nixpkgs/nixos/modules/security/acme.xml

<chapter xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="module-security-acme">

<title>SSL/TLS Certificates with ACME</title>

<para>NixOS supports automatic domain validation &amp; certificate
retrieval and renewal using the ACME protocol. This is currently only
implemented by and for Let's Encrypt. The alternative ACME client
<literal>simp_le</literal> is used under the hood.</para>

<section><title>Prerequisites</title>

<para>You need to have a running HTTP server for verification. The server must
have a webroot defined that can serve
<filename>.well-known/acme-challenge</filename>. This directory must be
writeable by the user that will run the ACME client.</para>

<para>For instance, this generic snippet could be used for Nginx:

<programlisting>
http {
  server {
    server_name _;
    listen 80;
    listen [::]:80;

    location /.well-known/acme-challenge {
      root /var/www/challenges;
    }

    location / {
      return 301 https://$host$request_uri;
    }
  }
}
</programlisting>
</para>

</section>

<section><title>Configuring</title>

<para>To enable ACME certificate retrieval &amp; renewal for a certificate for
<literal>foo.example.com</literal>, add the following in your
<filename>configuration.nix</filename>:

<programlisting>
<xref linkend="opt-security.acme.certs"/>."foo.example.com" = {
  <link linkend="opt-security.acme.certs._name_.webroot">webroot</link> = "/var/www/challenges";
  <link linkend="opt-security.acme.certs._name_.email">email</link> = "foo@example.com";
};
</programlisting>
</para>

<para>The private key <filename>key.pem</filename> and certificate
<filename>fullchain.pem</filename> will be put into
<filename>/var/lib/acme/foo.example.com</filename>. The target directory can
be configured with the option <xref linkend="opt-security.acme.directory"/>.
</para>

<para>Refer to <xref linkend="ch-options" /> for all available configuration
options for the <link linkend="opt-security.acme.certs">security.acme</link> module.</para>

</section>

<section><title>Using ACME certificates in Nginx</title>
<para>NixOS supports fetching ACME certificates for you by setting
  <literal><link linkend="opt-services.nginx.virtualHosts._name_.enableACME">enableACME</link> = true;</literal> in a virtualHost config. We
first create self-signed placeholder certificates in place of the
real ACME certs. The placeholder certs are overwritten when the ACME
certs arrive. For <literal>foo.example.com</literal> the config would
look like.
</para>

<programlisting>
services.nginx = {
  <link linkend="opt-services.nginx.enable">enable = true;</link>
  <link linkend="opt-services.nginx.virtualHosts">virtualHosts</link> = {
    "foo.example.com" = {
      <link linkend="opt-services.nginx.virtualHosts._name_.forceSSL">forceSSL</link> = true;
      <link linkend="opt-services.nginx.virtualHosts._name_.enableACME">enableACME</link> = true;
      locations."/" = {
        <link linkend="opt-services.nginx.virtualHosts._name_.locations._name_.root">root</link> = "/var/www";
      };
    };
  };
}
</programlisting>
</section>
</chapter>