archive/zip: only use Extended Timestamp on non-zero MS-DOS timestamps

We should preserve the fact that a roundtrip read on fields with the zero
value should remain the zero for those that are reasonable to stay that way.
If the zero value for a MS-DOS timestamp was used, then it is sensible for
that zero value to also be read back later.

Fixes #17403

Change-Id: I32c3915eab180e91ddd2499007374f7b85f0bd76
Reviewed-on: https://go-review.googlesource.com/30811
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/archive/zip/struct.go b/src/archive/zip/struct.go
index 8e6eb840f949fe7a757f82bbcb1eed805fa8b4fd..287571ed3aa09da158b9c4ec394e78fefad1c650 100644 (file)
--- a/src/archive/zip/struct.go
+++ b/src/archive/zip/struct.go
@@ -65,7 +65,7 @@ const (
        zip64ExtraId = 0x0001 // zip64 Extended Information Extra Field
        ntfsExtraId  = 0x000a // NTFS Extra Field
        unixExtraId  = 0x000d // UNIX Extra Field
-       exttsExtraId = 0x5455 // Extra Timestamp Extra Field
+       exttsExtraId = 0x5455 // Extended Timestamp Extra Field
 )
 
 // FileHeader describes a file within a zip file.

diff --git a/src/archive/zip/writer.go b/src/archive/zip/writer.go
index 2a747b8f37e542ad3d6439fb190832efae09f62d..4ab993d9497c31268330ed533e3622dd46d90122 100644 (file)
--- a/src/archive/zip/writer.go
+++ b/src/archive/zip/writer.go
@@ -99,14 +99,17 @@ func (w *Writer) Close() error {
                        b.uint32(h.UncompressedSize)
                }
 
-               mt := uint32(h.FileHeader.ModTime().Unix())
-               var mbuf [9]byte // 2x uint16 + uint8 + uint32
-               eb := writeBuf(mbuf[:])
-               eb.uint16(exttsExtraId)
-               eb.uint16(5)  // size = uint8 + uint32
-               eb.uint8(1)   // flags = modtime
-               eb.uint32(mt) // ModTime
-               h.Extra = append(h.Extra, mbuf[:]...)
+               // use Extended Timestamp Extra Field.
+               if h.ModifiedTime != 0 || h.ModifiedDate != 0 {
+                       mt := uint32(h.ModTime().Unix())
+                       var mbuf [9]byte // 2x uint16 + uint8 + uint32
+                       eb := writeBuf(mbuf[:])
+                       eb.uint16(exttsExtraId)
+                       eb.uint16(5)  // size = uint8 + uint32
+                       eb.uint8(1)   // flags = modtime
+                       eb.uint32(mt) // ModTime
+                       h.Extra = append(h.Extra, mbuf[:]...)
+               }
 
                b.uint16(uint16(len(h.Name)))
                b.uint16(uint16(len(h.Extra)))

diff --git a/src/archive/zip/zip_test.go b/src/archive/zip/zip_test.go
index 3a3c915d34e0a07f63e95550bad6b979eb205f00..f166b76e3f97590ede186515751579875628abcb 100644 (file)
--- a/src/archive/zip/zip_test.go
+++ b/src/archive/zip/zip_test.go
@@ -13,6 +13,7 @@ import (
        "internal/testenv"
        "io"
        "io/ioutil"
+       "reflect"
        "sort"
        "strings"
        "testing"
@@ -111,6 +112,44 @@ func TestFileHeaderRoundTrip64(t *testing.T) {
        testHeaderRoundTrip(fh, uint32max, fh.UncompressedSize64, t)
 }
 
+func TestZeroFileRoundTrip(t *testing.T) {
+       var b bytes.Buffer
+       w := NewWriter(&b)
+       if _, err := w.Create(""); err != nil {
+               t.Fatal(err)
+       }
+       if err := w.Close(); err != nil {
+               t.Fatal(err)
+       }
+       r, err := NewReader(bytes.NewReader(b.Bytes()), int64(b.Len()))
+       if err != nil {
+               t.Fatal(err)
+       }
+
+       // Verify that fields that should reasonably be the zero value stays
+       // as the zero value.
+       var want FileHeader
+       if len(r.File) != 1 {
+               t.Fatalf("len(r.File) = %d, want 1", len(r.File))
+       }
+       fh := r.File[0].FileHeader
+       got := FileHeader{
+               Name:               fh.Name,
+               ModifiedTime:       fh.ModifiedTime,
+               ModifiedDate:       fh.ModifiedDate,
+               UncompressedSize:   fh.UncompressedSize,
+               UncompressedSize64: fh.UncompressedSize64,
+               ExternalAttrs:      fh.ExternalAttrs,
+               Comment:            fh.Comment,
+       }
+       if len(fh.Extra) > 0 {
+               got.Extra = fh.Extra
+       }
+       if !reflect.DeepEqual(got, want) {
+               t.Errorf("FileHeader mismatch:\ngot  %#v\nwant %#v", got, want)
+       }
+}
+
 type repeatedByte struct {
        off int64
        b   byte