feat(seerr): Web/Container: Inject custom Seerr headers via nginx proxy

Dockerfile

@@ -1,11 +1,14 @@
 FROM nginx:alpine
 
+RUN apk add --no-cache jq
+
 EXPOSE 80
 
 ENV BASE_URL=""
 ENV SEERR_BASE_URL=""
 ENV SEERR_HEADER="null"
 ENV FLADDER_WEBPATH="/"
+ENV PORT=80
 
 COPY build/web /usr/share/nginx/html
 COPY docker-entrypoint.sh /docker-entrypoint.sh

Dockerfile-rootless

@@ -6,8 +6,10 @@ ENV BASE_URL=""
 ENV SEERR_BASE_URL=""
 ENV SEERR_HEADER="null"
 ENV FLADDER_WEBPATH="/"
+ENV PORT=8080
 
 USER root
+RUN apk add --no-cache jq
 COPY build/web /usr/share/nginx/html
 COPY docker-entrypoint.sh /docker-entrypoint.sh
 RUN mkdir -p /usr/share/nginx/html/assets/config && \
@@ -17,4 +19,4 @@ RUN mkdir -p /usr/share/nginx/html/assets/config && \
     chown -R nginx:nginx /etc/nginx/conf.d
 
 USER nginx
-CMD ["/docker-entrypoint.sh"]
+CMD ["/docker-entrypoint.sh"]

config/config.json

@@ -1,5 +1,5 @@
 {
 	"baseUrl": null,
 	"seerrBaseUrl": null,
-	"seerrHeader": null
+	"seerrProxyPath": null
 }

docker-compose.yml

@@ -7,5 +7,9 @@ services:
     environment:
       - BASE_URL=https://server-url #OPTIONAL: Locks the Fladder front-end to a certain jellyfin server
       - SEERR_BASE_URL=https://seerr-url #OPTIONAL: Presets Seerr base URL
-      - SEERR_HEADER={"key":"value"} #OPTIONAL: JSON object string of Seerr headers
+      # SEERR_HEADER is intended to e.g. bypass an OUTER auth wall which is in front of Seerr:
+      # Authelia, Authentik, forward-auth, Cloudflare Access, basic-auth on a reverse proxy, etc.)
+      # Do NOT put Seerr's own X-Api-Key here!
+      # /seerr-proxy/ is not authenticated by Fladder, so an X-Api-Key would let any HTTP caller act as a Seerr admin.
+      - SEERR_HEADER={"key":"value"} #OPTIONAL: JSON headers injected server-side via nginx proxy (requires SEERR_BASE_URL)
       - FLADDER_WEBPATH=/ #OPTIONAL: Configures a subpath to run Fladder at

docker-entrypoint.sh

@@ -1,33 +1,99 @@
 #!/bin/sh
 set -e
 
-# Generate config.json from environment variables
-cat > /usr/share/nginx/html/assets/config/config.json <<EOF
+CONFIG="/usr/share/nginx/html/assets/config/config.json"
+NGINX_CONF="/etc/nginx/conf.d/default.conf"
+
+strip_trailing_slashes() {
+  echo "$1" | sed 's|/*$||'
+}
+
+# Strip trailing slashes from SEERR_BASE_URL so proxy_pass doesn't emit a double slash.
+SEERR_BASE_URL=$(strip_trailing_slashes "$SEERR_BASE_URL")
+
+# --- Build config.json ---
+
+# Determine seerrProxyPath: set when both SEERR_BASE_URL and SEERR_HEADER are provided
+if [ -n "$SEERR_BASE_URL" ] && [ -n "$SEERR_HEADER" ] && [ "$SEERR_HEADER" != "null" ]; then
+  SEERR_PROXY_PATH="/seerr-proxy"
+else
+  SEERR_PROXY_PATH=""
+fi
+
+SEERR_PROXY_JSON=$([ -n "$SEERR_PROXY_PATH" ] && echo "\"$SEERR_PROXY_PATH\"" || echo null)
+
+cat > "$CONFIG" <<EOF
 {
   "baseUrl": "$BASE_URL",
-  "seerrBaseUrl": "$SEERR_BASE_URL"
+  "seerrBaseUrl": "$SEERR_BASE_URL",
+  "seerrProxyPath": $SEERR_PROXY_JSON
 }
 EOF
 
-# Normalize FLADDER_WEBPATH (e.g. /fladder/)
+# --- Normalize FLADDER_WEBPATH (e.g. /fladder/) ---
 WEBPATH=$(echo "${FLADDER_WEBPATH:-/}" | sed 's|^/*|/|; s|/*$|/|')
 
 # Update base href in index.html (always at root of build/web)
 if [ -f "/usr/share/nginx/html/index.html" ]; then
   sed -i "s|<base href=\"[^\"]*\">|<base href=\"$WEBPATH\">|g" /usr/share/nginx/html/index.html
 fi
 
-# Determine port (standard Nginx uses 80, rootless typically 8080)
-if [ "$(id -u)" = "0" ]; then
-    PORT=80
-else
-    PORT=8080
+# --- Determine port ---
+# Honor $PORT from env if set; otherwise default by uid (0 => 80, else 8080).
+PORT="${PORT:-$([ "$(id -u)" = "0" ] && echo 80 || echo 8080)}"
+
+# --- Build Seerr proxy block ---
+PROXY_BLOCK=""
+GEO_BLOCK=""
+if [ -n "$SEERR_PROXY_PATH" ]; then
+  # SEERR_HEADER must be a JSON object of strings. Validate up front so the jq
+  # iterations below don't abort with cryptic "cannot iterate over..." errors.
+  if ! printf '%s' "$SEERR_HEADER" | jq -e 'type == "object" and all(.[]; type == "string")' > /dev/null 2>&1; then
+    echo "Error: SEERR_HEADER must be a JSON object with string values, e.g. {\"Header-Name\":\"value\"}" >&2
+    exit 1
+  fi
+  # Keys are injected unquoted into the nginx directive — restrict to the common
+  # HTTP header-name form (alpha-start, then alphanumerics and hyphens) so a key
+  # containing whitespace or ';' can't escape the proxy_set_header directive.
+  if ! printf '%s' "$SEERR_HEADER" | jq -e 'all(keys_unsorted[]; test("^[A-Za-z][A-Za-z0-9-]*$"))' > /dev/null 2>&1; then
+    echo "Error: SEERR_HEADER keys must match ^[A-Za-z][A-Za-z0-9-]*\$ (standard HTTP header name format)" >&2
+    exit 1
+  fi
+  # CR/LF are forbidden in HTTP header values (RFC 9110 §5.5) — reject rather than escape.
+  if printf '%s' "$SEERR_HEADER" | jq -e '[.[] | test("[\r\n]")] | any' > /dev/null; then
+    echo "Error: SEERR_HEADER values must not contain newline or carriage return (invalid HTTP header values)" >&2
+    exit 1
+  fi
+  # nginx has no native escape for literal '$' in quoted strings; define a namespaced
+  # variable holding "$" at http level and substitute '$' -> '${seerr_literal_dollar}'
+  # in values. Namespace prefix avoids collision with user-mounted nginx configs.
+  # tojson handles " and \ escaping (nginx shares those conventions with JSON).
+  HEADER_DIRECTIVES=$(printf '%s' "$SEERR_HEADER" | jq -r '
+    to_entries[] |
+    "        proxy_set_header " + .key + " " + (.value | gsub("\\$"; "${seerr_literal_dollar}") | tojson) + ";"
+  ')
+
+  GEO_BLOCK='geo $seerr_literal_dollar {
+    default "$";
+}
+'
+  # Two '$' conventions coexist below:
+  #   \$proxy_host             — backslash escapes the shell; nginx sees $proxy_host (built-in variable).
+  #   ${seerr_literal_dollar}  — nginx-level reference to the geo-defined variable above, emits a literal '$'.
+  PROXY_BLOCK="
+    location ${SEERR_PROXY_PATH}/ {
+        proxy_pass \"${SEERR_BASE_URL}/\";
+        proxy_set_header Host \$proxy_host;
+        proxy_ssl_server_name on;
+${HEADER_DIRECTIVES}
+    }"
 fi
 
+# --- Emit nginx config ---
 if [ "$WEBPATH" = "/" ]; then
     echo "Configuring Fladder at root path"
-    cat > /etc/nginx/conf.d/default.conf <<EOF
-server {
+    cat > "$NGINX_CONF" <<EOF
+${GEO_BLOCK}server {
     listen $PORT;
     listen [::]:$PORT;
     server_name localhost;
@@ -37,14 +103,15 @@ server {
         index index.html;
         try_files \$uri \$uri/ /index.html;
     }
+${PROXY_BLOCK}
 }
 EOF
 else
     echo "Configuring Fladder on subpath: $WEBPATH"
-    WEBPATH_NO_SLASH=$(echo "$WEBPATH" | sed 's|/*$||')
-    
-    cat > /etc/nginx/conf.d/default.conf <<EOF
-server {
+    WEBPATH_NO_SLASH=$(strip_trailing_slashes "$WEBPATH")
+
+    cat > "$NGINX_CONF" <<EOF
+${GEO_BLOCK}server {
     listen $PORT;
     listen [::]:$PORT;
     server_name localhost;
@@ -60,6 +127,7 @@ server {
     location = $WEBPATH_NO_SLASH {
         return 301 $WEBPATH;
     }
+${PROXY_BLOCK}
 
     # Fallback for root or other paths
     location / {
@@ -69,5 +137,7 @@ server {
 EOF
 fi
 
+# --- Start nginx ---
+
 exec nginx -g "daemon off;"
 

lib/providers/seerr_api_provider.dart

@@ -2,6 +2,7 @@ import 'dart:developer';
 import 'dart:io';
 
 import 'package:chopper/chopper.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:riverpod_annotation/riverpod_annotation.dart';
 
@@ -62,7 +63,13 @@ class SeerrRequest implements Interceptor {
       ...?creds?.customHeaders,
     };
     final headers = {...authHeaders, ...customHeaders};
-    final apiBaseUri = Uri.parse(serverUrl);
+    // On web, route through the same-origin nginx proxy when seerrProxyPath is set.
+    // Nginx injects the headers server-side so the header values never reach the browser.
+    // Require a same-origin absolute path (starts with '/' but not '//') so a tampered
+    // config.json can't redirect Seerr traffic to a foreign host via Uri.base.resolve.
+    final proxyPath = FladderConfig.seerrProxyPath;
+    final isSafeProxyPath = proxyPath != null && proxyPath.startsWith('/') && !proxyPath.startsWith('//');
+    final apiBaseUri = (kIsWeb && isSafeProxyPath) ? Uri.base.resolve(proxyPath) : Uri.parse(serverUrl);
 
     Uri resolvedRequestUri;
     try {

lib/util/fladder_config.dart

@@ -10,16 +10,19 @@ class FladderConfig {
   static set seerrBaseUrl(String? value) => _instance._seerrBaseUrl = value;
   String? _seerrBaseUrl;
 
+  static String? get seerrProxyPath => _instance._seerrProxyPath;
+  static set seerrProxyPath(String? value) => _instance._seerrProxyPath = value;
+  String? _seerrProxyPath;
+
   static void fromJson(Map<String, dynamic> json) => _instance = FladderConfig._fromJson(json);
 
   factory FladderConfig._fromJson(Map<String, dynamic> json) {
     final config = FladderConfig._();
-    final newUrl = json['baseUrl'] as String?;
-    final newSeerrUrl = json['seerrBaseUrl'] as String?;
-
-    config._baseUrl = newUrl?.isEmpty == true ? null : newUrl;
-    config._seerrBaseUrl = newSeerrUrl?.isEmpty == true ? null : newSeerrUrl;
-
+    config._baseUrl = _nonEmpty(json['baseUrl'] as String?);
+    config._seerrBaseUrl = _nonEmpty(json['seerrBaseUrl'] as String?);
+    config._seerrProxyPath = _nonEmpty(json['seerrProxyPath'] as String?);
     return config;
   }
+
+  static String? _nonEmpty(String? s) => s?.isEmpty == true ? null : s;
 }