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readme.md

Caddy v2 Reverse Proxy

guide by example

Caddy as a reverse proxy - basics

Official documentation.

Install caddy v2
Create Caddyfile
The configuration file for caddy. This one with just two subdomains being routed to some two services on the LAN.

Caddyfile
```
a.blabla.org {
    reverse_proxy {
        to 192.168.1.222:80
    }
}

b.blabla.org {
    reverse_proxy server-blue:8080
}
```
b.blabla.org uses short hand notation when there are no other directives used.
Run caddy server
sudo caddy run in the directory with Caddyfile.

Give it time to get certificates and then check the a.blabla.org / b.blabla.org
It should just work with https and http->https redirect.

Caddy as a reverse proxy in docker

Caddy will be running as a docker container and will route traffic to other containers, or servers on the network.

files and directory structure

/home
└── ~
    └── docker
        └── caddy
            ├── 🗁 config
            ├── 🗁 data
            ├── 🗋 .env
            ├── 🗋 Caddyfile
            └── 🗋 docker-compose.yml

Create a new docker network
docker network create caddy_net
All the containers and caddy must be on the same network.
Create .env file

.env
```
MY_DOMAIN=blabla.org
DEFAULT_NETWORK=caddy_net
TZ=Europe/Prague
```
Domain names, api keys, email settings, ip addresses, database credentials, ... whatever is specific for one case and different for another, all of that ideally goes in to the .env file.

These variables will be available for docker-compose when running the docker-compose up command.
This allows compose files to be moved from system to system more freely and changes are done to the .env file.

Often variable should be available also inside the running container. For that it must be declared in the environment section of the compose file, as can be seen later in caddie's docker-compose.yml

extra info:
docker-compose config shows how compose will look with the variables filled in.

Create docker-compose.yml for caddy

docker-compose.yml

version: "3.7"
services:

  caddy:
    image: "caddy/caddy"
    container_name: "caddy"
    hostname: "caddy"
    restart: unless-stopped
    ports:
      - "80:80"
      - "443:443"
    environment:
      - MY_DOMAIN
    volumes:
      - ./Caddyfile:/etc/caddy/Caddyfile:ro
      - ./data:/data
      - ./config:/config

networks:
  default:
    external:
      name: $DEFAULT_NETWORK

Port 80 and 443 are mapped for http and https.
The Caddyfile is read-only bind-mounted from the docker host.
Directories config and data are also bind mounted and its where caddy will store configuration in json format and the certificates.
The same network is joined as for all other containers.

Create Caddyfile

Caddyfile
```
{
    # acme_ca https://acme-staging-v02.api.letsencrypt.org/directory
}

a.{$MY_DOMAIN} {
    reverse_proxy whoami:80
}

b.{$MY_DOMAIN} {
    reverse_proxy nginx:80
}
```
The value of {$MY_DOMAIN} is an enviromental variable provided by the compose and the .env file.
The subdomains point at docker containers by their hostname and port. So every docker container you spin should have hostname definied.
Commented out is the staging url for let's encrypt, useful for testing.
Setup some docker containers
Something to route to, targeted using the hostname and the exposed port.
These compose files need .env file with the same env variables for the DEFAULT_NETWORK as the caddy has.
Note the lack of published/mapped ports in the compose. Since the containers are all on the same bridge network, they can access each other on any port. Exposed ports are basicly just documentation.

extra info:
To know which ports containers have exposed - docker ps or docker inspect

whoami-compose.yml
```
version: "3.7"
services:

  whoami:
    image: "containous/whoami"
    container_name: "whoami"
    hostname: "whoami"

networks:
  default:
    external:
      name: $DEFAULT_NETWORK
```
nginx-compose.yml
```
version: "3.7"
services:

  nginx:
    image: nginx:latest
    container_name: nginx
    hostname: nginx

networks:
  default:
    external:
      name: $DEFAULT_NETWORK
```
Run it all
Caddy
- docker-compose up -d
Services
- docker-compose -f whoami-compose.yml up -d
- docker-compose -f nginx-compose.yml up -d
Give it time to get certificates, checking docker logs caddy as it goes, then visit the urls. It should lead to the services with https working.

If something is fucky use docker logs caddy to see what is happening.
Restarting the container docker container restart caddy can help. Or investigate inside docker exec -it caddy /bin/sh. For example trying to ping hosts that are suppose to be reachable, ping nginx should work.

There's also other possible issues, like bad port forwarding towards docker host, or trying to access domain from local network without dealing with it, for example by adding in to the hosts file ip and subdomain.domain of the docker host - 192.168.1.200 a.blabla.org

Caddy more info and various configurations

Worth reading the official documentation, especially these short pages

Caddy when used as a reverse proxy functions as a TLS termination proxy.
Https encrypted tunel ends with it, and the traffic can be analyzed and dealt with based on the settings.

By default, Caddy passes through Host header and adds X-Forwarded-For for the client IP. This means that 90% of the time the simple config just works

  b.blabla.org {
    reverse_proxy server-blue:8080
}

But there are some cases that want something extra, as shown in following examples.

Backend communication
Some containers might be set to communicate only through https 443 port. But since they are behind proxy and likely not fully configured, their certificates wont be singed, wont be trusted.

Caddies sub-directive transport sets how to communicate with the backend. Setting port to 443 or declaring tls makes it use https. Setting tls_insecure_skip_verify makes it trust whatever certificate is coming from the backend.

nextcloud.{$MY_DOMAIN} {
    reverse_proxy {
        to nextcloud:443
        transport http {
            tls
            tls_insecure_skip_verify
        }
    }
}

HSTS and redirects
Running Nextcloud behind any proxy likely shows few warning in its status page. It requires some redirects for service discovery to work and would really like if HSTS would be set
Like so:

nextcloud.{$MY_DOMAIN} {
    reverse_proxy nextcloud:80
    header Strict-Transport-Security max-age=31536000;
    redir /.well-known/carddav /remote.php/carddav 301
    redir /.well-known/caldav /remote.php/caldav 301
}

gzip and headers
This example is with Bitwarden password manager, which comes with its reverse proxy recommendations.

encode gzip enables compression. This lowers the bandwith use and speeds up loading of the sites. It is often set on the webserver running inside the docker container, but if not it can be enabled on caddy. You can check if your stuff has it enabled by using one of many online tools

Bitwarden also asks for some extra headers.
We can also see its use of websocket protocol for notifications at port 3012.

bitwarden.{$MY_DOMAIN} {
    encode gzip

    header / {
        # Enable cross-site filter (XSS) and tell browser to block detected attacks
        X-XSS-Protection "1; mode=block"
        # Disallow the site to be rendered within a frame (clickjacking protection)
        X-Frame-Options "DENY"
        # Prevent search engines from indexing (optional)
        X-Robots-Tag "none"
        # Server name removing
        -Server
    }

    # The negotiation endpoint is also proxied to Rocket
    reverse_proxy /notifications/hub/negotiate bitwarden:80

    # Notifications redirected to the websockets server
    reverse_proxy /notifications/hub bitwarden:3012

    # Proxy the Root directory to Rocket
    reverse_proxy bitwarden:80
}

logging
Official documentation.
If access logs for specific site are desired

bookstack.{$MY_DOMAIN} {
    log {
        output file /data/logs/bookstack_access.log {
            roll_size 20mb
            roll_keep 5
        }
    }
    reverse_proxy to bookstack:80
}

Caddy dns challenge

Caddy needs to be compiled with dns module imported... so this is untested. But I assume the configuration would go something like this:

DNS record
Using cloudflare.
Make sure A-Type record pointing test.blabla.org to the correct public IP exists, and that it is all properly forwarded from there to the docker host.

Caddyfile

Caddyfile

{
    # acme_ca https://acme-staging-v02.api.letsencrypt.org/directory
}

test.{$MY_DOMAIN} {
    reverse_proxy whoami:80
    tls {
      dns cloudflare
    }
}

.env file

.env

# GENERAL
MY_DOMAIN=blabla.org
DEFAULT_NETWORK=caddy_net
TZ=Europe/Prague

# CLOUDFLARE    
CLOUDFLARE_EMAIL=bastard@whatever.org
CLOUDFLARE_API_KEY=global-api-key-goes-here

Caddy basicauth

Official documentation.
If username/password check before accessing a service is required.

Add basicauth section to the Caddyfile

Password is bcrypt encrypted and then base64 salted.
In this case username and password are bastard / bastard

Caddyfile

{
    # acme_ca https://acme-staging-v02.api.letsencrypt.org/directory
}

b.{$MY_DOMAIN} {
    reverse_proxy whoami:80
    basicauth {
      bastard JDJhJDA0JDVkeTFJa1VjS3pHU3VHQ2ZSZ0pGMU9FeWdNcUd0Wk9RdWdzSzdXUXNhWFFLWW5pYkxXVEU2
    }
}