Encrypt pages at rest with a key per person

Pages are sealed with AES-256-GCM. Each person's key is derived (HKDF) from a master key in the settings file plus their Authentik issuer and subject. Plain files from earlier versions are read and re-saved encrypted. Mako refuses to open a notebook it cannot decrypt rather than overwrite it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/web/web_test.go

@@ -612,3 +612,68 @@ func TestFailCapitalizes(t *testing.T) {
 		t.Fatalf("%q", out["error"])
 	}
 }
+
+func TestNothingIsOnDiskInTheClear(t *testing.T) {
+	e := setup(t, nil)
+	a := e.signIn(alice)
+	e.do("POST", "/api/notes", map[string]string{"title": "Harbour plans", "body": "meet at midnight"}, a)
+	e.do("POST", "/api/notes", map[string]string{"body": "a quick thought"}, a)
+	files := 0
+	filepath.WalkDir(filepath.Join(e.dir, "data"), func(p string, d os.DirEntry, err error) error {
+		if err != nil || d.IsDir() {
+			return nil
+		}
+		files++
+		b, _ := os.ReadFile(p)
+		for _, s := range []string{"Harbour", "midnight", "quick thought", "Alice", "alice@"} {
+			if bytes.Contains(b, []byte(s)) {
+				t.Errorf("%s holds %q in the clear", p, s)
+			}
+		}
+		return nil
+	})
+	if files < 2 {
+		t.Fatalf("only %d files written", files)
+	}
+}
+
+func TestKeyIsMadeOnceAndKept(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "mako.json")
+	h, err := config.Load(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !h.NeedsSave() {
+		t.Fatal("a new file must be written")
+	}
+	h.Save()
+	key := h.Get().Key
+	if len(key) < 32 {
+		t.Fatalf("key %q", key)
+	}
+	h2, _ := config.Load(path)
+	if h2.NeedsSave() || h2.Get().Key != key {
+		t.Fatal("the key changed or was made again")
+	}
+	// a file from before encryption has a secret but no key: one is made and must be written
+	os.WriteFile(path, []byte(`{"secret":"old-secret"}`), 0o600)
+	h3, _ := config.Load(path)
+	if !h3.NeedsSave() || len(h3.Get().Key) < 32 {
+		t.Fatal("an old file gets no key")
+	}
+	// a key from the environment wins and is never written to the file
+	t.Setenv("MAKO_KEY", strings.Repeat("k", 40))
+	os.WriteFile(path, []byte(`{"secret":"old-secret"}`), 0o600)
+	h4, _ := config.Load(path)
+	h4.Save()
+	if h4.Get().Key != strings.Repeat("k", 40) {
+		t.Fatal("the environment key was not used")
+	}
+	if b, _ := os.ReadFile(path); strings.Contains(string(b), "kkkk") || strings.Contains(string(b), `"key"`) {
+		t.Fatalf("the environment key was written to the file: %s", b)
+	}
+	t.Setenv("MAKO_KEY", "too short")
+	if err := h4.Get().Check(); err == nil || !strings.Contains(err.Error(), "encryption key") {
+		t.Fatalf("a short key was accepted: %v", err)
+	}
+}