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It can also be a reverse proxy to serve multiple web services under one server. Its main features are its simple config setup and automatic HTTPS: It will automatically request and renew a LetsEncrypt certificate so that users of your service get a Browser-trusted and secure connection.
It can also be a reverse proxy to serve multiple web services under one server. Its main features are its simple config setup and automatic HTTPS: It will automatically request and renew a LetsEncrypt certificate so that users of your service get a Browser-trusted and secure connection.


== Get started ==
== Setup ==


To try out Caddy add the following minimal example to your [https://nixos.wiki/wiki/NixOS_modules NixOS module]:
To try out Caddy add the following minimal example to your [[NixOS modules | NixOS module]]:


<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">services.caddy = {
{
  enable = true;
  # ...
  virtualHosts."localhost".extraConfig = ''
  services.caddy = {
    respond "Hello, world!"
    enable = true;
  '';
    virtualHosts."localhost".extraConfig = ''
};</syntaxhighlight>
      respond "Hello, world!"
    '';
  };
} 
</syntaxhighlight>


This snippet will let Caddy respond on <code>http://localhost</code> and <code>https://localhost</code> with a dummy text "Hello world!". When no port is mentioned on virtualhost like just <code>localhost</code> instead of <code>localhost:8080</code>, Caddy listens on <code>80</code> and <code>443</code> by default and redirects requests from port 80 (unsecured) to 443 (secured).
This snippet will let Caddy respond on <code>http://localhost</code> and <code>https://localhost</code> with a dummy text "Hello world!". When no port is mentioned on virtualhost like just <code>localhost</code> instead of <code>localhost:8080</code>, Caddy listens on <code>80</code> and <code>443</code> by default and redirects requests from port 80 (unsecured) to 443 (secured).


==== Check http connection ====
Use <code>curl -iLk localhost</code> to verify the configuration.
 
You can use <code>curl</code> to test the http connections:
 
<syntaxhighlight lang="bash">
$ curl localhost -i -L -k
HTTP/1.1 308 Permanent Redirect
Location: https://localhost/
..
 
HTTP/2 200
alt-svc: h3=":443"; ma=2592000
content-type: text/plain; charset=utf-8
...
 
Hello, world!
</syntaxhighlight>
 
Here you can see that Caddy automatically redirects from an unsecure http://localhost to a secure https://localhost call.
For local addresses like "localhost" Caddy always generates and uses a self-signed certificate, which curl correctly doesn't trust; use the <code>-k</code> flag to ignore that.
 
==== Check http(s) connection ====
 
When virtualhost and "real" host aren't the same it gets complicated with HTTPS, so the following curl command works:
 
<syntaxhighlight lang="bash">
$ curl --connect-to <virtualhost>:443:<realhost>:443 https://<virtualhost> -k
Hello, world!
</syntaxhighlight>
 
Curl will set <code>Host</code> header and TLS <code>SNI</> in the request to <code><virtualhost></code> as desired by Caddy, but will make the actual request against the <code><realhost></code>, e.g. a load-balancer or ingress-controller.
 
Alternatively with http and automatic redirects to https you can extend that call:
 
<syntaxhighlight lang="bash">
$ curl --connect-to <virtualhost>:80:<realhost>:80 --connect-to <virtualhost>:443:<realhost>:443 https://<virtualhost> -k -L
Hello, world!
</syntaxhighlight>


* [https://curl.se/docs/manpage.html#--connect-to curl connect-to documentation]
For SSL to work, just supply a public domain and ensure HTTP and HTTPS ports are accessible. Caddy will automatically configure TLS:
* [https://www.claudiokuenzler.com/blog/693/curious-case-of-curl-ssl-tls-sni-http-host-header Curl on HTTPS, SNI, Host]
* [https://github.com/caddyserver/caddy/issues/2656#issuecomment-1627342466 curl to Caddy over HTTPS]


== Typical configurations ==
<syntaxhighlight lang="nix">services.caddy = {
 
=== SSL ===
 
Caddy will automatically try to acquire SSL certificates for the specified domain, in this example <code>example.org</code>. This requires you to configure the DNS records of your domain correctly, which should point to the address of your Caddy server. The [[firewall]] ports <code>80</code> and <code>443</code> needs to be opened.
 
<syntaxhighlight lang="nix">
services.caddy = {
   enable = true;
   enable = true;
   virtualHosts."example.org".extraConfig = ''
   virtualHosts."example.org".extraConfig = ''
     encode gzip
     respond "Hello, world!"
    file_server
    root * ${
      pkgs.runCommand "testdir" {} ''
        mkdir "$out"
        echo hello world > "$out/example.html"
      ''
    }
   '';
   '';
};  
};  
networking.firewall.allowedTCPPorts = [ 80 443];  
 
</syntaxhighlight>
networking.firewall.allowedTCPPorts = [ 80 443 ];</syntaxhighlight>
 
== Configuration ==


=== Reverse proxy ===
=== Reverse proxy ===
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   virtualHosts."example.org".extraConfig = ''
   virtualHosts."example.org".extraConfig = ''
     reverse_proxy http://10.25.40.6
     reverse_proxy http://10.25.40.6
  '';
  virtualHosts."another.example.org".extraConfig = ''
    reverse_proxy unix//run/gunicorn.sock
   '';
   '';
};
};
</syntaxhighlight>
</syntaxhighlight>In case you would like to forward the real client IP of the request to the backend, add following headers<syntaxhighlight lang="nix">
 
services.caddy = {
* [https://caddyserver.com/docs/quick-starts/reverse-proxy Caddy reverse proxy documentation]
  virtualHosts."example.org".extraConfig = ''
    reverse_proxy http://10.25.40.6 {
      header_down X-Real-IP {http.request.remote}
      header_down X-Forwarded-For {http.request.remote}
    }
  '';
};
</syntaxhighlight>Fur further reverse proxy configuration, see [https://caddyserver.com/docs/quick-starts/reverse-proxy upstream documentation].


=== Redirect ===
=== Redirect ===


Redirecting <code>example.org</code> and <code>old.example.org</code> to <code>www.example.org</code>
Permanent redirect of <code>example.org</code> and <code>old.example.org</code> to <code>www.example.org</code>


<syntaxhighlight lang="nix">
<syntaxhighlight lang="nix">
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   virtualHosts."example.org" = {
   virtualHosts."example.org" = {
     extraConfig = ''
     extraConfig = ''
       redir https://www.example.org
       redir https://www.example.org{uri} permanent
   '';
   '';
     serverAlias = [ "old.example.org" ];
     serverAliases = [ "old.example.org" ];
};
};
</syntaxhighlight>
</syntaxhighlight>
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You'll need a [[Phpfpm|PHP-FPM]] socket listening on Unix socket path <code>/var/run/phpfpm/localhost.sock</code>.
You'll need a [[Phpfpm|PHP-FPM]] socket listening on Unix socket path <code>/var/run/phpfpm/localhost.sock</code>.


== Debugging ==
=== Plug-ins ===
 
Following example is adding the plugin powerdns in version 1.0.1 to your Caddy binary
 
<syntaxhighlight lang="nix">
services.caddy = {
  enable = true;
  package = pkgs.caddy.withPlugins {
    plugins = [ "github.com/caddy-dns/powerdns@v1.0.1" ];
    hash = "sha256-F/jqR4iEsklJFycTjSaW8B/V3iTGqqGOzwYBUXxRKrc=";
  };
};
</syntaxhighlight>
 
Get the correct hash by leaving the string empty at first and after rebuild, insert the hash which the build process calculated.
 
 
In case a plugin has no version tag, you'll have to query it first. In this example we'll do this for the plugin caddy-webdav
 
<syntaxhighlight lang="sh">
$ go mod init temp
$ go get github.com/mholt/caddy-webdav
$ grep 'caddy-webdav' go.mod
        github.com/mholt/caddy-webdav v0.0.0-20241008162340-42168ba04c9d // indirect
</syntaxhighlight>
 
Add this version string to your final config
 
<syntaxhighlight lang="nix">
services.caddy = {
  enable = true;
  package = pkgs.caddy.withPlugins {
    plugins = [ "github.com/caddy-dns/caddy-webdav@v0.0.0-20241008162340-42168ba04c9d" ];
    hash = "sha256-F/jqR4iEsklJFycTjSaW8B/V3iTGqqGOzwYBUXxRKrc=";
  };
};
</syntaxhighlight>
 
=== uWSGI apps ===
Serving uWSGI apps with Caddy also requires a plugin, in this example we'll use [https://github.com/wxh06/caddy-uwsgi-transport caddy-uwsgi-transport]. See section above on how to fetch and update plugins.<syntaxhighlight lang="nix">
services.caddy = {
  package = pkgs.caddy.withPlugins {
    plugins = [ "github.com/BadAimWeeb/caddy-uwsgi-transport@v0.0.0-20240317192154-74a1008b9763" ];
    hash = "sha256-aEdletYtVFnQMlWL6YW4gUgrrTBatoCIuugA/yvMGmI=";
  };
  virtualHosts = {
    "myapp.example.org" = {
      extraConfig = ''
        reverse_proxy unix/${config.services.uwsgi.runDir}/myapp.sock {
          transport uwsgi
        }
      '';
  };
};
 
</syntaxhighlight>This example will serve a [[uWSGI]] app, provided by a unix socket file, on the host <code>myapp.example.org</code>.
 
=== Passing environment variable secrets/configuring acme_dns ===
To prevent any secrets from being put in the nix store (any NixOS setting that writes a config in the Nix store will expose any secret in it), you can use the following setting<syntaxhighlight lang="nixos">
services.caddy = {
  enable = true;
  globalConfig = ''   
    acme_dns PROVIDER {
      api_key {$APIKEY}
      api_secret_key {$APISECRETKEY}
    }
  '';
};
systemd.services.caddy.serviceConfig.EnvironmentFile = ["/path/to/envfile"];
</syntaxhighlight>And then at '''/path/to/envfile''':<syntaxhighlight>
APIKEY=YOURKEY
APISECRETKEY=OTHERKEY
</syntaxhighlight>
 
== Troubleshooting ==


=== Check used ports ===
=== Check used ports ===
To check if Caddy is running and listening as configured you can run <code>ss</code>:


To check if Caddy is running and listening as configured you can run <code>netstat</code>:
<syntaxhighlight lang="console">
 
$ sudo ss --listening --no-queues --numeric --processes --tcp --udp | grep 'Process\|caddy'
<syntaxhighlight lang="bash">
Netid State      Local Address:Port  Peer Address:Port Process
$ netstat -tulpn
tcp   LISTEN          127.0.0.1:2019       0.0.0.0:*   users:(("caddy",pid=1000,fd=10))
Active Internet connections (only servers)
tcp  LISTEN                  *:80               *:*    users:(("caddy",pid=1000,fd=11))
Proto Recv-Q Send-Q Local Address           Foreign Address         State      PID/Program name   
tcp  LISTEN                  *:443             *:*    users:(("caddy",pid=1000,fd=12))
tcp       0      0 127.0.0.1:2019         0.0.0.0:*               LISTEN      1202/caddy          
udp  UNCONN                  *:443             *:*    users:(("caddy",pid=1000,fd=13))
tcp6      0      0 :::80                   :::*                    LISTEN      1202/caddy        
tcp6      0      0 :::443                 :::*                    LISTEN      1202/caddy        
udp6      0      0 :::443                 :::*                                1202/caddy          
</syntaxhighlight>
</syntaxhighlight>
The tcp (ipv4) socket port 2019 is Caddy's management endpoint, for when you want manage its config via web REST calls instead of Nix (ignore).
The tcp (ipv4) socket port 2019 is Caddy's management endpoint, for when you want manage its config via web REST calls instead of Nix (ignore).
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=== Virtualhost and real host not identical ===
=== Virtualhost and real host not identical ===
When you connect to Caddy must ensure that the "Host" header matches the virtualhost entry of Caddy. For example, when testing locally a config like  
When you connect to Caddy must ensure that the "Host" header matches the virtualhost entry of Caddy. For example, when testing locally a config like  


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* [https://caddyserver.com/docs/caddyfile/directives/tls Caddy TLS settings documentation]
* [https://caddyserver.com/docs/caddyfile/directives/tls Caddy TLS settings documentation]
== See also ==
== See also ==


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[[Category:Applications]]
[[Category:Applications]]
[[Category:Web Servers]]
[[Category:Server]]
[[Category:Networking]]
Retrieved from "https://wiki.nixos.org/wiki/Caddy"