archive/zip: prevent writing data for a directory

When creating a directory, Writer.Create now returns a dummy
io.Writer that always returns an error on Write.

Fixes #24043

Change-Id: I7792f54440d45d22d0aa174cba5015ed5fab1c5c
Reviewed-on: https://go-review.googlesource.com/108615
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/archive/zip/writer.go b/src/archive/zip/writer.go
index 12675d60a0230303dab09cf78f8a6d0b0104baf2..f3abe8770c44b6f0a86c7b734bd73665be64fdad 100644 (file)
--- a/src/archive/zip/writer.go
+++ b/src/archive/zip/writer.go
@@ -11,6 +11,7 @@ import (
        "hash"
        "hash/crc32"
        "io"
+       "strings"
        "unicode/utf8"
 )
 
@@ -320,35 +321,43 @@ func (w *Writer) CreateHeader(fh *FileHeader) (io.Writer, error) {
                fh.Extra = append(fh.Extra, mbuf[:]...)
        }
 
-       fw := &fileWriter{
-               zipw:      w.cw,
-               compCount: &countWriter{w: w.cw},
-               crc32:     crc32.NewIEEE(),
-       }
-       comp := w.compressor(fh.Method)
-       if comp == nil {
-               return nil, ErrAlgorithm
-       }
-       var err error
-       fw.comp, err = comp(fw.compCount)
-       if err != nil {
-               return nil, err
-       }
-       fw.rawCount = &countWriter{w: fw.comp}
-
+       var (
+               ow io.Writer
+               fw *fileWriter
+       )
        h := &header{
                FileHeader: fh,
                offset:     uint64(w.cw.count),
        }
-       w.dir = append(w.dir, h)
-       fw.header = h
 
+       if strings.HasSuffix(fh.Name, "/") {
+               ow = dirWriter{}
+       } else {
+               fw = &fileWriter{
+                       zipw:      w.cw,
+                       compCount: &countWriter{w: w.cw},
+                       crc32:     crc32.NewIEEE(),
+               }
+               comp := w.compressor(fh.Method)
+               if comp == nil {
+                       return nil, ErrAlgorithm
+               }
+               var err error
+               fw.comp, err = comp(fw.compCount)
+               if err != nil {
+                       return nil, err
+               }
+               fw.rawCount = &countWriter{w: fw.comp}
+               fw.header = h
+               ow = fw
+       }
+       w.dir = append(w.dir, h)
        if err := writeHeader(w.cw, fh); err != nil {
                return nil, err
        }
-
+       // If we're creating a directory, fw is nil.
        w.last = fw
-       return fw, nil
+       return ow, nil
 }
 
 func writeHeader(w io.Writer, h *FileHeader) error {
@@ -401,6 +410,12 @@ func (w *Writer) compressor(method uint16) Compressor {
        return comp
 }
 
+type dirWriter struct{}
+
+func (dirWriter) Write([]byte) (int, error) {
+       return 0, errors.New("zip: write to directory")
+}
+
 type fileWriter struct {
        *header
        zipw      io.Writer

diff --git a/src/archive/zip/writer_test.go b/src/archive/zip/writer_test.go
index 38f32296fa87d263cedfde48c1476e71e81c4bb4..271a36729cc0d03121c6857294dc531b13283aee 100644 (file)
--- a/src/archive/zip/writer_test.go
+++ b/src/archive/zip/writer_test.go
@@ -299,6 +299,17 @@ func TestWriterFlush(t *testing.T) {
        }
 }
 
+func TestWriterDir(t *testing.T) {
+       w := NewWriter(ioutil.Discard)
+       dw, err := w.Create("dir/")
+       if err != nil {
+               t.Fatal(err)
+       }
+       if _, err := dw.Write([]byte("hello")); err == nil {
+               t.Error("Write to directory: got nil error, want non-nil")
+       }
+}
+
 func testCreate(t *testing.T, w *Writer, wt *WriteTest) {
        header := &FileHeader{
                Name:   wt.Name,