#right now there is a lot of logging to error_log so during an attack those logs will fill the disk eventually.
#a good idea would be to use a syslog server and log to a socket instead of a file for IO optimization
#logging could also be disabled in production

#depending on cluster setup some things can be changed here.
#keepalive 128; or proxy_bind on multiple local ips can be used to mitigate local port exhaustion
#most likely with this setup it's not the case
#if this runs on the same machine as the application server UNIX sockets should be used instead of TCP
upstream tor {
	server	127.0.0.1:9060;
	server	127.0.0.1:9070;
}
access_by_lua_no_postpone on;
lua_package_path "/etc/nginx/resty/?.lua;;";

init_by_lua_block {
	allowed_hosts = { "mainonion",
		"masterbalanceonion"
	}

	function in_array(tab, val)
		for index, value in ipairs(tab) do
			if value == val then
				return true
			end
		end
		return nil
	end

	function split(str, sep)
		local result = {}
		local regex = ("([^%s]+)"):format(sep)
		for each in str:gmatch(regex) do
			table.insert(result, each)
		end
		return result
		end

		local function calc_circuit(proxyheaderip)
		local cg = split(proxyheaderip, ":")
		local g1 = cg[5]
		local g2 = cg[6]

		local glen = string.len(g1)
		if (glen < 4) then
			for i = (4 - glen),1,-1 do
			 g1 = "0" .. g1
			 ::loop_label_1::
			end
		end
		glen = string.len(g2)
		if (glen < 4) then
			for i = (4 - glen),1,-1 do
				g2 = "0" .. g2
				::loop_label_2::
			end
		end

		local d1 = (string.sub(g1,1,1) .. string.sub(g1,2,2))
		local d2 = (string.sub(g1,3,3) .. string.sub(g1,4,4))
		local d3 = (string.sub(g2,1,1) .. string.sub(g2,2,2))
		local d4 = (string.sub(g2,3,3) .. string.sub(g2,4,4))
		local circuit_id = ((((bit.lshift(tonumber(d1, 16), 24)) + (bit.lshift(tonumber(d2, 16), 16))) + (bit.lshift(tonumber(d3, 16), 8))) + tonumber(d4, 16))
		return circuit_id
	end 

	function kill_circuit(premature, clientip, headerip)
		local circuitid = calc_circuit(headerip)
		local sockfile = "unix:/etc/tor/c1"
		local response = "Closing circuit " .. circuitid .. " "
		local sock = ngx.socket.tcp()
		sock:settimeout(1000)
		local ok, err = sock:connect(sockfile)
		if not ok then
			ngx.log(ngx.ERR, "failed to connect to tor: " .. err)
			return
		end
		ngx.log(ngx.ERR, "connected to tor")

		local bytes, err = sock:send("authenticate \"torauthpassword\"\n")
		if not bytes then
			ngx.log(ngx.ERR, "failed authenticate to tor: " .. err)
			return
		end
		local data, err, partial = sock:receive()
		if not data then
			ngx.log(ngx.ERR, "failed receive data from tor: " .. err)
			return
		end
		local response = response .. " " .. data

		local bytes, err = sock:send("closecircuit " .. circuitid .. "\n")
		if not bytes then
			ngx.log(ngx.ERR, "failed send data to tor: " .. err)
			return
		end
		local data, err, partial = sock:receive()
		if not data then
			ngx.log(ngx.ERR, "failed receive data from tor: " .. err)
			return
		end
		local response = response .. " " .. data

		ngx.log(ngx.ERR, response)
		sock:close()
		return
	 end	
}

#rate limits should be set to the maximum number of resources (css/images/iframes) a page will load. those should be kept to a minimum for optimization reasons
#limiting by proxy_protocol_addr won't work with V2 onions and maybe should be disabled.
#limiting by cookie_<name> works regarless and must be used, otherwise an attacker can solve a captcha by hand and add it to a script/bot

limit_req_zone $proxy_protocol_addr zone=circuits:50m rate=6r/s;
limit_req_zone $cookie_dcap zone=capcookie:50m rate=6r/s;

#proxy_protocol only makes sense with V3 onions (exportcircuitid) otherwise it will break things.
#kill_circuit won't be used without it
server {
	listen unix:/etc/tor/nginx1 proxy_protocol bind;
	allow unix:;
	deny all;

	#access_log /var/log/nginx/front_access.log;

	if ($http_x_tor2web) {
 		return 401;
	}

	error_page 401 @tor2web;
	
	location @tor2web {
		echo_status 401;
		default_type text/html;		
		echo <h1>It seems you are connecting over a Tor2Web Proxy.</h1><p>This is unsafe being that you are giving the proxy a privileged position where it can modify and/or inject content into the webpages you visit as well as track what you do.</p>;
		echo <p>When visiting please use the Tor Browser and go to the offical onion address. This keeps you private and safe.</body></html>;
	}

	more_clear_headers 'Server:*';
	more_clear_headers 'X-Page-Speed:*'; 
	more_clear_headers 'Vary*';
	more_clear_headers 'captcha-fails*';

	#what do do when rate limit is triggered, blacklist the cookie (if exists) and kill circuit
	location @ratelimit {
		error_log /var/log/nginx/front_error.log;
		access_by_lua_block {
		local pa = "no_proxy"
		if ngx.var.proxy_protocol_addr ~= nil then
			 pa = ngx.var.proxy_protocol_addr
		end
		local cook = require "resty.cookie"
		local cookie, err = cook:new()
		if not cookie then
			ngx.log(ngx.ERR, err)
			return
		end
		local field, err = cookie:get("dcap")
		if field then

			local blocked_cookies = ngx.shared.blocked_cookies
			blocked_cookies:set(field, 1, 3600)
		end

		ngx.log(ngx.ERR, "Rate limited " .. ngx.var.remote_addr .. "|" .. pa)

		if pa ~= "no_proxy" then
			 local ok, err = ngx.timer.at(0, kill_circuit, ngx.var.remote_addr, ngx.var.proxy_protocol_addr)
			 if not ok then
				ngx.log(ngx.ERR, "failed to create timer: ", err)
			 return
			 end
		end
		ngx.exit(444)
		}
	 }

	#what do do when waf is triggered, just show the error page and kill circuit for now.
	#naxsi seems to kick in before everything else except rate limiter but if it does trash traffic won't make it to the application servers anyway
	#doesn't make sense to blacklist cookie as it will annoy users

	location @waf {
		error_log /var/log/nginx/front_error.log;
		default_type text/html;
		content_by_lua_block {
			ngx.say("<head><title>Error</title></head>")
			ngx.say("<body bgcolor=\"white\">")
			ngx.say("<center><h1>Error</h1></center>")
			ngx.say("<hr><center><p>Your browser sent a request that this server could not understand.</p></center>")
			ngx.say("<center><p>Most likely your input contains invalid characters (\" , `, etc.) that except for passwords should not be used.</p></center>")
			ngx.say("<center><p>This may also happen if you are trying to send contact information or external links.</p></center>")
			ngx.say("<center><p>Please go back, check your input and try again.</p></center></body>")

			proxyip = "no_proxy"
			torip = ngx.var.remote_addr
			if ngx.var.proxy_protocol_addr ~= nil then
				 proxyip = ngx.var.proxy_protocol_addr
			end
			
			ngx.log(ngx.ERR, "WAF triggered " .. torip .. "|" .. proxyip)
			if proxyip ~= "no_proxy" then
				 local ok, err = ngx.timer.at(0, kill_circuit, torip, proxyip)
				 if not ok then
					ngx.log(ngx.ERR, "failed to create timer: ", err)
				 	return
				 end
			end
		}
	}

	location @502 {
		default_type text/html;
		content_by_lua_block {
			ngx.say("<head><title>502 Timeout</title></head>")
			ngx.say("<body bgcolor=\"white\">")
			ngx.say("<center><h1>502 Timeout</h1></center>")
			ngx.say("<hr><center><p>It seems this endgame front doesn't have a stable connection to the backend right now.</p></center>")
			ngx.say("<center><p>To fix it you can try to reload the page. If that doesn't work, and you end back here, get a new circuit.</p></center>")
			ngx.say("<center><p>If getting a new circuit doesn't work. Try to get a brand new Tor identity.</p></center>")
			ngx.say("<center><p>If getting a new Tor identity doesn't work come back later.</p></center></body>")
		}
	}

	
	location /kill {
		access_by_lua_block {
			proxyip = "no_proxy"
			torip = ngx.var.remote_addr
			if ngx.var.proxy_protocol_addr ~= nil then
				 proxyip = ngx.var.proxy_protocol_addr
			end
			
			ngx.log(ngx.ERR, "Kill area visited" .. torip .. "|" .. proxyip)

			local cook = require "resty.cookie"
			local cookie, err = cook:new()
			if not cookie then
				ngx.log(ngx.ERR, err)
				return
			end

			local field, err = cookie:get("dcap")
			if field then
				local blocked_cookies = ngx.shared.blocked_cookies
				blocked_cookies:set(field, 1, 3600)
			end

			if proxyip ~= "no_proxy" then
				 local ok, err = ngx.timer.at(0, kill_circuit, torip, proxyip)
				 if not ok then
					ngx.log(ngx.ERR, "failed to create timer: ", err)
				 	return
				 end
			end
			ngx.exit(444)
		}
	}
	location / {
		#access_log /var/log/nginx/front_access.log;
		error_log /var/log/nginx/front_error.log;

		#rate limits per circuit ID (won't work with V2 and maybe should be disabled)
		limit_req zone=circuits burst=10 nodelay;
		error_page 503 =503 @ratelimit;

		#rate limits based on captcha cookie. if an attacker or bot solves the capcha by hand and inputs the cookie in a script
		#the cookie will be blacklisted by all fronts (eventually) and subsequent requests dropped.

		limit_req zone=capcookie burst=10 nodelay;
		error_page 503 =503 @ratelimit;

		error_page 502 =502 @502;

		#check if access captca is solved and other things
		access_by_lua_file lua/cap.lua;

		SecRulesEnabled;
		#LearningMode;
		DeniedUrl "@waf";
		CheckRule "$SQL >= 8" BLOCK;
		CheckRule "$RFI >= 8" BLOCK;
		CheckRule "$TRAVERSAL >= 4" BLOCK;
		CheckRule "$EVADE >= 4" BLOCK;
		CheckRule "$XSS >= 8" BLOCK;
		include "/etc/nginx/naxsi_whitelist.rules";
		error_log /etc/nginx/naxsi.log;
		proxy_set_header Host $host;
		socks_pass socks5://tor;
		socks_set_host backendurl;
		socks_set_header Host $host; 
		socks_redirect off;
		socks_http_version 1.1;
		socks_next_upstream error timeout invalid_header http_500 http_502 http_503;
		#proxy_pass http://proxypassurl;

		header_filter_by_lua_block {
			local cookie, err = cook:new()
				if not cookie then
				ngx.log(ngx.ERR, err)
				return
			end
			local block_cookie = 0

			if ngx.resp.get_headers()['captcha-fails'] ~= nil then
				local field, err = cookie:get("dcap")
				if field then
					local failed = ngx.shared.failed
					local fl = failed:get(field)
					if fl ~= nil then
						fl = fl + 1
						else
						fl = 1
					end
					failed:set(field, fl, 3600)
					if fl > 3 then
						block_cookie = 1
						failed:delete(field)
					end
				end
			end

			if block_cookie > 0 then
			local field, err = cookie:get("dcap")
				if field then
					local blocked_cookies = ngx.shared.blocked_cookies
					blocked_cookies:set(field, 1, 3600)
				end
			end
		}
	}
}