Set default ciphers, set tls 1.2 via config, set curve prefs (#9315)

Config Checks at StartUp Part1

Config Checks; Tests for TLS Server

HSTS header implementation + tests

make gofmt happy with new go version...

make gofmt happy with new go version #2...

fix logic bug

fix typo

Fix unnecessary code block

2 files changed, 53 insertions, 2 deletions

diff --git a/web/handlers.go b/web/handlers.go
index 71a43bc48..9b0705a5b 100644
--- a/web/handlers.go
+++ b/web/handlers.go
@@ -75,6 +75,10 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set(model.HEADER_REQUEST_ID, c.RequestId)
 	w.Header().Set(model.HEADER_VERSION_ID, fmt.Sprintf("%v.%v.%v.%v", model.CurrentVersion, model.BuildNumber, c.App.ClientConfigHash(), c.App.License() != nil))
 
+	if *c.App.Config().ServiceSettings.TLSStrictTransport {
+		w.Header().Set("Strict-Transport-Security", fmt.Sprintf("max-age=%d", *c.App.Config().ServiceSettings.TLSStrictTransportMaxAge))
+	}
+
 	if h.IsStatic {
 		// Instruct the browser not to display us in an iframe unless is the same origin for anti-clickjacking
 		w.Header().Set("X-Frame-Options", "SAMEORIGIN")
diff --git a/web/handlers_test.go b/web/handlers_test.go
index 0b9073fff..6b68a9987 100644
--- a/web/handlers_test.go
+++ b/web/handlers_test.go
@@ -13,7 +13,7 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func handlerForTest(c *Context, w http.ResponseWriter, r *http.Request) {
+func handlerForHTTPErrors(c *Context, w http.ResponseWriter, r *http.Request) {
 	c.Err = model.NewAppError("loginWithSaml", "api.user.saml.not_available.app_error", nil, "", http.StatusFound)
 }
 
@@ -25,7 +25,7 @@ func TestHandlerServeHTTPErrors(t *testing.T) {
 	if err != nil {
 		panic(err)
 	}
-	handler := web.NewHandler(handlerForTest)
+	handler := web.NewHandler(handlerForHTTPErrors)
 
 	var flagtests = []struct {
 		name     string
@@ -57,3 +57,50 @@ func TestHandlerServeHTTPErrors(t *testing.T) {
 		})
 	}
 }
+
+func handlerForHTTPSecureTransport(c *Context, w http.ResponseWriter, r *http.Request) {
+}
+
+func TestHandlerServeHTTPSecureTransport(t *testing.T) {
+	a, err := app.New(app.StoreOverride(testStore), app.DisableConfigWatch)
+	defer a.Shutdown()
+
+	a.UpdateConfig(func(config *model.Config) {
+		*config.ServiceSettings.TLSStrictTransport = true
+		*config.ServiceSettings.TLSStrictTransportMaxAge = 6000
+	})
+
+	web := NewWeb(a, a.Srv.Router)
+	if err != nil {
+		panic(err)
+	}
+	handler := web.NewHandler(handlerForHTTPSecureTransport)
+
+	request := httptest.NewRequest("GET", "/api/v4/test", nil)
+
+	response := httptest.NewRecorder()
+	handler.ServeHTTP(response, request)
+	header := response.Header().Get("Strict-Transport-Security")
+
+	if header == "" {
+		t.Errorf("Strict-Transport-Security expected but not existent")
+	}
+
+	if header != "max-age=6000" {
+		t.Errorf("Expected max-age=6000, got %s", header)
+	}
+
+	a.UpdateConfig(func(config *model.Config) {
+		*config.ServiceSettings.TLSStrictTransport = false
+	})
+
+	request = httptest.NewRequest("GET", "/api/v4/test", nil)
+
+	response = httptest.NewRecorder()
+	handler.ServeHTTP(response, request)
+	header = response.Header().Get("Strict-Transport-Security")
+
+	if header != "" {
+		t.Errorf("Strict-Transport-Security header is not expected, but returned")
+	}
+}