! This is a cool email' | mailx -s 'Subject' -r 'Me <me@mydomain.com>' 'test.email@gmail.com' +reproducible_build: TLS certificate does not match: localhost:587 +/home/mediocregopher/dead.letter 10/313 +reproducible_build: ... message not sent +``` + +Damn. TLS is failing because I'm connecting over `localhost`, but maddy is +serving the TLS certs for `mydomain.com`. Since I haven't gone through the steps +of exposing maddy publicly yet (which would require port forwarding in my +router, as well as opening a port in iptables) I can't properly test this with +TLS not being required. _It's very important that I remember to re-require TLS +before putting anything public._ + +In the meantime I remove the `smtp-use-starttls` entry from my `~/.mailrc`, and +retry the `mailx` command. This time I get a different error: + +``` +reproducible_build: SMTP server: 523 5.7.10 TLS is required +``` + +It turns out there's a further configuration directive I need to add, this time +in `maddy.conf`. Within my `submission` configuration block I add the following +line: + +``` +insecure_auth true +``` + +This allows plaintext auth over non-TLS connections. Kind of sketchy, but again +I'll undo this before putting anything public. + +Finally, I try the `mailx` command one more time, and it successfully returns! + +Unfortunately, no email is ever received in my gmail :( I check the maddy logs +and see what I feared most all along: + +``` +Jun 29 08:44:58 maddy[127396]: remote: cannot use MX {"domain":"gmail.com","io_op":"dial","msg_id":"5c23d76a-60db30e7","reason":"dial tcp 142.250.152.26:25: connect: connection timed out","remote_addr":"142.250.152. +26:25","remote_server":"alt1.gmail-smtp-in.l.google.com.","smtp_code":450,"smtp_enchcode":"4.4.2","smtp_msg":"Network I/O error"} +``` + +My ISP is blocking outbound connections on port 25. This is classic email +bullshit; ISPs essentially can't allow outbound SMTP connections, as email is so +easily abusable it would drastically increase the amount of spam being sent from +their networks. + +## Lessons Learned + +The next attempt will involve an external VPS which allows SMTP, and a lot more +interesting configuration. But for now I'm forced to turn off maddy and let this +dream sit for a little while longer. + +[miab]: https://mailinabox.email/ +[maddy]: https://maddy.email +[nixpkgs]: https://search.nixos.org/packages?channel=21.05&from=0&size=50&sort=relevance&query=maddy +[tutorial]: https://maddy.email/tutorials/setting-up/ +[le]: https://letsencrypt.org/ +[snail]: https://wiki.archlinux.org/title/S-nail |