lib/api: Refactor to run tests in parallel (#5998)

This is an experiment in testing, based on the advise to always call
t.Parallel() at the start of every test. Doing so makes tests run in
parallel, which is usually faster, but also exposes package level state
and potential race conditions better.

To support this I had to redesign the CSRF manager to not be package
global, which was indeed an improvement. And tests run five times faster
now.

lib/api/api.go

@@ -310,7 +310,7 @@ func (s *service) serve(stop chan struct{}) {
 
 	// Wrap everything in CSRF protection. The /rest prefix should be
 	// protected, other requests will grant cookies.
-	handler := csrfMiddleware(s.id.String()[:5], "/rest", guiCfg, mux)
+	var handler http.Handler = newCsrfManager(s.id.String()[:5], "/rest", guiCfg, mux, locations.Get(locations.CsrfTokens))
 
 	// Add our version and ID as a header to responses
 	handler = withDetailsMiddleware(s.id, handler)

lib/api/api_auth_test.go

@@ -19,6 +19,8 @@ func init() {
 }
 
 func TestStaticAuthOK(t *testing.T) {
+	t.Parallel()
+
 	ok := authStatic("user", "pass", "user", string(passwordHashBytes))
 	if !ok {
 		t.Fatalf("should pass auth")
@@ -26,6 +28,8 @@ func TestStaticAuthOK(t *testing.T) {
 }
 
 func TestSimpleAuthUsernameFail(t *testing.T) {
+	t.Parallel()
+
 	ok := authStatic("userWRONG", "pass", "user", string(passwordHashBytes))
 	if ok {
 		t.Fatalf("should fail auth")
@@ -33,6 +37,8 @@ func TestSimpleAuthUsernameFail(t *testing.T) {
 }
 
 func TestStaticAuthPasswordFail(t *testing.T) {
+	t.Parallel()
+
 	ok := authStatic("user", "passWRONG", "user", string(passwordHashBytes))
 	if ok {
 		t.Fatalf("should fail auth")

lib/api/api_csrf.go

@@ -13,83 +13,103 @@ import (
 	"os"
 	"strings"
 
-	"github.com/syncthing/syncthing/lib/config"
-	"github.com/syncthing/syncthing/lib/locations"
 	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/rand"
 	"github.com/syncthing/syncthing/lib/sync"
 )
 
-// csrfTokens is a list of valid tokens. It is sorted so that the most
-// recently used token is first in the list. New tokens are added to the front
-// of the list (as it is the most recently used at that time). The list is
-// pruned to a maximum of maxCsrfTokens, throwing away the least recently used
-// tokens.
-var csrfTokens []string
-var csrfMut = sync.NewMutex()
-
 const maxCsrfTokens = 25
 
+type csrfManager struct {
+	// tokens is a list of valid tokens. It is sorted so that the most
+	// recently used token is first in the list. New tokens are added to the front
+	// of the list (as it is the most recently used at that time). The list is
+	// pruned to a maximum of maxCsrfTokens, throwing away the least recently used
+	// tokens.
+	tokens    []string
+	tokensMut sync.Mutex
+
+	unique          string
+	prefix          string
+	apiKeyValidator apiKeyValidator
+	next            http.Handler
+	saveLocation    string
+}
+
+type apiKeyValidator interface {
+	IsValidAPIKey(key string) bool
+}
+
 // Check for CSRF token on /rest/ URLs. If a correct one is not given, reject
 // the request with 403. For / and /index.html, set a new CSRF cookie if none
 // is currently set.
-func csrfMiddleware(unique string, prefix string, cfg config.GUIConfiguration, next http.Handler) http.Handler {
-	loadCsrfTokens()
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		// Allow requests carrying a valid API key
-		if cfg.IsValidAPIKey(r.Header.Get("X-API-Key")) {
-			// Set the access-control-allow-origin header for CORS requests
-			// since a valid API key has been provided
-			w.Header().Add("Access-Control-Allow-Origin", "*")
-			next.ServeHTTP(w, r)
-			return
-		}
+func newCsrfManager(unique string, prefix string, apiKeyValidator apiKeyValidator, next http.Handler, saveLocation string) *csrfManager {
+	m := &csrfManager{
+		tokensMut:       sync.NewMutex(),
+		unique:          unique,
+		prefix:          prefix,
+		apiKeyValidator: apiKeyValidator,
+		next:            next,
+		saveLocation:    saveLocation,
+	}
+	m.load()
+	return m
+}
 
-		if strings.HasPrefix(r.URL.Path, "/rest/debug") {
-			// Debugging functions are only available when explicitly
-			// enabled, and can be accessed without a CSRF token
-			next.ServeHTTP(w, r)
-			return
-		}
+func (m *csrfManager) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Allow requests carrying a valid API key
+	if m.apiKeyValidator.IsValidAPIKey(r.Header.Get("X-API-Key")) {
+		// Set the access-control-allow-origin header for CORS requests
+		// since a valid API key has been provided
+		w.Header().Add("Access-Control-Allow-Origin", "*")
+		m.next.ServeHTTP(w, r)
+		return
+	}
 
-		// Allow requests for anything not under the protected path prefix,
-		// and set a CSRF cookie if there isn't already a valid one.
-		if !strings.HasPrefix(r.URL.Path, prefix) {
-			cookie, err := r.Cookie("CSRF-Token-" + unique)
-			if err != nil || !validCsrfToken(cookie.Value) {
-				l.Debugln("new CSRF cookie in response to request for", r.URL)
-				cookie = &http.Cookie{
-					Name:  "CSRF-Token-" + unique,
-					Value: newCsrfToken(),
-				}
-				http.SetCookie(w, cookie)
+	if strings.HasPrefix(r.URL.Path, "/rest/debug") {
+		// Debugging functions are only available when explicitly
+		// enabled, and can be accessed without a CSRF token
+		m.next.ServeHTTP(w, r)
+		return
+	}
+
+	// Allow requests for anything not under the protected path prefix,
+	// and set a CSRF cookie if there isn't already a valid one.
+	if !strings.HasPrefix(r.URL.Path, m.prefix) {
+		cookie, err := r.Cookie("CSRF-Token-" + m.unique)
+		if err != nil || !m.validToken(cookie.Value) {
+			l.Debugln("new CSRF cookie in response to request for", r.URL)
+			cookie = &http.Cookie{
+				Name:  "CSRF-Token-" + m.unique,
+				Value: m.newToken(),
 			}
-			next.ServeHTTP(w, r)
-			return
+			http.SetCookie(w, cookie)
 		}
+		m.next.ServeHTTP(w, r)
+		return
+	}
 
-		// Verify the CSRF token
-		token := r.Header.Get("X-CSRF-Token-" + unique)
-		if !validCsrfToken(token) {
-			http.Error(w, "CSRF Error", 403)
-			return
-		}
+	// Verify the CSRF token
+	token := r.Header.Get("X-CSRF-Token-" + m.unique)
+	if !m.validToken(token) {
+		http.Error(w, "CSRF Error", http.StatusForbidden)
+		return
+	}
 
-		next.ServeHTTP(w, r)
-	})
+	m.next.ServeHTTP(w, r)
 }
 
-func validCsrfToken(token string) bool {
-	csrfMut.Lock()
-	defer csrfMut.Unlock()
-	for i, t := range csrfTokens {
+func (m *csrfManager) validToken(token string) bool {
+	m.tokensMut.Lock()
+	defer m.tokensMut.Unlock()
+	for i, t := range m.tokens {
 		if t == token {
 			if i > 0 {
 				// Move this token to the head of the list. Copy the tokens at
 				// the front one step to the right and then replace the token
 				// at the head.
-				copy(csrfTokens[1:], csrfTokens[:i+1])
-				csrfTokens[0] = token
+				copy(m.tokens[1:], m.tokens[:i+1])
+				m.tokens[0] = token
 			}
 			return true
 		}
@@ -97,40 +117,47 @@ func validCsrfToken(token string) bool {
 	return false
 }
 
-func newCsrfToken() string {
+func (m *csrfManager) newToken() string {
 	token := rand.String(32)
 
-	csrfMut.Lock()
-	csrfTokens = append([]string{token}, csrfTokens...)
-	if len(csrfTokens) > maxCsrfTokens {
-		csrfTokens = csrfTokens[:maxCsrfTokens]
+	m.tokensMut.Lock()
+	m.tokens = append([]string{token}, m.tokens...)
+	if len(m.tokens) > maxCsrfTokens {
+		m.tokens = m.tokens[:maxCsrfTokens]
 	}
-	defer csrfMut.Unlock()
+	defer m.tokensMut.Unlock()
 
-	saveCsrfTokens()
+	m.save()
 
 	return token
 }
 
-func saveCsrfTokens() {
+func (m *csrfManager) save() {
 	// We're ignoring errors in here. It's not super critical and there's
 	// nothing relevant we can do about them anyway...
 
-	name := locations.Get(locations.CsrfTokens)
-	f, err := osutil.CreateAtomic(name)
+	if m.saveLocation == "" {
+		return
+	}
+
+	f, err := osutil.CreateAtomic(m.saveLocation)
 	if err != nil {
 		return
 	}
 
-	for _, t := range csrfTokens {
+	for _, t := range m.tokens {
 		fmt.Fprintln(f, t)
 	}
 
 	f.Close()
 }
 
-func loadCsrfTokens() {
-	f, err := os.Open(locations.Get(locations.CsrfTokens))
+func (m *csrfManager) load() {
+	if m.saveLocation == "" {
+		return
+	}
+
+	f, err := os.Open(m.saveLocation)
 	if err != nil {
 		return
 	}
@@ -138,6 +165,6 @@ func loadCsrfTokens() {
 
 	s := bufio.NewScanner(f)
 	for s.Scan() {
-		csrfTokens = append(csrfTokens, s.Text())
+		m.tokens = append(m.tokens, s.Text())
 	}
 }

lib/api/api_test.go

@@ -53,7 +53,7 @@ func TestMain(m *testing.M) {
 }
 
 func TestCSRFToken(t *testing.T) {
-	defer os.Remove(token)
+	t.Parallel()
 
 	max := 250
 	int := 5
@@ -62,11 +62,13 @@ func TestCSRFToken(t *testing.T) {
 		int = 2
 	}
 
-	t1 := newCsrfToken()
-	t2 := newCsrfToken()
+	m := newCsrfManager("unique", "prefix", config.GUIConfiguration{}, nil, "")
+
+	t1 := m.newToken()
+	t2 := m.newToken()
 
-	t3 := newCsrfToken()
-	if !validCsrfToken(t3) {
+	t3 := m.newToken()
+	if !m.validToken(t3) {
 		t.Fatal("t3 should be valid")
 	}
 
@@ -74,27 +76,29 @@ func TestCSRFToken(t *testing.T) {
 		if i%int == 0 {
 			// t1 and t2 should remain valid by virtue of us checking them now
 			// and then.
-			if !validCsrfToken(t1) {
+			if !m.validToken(t1) {
 				t.Fatal("t1 should be valid at iteration", i)
 			}
-			if !validCsrfToken(t2) {
+			if !m.validToken(t2) {
 				t.Fatal("t2 should be valid at iteration", i)
 			}
 		}
 
 		// The newly generated token is always valid
-		t4 := newCsrfToken()
-		if !validCsrfToken(t4) {
+		t4 := m.newToken()
+		if !m.validToken(t4) {
 			t.Fatal("t4 should be valid at iteration", i)
 		}
 	}
 
-	if validCsrfToken(t3) {
+	if m.validToken(t3) {
 		t.Fatal("t3 should have expired by now")
 	}
 }
 
 func TestStopAfterBrokenConfig(t *testing.T) {
+	t.Parallel()
+
 	cfg := config.Configuration{
 		GUI: config.GUIConfiguration{
 			RawAddress: "127.0.0.1:0",
@@ -135,6 +139,8 @@ func TestStopAfterBrokenConfig(t *testing.T) {
 }
 
 func TestAssetsDir(t *testing.T) {
+	t.Parallel()
+
 	// For any given request to $FILE, we should return the first found of
 	//  - assetsdir/$THEME/$FILE
 	//  - compiled in asset $THEME/$FILE
@@ -209,6 +215,8 @@ func expectURLToContain(t *testing.T, url, exp string) {
 }
 
 func TestDirNames(t *testing.T) {
+	t.Parallel()
+
 	names := dirNames("testdata")
 	expected := []string{"config", "default", "foo", "testfolder"}
 	if diff, equal := messagediff.PrettyDiff(expected, names); !equal {
@@ -225,6 +233,8 @@ type httpTestCase struct {
 }
 
 func TestAPIServiceRequests(t *testing.T) {
+	t.Parallel()
+
 	const testAPIKey = "foobarbaz"
 	cfg := new(mockedConfig)
 	cfg.gui.APIKey = testAPIKey
@@ -435,6 +445,8 @@ func testHTTPRequest(t *testing.T, baseURL string, tc httpTestCase, apikey strin
 }
 
 func TestHTTPLogin(t *testing.T) {
+	t.Parallel()
+
 	cfg := new(mockedConfig)
 	cfg.gui.User = "üser"
 	cfg.gui.Password = "$2a$10$IdIZTxTg/dCNuNEGlmLynOjqg4B1FvDKuIV5e0BB3pnWVHNb8.GSq" // bcrypt of "räksmörgås" in UTF-8
@@ -542,6 +554,8 @@ func startHTTP(cfg *mockedConfig) (string, error) {
 }
 
 func TestCSRFRequired(t *testing.T) {
+	t.Parallel()
+
 	const testAPIKey = "foobarbaz"
 	cfg := new(mockedConfig)
 	cfg.gui.APIKey = testAPIKey
@@ -615,6 +629,8 @@ func TestCSRFRequired(t *testing.T) {
 }
 
 func TestRandomString(t *testing.T) {
+	t.Parallel()
+
 	const testAPIKey = "foobarbaz"
 	cfg := new(mockedConfig)
 	cfg.gui.APIKey = testAPIKey
@@ -664,6 +680,8 @@ func TestRandomString(t *testing.T) {
 }
 
 func TestConfigPostOK(t *testing.T) {
+	t.Parallel()
+
 	cfg := bytes.NewBuffer([]byte(`{
 		"version": 15,
 		"folders": [
@@ -685,6 +703,8 @@ func TestConfigPostOK(t *testing.T) {
 }
 
 func TestConfigPostDupFolder(t *testing.T) {
+	t.Parallel()
+
 	cfg := bytes.NewBuffer([]byte(`{
 		"version": 15,
 		"folders": [
@@ -720,6 +740,8 @@ func testConfigPost(data io.Reader) (*http.Response, error) {
 }
 
 func TestHostCheck(t *testing.T) {
+	t.Parallel()
+
 	// An API service bound to localhost should reject non-localhost host Headers
 
 	cfg := new(mockedConfig)
@@ -878,6 +900,8 @@ func TestHostCheck(t *testing.T) {
 }
 
 func TestAddressIsLocalhost(t *testing.T) {
+	t.Parallel()
+
 	testcases := []struct {
 		address string
 		result  bool
@@ -921,6 +945,8 @@ func TestAddressIsLocalhost(t *testing.T) {
 }
 
 func TestAccessControlAllowOriginHeader(t *testing.T) {
+	t.Parallel()
+
 	const testAPIKey = "foobarbaz"
 	cfg := new(mockedConfig)
 	cfg.gui.APIKey = testAPIKey
@@ -949,6 +975,8 @@ func TestAccessControlAllowOriginHeader(t *testing.T) {
 }
 
 func TestOptionsRequest(t *testing.T) {
+	t.Parallel()
+
 	const testAPIKey = "foobarbaz"
 	cfg := new(mockedConfig)
 	cfg.gui.APIKey = testAPIKey
@@ -982,6 +1010,8 @@ func TestOptionsRequest(t *testing.T) {
 }
 
 func TestEventMasks(t *testing.T) {
+	t.Parallel()
+
 	cfg := new(mockedConfig)
 	defSub := new(mockedEventSub)
 	diskSub := new(mockedEventSub)
@@ -1014,6 +1044,8 @@ func TestEventMasks(t *testing.T) {
 }
 
 func TestBrowse(t *testing.T) {
+	t.Parallel()
+
 	pathSep := string(os.PathSeparator)
 
 	tmpDir, err := ioutil.TempDir("", "syncthing")
@@ -1066,6 +1098,8 @@ func TestBrowse(t *testing.T) {
 }
 
 func TestPrefixMatch(t *testing.T) {
+	t.Parallel()
+
 	cases := []struct {
 		s        string
 		prefix   string