dnsbl feature

confs/dnsbl.conf

@@ -0,0 +1,84 @@
+access_by_lua_block {
+
+	-- get client IP
+	local ip = ngx.var.remote_addr
+	
+	-- check if IP is in cache
+	local cached = ngx.shared.dnsblcache:get(ip)
+	if cached ~= nil then
+		if cached == "ok" then
+			ngx.exit(ngx.OK)
+		else
+			ngx.exit(ngx.HTTP_FORBIDDEN)
+		end
+	end
+	
+	-- get the reverse DNS
+	local rdns = ""
+	local both = false
+	local resolver = require "resty.dns.resolver"
+	local resolvers = {%DNSBL_RESOLVERS%}
+	local r, err = resolver:new{nameservers=resolvers, retrans=2, timeout=2000}
+	if not r then
+		ngx.exit(ngx.OK)
+	end
+	local answers, err = r:reverse_query(ip)
+	if not answers.errcode then
+		for ak, av in pairs(answers) do
+			if av.ptrdname then
+				rdns = av.ptrdname
+				break
+			end
+		end
+	end
+	if rdns ~= "" then
+		local answers, err, tries = r:query(rdns, nil, {})
+		for ak, av in pairs(answers) do
+			if av.address and av.address == ip then
+				both = true
+				break
+			end
+		end
+	end
+	
+	-- check if it's a legitimate SE crawler 
+	local ips = {"23.21.227.69", "40.88.21.235", "50.16.241.113", "50.16.241.114", "50.16.241.117", "50.16.247.234", "52.204.97.54", "52.5.190.19", "54.197.234.188", "54.208.100.253", "54.208.102.37", "107.21.1.8"}
+	local domains = {".googlebot.com", ".google.com", ".search.msn.com", ".crawl.yahoot.net", ".crawl.baidu.jp", ".crawl.baidu.com", ".yandex.com", ".yandex.ru", ".yandex.net"}
+	for k, v in pairs(ips) do
+		if v == ip then
+			ngx.shared.dnsblcache:set(ip, "ok", 86400)
+			ngx.exit(ngx.OK)
+		end
+	end
+	if both and rdns ~= "" then
+		for k, v in pairs(domains) do
+			if rdns:sub(-#v) == v then
+				ngx.shared.dnsblcache:set(ip, "ok", 86400)
+				ngx.exit(ngx.OK)
+			end
+		end
+	end
+	
+	-- dnsbl check
+	local dnsbls = {%DNSBL_LIST%}
+	for k, v in pairs(dnsbls) do
+		local name = resolver.arpa_str(ip)
+		name = name:gsub("%.in%-addr%.arpa", ""):gsub("%.ip6%.arpa", "") .. "." .. v
+		local answers, err, tries = r:query(name, nil, {})
+		if not answers.errcode then 
+			for ak, av in pairs(answers) do
+				if av.address then
+					a,b,c,d = av.address:match("([%d]+).([%d]+).([%d]+).([%d]+)")
+					if a == "127" then
+						ngx.shared.dnsblcache:set(ip, "dnsbl", 86400)
+						ngx.exit(ngx.HTTP_FORBIDDEN)
+					end
+				end
+			end
+		end
+	end
+	
+	-- legitimate user
+	ngx.shared.dnsblcache:set(ip, "ok", 86400)
+	ngx.exit(ngx.OK)
+}

confs/nginx.conf

@@ -67,7 +67,8 @@ http {
 
 	# lua path
 	lua_package_path "/usr/local/lib/lua/?.lua;;";
-	# lua_shared_dict somecache 10m;
+	%DNSBL_CACHE%
+	lua_shared_dict dnsblcache 10m;
 
 	# server config
 	include /etc/nginx/server.conf;

confs/server.conf

@@ -11,6 +11,7 @@ server {
 	{
 		return 405;
 	}
+	%DNSBL%
 	%AUTH_BASIC%
 	%USE_PHP%
 	%HEADER_SERVER%