Unix socket admin endpoint doesn't accept "localhost" as host name. #6832
Description
Hey everyone,
the documentation states:
origins configures the list of origins that are allowed to connect to the endpoint.
A default is intelligently chosen:
if the listen address is loopback (e.g. localhost or a loopback IP, or a unix socket) then the allowed origins are localhost, ::1 and 127.0.0.1, joined with the listen address port (so localhost:2019 is a valid origin).
However, it seems like localhost as hostname gets rejected:
/etc/caddy # caddy --version
v2.9.1 h1:OEYiZ7DbCzAWVb6TNEkjRcSCRGHVoZsJinoDR/n9oaY=
/etc/caddy # curl --version
curl 8.12.0 (x86_64-alpine-linux-musl) libcurl/8.12.0 OpenSSL/3.3.2 zlib/1.3.1 brotli/1.1.0 zstd/1.5.6 c-ares/1.33.1 libidn2/2.3.7 libpsl/0.21.5 nghttp2/1.62.1
Release-Date: 2025-02-05
Protocols: dict file ftp ftps gopher gophers http https imap imaps ipfs ipns mqtt pop3 pop3s rtsp smb smbs smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS brotli HSTS HTTP2 HTTPS-proxy IDN IPv6 Largefile libz NTLM PSL SSL threadsafe TLS-SRP UnixSockets zstd
/etc/caddy # echo $CADDY_ADMIN
unix//var/run/caddy.sock
/etc/caddy # caddy reload
2025/02/09 19:22:57.702 INFO using adjacent Caddyfile
2025/02/09 19:22:57.703 INFO adapted config to JSON {"adapter": "caddyfile"}
/etc/caddy # curl --unix-socket /var/run/caddy.sock http://127.0.0.1/reverse_proxy/upstreams
[]
/etc/caddy # curl --unix-socket /var/run/caddy.sock http://localhost/reverse_proxy/upstreams
{"error":"host not allowed: localhost"}
I can also observe this behaviour with caddy 2.8.4.