hotfix(config) allow specifying 'headers' via config file

This fixes a bug introduced in 976dd87 (#3300) where the `headers`
config option were not properly written to `.kong_env`. This would be an
issue when the value was specified from the configuration file (vs. via
environment variables).

From #3419

Signed-off-by: Thibault Charbonnier <thibaultcha@me.com>

kong/conf_loader.lua

@@ -607,31 +607,33 @@ local function load(path, custom_conf)
 
   -- load headers configuration
   do
-    local headers_enabled = {}
+    local enabled_headers = {}
 
     for _, v in pairs(header_key_to_name) do
-      headers_enabled[v] = false
+      enabled_headers[v] = false
     end
 
     if #conf.headers > 0 and conf.headers[1] ~= "off" then
       for _, token in ipairs(conf.headers) do
         if token ~= "off" then
-          headers_enabled[header_key_to_name[string.lower(token)]] = true
+          enabled_headers[header_key_to_name[string.lower(token)]] = true
         end
       end
     end
 
-    if headers_enabled.server_tokens then
-      headers_enabled[headers.VIA] = true
-      headers_enabled[headers.SERVER] = true
+    if enabled_headers.server_tokens then
+      enabled_headers[headers.VIA] = true
+      enabled_headers[headers.SERVER] = true
     end
 
-    if headers_enabled.latency_tokens then
-      headers_enabled[headers.PROXY_LATENCY] = true
-      headers_enabled[headers.UPSTREAM_LATENCY] = true
+    if enabled_headers.latency_tokens then
+      enabled_headers[headers.PROXY_LATENCY] = true
+      enabled_headers[headers.UPSTREAM_LATENCY] = true
     end
 
-    conf.headers = headers_enabled
+    conf.enabled_headers = setmetatable(enabled_headers, {
+      __tostring = function() return "" end,
+    })
   end
 
   -- load absolute paths

kong/error_handlers.lua

@@ -58,7 +58,7 @@ return function(ngx)
   local status = ngx.status
   message = BODIES["s" .. status] and BODIES["s" .. status] or format(BODIES.default, status)
 
-  if singletons.configuration.headers[constants.HEADERS.SERVER] then
+  if singletons.configuration.enabled_headers[constants.HEADERS.SERVER] then
     ngx.header[constants.HEADERS.SERVER] = SERVER_HEADER
   end
 

kong/runloop/handler.lua

@@ -713,20 +713,20 @@ return {
       local header = ngx.header
 
       if ctx.KONG_PROXIED then
-        if singletons.configuration.headers[constants.HEADERS.UPSTREAM_LATENCY] then
+        if singletons.configuration.enabled_headers[constants.HEADERS.UPSTREAM_LATENCY] then
           header[constants.HEADERS.UPSTREAM_LATENCY] = ctx.KONG_WAITING_TIME
         end
 
-        if singletons.configuration.headers[constants.HEADERS.PROXY_LATENCY] then
+        if singletons.configuration.enabled_headers[constants.HEADERS.PROXY_LATENCY] then
           header[constants.HEADERS.PROXY_LATENCY] = ctx.KONG_PROXY_LATENCY
         end
 
-        if singletons.configuration.headers[constants.HEADERS.VIA] then
+        if singletons.configuration.enabled_headers[constants.HEADERS.VIA] then
           header[constants.HEADERS.VIA] = server_header
         end
 
       else
-        if singletons.configuration.headers[constants.HEADERS.SERVER] then
+        if singletons.configuration.enabled_headers[constants.HEADERS.SERVER] then
           header[constants.HEADERS.SERVER] = server_header
 
         else

spec/02-integration/05-proxy/13-server_tokens_spec.lua

@@ -1,5 +1,6 @@
 local helpers = require "spec.helpers"
 local constants = require "kong.constants"
+local cjson = require "cjson"
 
 
 local default_server_header = _KONG._NAME .. "/" .. _KONG._VERSION
@@ -492,6 +493,25 @@ describe("headers [#" .. strategy .. "]", function()
         assert.is_nil(res.headers[constants.HEADERS.PROXY_LATENCY])
       end)
 
+      it("can be specified via configuration file", function()
+        -- A regression test added with https://github.com/Kong/kong/pull/3419
+        -- to ensure that the `headers` configuration value can be specified
+        -- via the configuration file (vs. environment variables as the rest
+        -- of this test suite uses).
+        -- This regression occured because of the dumping of config values into
+        -- .kong_env (and the lack of serialization for the `headers` table).
+        assert(helpers.kong_exec("restart -c spec/fixtures/headers.conf"))
+
+        local admin_client = helpers.admin_client()
+        local res = assert(admin_client:send {
+          method = "GET",
+          path   = "/",
+        })
+        local body = assert.res_status(200, res)
+        local json = cjson.decode(body)
+        assert.equal("server_tokens", json.configuration.headers[1])
+        assert.equal("X-Kong-Proxy-Latency", json.configuration.headers[2])
+      end)
     end)
 
     describe("(with headers='server_tokens, off, X-Kong-Proxy-Latency')", function()

spec/fixtures/headers.conf

@@ -0,0 +1,28 @@
+# 1st digit is 9 for our test instances
+admin_listen = 127.0.0.1:9001
+proxy_listen = 0.0.0.0:9000, 0.0.0.0:9443 ssl
+
+ssl_cert = spec/fixtures/kong_spec.crt
+ssl_cert_key = spec/fixtures/kong_spec.key
+
+admin_ssl_cert = spec/fixtures/kong_spec.crt
+admin_ssl_cert_key = spec/fixtures/kong_spec.key
+
+dns_resolver = 8.8.8.8
+database = postgres
+pg_host = 127.0.0.1
+pg_port = 5432
+pg_database = kong_tests
+cassandra_keyspace = kong_tests
+cassandra_timeout = 10000
+anonymous_reports = off
+
+dns_hostsfile = spec/fixtures/hosts
+
+nginx_worker_processes = 1
+nginx_optimizations = off
+
+prefix = servroot
+log_level = debug
+
+headers = server_tokens, X-Kong-Proxy-Latency