From: Guillaume J. Charmes <guillaume@charmes.net>
Date: Wed, 14 May 2014 17:15:43 +0000 (-0700)
Subject: archive/tar: Fix bug preventing untar
X-Git-Tag: go1.3beta2~71
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=51f3cbabfc58c0db89b1142f94d794b59727f572;p=gostls13.git

archive/tar: Fix bug preventing untar

Do not use ustar format if we need the GNU one.
Change \000 to \x00 for consistency
Check for "ustar\x00" instead of "ustar\x00\x00" for conistency with tar
and compatiblity with archive generated with older code (which was ustar\x00\x20\x00)
Add test for long name + big file.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/99050043
---

diff --git a/src/pkg/archive/tar/reader.go b/src/pkg/archive/tar/reader.go
index d15e120792..e6ac538aad 100644
--- a/src/pkg/archive/tar/reader.go
+++ b/src/pkg/archive/tar/reader.go
@@ -468,14 +468,14 @@ func (tr *Reader) readHeader() *Header {
 	// so its magic bytes, like the rest of the block, are NULs.
 	magic := string(s.next(8)) // contains version field as well.
 	var format string
-	switch magic {
-	case "ustar\x0000": // POSIX tar (1003.1-1988)
+	switch {
+	case magic[:6] == "ustar\x00": // POSIX tar (1003.1-1988)
 		if string(header[508:512]) == "tar\x00" {
 			format = "star"
 		} else {
 			format = "posix"
 		}
-	case "ustar  \x00": // old GNU tar
+	case magic == "ustar  \x00": // old GNU tar
 		format = "gnu"
 	}
 
diff --git a/src/pkg/archive/tar/testdata/writer-big-long.tar b/src/pkg/archive/tar/testdata/writer-big-long.tar
new file mode 100644
index 0000000000..5960ee8247
Binary files /dev/null and b/src/pkg/archive/tar/testdata/writer-big-long.tar differ
diff --git a/src/pkg/archive/tar/writer.go b/src/pkg/archive/tar/writer.go
index 9ee9499297..6eff6f6f84 100644
--- a/src/pkg/archive/tar/writer.go
+++ b/src/pkg/archive/tar/writer.go
@@ -218,8 +218,8 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
 				tw.cString(prefixHeaderBytes, prefix, false, paxNone, nil)
 
 				// Use the ustar magic if we used ustar long names.
-				if len(prefix) > 0 {
-					copy(header[257:265], []byte("ustar\000"))
+				if len(prefix) > 0 && !tw.usedBinary {
+					copy(header[257:265], []byte("ustar\x00"))
 				}
 			}
 		}
diff --git a/src/pkg/archive/tar/writer_test.go b/src/pkg/archive/tar/writer_test.go
index 2b9ea658db..512fab1a6f 100644
--- a/src/pkg/archive/tar/writer_test.go
+++ b/src/pkg/archive/tar/writer_test.go
@@ -103,6 +103,29 @@ var writerTests = []*writerTest{
 			},
 		},
 	},
+	// The truncated test file was produced using these commands:
+	//   dd if=/dev/zero bs=1048576 count=16384 > (longname/)*15 /16gig.txt
+	//   tar -b 1 -c -f- (longname/)*15 /16gig.txt | dd bs=512 count=8 > writer-big-long.tar
+	{
+		file: "testdata/writer-big-long.tar",
+		entries: []*writerTestEntry{
+			{
+				header: &Header{
+					Name:     strings.Repeat("longname/", 15) + "16gig.txt",
+					Mode:     0644,
+					Uid:      1000,
+					Gid:      1000,
+					Size:     16 << 30,
+					ModTime:  time.Unix(1399583047, 0),
+					Typeflag: '0',
+					Uname:    "guillaume",
+					Gname:    "guillaume",
+				},
+				// fake contents
+				contents: strings.Repeat("\x00", 4<<10),
+			},
+		},
+	},
 	// This file was produced using gnu tar 1.17
 	// gnutar  -b 4 --format=ustar (longname/)*15 + file.txt
 	{