ipx-web: pass the tunnel's Access headers when it arrives as ::ffff: (#209)

Caddy listens dual-stack, so the ipx_default gateway connects as ::ffff:192.168.64.1, and
remote_ip 192.168.64.1 does not match it: every Cf-Access-* header was stripped, the
tunnel's too. The browser suite binds Caddy to 127.0.0.1, IPv4 only, so it never saw it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -20,6 +20,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `docker-compose.yml` is a sample to start from, ipx alone on SQLite with its folders beside the file, instead of a copy of the author's server (#208).
 - The source is a Cargo workspace: the daemon in `crates/ipx`, feed fetching and parsing in `crates/feed`. `cargo build --release` still makes `target/release/ipx` (#202).
 
+### Fixed
+
+- Signing in through Cloudflare Access works behind ipx-web: Caddy took the tunnel's address for someone else's and dropped its sign-in headers (#209).
+
 ## [0.12.0] - 2026-10-11
 
 ### Added

web/Caddyfile

@@ -2,7 +2,7 @@
 # so the session cookie, live updates and Cloudflare Access work as they did when ipx served it.
 #   IPX_UPSTREAM  where ipx is, host:port            (ipx:8099)
 #   WEB_BIND      where to listen                    (:8080)
-#   TUNNEL_PEER   the one address whose Cf-Access-* headers are passed on: where cloudflared's
+#   TUNNEL_PEER   the one IPv4 address whose Cf-Access-* headers are passed on: where cloudflared's
 #                 requests come from. Nobody else's are, so nobody else can claim to be signed in
 #                 by Cloudflare. Unset passes none.
 {
@@ -13,8 +13,10 @@
 http://{$WEB_BIND::8080} {
 	root * {$WEB_ROOT:/srv}
 
-	# Before anything else, so no page or API call sees them: only ipx sets these.
-	@forged not remote_ip {$TUNNEL_PEER:255.255.255.255}
+	# Before anything else, so no page or API call sees them: only ipx sets these. Both forms of
+	# the peer: Caddy listens dual-stack, so an IPv4 peer arrives as ::ffff:a.b.c.d, which the
+	# plain address does not match, and the tunnel's headers were stripped too (#209).
+	@forged not remote_ip {$TUNNEL_PEER:255.255.255.255} ::ffff:{$TUNNEL_PEER:255.255.255.255}
 	request_header @forged -Cf-Access-Authenticated-User-Email
 	request_header @forged -Cf-Access-Jwt-Assertion