archive/tar: fix the archive/tar.Writer CVE

The remainder of:
golang/go@0bf7ee9

Reference from #76 (comment)

Signed-off-by: Vincent Batts <[email protected]>

Author: vbatts

archive/tar/reader_test.go

@@ -6,6 +6,7 @@ package tar
 
 import (
 	"bytes"
+	"compress/bzip2"
 	"crypto/md5"
 	"errors"
 	"fmt"
@@ -243,6 +244,9 @@ func TestReader(t *testing.T) {
 	}, {
 		file: "testdata/pax-bad-hdr-file.tar",
 		err:  ErrHeader,
+	}, {
+		file: "testdata/pax-bad-hdr-large.tar.bz2",
+		err:  ErrFieldTooLong,
 	}, {
 		file: "testdata/pax-bad-mtime-file.tar",
 		err:  ErrHeader,
@@ -625,9 +629,14 @@ func TestReader(t *testing.T) {
 			}
 			defer f.Close()
 
+			var fr io.Reader = f
+			if strings.HasSuffix(v.file, ".bz2") {
+				fr = bzip2.NewReader(fr)
+			}
+
 			// Capture all headers and checksums.
 			var (
-				tr      = NewReader(f)
+				tr      = NewReader(fr)
 				hdrs    []*Header
 				chksums []string
 				rdbuf   = make([]byte, 8)

archive/tar/testdata/pax-bad-hdr-large.tar.bz2

@@ -199,6 +199,9 @@ func (tw *Writer) writePAXHeader(hdr *Header, paxHdrs map[string]string) error {
 			flag = TypeXHeader
 		}
 		data := buf.String()
+		if len(data) > maxSpecialFileSize {
+			return ErrFieldTooLong
+		}
 		if err := tw.writeRawFile(name, data, flag, FormatPAX); err != nil || isGlobal {
 			return err // Global headers return here
 		}

archive/tar/writer.go

@@ -1006,6 +1006,33 @@ func TestIssue12594(t *testing.T) {
 	}
 }
 
+func TestWriteLongHeader(t *testing.T) {
+	for _, test := range []struct {
+		name string
+		h    *Header
+	}{{
+		name: "name too long",
+		h:    &Header{Name: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "linkname too long",
+		h:    &Header{Linkname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "uname too long",
+		h:    &Header{Uname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "gname too long",
+		h:    &Header{Gname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "PAX header too long",
+		h:    &Header{PAXRecords: map[string]string{"GOLANG.x": strings.Repeat("a", maxSpecialFileSize)}},
+	}} {
+		w := NewWriter(io.Discard)
+		if err := w.WriteHeader(test.h); err != ErrFieldTooLong {
+			t.Errorf("%v: w.WriteHeader() = %v, want ErrFieldTooLong", test.name, err)
+		}
+	}
+}
+
 // testNonEmptyWriter wraps an io.Writer and ensures that
 // Write is never called with an empty buffer.
 type testNonEmptyWriter struct{ io.Writer }