archive/tar: avoid writing ModTime that is out of range.

Update #4358
Still to do: support binary numeric format in Reader.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6818101

diff --git a/src/pkg/archive/tar/tar_test.go b/src/pkg/archive/tar/tar_test.go
index 0adc17900339c90fddadb865c3c89f5fc832bad3..a509f3c00af92d791ef1f89c08c3c35d6e6b3366 100644 (file)
--- a/src/pkg/archive/tar/tar_test.go
+++ b/src/pkg/archive/tar/tar_test.go
@@ -5,7 +5,10 @@
 package tar
 
 import (
+       "bytes"
+       "io/ioutil"
        "os"
+       "reflect"
        "testing"
        "time"
 )
@@ -54,3 +57,43 @@ func (symlink) Mode() os.FileMode  { return os.ModeSymlink }
 func (symlink) ModTime() time.Time { return time.Time{} }
 func (symlink) IsDir() bool        { return false }
 func (symlink) Sys() interface{}   { return nil }
+
+func TestRoundTrip(t *testing.T) {
+       data := []byte("some file contents")
+
+       var b bytes.Buffer
+       tw := NewWriter(&b)
+       hdr := &Header{
+               Name:    "file.txt",
+               Size:    int64(len(data)),
+               ModTime: time.Now(),
+       }
+       // tar only supports second precision.
+       hdr.ModTime = hdr.ModTime.Add(-time.Duration(hdr.ModTime.Nanosecond()) * time.Nanosecond)
+       if err := tw.WriteHeader(hdr); err != nil {
+               t.Fatalf("tw.WriteHeader: %v", err)
+       }
+       if _, err := tw.Write(data); err != nil {
+               t.Fatalf("tw.Write: %v", err)
+       }
+       if err := tw.Close(); err != nil {
+               t.Fatalf("tw.Close: %v", err)
+       }
+
+       // Read it back.
+       tr := NewReader(&b)
+       rHdr, err := tr.Next()
+       if err != nil {
+               t.Fatalf("tr.Next: %v", err)
+       }
+       if !reflect.DeepEqual(rHdr, hdr) {
+               t.Errorf("Header mismatch.\n got %+v\nwant %+v", rHdr, hdr)
+       }
+       rData, err := ioutil.ReadAll(tr)
+       if err != nil {
+               t.Fatalf("Read: %v", err)
+       }
+       if !bytes.Equal(rData, data) {
+               t.Errorf("Data mismatch.\n got %q\nwant %q", rData, data)
+       }
+}

diff --git a/src/pkg/archive/tar/writer.go b/src/pkg/archive/tar/writer.go
index a9c8fdbbc9ae26f2ac5ba6adf5af822ff287b544..5af504b437d0af0e94495911dd791ba048455174 100644 (file)
--- a/src/pkg/archive/tar/writer.go
+++ b/src/pkg/archive/tar/writer.go
@@ -12,6 +12,7 @@ import (
        "fmt"
        "io"
        "strconv"
+       "time"
 )
 
 var (
@@ -110,6 +111,12 @@ func (tw *Writer) numeric(b []byte, x int64) {
        b[0] |= 0x80 // highest bit indicates binary format
 }
 
+var (
+       minTime = time.Unix(0, 0)
+       // There is room for 11 octal digits (33 bits) of mtime.
+       maxTime = minTime.Add((1<<33 - 1) * time.Second)
+)
+
 // WriteHeader writes hdr and prepares to accept the file's contents.
 // WriteHeader calls Flush if it is not the first header.
 // Calling after a Close will return ErrWriteAfterClose.
@@ -133,19 +140,25 @@ func (tw *Writer) WriteHeader(hdr *Header) error {
        // TODO(dsymonds): handle names longer than 100 chars
        copy(s.next(100), []byte(hdr.Name))
 
-       tw.octal(s.next(8), hdr.Mode)              // 100:108
-       tw.numeric(s.next(8), int64(hdr.Uid))      // 108:116
-       tw.numeric(s.next(8), int64(hdr.Gid))      // 116:124
-       tw.numeric(s.next(12), hdr.Size)           // 124:136
-       tw.numeric(s.next(12), hdr.ModTime.Unix()) // 136:148
-       s.next(8)                                  // chksum (148:156)
-       s.next(1)[0] = hdr.Typeflag                // 156:157
-       tw.cString(s.next(100), hdr.Linkname)      // linkname (157:257)
-       copy(s.next(8), []byte("ustar\x0000"))     // 257:265
-       tw.cString(s.next(32), hdr.Uname)          // 265:297
-       tw.cString(s.next(32), hdr.Gname)          // 297:329
-       tw.numeric(s.next(8), hdr.Devmajor)        // 329:337
-       tw.numeric(s.next(8), hdr.Devminor)        // 337:345
+       // Handle out of range ModTime carefully.
+       var modTime int64
+       if !hdr.ModTime.Before(minTime) && !hdr.ModTime.After(maxTime) {
+               modTime = hdr.ModTime.Unix()
+       }
+
+       tw.octal(s.next(8), hdr.Mode)          // 100:108
+       tw.numeric(s.next(8), int64(hdr.Uid))  // 108:116
+       tw.numeric(s.next(8), int64(hdr.Gid))  // 116:124
+       tw.numeric(s.next(12), hdr.Size)       // 124:136
+       tw.numeric(s.next(12), modTime)        // 136:148
+       s.next(8)                              // chksum (148:156)
+       s.next(1)[0] = hdr.Typeflag            // 156:157
+       tw.cString(s.next(100), hdr.Linkname)  // linkname (157:257)
+       copy(s.next(8), []byte("ustar\x0000")) // 257:265
+       tw.cString(s.next(32), hdr.Uname)      // 265:297
+       tw.cString(s.next(32), hdr.Gname)      // 297:329
+       tw.numeric(s.next(8), hdr.Devmajor)    // 329:337
+       tw.numeric(s.next(8), hdr.Devminor)    // 337:345
 
        // Use the GNU magic instead of POSIX magic if we used any GNU extensions.
        if tw.usedBinary {