Save files in local storage as umask (#21198)

Go creates temporary files as 600, but sometimes we want the group to be able to read them (for example,
for another user to back up the storage)

This PR applies the umask to the renamed tmp files in local storage.

Co-authored-by: wxiaoguang <[email protected]>

Author: catdevnull

Diff for: modules/storage/local.go

@@ -102,6 +102,10 @@ func (l *LocalStorage) Save(path string, r io.Reader, size int64) (int64, error)
 	if err := util.Rename(tmp.Name(), p); err != nil {
 		return 0, err
 	}
+	// Golang's tmp file (os.CreateTemp) always have 0o600 mode, so we need to change the file to follow the umask (as what Create/MkDir does)
+	if err := util.ApplyUmask(p, os.ModePerm); err != nil {
+		return 0, err
+	}
 
 	tmpRemoved = true
 

Diff for: modules/util/file_unix.go

@@ -0,0 +1,28 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build !windows
+
+package util
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+var defaultUmask int
+
+func init() {
+	// at the moment, the umask could only be gotten by calling unix.Umask(newUmask)
+	// use 0o077 as temp new umask to reduce the risks if this umask is used anywhere else before the correct umask is recovered
+	tempUmask := 0o077
+	defaultUmask = unix.Umask(tempUmask)
+	unix.Umask(defaultUmask)
+}
+
+func ApplyUmask(f string, newMode os.FileMode) error {
+	mod := newMode & ^os.FileMode(defaultUmask)
+	return os.Chmod(f, mod)
+}

Diff for: modules/util/file_unix_test.go

@@ -0,0 +1,36 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build !windows
+
+package util
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestApplyUmask(t *testing.T) {
+	f, err := os.CreateTemp(t.TempDir(), "test-filemode-")
+	assert.NoError(t, err)
+
+	err = os.Chmod(f.Name(), 0o777)
+	assert.NoError(t, err)
+	st, err := os.Stat(f.Name())
+	assert.NoError(t, err)
+	assert.EqualValues(t, 0o777, st.Mode().Perm()&0o777)
+
+	oldDefaultUmask := defaultUmask
+	defaultUmask = 0o037
+	defer func() {
+		defaultUmask = oldDefaultUmask
+	}()
+	err = ApplyUmask(f.Name(), os.ModePerm)
+	assert.NoError(t, err)
+	st, err = os.Stat(f.Name())
+	assert.NoError(t, err)
+	assert.EqualValues(t, 0o740, st.Mode().Perm()&0o777)
+}

Diff for: modules/util/file_windows.go

@@ -0,0 +1,16 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build windows
+
+package util
+
+import (
+	"os"
+)
+
+func ApplyUmask(f string, newMode os.FileMode) error {
+	// do nothing for Windows, because Windows doesn't use umask
+	return nil
+}