archive/zip: only preallocate File slice if reasonably sized
Since the number of files in the EOCD record isn't validated, it isn't
safe to preallocate Reader.Files using that field. A malformed archive
can indicate it contains up to 1 << 128 - 1 files. We can still safely
preallocate the slice by checking if the specified number of files in
the archive is reasonable, given the size of the archive.
Thanks to the OSS-Fuzz project for discovering this issue and to
Emmanuel Odeke for reporting it.
Fixes #46242
Fixes CVE-2021-33196
Change-Id: I3c76d8eec178468b380d87fdb4a3f2cb06f0ee76
Reviewed-on: https://go-review.googlesource.com/c/go/+/318909
Trust: Roland Shoemaker <roland@golang.org>
Trust: Katie Hockman <katie@golang.org>
Trust: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/src/archive/zip/reader.go b/src/archive/zip/reader.go
index 808cf27..2d53f4c 100644
--- a/src/archive/zip/reader.go
+++ b/src/archive/zip/reader.go
@@ -96,7 +96,15 @@
return err
}
z.r = r
- z.File = make([]*File, 0, end.directoryRecords)
+ // Since the number of directory records is not validated, it is not
+ // safe to preallocate z.File without first checking that the specified
+ // number of files is reasonable, since a malformed archive may
+ // indicate it contains up to 1 << 128 - 1 files. Since each file has a
+ // header which will be _at least_ 30 bytes we can safely preallocate
+ // if (data size / 30) >= end.directoryRecords.
+ if (uint64(size)-end.directorySize)/30 >= end.directoryRecords {
+ z.File = make([]*File, 0, end.directoryRecords)
+ }
z.Comment = end.comment
rs := io.NewSectionReader(r, 0, size)
if _, err = rs.Seek(int64(end.directoryOffset), io.SeekStart); err != nil {
diff --git a/src/archive/zip/reader_test.go b/src/archive/zip/reader_test.go
index 35e681e..37dafe6 100644
--- a/src/archive/zip/reader_test.go
+++ b/src/archive/zip/reader_test.go
@@ -1325,3 +1325,62 @@
})
}
}
+
+func TestCVE202133196(t *testing.T) {
+ // Archive that indicates it has 1 << 128 -1 files,
+ // this would previously cause a panic due to attempting
+ // to allocate a slice with 1 << 128 -1 elements.
+ data := []byte{
+ 0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x08, 0x08,
+ 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x02,
+ 0x03, 0x62, 0x61, 0x65, 0x03, 0x04, 0x00, 0x00,
+ 0xff, 0xff, 0x50, 0x4b, 0x07, 0x08, 0xbe, 0x20,
+ 0x5c, 0x6c, 0x09, 0x00, 0x00, 0x00, 0x03, 0x00,
+ 0x00, 0x00, 0x50, 0x4b, 0x01, 0x02, 0x14, 0x00,
+ 0x14, 0x00, 0x08, 0x08, 0x08, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0xbe, 0x20, 0x5c, 0x6c, 0x09, 0x00,
+ 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x03, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x01, 0x02, 0x03, 0x50, 0x4b, 0x06, 0x06, 0x2c,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2d,
+ 0x00, 0x2d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff,
+ 0xff, 0xff, 0xff, 0x31, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x3a, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x50, 0x4b, 0x06, 0x07, 0x00,
+ 0x00, 0x00, 0x00, 0x6b, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x50,
+ 0x4b, 0x05, 0x06, 0x00, 0x00, 0x00, 0x00, 0xff,
+ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+ 0xff, 0xff, 0xff, 0x00, 0x00,
+ }
+ _, err := NewReader(bytes.NewReader(data), int64(len(data)))
+ if err != ErrFormat {
+ t.Fatalf("unexpected error, got: %v, want: %v", err, ErrFormat)
+ }
+
+ // Also check that an archive containing a handful of empty
+ // files doesn't cause an issue
+ b := bytes.NewBuffer(nil)
+ w := NewWriter(b)
+ for i := 0; i < 5; i++ {
+ _, err := w.Create("")
+ if err != nil {
+ t.Fatalf("Writer.Create failed: %s", err)
+ }
+ }
+ if err := w.Close(); err != nil {
+ t.Fatalf("Writer.Close failed: %s", err)
+ }
+ r, err := NewReader(bytes.NewReader(b.Bytes()), int64(b.Len()))
+ if err != nil {
+ t.Fatalf("NewReader failed: %s", err)
+ }
+ if len(r.File) != 5 {
+ t.Errorf("Archive has unexpected number of files, got %d, want 5", len(r.File))
+ }
+}
