Upgrading Caddy reverse proxy from v1 to v2 syntax

route, strip_prefix, rewrite, reverse_proxy

proxy to reverse_proxy
1. Custom path
2. Backend with custom path
header_upstream to header_up
header_downstream to header_down
HTTP only (disable HTTPS/TLS)
Redirect www subdomain
header and reverse_proxy
Disable HTTP → HTTPS redirects
TLS client authentication
Administration endpoint

Caddy v2 brought many major changes, particularly to the Caddyfile syntax. This site is powered by the reverse proxy feature of Caddy, so I need to make sure everything works before I finally upgrade. While v2 has been released for more than 2 weeks by now (after months of beta testing), I only managed get my feet wet last weekend, even though I should’ve done it during the beta releases. After testing v2 on a local server (plus some forum posts), I would say it is mostly working. While v2.0 has reached feature parity with v1, Caddyfile has not; there are two TLS/HTTPS options that are not yet supported in Caddyfile (see #3219, #3334; planned to be released in v2.1). So, if you don’t need HTTPS–like my Tor and I2P proxies–it should be safe to upgrade.

(Edit: 16 Feb 2021) v2.1 implemented #3219 and #3334, I’ve updated this post accordingly.

proxy to reverse_proxy §

proxy directive is updated to reverse_proxy.

Reverse proxy the whole website:

v1
proxy / https://backend.com

In v2, the matcher needs *:

v2
reverse_proxy /* https://backend.com

If no matcher is specified, it defaults to /* which match every path:

v2
reverse_proxy https://backend.com

Custom path §

Reverse proxy a certain path, like /api:

v2
reverse_proxy /api/* https://backend.com

Requests to https://example.com/api/foo/bar/ is redirected to https://backend.com/api/foo/bar/.

To remove the path prefix:

v1
proxy /api https://backend.com {
  without /api
}

Requests to https://example.com/api/foo/bar/ is redirected to https://backend.com/foo/bar/.

v2 doesn’t have without directive, instead you need to use route the request and remove the prefix using uri strip_prefix:

v2.0
route /api/* {
  uri strip_prefix /api
  reverse_proxy https://backend.com
}

v2.1 adds handle_path directive which integrates prefix stripping:

v2.1
handle_path /api/* {
  reverse_proxy https://backend.com
}

Backend with custom path §

Reverse proxy with custom path:

v1
proxy /img https://backend.com/img/blog {
  without /img
}

v2 doesn’t support custom path, instead you need to use rewrite to prepend the path:

v2.0
route /img/* {
  uri strip_prefix /img

  rewrite * /img/blog{path}

  reverse_proxy https://backend.com
}

v2.1
handle_path /img/* {
  rewrite * /img/blog{path}
  reverse_proxy https://backend.com
}

header_upstream to header_up §

v1
proxy / https://backend.com {
  header_upstream Host backend.com
}

v2
reverse_proxy https://backend.com {
  header_up Host backend.com
}

header_downstream to header_down §

v1
proxy / https://backend.com {
  header_downstream -server
}

v2
reverse_proxy https://backend.com {
  header_up -server
}

HTTP only (disable HTTPS/TLS) §

v1
example.com:8080 {
  tls off
}

In v2, tls doesn’t have off option, instead you can specify http:// to listen on HTTP only:

v2
http://example.com:8080 {

}

Redirect www subdomain §

Remove www. subdomain with HTTP 301 Permanent redirect:

v1
example.com www.example.com {
  redir 301 {
    if {label1} is www
    / https://example.com{uri}
  }
}

v2.0
example.com www.example.com {
  @www {
    host www.example.com
  }
  redir @www https://example.com{uri} permanent
}

v2.1 supports single-line matcher:

v2.1
example.com www.example.com {
  @www host www.example.com
  redir @www https://example.com{uri} permanent
}

Add www. subdomain:

v1
example.com www.example.com {
  redir 301 {
    if {label1} is example
    / https://www.example.com{uri}
  }
}

v2.0
example.com www.example.com {
  @www {
    host example.com
  }
  redir @www https://www.example.com{uri} permanent
}

v2.1
example.com www.example.com {
  @www host example.com
  redir @www https://www.example.com{uri} permanent
}

header and reverse_proxy §

header directive still keeps similar syntax, but operates a bit different. In v2, when used alongside with reverse_proxy, Caddy modifies the header before receiving header response from the backend. This behaviour is apparent when you want to replace existing header(s); instead of replacing, Caddy adds the header and results in duplicate headers. To avoid this issue, you should use defer:

v2
header {
  -server
  Referrer-Policy "no-referrer"
  defer
}

Disable HTTP → HTTPS redirects §

In v2, Caddy automatically listens on HTTP (port 80) and redirects to HTTPS, whereas in v1, you need add a separate redir 301. This is handy is most use cases, but doesn’t apply to my use case–listens on HTTPS only.

In v2.0, this can only be disabled in JSON.

v2.1 supports configuring Automatic HTTPS in Caddyfile using auto_https global option:

Caddyfile
{
  auto_https disable_redirects
}

TLS client authentication §

Client authentication adds another step to TLS connection process whereby a client needs to present a certificate (that has been signed by a CA certificate) to the server (which has the CA certificate) when it attempts to establish a TLS connection. Once the client is authenticated, the process is reversed and client authenticates the server instead. The padlock icon next to the web address indicates that the website’s certificate is valid. Client authentication is only used in private web server to restrict access to authorised clients only. In my case, I restrict my origin server to Cloudflare CDN only; mdleom.com is only accessible via Cloudflare, direct connection to the origin server will be dropped.

In v2.0, this can only be disabled in JSON.

v2.1 supports configuring client authentication in Caddyfile using client_auth option in tls directive:

v1.0
example.com {
  tls cert.pem cert.key {
    clients origin-pull-ca.pem
  }
}

v2.1
example.com {
  tls cert.pem cert.key {
    client_auth {
      mode require_and_verify
      trusted_ca_cert_file origin-pull-ca.pem
      # base64 DER-encoded CA cert is also supported
      # trusted_ca_cert MIIDSzCCAjOgAwIBAg
    }
  }
}

Administration endpoint §

Admin endpoint is the highlight feature of v2.0; new config can be loaded without restarting Caddy. It is enabled by default and listens on http://localhost:2019.

To disable it:

{
  admin off
}