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134 lines
3.4 KiB
Go
134 lines
3.4 KiB
Go
// Copyright (c) 2015-2021 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package safe
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import (
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"errors"
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"io/ioutil"
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"os"
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"path/filepath"
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)
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// File represents safe file descriptor.
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type File struct {
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name string
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tmpfile *os.File
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closed bool
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aborted bool
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}
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// Write writes len(b) bytes to the temporary File. In case of error, the temporary file is removed.
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func (file *File) Write(b []byte) (n int, err error) {
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if file.closed {
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err = errors.New("write on closed file")
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return
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}
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if file.aborted {
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err = errors.New("write on aborted file")
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return
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}
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defer func() {
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if err != nil {
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os.Remove(file.tmpfile.Name())
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file.aborted = true
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}
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}()
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n, err = file.tmpfile.Write(b)
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return
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}
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// Close closes the temporary File and renames to the named file. In case of error, the temporary file is removed.
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func (file *File) Close() (err error) {
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defer func() {
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if err != nil {
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os.Remove(file.tmpfile.Name())
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file.aborted = true
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}
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}()
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if file.closed {
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err = errors.New("close on closed file")
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return
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}
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if file.aborted {
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err = errors.New("close on aborted file")
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return
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}
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if err = file.tmpfile.Close(); err != nil {
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return
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}
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err = os.Rename(file.tmpfile.Name(), file.name)
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file.closed = true
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return
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}
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// Abort aborts the temporary File by closing and removing the temporary file.
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func (file *File) Abort() (err error) {
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if file.closed {
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err = errors.New("abort on closed file")
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return
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}
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if file.aborted {
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err = errors.New("abort on aborted file")
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return
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}
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file.tmpfile.Close()
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err = os.Remove(file.tmpfile.Name())
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file.aborted = true
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return
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}
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// CreateFile creates the named file safely from unique temporary file.
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// The temporary file is renamed to the named file upon successful close
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// to safeguard intermediate state in the named file. The temporary file
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// is created in the name of the named file with suffixed unique number
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// and prefixed "$tmpfile" string. While creating the temporary file,
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// missing parent directories are also created. The temporary file is
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// removed if case of any intermediate failure. Not removed temporary
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// files can be cleaned up by identifying them using "$tmpfile" prefix
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// string.
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func CreateFile(name string) (*File, error) {
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// ioutil.TempFile() fails if parent directory is missing.
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// Create parent directory to avoid such error.
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dname := filepath.Dir(name)
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if err := os.MkdirAll(dname, 0700); err != nil {
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return nil, err
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}
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fname := filepath.Base(name)
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tmpfile, err := ioutil.TempFile(dname, "$tmpfile."+fname+".")
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if err != nil {
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return nil, err
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}
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if err = os.Chmod(tmpfile.Name(), 0600); err != nil {
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if rerr := os.Remove(tmpfile.Name()); rerr != nil {
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err = rerr
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}
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return nil, err
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}
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return &File{name: name, tmpfile: tmpfile}, nil
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}
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