add email auth validation with middleware

backend/app/rest/api/rest.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"regexp"
 	"strings"
 	"sync"
 	"time"
@@ -224,6 +225,7 @@ func (s *Rest) routes() chi.Router {
 	router.Group(func(r chi.Router) {
 		r.Use(middleware.Timeout(5 * time.Second))
 		r.Use(logInfoWithBody, tollbooth_chi.LimitHandler(tollbooth.NewLimiter(10, nil)), middleware.NoCache)
+		r.Use(validEmaiAuth()) // reject suspicious email logins
 		r.Mount("/auth", authHandler)
 	})
 
@@ -650,6 +652,34 @@ func subscribersOnly(enable bool) func(http.Handler) http.Handler {
 	}
 }
 
+// validEmaiAuth is a middleware for auth endpoints for email method.
+// it rejects login request if user or email are suspicious
+func validEmaiAuth() func(http.Handler) http.Handler {
+
+	// matches ui side validation, adding min/max limitation
+	reUser := regexp.MustCompile(`^[\p{L}\d\s_]{4,64}$`)
+
+	return func(h http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+
+			if !strings.Contains(r.URL.Path, "/email/login") {
+				// not email login, skip the check
+				h.ServeHTTP(w, r)
+				return
+			}
+
+			if u := r.URL.Query().Get("user"); u != "" {
+				if !reUser.MatchString(u) {
+					http.Error(w, "Access denied", http.StatusForbidden)
+					return
+				}
+			}
+			h.ServeHTTP(w, r)
+		}
+		return http.HandlerFunc(fn)
+	}
+}
+
 func parseError(err error, defaultCode int) (code int) {
 	code = defaultCode
 

backend/app/rest/api/rest_test.go

@@ -389,6 +389,34 @@ func TestRest_subscribersOnly(t *testing.T) {
 	}
 }
 
+func Test_validEmaiAuth(t *testing.T) {
+	tbl := []struct {
+		req    string
+		status int
+	}{
+		{"/auth/email/login?site=remark42&address=umputun%example.com&user=someone", http.StatusOK},
+		{"/auth/email/login?site=remark42&address=umputun%example.com&user=someone+blah", http.StatusOK},
+		{"/auth/email/login?site=remark42&address=umputun%example.com&user=Евгений+Умпутун", http.StatusOK},
+		{"/auth/email/login?site=remark42&address=umputun%example.com&user=12", http.StatusForbidden},
+		{"/auth/email/login?site=remark42&address=umputun%example.com&user=..blah+blah", http.StatusForbidden},
+		{"/auth/email/login?site=remark42&address=umputun%example.com&user=someonelooong+loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong", http.StatusForbidden},
+		{"/auth/twitter/login?site=remark42&address=umputun%example.com&user=..blah+blah", http.StatusOK},
+		{"/auth/email/login?site=remark42&address=umputun%example.com", http.StatusOK},
+	}
+
+	for i, tt := range tbl {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			req := httptest.NewRequest("GET", "http://example.com"+tt.req, http.NoBody)
+			w := httptest.NewRecorder()
+			h := validEmaiAuth()(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
+			h.ServeHTTP(w, req)
+			resp := w.Result()
+			assert.Equal(t, tt.status, resp.StatusCode)
+			assert.NoError(t, resp.Body.Close())
+		})
+	}
+}
+
 // randomPath pick a file or folder name which is not in use for sure
 func randomPath(tempDir, basename, suffix string) (string, error) {
 	for i := 0; i < 10; i++ {