v0.332.0 (live rc.2 + security review): the pass redirect is absolute; no pass for a cross-site request; no dot-segments in to (R-1100)

controller/internal/web/files_sso.go

@@ -184,7 +184,8 @@ func (s *Server) filesCookieKey(r *http.Request) (present, ok bool) {
 	return true, s.filesSessionAlive(parts[0])
 }
 
-// safeFilesPath accepts a FileBrowser path to go to after the pass: "/" or under /files/ — never another host.
+// safeFilesPath accepts a FileBrowser path to go to after the pass: "/" or under /files/ — never another host, and never
+// a dot-segment that a browser would resolve out of /files/ (onto FileBrowser's API, say).
 func safeFilesPath(p string) string {
 	if p == "" || p == "/" {
 		return "/"
@@ -192,6 +193,16 @@ func safeFilesPath(p string) string {
 	if !strings.HasPrefix(p, "/files/") || strings.HasPrefix(p, "//") || strings.ContainsAny(p, "\\\r\n") {
 		return "/"
 	}
+	path, _, _ := strings.Cut(p, "?")
+	dec, err := url.PathUnescape(path)
+	if err != nil {
+		return "/"
+	}
+	for _, seg := range strings.Split(dec, "/") {
+		if seg == ".." || seg == "." {
+			return "/"
+		}
+	}
 	return p
 }
 
@@ -229,6 +240,14 @@ func (s *Server) ServeFilesOpen(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/", http.StatusFound)
 		return
 	}
+	// A pass is minted only for the household's own press (the dashboard page: same-origin) or a typed or bookmarked
+	// address (none) — never for a request another site started. A browser that sends no Sec-Fetch-Site (an old one) is
+	// let through: the pass opens only the household's own files on this box. Pinned by TestFilesSSO_R1100_CrossSiteNoPass.
+	if sfs := r.Header.Get("Sec-Fetch-Site"); sfs == "cross-site" {
+		s.logger.Printf("[WARN] [web] files sign-in: a pass asked for from another site — refused, visitor %s", clientIP(r))
+		http.Redirect(w, r, "/", http.StatusFound)
+		return
+	}
 	c, err := r.Cookie(sessionCookieName)
 	if err != nil || !s.isValidSession(c.Value) {
 		http.Redirect(w, r, "/login?"+url.Values{"next": {filesOpenPath + "?" + url.Values{"to": {to}}.Encode()}}.Encode(), http.StatusFound)
@@ -291,7 +310,10 @@ func (s *Server) ServeFilesAuth(w http.ResponseWriter, r *http.Request) {
 		http.SetCookie(w, &http.Cookie{Name: fileBrowserJWTCookie, Value: "", Path: "/", Domain: host, MaxAge: -1, HttpOnly: true, Secure: true})
 		s.logger.Printf("[INFO] [web] files sign-in: a signed-in household browser passed — visitor %s", clientIP(r))
 		w.Header().Set("Cache-Control", "no-store")
-		http.Redirect(w, r, safeFilesPath(rd), http.StatusFound)
+		// ABSOLUTE, like the setup gate's: traefik makes a relative Location in a forwardAuth answer absolute against
+		// the AUTH server's address — measured on 9201, "/files/" became http://felhom-controller:8080/files/.
+		// Pinned by TestFilesSSO_R1100_HouseholdOpensTheFolderWithoutALogin.
+		http.Redirect(w, r, "https://"+host+safeFilesPath(rd), http.StatusFound)
 		return
 	}
 

controller/internal/web/files_sso_test.go

@@ -122,8 +122,13 @@ func TestFilesSSO_R1100_HouseholdOpensTheFolderWithoutALogin(t *testing.T) {
 	}
 	w := filesAsk(s, "files.example.hu", pass, htmlAccept)
 	fc := filesCookieIn(w, filesCookieName)
-	if w.Code != http.StatusFound || w.Header().Get("Location") != folder {
-		t.Fatalf("the pass answer: %d → %q, want 302 → %s", w.Code, w.Header().Get("Location"), folder)
+	// Absolute: traefik makes a relative Location in a forwardAuth answer absolute against the controller's own
+	// address (measured on 9201 with rc.2: "/files/" → http://felhom-controller:8080/files/).
+	//
+	// COMPANION RED-PROOF (observed 2026-10-19, the live rc.2 shape): redirect to safeFilesPath(rd) alone → this fails
+	// with `the pass answer: 302 → "/files/HDD%202/media"`. Restored.
+	if w.Code != http.StatusFound || w.Header().Get("Location") != "https://files.example.hu"+folder {
+		t.Fatalf("the pass answer: %d → %q, want 302 → https://files.example.hu%s", w.Code, w.Header().Get("Location"), folder)
 	}
 	if fc == nil || fc.Domain != "" || !fc.HttpOnly || !fc.Secure || fc.SameSite != http.SameSiteLaxMode || fc.Path != "/" {
 		t.Fatalf("the files cookie must be host-only, HttpOnly, Secure, Lax: %+v", fc)
@@ -340,3 +345,39 @@ func TestFilesSSO_R1100_DataTabLoginNote(t *testing.T) {
 		t.Fatal("without the one sign-in the note must stay")
 	}
 }
+
+// A pass is never minted for a request another site started (a CSRF that would sign the household into its own files at
+// a path the other site picked), and a dot-segment never leaves /files/.
+//
+// COMPANION RED-PROOF (observed 2026-10-19): drop the Sec-Fetch-Site check in ServeFilesOpen → this fails with "a
+// cross-site request got a pass"; drop the dot-segment loop in safeFilesPath → "safeFilesPath(\"/files/../api/x\")". Restored.
+func TestFilesSSO_R1100_CrossSiteNoPass(t *testing.T) {
+	s := newFilesServer(t)
+	sess := sessionCookie(s)
+	for _, sfs := range []string{"same-origin", "none", ""} {
+		r := httptest.NewRequest(http.MethodGet, "https://felhom.example.hu"+filesOpenPath+"?to=%2F", nil)
+		r.AddCookie(sess)
+		if sfs != "" {
+			r.Header.Set("Sec-Fetch-Site", sfs)
+		}
+		if passFrom(t, s.filesEntry(r), "files.example.hu") == "" {
+			t.Fatalf("Sec-Fetch-Site %q: the household's own press got no pass", sfs)
+		}
+	}
+	for _, sfs := range []string{"cross-site"} {
+		r := httptest.NewRequest(http.MethodGet, "https://felhom.example.hu"+filesOpenPath+"?to=%2F", nil)
+		r.AddCookie(sess)
+		r.Header.Set("Sec-Fetch-Site", sfs)
+		if passFrom(t, s.filesEntry(r), "files.example.hu") != "" {
+			t.Fatal("a cross-site request got a pass")
+		}
+	}
+	for _, bad := range []string{"/files/../api/x", "/files/%2e%2e/api/x", "/files/a/./b", "/files/%2E%2E"} {
+		if got := safeFilesPath(bad); got != "/" {
+			t.Fatalf("safeFilesPath(%q) = %q", bad, got)
+		}
+	}
+	if got := safeFilesPath("/files/M%C3%A9dia%20&%20k%C3%B6nyvt%C3%A1r/a..b"); got == "/" {
+		t.Fatal("a name with two dots inside it is a real folder name")
+	}
+}