From 98cd70faea97d7ca437814008fa3a5d6ef20fc31 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Karol=20Wypch=C5=82o?= <kwypchlo@gmail.com>
Date: Mon, 21 Sep 2020 18:29:47 +0200
Subject: [PATCH] Fix broken hns redirect (#415)

---
 docker/nginx/conf.d/client.conf | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/docker/nginx/conf.d/client.conf b/docker/nginx/conf.d/client.conf
index 34b9dafb..ca85072f 100644
--- a/docker/nginx/conf.d/client.conf
+++ b/docker/nginx/conf.d/client.conf
@@ -130,24 +130,42 @@ server {
 	location /hns {
 		include /etc/nginx/conf.d/include/proxy-buffer;
 
+		# variable definititions - we need to define a variable to be able to access it in lua by ngx.var.something
 		set $skylink ''; # placeholder for the raw 46 bit skylink
 		set $rest ''; # placeholder for the rest of the url that gets appended to skylink (path and args)
 		
 		# resolve handshake domain by requesting to /hnsres endpoint and assign correct values to $skylink and $rest
 		access_by_lua_block {
 			local json = require('cjson')
+			
+			-- match the request_uri and extract the hns domain and anything that is passed in the uri after it
+			-- example: /hns/something/foo/bar?baz=1 matches:
+			-- > hns_domain_name: something
+			-- > request_uri_rest: /foo/bar/?baz=1
 			local hns_domain_name, request_uri_rest = string.match(ngx.var.request_uri, "/hns/([^/?]+)(.*)")
+
+			-- make a get request to /hnsres endpoint with the domain name from request_uri
 			local hnsres_res = ngx.location.capture("/hnsres/" .. hns_domain_name)
 
+			-- we want to fail with a generic 404 when /hnsres returns anything but 200 OK with a skylink
 			if hnsres_res.status ~= ngx.HTTP_OK then
 				ngx.exit(ngx.HTTP_NOT_FOUND)
 			end
 
+			-- since /hnsres endpoint response is a json, we need to decode it before we access it
+			-- example response: '{"skylink":"sia://XABvi7JtJbQSMAcDwnUnmp2FKDPjg8_tTTFP4BwMSxVdEg"}'
 			local hnsres_json = json.decode(hnsres_res.body)
-			local skylink_prefix, skylink, skylink_rest = string.match(hnsres_json.skylink, "(sia://)([^/?]+)(.*)")
+
+			-- try to match the skylink with sia:// prefix
+			local skylink, skylink_rest = string.match(hnsres_json.skylink, "sia://([^/?]+)(.*)")
+
+			-- in case the skylink did not match, assume that there is no sia:// prefix and try to match again
+			if skylink == nil then
+				skylink, skylink_rest = string.match(hnsres_json.skylink, "/?([^/?]+)(.*)")
+			end
 
 			ngx.var.skylink = skylink
-			if request_uri_rest == "" or (request_uri_rest == "/" and skylink_rest ~= "") then
+			if request_uri_rest == "/" and skylink_rest ~= "" and skylink_rest ~= "/" then
 				ngx.var.rest = skylink_rest
 			else
 				ngx.var.rest = request_uri_rest
@@ -163,10 +181,15 @@ server {
 		# in case siad returns location header, we need to replace the skylink with the domain name
 		header_filter_by_lua_block {
 			if ngx.header.location then
+				-- match hns domain from the request_uri
 				local hns_domain_name = string.match(ngx.var.request_uri, "/hns/([^/?]+)")
-				local location = string.gsub(ngx.header.location, ngx.var.skylink, hns_domain_name)
 
-				ngx.header.location = location
+				-- match location redirect part after the skylink
+				local location_rest = string.match(ngx.header.location, "[^/?]+(.*)");
+
+				-- because siad will set the location header to ie. XABvi7JtJbQSMAcDwnUnmp2FKDPjg8_tTTFP4BwMSxVdEg/index.html
+				-- we need to replace the skylink with the domain_name so we are not redirected to skylink
+				ngx.header.location = hns_domain_name .. location_rest
 			end
 		}
 	}