feat: add TRUSTED_PROXIES to choose who nginx takes client IPs from (GHSA-7j7m-85p4-2cpm)

docker/entrypoint.sh

@@ -68,6 +68,25 @@ fi
 mkdir -p /tmp/nginx
 envsubst '${PORT} ${SSL_PORT} ${SSL_CERT_PATH} ${SSL_KEY_PATH}' < $NGINX_CONF_SOURCE > /tmp/nginx/nginx.conf
 
+# Which proxies may set the client IP through X-Forwarded-For. Unset keeps
+# the private ranges in the template.
+if [ -n "$TRUSTED_PROXIES" ]; then
+    REAL_IP_LINES=""
+    for proxy in $(echo "$TRUSTED_PROXIES" | tr ',' ' '); do
+        case "$proxy" in
+            *[!0-9a-fA-F:./]*) echo "Ignoring invalid TRUSTED_PROXIES entry: $proxy" ;;
+            *) REAL_IP_LINES="${REAL_IP_LINES}    set_real_ip_from ${proxy};\n" ;;
+        esac
+    done
+    echo "Trusting X-Forwarded-For from: $TRUSTED_PROXIES"
+    awk -v lines="$REAL_IP_LINES" '
+        /# BEGIN TRUSTED_PROXIES/ { printf "%s", lines; skip = 1; next }
+        /# END TRUSTED_PROXIES/ { skip = 0; next }
+        !skip
+    ' /tmp/nginx/nginx.conf > /tmp/nginx/nginx.conf.tmp
+    mv /tmp/nginx/nginx.conf.tmp /tmp/nginx/nginx.conf
+fi
+
 if [ "$ENABLE_SSL" = "true" ] && [ "$PORT" = "$SSL_PORT" ]; then
     echo "HTTP and HTTPS use port $SSL_PORT; disabling the HTTP redirect listener"
     sed -i '/# BEGIN HTTP_REDIRECT_SERVER/,/# END HTTP_REDIRECT_SERVER/d' /tmp/nginx/nginx.conf

docker/nginx-https.conf

@@ -41,10 +41,12 @@ http {
         image/svg+xml;
     client_header_timeout 300s;
 
+    # BEGIN TRUSTED_PROXIES
     set_real_ip_from 127.0.0.1;
     set_real_ip_from 10.0.0.0/8;
     set_real_ip_from 172.16.0.0/12;
     set_real_ip_from 192.168.0.0/16;
+    # END TRUSTED_PROXIES
     real_ip_header X-Forwarded-For;
     real_ip_recursive on;
 

docker/nginx.conf

@@ -41,10 +41,12 @@ http {
         image/svg+xml;
     client_header_timeout 300s;
 
+    # BEGIN TRUSTED_PROXIES
     set_real_ip_from 127.0.0.1;
     set_real_ip_from 10.0.0.0/8;
     set_real_ip_from 172.16.0.0/12;
     set_real_ip_from 192.168.0.0/16;
+    # END TRUSTED_PROXIES
     real_ip_header X-Forwarded-For;
     real_ip_recursive on;