158 lines
3.5 KiB
Go
158 lines
3.5 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package multipart
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import (
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"bytes"
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"errors"
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"io"
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"io/ioutil"
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"net/textproto"
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"os"
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)
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// TODO(adg,bradfitz): find a way to unify the DoS-prevention strategy here
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// with that of the http package's ParseForm.
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// ReadForm parses an entire multipart message whose parts have
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// a Content-Disposition of "form-data".
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// It stores up to maxMemory bytes of the file parts in memory
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// and the remainder on disk in temporary files.
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func (r *Reader) ReadForm(maxMemory int64) (f *Form, err error) {
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form := &Form{make(map[string][]string), make(map[string][]*FileHeader)}
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defer func() {
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if err != nil {
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form.RemoveAll()
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}
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}()
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maxValueBytes := int64(10 << 20) // 10 MB is a lot of text.
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for {
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p, err := r.NextPart()
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if err == io.EOF {
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break
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}
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if err != nil {
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return nil, err
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}
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name := p.FormName()
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if name == "" {
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continue
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}
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filename := p.FileName()
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var b bytes.Buffer
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if filename == "" {
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// value, store as string in memory
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n, err := io.CopyN(&b, p, maxValueBytes)
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if err != nil && err != io.EOF {
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return nil, err
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}
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maxValueBytes -= n
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if maxValueBytes == 0 {
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return nil, errors.New("multipart: message too large")
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}
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form.Value[name] = append(form.Value[name], b.String())
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continue
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}
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// file, store in memory or on disk
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fh := &FileHeader{
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Filename: filename,
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Header: p.Header,
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}
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n, err := io.CopyN(&b, p, maxMemory+1)
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if err != nil && err != io.EOF {
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return nil, err
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}
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if n > maxMemory {
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// too big, write to disk and flush buffer
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file, err := ioutil.TempFile("", "multipart-")
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if err != nil {
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return nil, err
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}
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defer file.Close()
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_, err = io.Copy(file, io.MultiReader(&b, p))
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if err != nil {
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os.Remove(file.Name())
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return nil, err
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}
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fh.tmpfile = file.Name()
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} else {
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fh.content = b.Bytes()
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maxMemory -= n
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}
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form.File[name] = append(form.File[name], fh)
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}
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return form, nil
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}
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// Form is a parsed multipart form.
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// Its File parts are stored either in memory or on disk,
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// and are accessible via the *FileHeader's Open method.
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// Its Value parts are stored as strings.
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// Both are keyed by field name.
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type Form struct {
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Value map[string][]string
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File map[string][]*FileHeader
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}
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// RemoveAll removes any temporary files associated with a Form.
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func (f *Form) RemoveAll() error {
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var err error
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for _, fhs := range f.File {
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for _, fh := range fhs {
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if fh.tmpfile != "" {
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e := os.Remove(fh.tmpfile)
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if e != nil && err == nil {
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err = e
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}
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}
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}
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}
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return err
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}
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// A FileHeader describes a file part of a multipart request.
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type FileHeader struct {
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Filename string
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Header textproto.MIMEHeader
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content []byte
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tmpfile string
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}
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// Open opens and returns the FileHeader's associated File.
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func (fh *FileHeader) Open() (File, error) {
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if b := fh.content; b != nil {
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r := io.NewSectionReader(bytes.NewReader(b), 0, int64(len(b)))
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return sectionReadCloser{r}, nil
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}
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return os.Open(fh.tmpfile)
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}
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// File is an interface to access the file part of a multipart message.
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// Its contents may be either stored in memory or on disk.
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// If stored on disk, the File's underlying concrete type will be an *os.File.
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type File interface {
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io.Reader
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io.ReaderAt
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io.Seeker
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io.Closer
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}
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// helper types to turn a []byte into a File
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type sectionReadCloser struct {
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*io.SectionReader
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}
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func (rc sectionReadCloser) Close() error {
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return nil
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}
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