Notify users if they were blocked due to proxy

src/lib/quota/index.js

@@ -38,5 +38,14 @@ function add(req, count) {
 	return limiter.add(identifier, count)
 }
 
+function isProxyNetwork(req) {
+	if (!constants.quota.enabled) return false // no need to try to perform detection if we didn't even load the lists
+
+	const ip = getIPFromReq(req)
+	const identifier = getIdentifier(ip)
+	return identifier === "proxy"
+}
+
 module.exports.remaining = remaining
 module.exports.add = add
+module.exports.isProxyNetwork = isProxyNetwork

src/site/api/routes.js

@@ -159,7 +159,8 @@ module.exports = [
 				} else if (error === constants.symbols.extractor_results.AGE_RESTRICTED) {
 					return render(403, "pug/age_gated.pug", {settings})
 				} else if (error === constants.symbols.QUOTA_REACHED) {
-					return render(429, "pug/quota_reached.pug")
+					const isProxyNetwork = quota.isProxyNetwork(req)
+					return render(429, "pug/quota_reached.pug", {isProxyNetwork})
 				} else {
 					throw error
 				}
@@ -302,7 +303,8 @@ module.exports = [
 				} else if (error === constants.symbols.RATE_LIMITED) {
 					return render(503, "pug/blocked_graphql.pug")
 				} else if (error === constants.symbols.QUOTA_REACHED) {
-					return render(429, "pug/quota_reached.pug")
+					const isProxyNetwork = quota.isProxyNetwork(req)
+					return render(429, "pug/quota_reached.pug", {isProxyNetwork})
 				} else {
 					throw error
 				}

src/site/pug/quota_reached.pug

@@ -1,3 +1,5 @@
+//- Needs isProxyNetwork
+
 include includes/error.pug
 
 doctype html
@@ -10,5 +12,11 @@ html
 			| Each person has a limited number of requests to Bibliogram.
 			| You have reached that limit. You cannot load any more data on this instance.
 			| Your quota will reset automatically after some time has passed.
+			if isProxyNetwork
+				|
+				|
+				| However, this website has detected that you are using a proxy network, like Tor or a VPN.
+				| To prevent bot abuse, all users on proxy networks share the same request quota.
+			|
 			|
 			|