feat(resolver): Support for alternate Host header

Proxying can now be triggered via a `Host` or a `X-Host-Override`
header. Multiple values can be given to each of those headers.

Fix #203

kong/constants.lua

@@ -26,10 +26,9 @@ return {
     ID = "id",
     TIMESTAMP = "timestamp"
   },
+  -- Non standard headers, specific to Kong
   HEADERS = {
-    SERVER = "Server",
-    VIA = "Via",
-    CONTENT_TYPE = "Content-Type",
+    HOST_OVERRIDE = "X-Host-Override",
     PROXY_TIME = "X-Kong-Proxy-Time",
     API_TIME = "X-Kong-Api-Time",
     CONSUMER_ID = "X-Consumer-ID",

kong/kong.lua

@@ -191,7 +191,7 @@ function _M.exec_plugins_header_filter()
   ngx.ctx.proxy_ended_at = timestamp.get_utc() -- Setting a property that will be available for every plugin
 
   if not ngx.ctx.stop_phases then
-    ngx.header[constants.HEADERS.VIA] = constants.NAME.."/"..constants.VERSION
+    ngx.header["Via"] = constants.NAME.."/"..constants.VERSION
 
     for _, plugin in ipairs(plugins) do
       local conf = ngx.ctx.plugin_conf[plugin.name]

kong/resolver/access.lua

@@ -1,6 +1,7 @@
 local url = require("socket.url")
 local cache = require "kong.tools.database_cache"
 local stringy = require "stringy"
+local constants = require "kong.constants"
 local responses = require "kong.tools.responses"
 
 local _M = {}
@@ -24,7 +25,7 @@ local function get_host_from_url(val)
 
   local port
   if parsed_url.port then
-     port = parsed_url.port
+    port = parsed_url.port
   elseif parsed_url.scheme == "https" then
     port = 443
   end
@@ -37,18 +38,24 @@ local function skip_authentication(headers)
   return headers["expect"] and stringy.startswith(headers["expect"], "100")
 end
 
--- Retrieve the API from the Host that has been requested
-function _M.execute(conf)
-  local hosts = ngx.req.get_headers()["host"] -- Multiple "Host" can have been requested
-  if type(hosts) == "string" then
-    hosts = { hosts }
-  elseif not hosts then
-    hosts = {}
+-- Retrieve the API from the Host header that has been requested.
+function _M.execute()
+  -- Search for a Host header in all `Host` and `X-Host-Override` headers
+  local hosts_headers = {}
+  for _, header_name in ipairs({"Host", constants.HEADERS.HOST_OVERRIDE}) do
+    local host = ngx.req.get_headers()[header_name]
+    if type(host) == "string" then -- single header
+      table.insert(hosts_headers, host)
+    elseif type(host) == "table" then -- multiple headers
+      for _, v in ipairs(host) do
+        table.insert(hosts_headers, v)
+      end
+    end
   end
 
-  -- Find the API
-  local api = nil
-  for _, host in ipairs(hosts) do
+  -- Find the API from one of the given hosts
+  local api
+  for _, host in ipairs(hosts_headers) do
     api = cache.get_and_set(cache.api_key(host), function()
       local apis, err = dao.apis:find_by_keys { public_dns = host }
       if err then
@@ -61,13 +68,13 @@ function _M.execute(conf)
   end
 
   if not api then
-    return responses.send_HTTP_NOT_FOUND("API not found with Host: "..table.concat(hosts, ","))
+    return responses.send_HTTP_NOT_FOUND("API not found with Host: "..table.concat(hosts_headers, ","))
   end
 
   -- Setting the backend URL for the proxy_pass directive
   ngx.var.backend_url = get_backend_url(api)..ngx.var.request_uri
 
-  ngx.req.set_header("host", get_host_from_url(ngx.var.backend_url))
+  ngx.req.set_header("Host", get_host_from_url(ngx.var.backend_url))
 
   -- There are some requests whose authentication needs to be skipped
   if not skip_authentication(ngx.req.get_headers()) then

kong/tools/responses.lua

@@ -54,8 +54,8 @@ local function send_response(status_code)
     end
 
     ngx.status = status_code
-    ngx.header[constants.HEADERS.CONTENT_TYPE] = "application/json; charset=utf-8"
-    ngx.header[constants.HEADERS.SERVER] = constants.NAME.."/"..constants.VERSION
+    ngx.header["Content-Type"] = "application/json; charset=utf-8"
+    ngx.header["Server"] = constants.NAME.."/"..constants.VERSION
 
     if type(response_default_content[status_code]) == "function" then
       content = response_default_content[status_code](content)

spec/integration/proxy/resolver_spec.lua

@@ -33,12 +33,12 @@ describe("Resolver", function()
 
   describe("Existing API", function()
 
-    it("should return Success when the API is in Kong", function()
+    it("should proxy when the API is in Kong", function()
       local response, status = http_client.get(STUB_GET_URL, nil, { host = "test4.com"})
       assert.are.equal(200, status)
     end)
 
-    it("should return Success when the Host header is not trimmed", function()
+    it("should proxy when the Host header is not trimmed", function()
       local response, status = http_client.get(STUB_GET_URL, nil, { host = "   test4.com  "})
       assert.are.equal(200, status)
     end)
@@ -57,7 +57,7 @@ describe("Resolver", function()
       assert.falsy(headers.via)
     end)
 
-    it("should return Success when the API is in Kong and one Host headers is being sent via plain TCP", function()
+    it("should proxy when the API is in Kong and one Host header is being sent via plain TCP", function()
       local parsed_url = url.parse(STUB_GET_URL)
       local host = parsed_url.host
       local port = parsed_url.port
@@ -76,7 +76,7 @@ describe("Resolver", function()
       assert.truthy(stringy.startswith(response, "HTTP/1.1 200 OK"))
     end)
 
-    it("should return Success when the API is in Kong and multiple Host headers are being sent via plain TCP", function()
+    it("should proxy when the API is in Kong and multiple Host headers are being sent via plain TCP", function()
       local parsed_url = url.parse(STUB_GET_URL)
       local host = parsed_url.host
       local port = parsed_url.port
@@ -95,6 +95,10 @@ describe("Resolver", function()
       assert.truthy(stringy.startswith(response, "HTTP/1.1 200 OK"))
     end)
 
-  end)
+    it("should proxy when the request has no Host header but the X-Override-Host header", function()
+      local _, status = http_client.get(STUB_GET_URL, nil, { ["X-Host-Override"] = "test4.com"})
+      assert.are.equal(200, status)
+    end)
 
+  end)
 end)