fix(responses) to respect headers configuration option

kong/tools/responses.lua

@@ -17,7 +17,8 @@
 --
 --    -- Raw send() helper:
 --    return responses.send(418, "This is a teapot")
-
+local singletons = require "kong.singletons"
+local constants = require "kong.constants"
 local cjson = require "cjson.safe"
 local meta = require "kong.meta"
 
@@ -122,7 +123,18 @@ local function send_response(status_code)
     end
 
     ngx.status = status_code
-    ngx.header["Server"] = server_header
+
+    if singletons and singletons.configuration then
+      if singletons.configuration.enabled_headers[constants.HEADERS.SERVER] then
+        ngx.header[constants.HEADERS.SERVER] = server_header
+
+      else
+        ngx.header[constants.HEADERS.SERVER] = nil
+      end
+
+    else
+      ngx.header[constants.HEADERS.SERVER] = server_header
+    end
 
     if headers then
       for k, v in pairs(headers) do

spec/01-unit/009-responses_spec.lua

@@ -192,4 +192,33 @@ describe("Response helpers", function()
       assert.spy(s).was.called_with(ngx.ctx)
     end)
   end)
+
+  describe("server tokens", function()
+    it("are sent by default", function()
+      responses.send_HTTP_OK("OK")
+      assert.equal(ngx.status, responses.status_codes.HTTP_OK)
+      assert.equal(meta._SERVER_TOKENS, ngx.header["Server"])
+    end)
+    it("are sent when enabled", function()
+      local singletons = require "kong.singletons"
+      singletons.configuration = {
+        enabled_headers = {
+          ["server_tokens"] = true
+        },
+      },
+      responses.send_HTTP_OK("OK")
+      assert.equal(ngx.status, responses.status_codes.HTTP_OK)
+      assert.equal(meta._SERVER_TOKENS, ngx.header["Server"])
+    end)
+    it("are not sent when disabled", function()
+      local singletons = require "kong.singletons"
+      singletons.configuration = {
+        enabled_headers = {
+        },
+      },
+      responses.send_HTTP_OK("OK")
+      assert.equal(ngx.status, responses.status_codes.HTTP_OK)
+      assert.is_nil(ngx.header["Server"])
+    end)
+  end)
 end)