server: Added DNS resolution when setting trust proxy since IPs are temporary in Docker.

package-lock.json

@@ -3405,6 +3405,11 @@
         "loose-envify": "^1.0.0"
       }
     },
+    "ip": {
+      "version": "1.1.5",
+      "resolved": "https://registry.npmjs.org/ip/-/ip-1.1.5.tgz",
+      "integrity": "sha1-vd7XARQpCCjAoDnnLvJfWq7ENUo="
+    },
     "ipaddr.js": {
       "version": "1.8.0",
       "resolved": "https://registry.npmjs.org/ipaddr.js/-/ipaddr.js-1.8.0.tgz",

package.json

@@ -26,6 +26,7 @@
     "express-session": "^1.15.6",
     "graphql-query-compress": "^1.1.0",
     "http-proxy-middleware": "^0.19.1",
+    "ip": "^1.1.5",
     "isomorphic-fetch": "^2.2.1",
     "jsonwebtoken": "^8.3.0",
     "lasso": "^3.2.6",

server.js

@@ -9,6 +9,8 @@ const config = require("./config")
 const express = require("express")
 const proxy = require("express-http-proxy")
 const proxy2 = require("http-proxy-middleware")
+const ip = require("ip")
+const dns = require("dns")
 const lasso = require("lasso")
 const lassoMiddleware = require("lasso/middleware")
 const markoExpress = require("marko/express")
@@ -26,7 +28,26 @@ lasso.configure(require("./marko-config"))
 
 // Set trusted proxy
 if (config.trustedProxy != null) {
-  app.set('trust proxy', config.trustedProxy)
+  if (ip.isV4Format(config.trustedProxy) || ip.isV6Format(config.trustedProxy)) {
+    app.set('trust proxy', config.trustedProxy)
+
+    console.log("Trusting proxy", config.trustedProxy);
+  } else {
+    dns.resolve4(config.trustedProxy, (err, res) => {
+      if (err != null) {
+        console.error("Failed to resolve trustedProxy hostname")
+        console.error(err)
+        process.exit(1)
+      }
+      if (res.length === 0) {
+        console.error("No results for trustedProxy hostname")
+        process.exit(1)
+      }
+
+      console.log("Trusting proxy", res[0], `(${config.trustedProxy})`);
+      app.set('trust proxy', res[0])
+    })
+  }
 }
 
 // Apply middleware