caddy: Reverse Proxy¶
Index
Features¶
Reverse Proxy HTTP, HTTPS, FastCGI, WebSockets, gRPC, FastCGI (usually PHP), and more!
Main features of this plugin:
Easy to configure and reliable! Reverse Proxy any HTTP/HTTPS or WebSocket application in minutes.
Hard to break! Extensive validations of the configuration on each save and apply.
Automatic Let’s Encrypt and ZeroSSL Certificates with HTTP-01 and TLS-ALPN-01 challenge
DNS-01 challenge and Dynamic DNS with supported DNS Providers built right in
Use custom certificates from OPNsense certificate store
Wildcard Domain and Subdomain support
Access Lists to restrict access based on static networks
Basic Auth to restrict access by username and password
Syslog-ng integration and HTTP Access Log
NTLM Transport
Header manipulation
How-To install¶
Install “os-caddy” from the OPNsense Plugins.
Prepare OPNsense for Caddy after installation¶
Attention
Caddy uses port 80 and 443. So the OPNsense WebUI or other plugins can’t bind to these ports.
Go to System - Settings - Administration
Change the TCP Port to 8443 (example), don’t forget to adjust the firewall rules to allow access to the WebUI. On LAN there is a hidden anti-lockout rule that takes care of this automatically. On other interfaces, make sure to add explicit rules.
Enable the checkbox for HTTP Redirect - Disable web GUI redirect rule.
Go to Firewall - Rules - WAN
Create Firewall rules that allow
HTTP
andHTTPS
to destinationThis Firewall
onWAN
Option |
Values |
---|---|
Interface |
|
TCP/IP Version |
|
Protocol |
|
Source |
|
Destination |
|
Destination port range |
from: |
Description |
|
Option |
Values |
---|---|
Interface |
|
TCP/IP Version |
|
Protocol |
|
Source |
|
Destination |
|
Destination port range |
from: |
Description |
|
Go to Firewall - Rules - LAN and create the same rules for the LAN interface. Now external and internal clients can connect to Caddy, and Let’s Encrypt or ZeroSSL certificates will be issued automatically.
FAQ¶
A DNS Provider is not required. With a static WAN IP, just skip the DNS Provider configuration and don’t check the DNS-01 and Dynamic DNS checkboxes. Let’s Encrypt will work with HTTP-01 (Port 80) or TLS-ALPN-01 (Port 443) challenge automatically.
Port Forwards, NAT Reflection or Split Horizon DNS are not required. Only create Firewall rules that allow traffic to hit the ports that Caddy opens. They are TCP/UDP 80 and 443.
Firewall rules to allow Caddy to reach upstream destinations are not required. OPNsense has a default rule that allows all traffic originating from it to be allowed.
ACME Clients on reverse proxied upstream destinations won’t be able to issue certificates. Caddy intercepts
/.well-known/acme-challenge
. This can potentially be solved by using the HTTP-01 challenge redirection option in the advanced mode of domains.When using Caddy with IPv6, it’s best to have a GUA (Global Unicast Address) on the WAN interface, since otherwise the TLS-ALPN-01 challenge might fail.
Let’s Encrypt or ZeroSSL can’t be explicitely chosen. Caddy automatically issues one of these options, determined by speed and availability. These certificates can be found in
/var/db/caddy/data/caddy/certificates
.
Attention
There is no TCP/UDP stream, load balancing and WAF (Web Application Firewall) support in this plugin. Caddy itself could support these features, but this plugin is focused on ease of configuration. For a business ready Reverse Proxy with WAF functionality, use OPNWAF. For TCP/UDP streaming, use either nginx or ha-proxy.
Tip
As an alternative to a WAF, it’s simple to integrate Caddy with CrowdSec. Check the tutorial section for guidance.
caddy: Configuration¶
Note
Caddy can be found in “Services: Caddy Web Server”. Some options are hidden in advanced mode.
General Settings - General¶
Option |
Description |
---|---|
enabled |
enable or disable Caddy. If enabled, Caddy will serve the configuration and autostart with the OPNsense. |
ACME Email |
e.g. info@example.com, it’s optional for receiving Email updates on Let’s Encrypt certificates. |
Auto HTTPS |
On (default) creates automatic Let’s Encrypt certificates for all domains that don’t have more specific options set, like custom certificates. |
Trusted Proxies |
If Cloudflare or another CDN provider is used, create an Access List with the IP addresses of that CDN and add it here. Add the same Access List to the domain this CDN tries to reach. |
Abort Connections |
This option, when enabled, aborts all connections to the domain that don’t match any specified handler or access list. This setting doesn’t affect Let’s Encrypt’s ability to issue certificates, ensuring secure connections regardless of the option’s status. If unchecked, the domain remains accessible even without a matching handler, allowing for connectivity and certificate checks, even in the absence of a configured upstream destination. When using Access Lists, enabling this option is recommended to reject unauthorized connections outright. Without this option, unmatched IP addresses will encounter an empty page instead of an explicit rejection, though the Access Lists continue to function and restrict access. |
General Settings - DNS Provider¶
Option |
Description |
---|---|
DNS Provider |
Select the DNS provider for the DNS-01 Challenge and Dynamic DNS. This is optional, since certificates will be requested from Let’s Encrypt via HTTP-01 or TLS-ALPN-01 challenge when this option is unset. Needed for wildcard certificates, and for dynamic DNS. To use the DNS-01 challenge and dynamic DNS, enable the checkbox in a domain or subdomain. For more information: https://github.com/caddy-dns |
DNS API Fields |
These fields are for the API settings of the chosen DNS Provider. All of these fields can be left empty if they are optional with the chosen provider. The help text in the plugin will list all available providers and their expected configurations. There are additional fields if DNS providers require more fields for their configurations. |
General Settings - Dynamic DNS¶
Option |
Description |
---|---|
DynDns IP Version |
Leave on None to set IPv4 A-Records and IPv6 AAAA-Records. Select Ipv4 only for setting A-Records. Select IPv6 only for setting AAAA-Records. |
DynDns Check Interval |
Interval to poll for changes of the IP address. The default is 5 minutes. Can be a number between 1 to 1440 minutes. |
DynDns TTL |
Set the TTL (time to live) for DNS Records. The default is 1 hour. Can be a number between 1 to 24 hours. |
DynDns Check Http |
Optionally, enter an URL to test the current IP address of the firewall via HTTP procotol. Generally, this is not needed. Caddy uses default providers to test the current IP addresses. For using a custom one, enter the https:// link to an IP address testing website. |
DynDns Check Interface |
Optionally, select an interface to extract the current IP address of the firewall. At most, one current IPv6 Global Unicast Address and one current IPv4 non-RFC1918 Address will be extracted. |
General Settings - Log Settings¶
Option |
Description |
---|---|
Log Credentials |
Log all Cookies and Authorization Headers in HTTP request logging. Use combined with HTTP Access Log in a domain. Enable this option only for troubleshooting. |
Log Access in Plain Format |
Don’t send HTTP access logs to the central OPNsense logging facility but save them in plain Caddy JSON format in a subdirectory instead. Only effective for domains that have HTTP Access Log enabled. The feature is intended to have access log files processed by e.g. CrowdSec. They can be found in |
Keep Plain Access Logs for (days) |
How many days until the plain format log files are deleted. The default is 10 days. |
Reverse Proxy - Domains¶
Option |
Description |
---|---|
enabled |
enable or disable this domain |
Domain |
Can either be a domain name or an IP address. If a domain name is chosen, Caddy will automatically try to get a Let’s Encrypt or ZeroSSL certificate, and the headers and real IP address will be automatically passed to the upstream destination. |
Port |
Should be the port the OPNsense will listen on. Don’t forget to create Firewall rules that allow traffic to this port on |
Description |
The description is mandatory. Create descriptions for each domain. Since there could be multiples of the same domain with different ports, do it like this: |
>DNS |
DNS options |
Dynamic DNS |
Enable Dynamic DNS. As the option above, the DNS Provider is a requirement. The DNS Records of this domain will be automatically updated with the chosen DNS Provider. |
>Trust |
Certificate options |
DNS-01 challenge |
Enable this for using DNS-01 instead of HTTP-01 and TLS-ALPN-01 challenge. This can be set per entry, so both types of challenges can be used at the same time for different entries. This option needs the General Settings - DNS Provider configured. |
HTTP-01 challenge redirection |
Enter a domain name or IP address. The HTTP-01 challenge will be redirected to that destination. This enables a server behind Caddy to serve |
Custom Certificate |
Use a certificate imported or generated in System - Trust - Certificates. The chain is generated automatically. Certificate + Intermediate CA + Root CA, Certificate + Root CA and self signed Certificate are all fully supported. Only SAN certificates will work. |
>Access |
Access options |
Access List |
Restrict the access to this domain to a list of IP addresses defined in the Access Tab. This doesn’t influence Let’s Encrypt certificate generation. |
Basic Auth |
Restrict the access to this domain to one or multiple users defined in the Access Tab. This doesn’t influence the Let’s Encrypt certificate generation. |
HTTP Access Log |
Enable the HTTP request logging for this domain and its subdomains. This option is mostly for troubleshooting or log analyzing tools like CrowdSec, since it will log every single request. |
Reverse Proxy - Subdomains¶
Option |
Description |
---|---|
Domain |
Choose a wildcard domain prepared in domains, it has to be formatted like |
Subdomain |
Create a name that is seated under the wildcard domain, for example |
Note
For the other options refer to Reverse Proxy - Domains. It’s best to leave Access Lists and Basic Auth unconfigured in wildcard domains, and set these per subdomain.
Reverse Proxy - Handler¶
Attention
Leaving Handle Path empty creates a catch-all handler that proxies all traffic while retaining the original path. This is strongly recommended.
Option |
Description |
---|---|
enabled |
enable or disable this handler |
Domain |
Select a domain. |
Subdomain |
Select a subdomain. This will put the handler on the subdomain instead of the domain. Use only with wildcard domains and subdomains. |
Handle Type |
handle or handle path can be chosen. If in doubt, always use handle, the most common option. handle path is used to strip the path from the URI. |
Handle Path |
Leave this empty to create a catch all location or enter a location like /foo/* or /foo/bar*. |
>Header |
Header options |
Header Manipulation |
Select one or multiple header manipulations. These will be set to this handler. |
>Upstream |
Upstream options |
Upstream Domain |
Should be an internal domain name or an IP Address of the upstream destination that should receive the reverse proxied traffic. |
Upstream Port |
Should be the port the upstream destination listens on. This can be left empty to use Caddy default port 80. |
Upstream Path |
When using “reverse_proxy” (default), in case the backend application resides in a sub-path of the web root and its path shouldn’t be visible in the frontend URL, this setting can be used to prepend an initial path starting with ‘/’ to every backend request. Java applications running in a servlet container like Tomcat are known to behave this way, so set it to e.g. ‘/guacamole’ to access Apache Guacamole at the frontend root URL without needing a redirect. |
>Trust |
Certificate options |
TLS |
If the upstream destination only accepts HTTPS, enable this option. If the upstream destination has a globally trusted certificate, this TLS option is the only needed one. |
NTLM |
If the upstream destination needs NTLM authentication, enable this option together with TLS. For example: Exchange Server. |
TLS Insecure Skip Verify |
Turns off TLS handshake verification, making the connection insecure and vulnerable to man-in-the-middle attacks. Do not use in production. |
TLS Trusted CA Certificates |
Choose a CA certificate to trust for the upstream destination connection. Import a self-signed certificate or a CA certificate into the OPNsense System - Trust - Authorities store, and select it here. |
TLS Server Name |
If the SAN (Subject Alternative Name) of the offered trusted CA certificate or self-signed certificate doesn’t match with the IP address or hostname of the Upstream Domain, enter it here. This will change the SNI (Server Name Identification) of Caddy to the TLS Server Name. IP address e.g. |
Attention
Only use TLS Insecure Skip Verify if absolutely necessary. Using it makes the connection to the upstream destination insecure. It might look like an easy way out for all kinds of certiciate issues, but in the end it is always a bad choice and proper certificate handling is strongly preferred. Please use the TLS, TLS Trusted CA Certificates and TLS Server Name options instead to get a secure TLS connection to the upstream destination. Another option is to use plain HTTP, since it doesn’t imply that the connection is secure and encrypted.
Reverse Proxy - Access Lists¶
Option |
Description |
---|---|
Access List name |
Choose a name for the Access List, for example |
Client IP Addresses |
Enter any number of IPv4 and IPv6 addresses or networks that this access list should contain. For matching only internal networks, add |
HTTP Response Code |
Set a custom HTTP response code that should be returned to the requesting client when the access list doesn’t match. Setting this will replace “Abort Connections”, all clients will stay connected but will receive the response code. Generally, using “Abort Connections” is recommended, because it will actively disconnect clients without serving anything. |
HTTP Response Message |
Set a custom HTTP response message in addition to the HTTP response code. |
Invert List |
Invert the logic of the access list. If unchecked, the Client IP Addresses will be allowed. If checked, the Client IP Addresses will be blocked. |
Note
Go back to domains or subdomains and add the access list to them. All handlers created under these domains will get an additional matcher. That means, the requests still reach Caddy, but if the IP Addresses don’t match with the access list, the request will be dropped before being reverse proxied.
Reverse Proxy - Basic Auth¶
Option |
Description |
---|---|
User |
Enter a username. Afterwards, select it in domains or subdomains to restrict access with basic auth. Usernames are only allowed to have alphanumeric characters. |
Password |
Enter a password. Write it down. It will be hashed with bcrypt. It can only be set and changed but won’t be visible anymore. The hash can’t be turned back into the original password. |
Note
Basic auth matches after access lists, so set both to first restrict access by IP address, and then additionally by username and password. Don’t set basic auth on top of a wildcard domain directly, always set it on the subdomains instead.
Reverse Proxy - Headers¶
Option |
Description |
---|---|
Header |
|
Header Type |
Enter a header, for example |
Header Value |
Enter a value for the above header. One of the most common options is |
Header Replace |
If a regular expression is used to search for a Header Value, here the replacement string can be set. For example: |
Attention
Setting headers to handlers should be considered an advanced option for experts. Please don’t set them without any reason. Caddy uses safe defaults. https://caddyserver.com/docs/caddyfile/directives/reverse_proxy#defaults
caddy: Tutorials¶
Attention
The tutorial section implies that Prepare OPNsense for Caddy after installation has been followed.
Creating a simple reverse proxy¶
Note
Make sure the chosen domain is externally resolvable. Create an A-Record with an external DNS Provider that points to the external IP Address of the OPNsense.
Go to Services - Caddy Web Server - General Settings
Check enabled and press Save
Go to Services - Caddy Web Server - Reverse Proxy - Domains
Press + to create a new domain
Options |
Values |
---|---|
Domain: |
|
Press Save
Go to Services - Caddy Web Server - Reverse Proxy - Handler
Press + to create a new Handler
Options |
Values |
---|---|
Domain: |
|
Upstream Domain: |
|
Press Save and Apply
Note
After just a few seconds the Let’s Encrypt certificate will be installed and the reverse proxy works. Check the Logfile for that. Now the TLS Termination reverse proxy is configured.
Note
Result: HTTPS foo.example.com:80/443 –> OPNsense (Caddy) –> HTTP 192.168.10.1:80
Using dynamic DNS¶
Go to Services - Caddy Web Server - General Settings - DNS Provider
Select one of the supported DNS Providers from the list
Input the DNS API Key, and any number of the additional required fields in Additional Fields. Read the full help for details.
Go to Services - Caddy Web Server - General Settings - Dynamic DNS
Choose if DynDns IP Version should include IPv4 and/or IPv6.
Press Save
Go to Services - Caddy Web Server - Reverse Proxy – Domains
Press + to create a new Domain.
mydomain.duckdns.org
is an example if duckdns is used as DNS Provider.
Options |
Values |
---|---|
Domain: |
|
Dynamic DNS: |
|
Go to Services - Caddy Web Server - Reverse Proxy – Handlers
Press + to create a new handler
Options |
Values |
---|---|
Domain: |
|
Upstream Domain: |
|
Press Save and Apply
Note
Now Caddy listens on Port 80 and 443, and reverse proxies everything from mydomain.duckdns.org to 192.168.1.1:80. All headers and the real IP are automatically passed to the upstream destination. Let’s Encrypt Certificate and Dynamic DNS Updates are all handled automatically.
Creating a wildcard reverse proxy¶
Go to Services - Caddy Web Server - General Settings - DNS Provider
Select one of the supported DNS Providers from the list
Input the DNS API Key, and any number of the additional required fields in Additional Fields. Read the full help for details.
Go to Services - Caddy Web Server - Reverse Proxy – Domains
Create
*.example.com
as domain and activate the DNS-01 checkbox. Alternatively, use a certificate imported or generated in System - Trust - Certificates. It has to be a wildcard certificate.Create all subdomains in relation to the
*.example.com
domain. So for examplefoo.example.com
andbar.example.com
.
Go to Services - Caddy Web Server - Reverse Proxy – Handlers
Create a Handler with
*.example.com
as domain andfoo.example.com
as subdomain. Mostly the same configuration as with normal domains is possible. There are some features that are only possible with normal domains.
Tip
If in doubt, don’t use subdomains. If there should be foo.example.com
, bar.example.com
and example.com
, just create them as three normal domains. This way, there is the most flexibility, and the most features are supported.
Reverse proxy the OPNsense WebUI¶
Open the OPNsense WebUI in a Browser (e.g. Chrome or Firefox). Inspect the certificate. Copy the SAN for later use, for example
OPNsense.localdomain
.Save the certificate as .pem file. Open it up with a text editor, and copy the contents into a new entry in System - Trust - Authorities. Name the certificate
opnsense-selfsigned
.Add a new Domain in Caddy, for example
opn.example.com
. Make sure the name is externally resolvable to the WAN IP of the OPNsense.Add a new Handler with the following options:
Options |
Values |
---|---|
Domain: |
|
Upstream Domain: |
|
Upstream Port: |
|
TLS: |
|
TLS Trusted CA Certificates: |
|
TLS Server Name: |
|
Press Save and Apply
Go to System - Settings - Administration
Input
opn.example.com
in Alternate Hostnames to prevent the error The HTTP_REFERER “https://opn.example.com/” does not match the predefined settings after logging in.Press Save
Note
Open https://opn.example.com
and it should serve the reverse proxied OPNsense WebUI. Check the log file for errors if it doesn’t work, most of the time the TLS Server Name doesn’t match the SAN of the TLS Trusted CA Certificate. Caddy doesn’t support CN (Common Name) in certificate since it’s been deprecated since many years. Only SAN certificates work.
Attention
Create an access list to restrict access to the WebUI. Add that access list to this domain.
Redirect ACME HTTP-01 challenge¶
Sometimes an application behind Caddy uses its own ACME Client to get certificates, most likely with the HTTP-01 challenge. This plugin has a built in mechanism to redirect this challenge type easily to a destination behind it.
Note
Make sure the chosen domain is externally resolvable. Create an A-Record with an external DNS Provider that points to the external IP Address of the OPNsense. In case of IPv6 availability, it is mandatory to create an AAAA-Record too, otherwise the TLS-ALPN-01 challenge might fail.
Attention
It is mandatory that the domain in Caddy uses an empty port or 443 in the GUI, otherwise it can’t use the TLS-ALPN-01 challenge for itself. The upstream destination has to listen on Port 80 and serve /.well-known/acme-challenge/
, for the same domain that is configured in Caddy.
Go to Services - Caddy Web Server - Reverse Proxy - Domains
Press + to create a new domain
enable advanced mode
Options |
Values |
---|---|
Domain: |
|
Description: |
|
HTTP-01 challenge redirection: |
|
Press Save
Go to Services - Caddy Web Server - Reverse Proxy - Handler
Press + to create a new Handler
Options |
Values |
---|---|
Domain: |
|
Upstream Domain: |
|
Upstream Port: |
|
TLS: |
|
TLS Server Name: |
|
Press Save and Apply
Note
With this configuration, Caddy will eventually choose the TLS-ALPN-01 challenge for its own foo.example.com
domain, and reverse proxy the HTTP-01 challenge to 192.168.10.1
, where the upstream destination can listen on port 80 for foo.example.com
and solve its own challenge for a certificate. With TLS enabled in the Handler, an encrypted connection is automatically possible. The automatic HTTP to HTTPS redirection is also taken care of.
Reverse Proxy to an upstream webserver serving vhosts¶
Sometimes it is necessary to alter the host header in order to reverse proxy to another webserver with vhosts. Since Caddy passes the original host header by default (e.g. app.external.example.com
), if the upstream destination listens on a different hostname (e.g. app.internal.example.com
), it wouldn’t be able to serve this request.
Go to Services - Caddy Web Server - Reverse Proxy - Domains
Press + to create a new domain
Options |
Values |
---|---|
Domain: |
|
Press Save
Go to Services - Caddy Web Server - Reverse Proxy - Headers
Press + to create a new header
Options |
Values |
---|---|
Header: |
|
Header Type: |
|
Header Value: |
|
Press Save
Go to Services - Caddy Web Server - Reverse Proxy - Handler
Press + to create a new Handler
Options |
Values |
---|---|
Domain: |
|
Upstream Domain: |
|
Header Manipulation: |
|
Press Save and Apply
Tip
Since (most) headers retain their original value when being proxied, it is often necessary to override the Host header with the configured upstream address when proxying to HTTPS, such that the Host header matches the TLS ServerName value. https://caddyserver.com/docs/caddyfile/directives/reverse_proxy#https
Integrating Caddy with CrowdSec¶
Tip
CrowdSec is a powerful alternative to a WAF. It uses logs to dynamically ban IP addresses of known bad actors. The Caddy plugin is prepared to emit the json logs for this integration.
Go to Services - Caddy Web Server - General Settings - Log Settings
Enable Log HTTP Access in JSON Format
Press Save
Go to Services - Caddy Web Server - Reverse Proxy – Domains
Open each domain that should be monitored by CrowdSec
Open Access
Enable HTTP Access Log
Note
Now the HTTP access logs will appear in /var/log/caddy/access
in json format, one file for each domain.
Next, connect to the OPNsense via SSH or console, go into the shell with Option 8.
Attention
This step requires the os-crowdsec
plugin.
Once in the shell, install the caddy collection from CrowdSec Hub.
cscli collections install crowdsecurity/caddy
Create the configuration file as
/usr/local/etc/crowdsec/acquis.d/caddy.yaml
with the following content:
filenames:
- /var/log/caddy/access/*.log
force_inotify: true
poll_without_inotify: true
labels:
type: caddy
Go into the OPNsense WebUI and restart CrowdSec.
Using custom configuration files¶
The Caddyfile has an additional import from the path
/usr/local/etc/caddy/caddy.d/
. Place custom configuration files inside that adhere to the Caddyfile syntax.*.global
files will be imported into the global block of the Caddyfile.*.conf
files will be imported at the end of the Caddyfile. Don’t forget to test the custom configuration withcaddy run --config /usr/local/etc/caddy/Caddyfile
.With these imports, the full potential of Caddy can be unlocked. The GUI options will remain focused on the reverse proxy.