Can Caddy redirect an incoming request based on header values?

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1

1. Caddy version (caddy version):

v2.2.1 h1:Q62GWHMtztnvyRU+KPOpw6fNfeCD3SkwH7SfT1Tgt2c=

2. How I run Caddy:

official systemd unit from the github repo, no alterations

a. System environment:

ubuntu 18.04 lts, systemd controlled start

b. Command:

systemctl start caddy

c. Service/unit/compose file:

official service unit from github

d. My complete Caddyfile or JSON config:

(gen) {
	encode gzip
	try_files {path} {path}.html
	php_fastcgi unix//var/run/php/php7.4-fpm.sock
	file_server
	handle_errors {
		rewrite * /{http.error.status_code}
		reverse_proxy https://http.cat {
			header_up Host http.cat
		}
	}
	log {
		format console
		output file /var/log/caddy.log {
			roll_size 25mb
			roll_keep 20
			roll_keep_for 720h
		}
	}
}

(dns) {
	tls {
		dns digitalocean redacted lol
	}
}

(header-gen) {
	header {
		Strict-Transport-Security "max-age=31536000; includeSubdomains; preload"
		X-XSS-Protection "1; mode=block"
		X-Content-Type-Options "nosniff"
		X-Frame-Options "DENY"
	}
}

eiphax.tech {
	header {
		Strict-Transport-Security "max-age=31536000; preload"
		X-XSS-Protection "1; mode=block"
		X-Content-Type-Options "nosniff"
		X-Frame-Options "DENY"
	}
	root * /var/www/eipdox
	import gen
}

facts.eiphax.tech {
	import header-gen
	root * /var/www/eipdox/facts
	import gen
}

soultrader.net.au {
	import header-gen
	root * /var/www/st
	import gen
}

blog.eiphax.tech {
	import header-gen
	root * /var/www/blog
	import gen
}

album.eiphax.tech {
	import header-gen
	root * /var/www/lychee/public
	import gen
}

bin.eiphax.tech {
	import header-gen
	root * /var/www/eipbin
	import gen
}

3ds.eiphax.tech {
	import header-gen
	root * /var/www/eipdox/3ds
	import gen
}

http://wiiu.eiphax.tech {
	root * /var/www/eipdox/wiiu
	import gen
}

https://wiiu.eiphax.tech {
	root * /var/www/eipdox/wiiu
	import gen
}

nx.eiphax.tech {
	import header-gen
	root * /var/www/eipdox/nx
	import gen
}

nintendohomebrew.com {
	header {
		Strict-Transport-Security "max-age=31536000; preload"
		X-XSS-Protection "1; mode=block"
		X-Content-Type-Options "nosniff"
		X-Frame-Options "DENY"
	}
	root * /var/www/eipdox/nh
	import gen
}

http://bhax.nintendohomebrew.com {
	root * /var/www/bhax/web/nbhax
	try_files {path} {path}.html
	encode gzip
}

bfm.nintendohomebrew.com {
	import header-gen
	root * /var/www/eipdox/nh/seed
	reverse_proxy localhost:8082
	encode gzip
	file_server
	handle_errors {
		rewrite * /{http.error.status_code}
		reverse_proxy https://http.cat {
			header_up Host http.cat
		}
	}
	log {
		level error
		format console
		output file /var/log/bfm_error.log {
			roll_size 25mb
			roll_keep 20
			roll_keep_for 720h
		}
	}
}

http://part1dumper.nintendohomebrew.com https://part1dumper.nintendohomebrew.com {
	reverse_proxy localhost:8081
}

shitpost.lol {
	import header-gen
	root * /var/www/sp
	import gen
}

hacc.me please.hacc.me {
	import header-gen
	root * /var/www/hacc
	import gen
}

friigaemsworld.com {
	import header-gen
	root * /var/www/frigam
	import gen
}

uwu.tax {
	import header-gen
	root * /var/www/uwu
	import gen
}

conversation.id {
	import header-gen
	root * /var/www/conv
	import gen
}

puebes.com {
	import header-gen
	root * /var/www/puebes
	import gen
}

3. The problem I’m having:

not a problem, per se, but i’m wanting to see if i can intercept an incoming request for example.com/foo/bar.png, check the referrer (which caddy already seems to capture based on logs), and if referrer = foo, serve foo.png from the same directory, if referrer = any other, serve bar.png as originally requested

5. What I already tried:

nothing, yet… i’ve had a look at rewrite and uri, but they don’t seem to have the “if > then” that i think i need. i’ve also looked at placeholders, and i guess i’d be using {header.Referer} but i don’t know how to actually implement what i’m thinking here.

6. Links to relevant resources:

2

Yeah, you want to use request matchers:

So something like this maybe:

@hasFoo header Referer *foo*
rewrite @hasFoo /foo/foo.png

But I’m not totally clear on your goal (the explanation isn’t generalized enough) so that’s the best assumption I can make.

3

You need to read about matchers: here. I linked the bit about header fields, but near the top you need to read about whether matches are ANDed or ORed.

Paul

4

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