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archive/tar: centralize all information about tar header format

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The Reader and Writer have hard-coded constants regarding the
offsets and lengths of certain fields in the tar format sprinkled
all over. This makes it harder to verify that the offsets are
correct since a reviewer would need to search for them throughout
the code. Instead, all information about the layout of header
fields should be centralized in one single file. This has the
advantage of being both centralized, and also acting as a form
of documentation about the header struct format.

This method was chosen over using "encoding/binary" since that
method would cause an allocation of a header struct every time
binary.Read was called. This method causes zero allocations and
its logic is no longer than if structs were declared.

Updates #12594

Change-Id: Ic7a0565d2a2cd95d955547ace3b6dea2b57fab34
Reviewed-on: https://go-review.googlesource.com/14669
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Joe Tsai 2015-09-17 00:22:56 -07:00 committed by Brad Fitzpatrick
parent 88d3db0a5b
commit 30bfafc319
5 changed files with 312 additions and 207 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
src/archive/tar/common.go
View File

@ -21,10 +21,8 @@ import (
"time"
)
// Header type flags.
const (
blockSize = 512
// Types
TypeReg = '0' // regular file
TypeRegA = '\x00' // regular file
TypeLink = '1' // hard link
@ -61,12 +59,6 @@ type Header struct {
Xattrs map[string]string
}
// File name constants from the tar spec.
const (
fileNameSize = 100 // Maximum number of bytes in a standard tar name.
fileNamePrefixSize = 155 // Maximum number of ustar extension bytes.
)
// FileInfo returns an os.FileInfo for the Header.
func (h *Header) FileInfo() os.FileInfo {
return headerFileInfo{h}
@ -279,33 +271,6 @@ func FileInfoHeader(fi os.FileInfo, link string) (*Header, error) {
return h, nil
}
var zeroBlock = make([]byte, blockSize)
// POSIX specifies a sum of the unsigned byte values, but the Sun tar uses signed byte values.
// We compute and return both.
func checksum(header []byte) (unsigned int64, signed int64) {
for i := 0; i < len(header); i++ {
if i == 148 {
// The chksum field (header[148:156]) is special: it should be treated as space bytes.
unsigned += ' ' * 8
signed += ' ' * 8
i += 7
continue
}
unsigned += int64(header[i])
signed += int64(int8(header[i]))
}
return
}
type slicer []byte
func (sp *slicer) next(n int) (b []byte) {
s := *sp
b, *sp = s[0:n], s[n:]
return
}
func isASCII(s string) bool {
for _, c := range s {
if c >= 0x80 {

197
src/archive/tar/format.go Normal file
View File

@ -0,0 +1,197 @@
// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tar
// Constants to identify various tar formats.
const (
// The format is unknown.
formatUnknown = (1 << iota) / 2 // Sequence of 0, 1, 2, 4, 8, etc...
// The format of the original Unix V7 tar tool prior to standardization.
formatV7
// The old and new GNU formats, which are incompatible with USTAR.
// This does cover the old GNU sparse extension.
// This does not cover the GNU sparse extensions using PAX headers,
// versions 0.0, 0.1, and 1.0; these fall under the PAX format.
formatGNU
// Schily's tar format, which is incompatible with USTAR.
// This does not cover STAR extensions to the PAX format; these fall under
// the PAX format.
formatSTAR
// USTAR is the former standardization of tar defined in POSIX.1-1988.
// This is incompatible with the GNU and STAR formats.
formatUSTAR
// PAX is the latest standardization of tar defined in POSIX.1-2001.
// This is an extension of USTAR and is "backwards compatible" with it.
//
// Some newer formats add their own extensions to PAX, such as GNU sparse
// files and SCHILY extended attributes. Since they are backwards compatible
// with PAX, they will be labelled as "PAX".
formatPAX
)
// Magics used to identify various formats.
const (
magicGNU, versionGNU = "ustar ", " \x00"
magicUSTAR, versionUSTAR = "ustar\x00", "00"
trailerSTAR = "tar\x00"
)
// Size constants from various tar specifications.
const (
blockSize = 512 // Size of each block in a tar stream
nameSize = 100 // Max length of the name field in USTAR format
prefixSize = 155 // Max length of the prefix field in USTAR format
)
var zeroBlock block
type block [blockSize]byte
// Convert block to any number of formats.
func (b *block) V7() *headerV7 { return (*headerV7)(b) }
func (b *block) GNU() *headerGNU { return (*headerGNU)(b) }
func (b *block) STAR() *headerSTAR { return (*headerSTAR)(b) }
func (b *block) USTAR() *headerUSTAR { return (*headerUSTAR)(b) }
func (b *block) Sparse() sparseArray { return (sparseArray)(b[:]) }
// GetFormat checks that the block is a valid tar header based on the checksum.
// It then attempts to guess the specific format based on magic values.
// If the checksum fails, then formatUnknown is returned.
func (b *block) GetFormat() (format int) {
// Verify checksum.
var p parser
value := p.parseOctal(b.V7().Chksum())
chksum1, chksum2 := b.ComputeChecksum()
if p.err != nil || (value != chksum1 && value != chksum2) {
return formatUnknown
}
// Guess the magic values.
magic := string(b.USTAR().Magic())
version := string(b.USTAR().Version())
trailer := string(b.STAR().Trailer())
switch {
case magic == magicUSTAR && trailer == trailerSTAR:
return formatSTAR
case magic == magicUSTAR:
return formatUSTAR
case magic == magicGNU && version == versionGNU:
return formatGNU
default:
return formatV7
}
}
// SetFormat writes the magic values necessary for specified format
// and then updates the checksum accordingly.
func (b *block) SetFormat(format int) {
// Set the magic values.
switch format {
case formatV7:
// Do nothing.
case formatGNU:
copy(b.GNU().Magic(), magicGNU)
copy(b.GNU().Version(), versionGNU)
case formatSTAR:
copy(b.STAR().Magic(), magicUSTAR)
copy(b.STAR().Version(), versionUSTAR)
copy(b.STAR().Trailer(), trailerSTAR)
case formatUSTAR, formatPAX:
copy(b.USTAR().Magic(), magicUSTAR)
copy(b.USTAR().Version(), versionUSTAR)
default:
panic("invalid format")
}
// Update checksum.
// This field is special in that it is terminated by a NULL then space.
var f formatter
field := b.V7().Chksum()
chksum, _ := b.ComputeChecksum() // Possible values are 256..128776
f.formatOctal(field[:7], chksum) // Never fails since 128776 < 262143
field[7] = ' '
}
// ComputeChecksum computes the checksum for the header block.
// POSIX specifies a sum of the unsigned byte values, but the Sun tar used
// signed byte values.
// We compute and return both.
func (b *block) ComputeChecksum() (unsigned, signed int64) {
for i, c := range b {
if 148 <= i && i < 156 {
c = ' ' // Treat the checksum field itself as all spaces.
}
unsigned += int64(uint8(c))
signed += int64(int8(c))
}
return unsigned, signed
}
type headerV7 [blockSize]byte
func (h *headerV7) Name() []byte { return h[000:][:100] }
func (h *headerV7) Mode() []byte { return h[100:][:8] }
func (h *headerV7) UID() []byte { return h[108:][:8] }
func (h *headerV7) GID() []byte { return h[116:][:8] }
func (h *headerV7) Size() []byte { return h[124:][:12] }
func (h *headerV7) ModTime() []byte { return h[136:][:12] }
func (h *headerV7) Chksum() []byte { return h[148:][:8] }
func (h *headerV7) TypeFlag() []byte { return h[156:][:1] }
func (h *headerV7) LinkName() []byte { return h[157:][:100] }
type headerGNU [blockSize]byte
func (h *headerGNU) V7() *headerV7 { return (*headerV7)(h) }
func (h *headerGNU) Magic() []byte { return h[257:][:6] }
func (h *headerGNU) Version() []byte { return h[263:][:2] }
func (h *headerGNU) UserName() []byte { return h[265:][:32] }
func (h *headerGNU) GroupName() []byte { return h[297:][:32] }
func (h *headerGNU) DevMajor() []byte { return h[329:][:8] }
func (h *headerGNU) DevMinor() []byte { return h[337:][:8] }
func (h *headerGNU) AccessTime() []byte { return h[345:][:12] }
func (h *headerGNU) ChangeTime() []byte { return h[357:][:12] }
func (h *headerGNU) Sparse() sparseArray { return (sparseArray)(h[386:][:24*4+1]) }
func (h *headerGNU) RealSize() []byte { return h[483:][:12] }
type headerSTAR [blockSize]byte
func (h *headerSTAR) V7() *headerV7 { return (*headerV7)(h) }
func (h *headerSTAR) Magic() []byte { return h[257:][:6] }
func (h *headerSTAR) Version() []byte { return h[263:][:2] }
func (h *headerSTAR) UserName() []byte { return h[265:][:32] }
func (h *headerSTAR) GroupName() []byte { return h[297:][:32] }
func (h *headerSTAR) DevMajor() []byte { return h[329:][:8] }
func (h *headerSTAR) DevMinor() []byte { return h[337:][:8] }
func (h *headerSTAR) Prefix() []byte { return h[345:][:131] }
func (h *headerSTAR) AccessTime() []byte { return h[476:][:12] }
func (h *headerSTAR) ChangeTime() []byte { return h[488:][:12] }
func (h *headerSTAR) Trailer() []byte { return h[508:][:4] }
type headerUSTAR [blockSize]byte
func (h *headerUSTAR) V7() *headerV7 { return (*headerV7)(h) }
func (h *headerUSTAR) Magic() []byte { return h[257:][:6] }
func (h *headerUSTAR) Version() []byte { return h[263:][:2] }
func (h *headerUSTAR) UserName() []byte { return h[265:][:32] }
func (h *headerUSTAR) GroupName() []byte { return h[297:][:32] }
func (h *headerUSTAR) DevMajor() []byte { return h[329:][:8] }
func (h *headerUSTAR) DevMinor() []byte { return h[337:][:8] }
func (h *headerUSTAR) Prefix() []byte { return h[345:][:155] }
type sparseArray []byte
func (s sparseArray) Entry(i int) sparseNode { return (sparseNode)(s[i*24:]) }
func (s sparseArray) IsExtended() []byte { return s[24*s.MaxEntries():][:1] }
func (s sparseArray) MaxEntries() int { return len(s) / 24 }
type sparseNode []byte
func (s sparseNode) Offset() []byte { return s[00:][:12] }
func (s sparseNode) NumBytes() []byte { return s[12:][:12] }

165
src/archive/tar/reader.go
View File

@ -29,11 +29,11 @@ const maxNanoSecondIntSize = 9
// The Next method advances to the next file in the archive (including the first),
// and then it can be treated as an io.Reader to access the file's data.
type Reader struct {
r io.Reader
err error
pad int64 // amount of padding (ignored) after current file entry
curr numBytesReader // reader for current file entry
hdrBuff [blockSize]byte // buffer to use in readHeader
r io.Reader
err error
pad int64 // amount of padding (ignored) after current file entry
curr numBytesReader // reader for current file entry
blk block // buffer to use as temporary local storage
}
type parser struct {
@ -98,17 +98,6 @@ const (
paxGNUSparseRealSize = "GNU.sparse.realsize"
)
// Keywords for old GNU sparse headers
const (
oldGNUSparseMainHeaderOffset = 386
oldGNUSparseMainHeaderIsExtendedOffset = 482
oldGNUSparseMainHeaderNumEntries = 4
oldGNUSparseExtendedHeaderIsExtendedOffset = 504
oldGNUSparseExtendedHeaderNumEntries = 21
oldGNUSparseOffsetSize = 12
oldGNUSparseNumBytesSize = 12
)
// NewReader creates a new Reader reading from r.
func NewReader(r io.Reader) *Reader { return &Reader{r: r} }
@ -542,17 +531,6 @@ func (tr *Reader) skipUnread() error {
return tr.err
}
func (tr *Reader) verifyChecksum(header []byte) bool {
if tr.err != nil {
return false
}
var p parser
given := p.parseOctal(header[148:156])
unsigned, signed := checksum(header)
return p.err == nil && (given == unsigned || given == signed)
}
// readHeader reads the next block header and assumes that the underlying reader
// is already aligned to a block boundary.
//
@ -561,19 +539,16 @@ func (tr *Reader) verifyChecksum(header []byte) bool {
// * Exactly 1 block of zeros is read and EOF is hit.
// * At least 2 blocks of zeros are read.
func (tr *Reader) readHeader() *Header {
header := tr.hdrBuff[:]
copy(header, zeroBlock)
if _, tr.err = io.ReadFull(tr.r, header); tr.err != nil {
if _, tr.err = io.ReadFull(tr.r, tr.blk[:]); tr.err != nil {
return nil // io.EOF is okay here
}
// Two blocks of zero bytes marks the end of the archive.
if bytes.Equal(header, zeroBlock[0:blockSize]) {
if _, tr.err = io.ReadFull(tr.r, header); tr.err != nil {
if bytes.Equal(tr.blk[:], zeroBlock[:]) {
if _, tr.err = io.ReadFull(tr.r, tr.blk[:]); tr.err != nil {
return nil // io.EOF is okay here
}
if bytes.Equal(header, zeroBlock[0:blockSize]) {
if bytes.Equal(tr.blk[:], zeroBlock[:]) {
tr.err = io.EOF
} else {
tr.err = ErrHeader // zero block and then non-zero block
@ -581,71 +556,55 @@ func (tr *Reader) readHeader() *Header {
return nil
}
if !tr.verifyChecksum(header) {
// Verify the header matches a known format.
format := tr.blk.GetFormat()
if format == formatUnknown {
tr.err = ErrHeader
return nil
}
// Unpack
var p parser
hdr := new(Header)
s := slicer(header)
hdr.Name = p.parseString(s.next(100))
hdr.Mode = p.parseNumeric(s.next(8))
hdr.Uid = int(p.parseNumeric(s.next(8)))
hdr.Gid = int(p.parseNumeric(s.next(8)))
hdr.Size = p.parseNumeric(s.next(12))
hdr.ModTime = time.Unix(p.parseNumeric(s.next(12)), 0)
s.next(8) // chksum
hdr.Typeflag = s.next(1)[0]
hdr.Linkname = p.parseString(s.next(100))
// Unpack the V7 header.
v7 := tr.blk.V7()
hdr.Name = p.parseString(v7.Name())
hdr.Mode = p.parseNumeric(v7.Mode())
hdr.Uid = int(p.parseNumeric(v7.UID()))
hdr.Gid = int(p.parseNumeric(v7.GID()))
hdr.Size = p.parseNumeric(v7.Size())
hdr.ModTime = time.Unix(p.parseNumeric(v7.ModTime()), 0)
hdr.Typeflag = v7.TypeFlag()[0]
hdr.Linkname = p.parseString(v7.LinkName())
// The remainder of the header depends on the value of magic.
// The original (v7) version of tar had no explicit magic field,
// 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 {
case magic[:6] == "ustar\x00": // POSIX tar (1003.1-1988)
if string(header[508:512]) == "tar\x00" {
format = "star"
} else {
format = "posix"
}
case magic == "ustar \x00": // old GNU tar
format = "gnu"
}
switch format {
case "posix", "gnu", "star":
hdr.Uname = p.parseString(s.next(32))
hdr.Gname = p.parseString(s.next(32))
devmajor := s.next(8)
devminor := s.next(8)
// Unpack format specific fields.
if format > formatV7 {
ustar := tr.blk.USTAR()
hdr.Uname = p.parseString(ustar.UserName())
hdr.Gname = p.parseString(ustar.GroupName())
if hdr.Typeflag == TypeChar || hdr.Typeflag == TypeBlock {
hdr.Devmajor = p.parseNumeric(devmajor)
hdr.Devminor = p.parseNumeric(devminor)
hdr.Devmajor = p.parseNumeric(ustar.DevMajor())
hdr.Devminor = p.parseNumeric(ustar.DevMinor())
}
var prefix string
switch format {
case "posix", "gnu":
prefix = p.parseString(s.next(155))
case "star":
prefix = p.parseString(s.next(131))
hdr.AccessTime = time.Unix(p.parseNumeric(s.next(12)), 0)
hdr.ChangeTime = time.Unix(p.parseNumeric(s.next(12)), 0)
case formatUSTAR, formatGNU:
// TODO(dsnet): Do not use the prefix field for the GNU format!
// See golang.org/issues/12594
ustar := tr.blk.USTAR()
prefix = p.parseString(ustar.Prefix())
case formatSTAR:
star := tr.blk.STAR()
prefix = p.parseString(star.Prefix())
hdr.AccessTime = time.Unix(p.parseNumeric(star.AccessTime()), 0)
hdr.ChangeTime = time.Unix(p.parseNumeric(star.ChangeTime()), 0)
}
if len(prefix) > 0 {
hdr.Name = prefix + "/" + hdr.Name
}
}
if p.err != nil {
tr.err = p.err
return nil
}
nb := hdr.Size
if isHeaderOnlyType(hdr.Typeflag) {
nb = 0
@ -662,14 +621,14 @@ func (tr *Reader) readHeader() *Header {
// Check for old GNU sparse format entry.
if hdr.Typeflag == TypeGNUSparse {
// Get the real size of the file.
hdr.Size = p.parseNumeric(header[483:495])
hdr.Size = p.parseNumeric(tr.blk.GNU().RealSize())
if p.err != nil {
tr.err = p.err
return nil
}
// Read the sparse map.
sp := tr.readOldGNUSparseMap(header)
sp := tr.readOldGNUSparseMap(&tr.blk)
if tr.err != nil {
return nil
}
@ -681,26 +640,24 @@ func (tr *Reader) readHeader() *Header {
}
}
if p.err != nil {
tr.err = p.err
return nil
}
return hdr
}
// readOldGNUSparseMap reads the sparse map as stored in the old GNU sparse format.
// The sparse map is stored in the tar header if it's small enough. If it's larger than four entries,
// then one or more extension headers are used to store the rest of the sparse map.
func (tr *Reader) readOldGNUSparseMap(header []byte) []sparseEntry {
func (tr *Reader) readOldGNUSparseMap(blk *block) []sparseEntry {
var p parser
isExtended := header[oldGNUSparseMainHeaderIsExtendedOffset] != 0
spCap := oldGNUSparseMainHeaderNumEntries
if isExtended {
spCap += oldGNUSparseExtendedHeaderNumEntries
}
sp := make([]sparseEntry, 0, spCap)
s := slicer(header[oldGNUSparseMainHeaderOffset:])
// Read the four entries from the main tar header
for i := 0; i < oldGNUSparseMainHeaderNumEntries; i++ {
offset := p.parseNumeric(s.next(oldGNUSparseOffsetSize))
numBytes := p.parseNumeric(s.next(oldGNUSparseNumBytesSize))
var s sparseArray = blk.GNU().Sparse()
var sp = make([]sparseEntry, 0, s.MaxEntries())
for i := 0; i < s.MaxEntries(); i++ {
offset := p.parseOctal(s.Entry(i).Offset())
numBytes := p.parseOctal(s.Entry(i).NumBytes())
if p.err != nil {
tr.err = p.err
return nil
@ -711,17 +668,17 @@ func (tr *Reader) readOldGNUSparseMap(header []byte) []sparseEntry {
sp = append(sp, sparseEntry{offset: offset, numBytes: numBytes})
}
for isExtended {
for s.IsExtended()[0] > 0 {
// There are more entries. Read an extension header and parse its entries.
sparseHeader := make([]byte, blockSize)
if _, tr.err = io.ReadFull(tr.r, sparseHeader); tr.err != nil {
var blk block
if _, tr.err = io.ReadFull(tr.r, blk[:]); tr.err != nil {
return nil
}
isExtended = sparseHeader[oldGNUSparseExtendedHeaderIsExtendedOffset] != 0
s = slicer(sparseHeader)
for i := 0; i < oldGNUSparseExtendedHeaderNumEntries; i++ {
offset := p.parseNumeric(s.next(oldGNUSparseOffsetSize))
numBytes := p.parseNumeric(s.next(oldGNUSparseNumBytesSize))
s = blk.Sparse()
for i := 0; i < s.MaxEntries(); i++ {
offset := p.parseOctal(s.Entry(i).Offset())
numBytes := p.parseOctal(s.Entry(i).NumBytes())
if p.err != nil {
tr.err = p.err
return nil

98
src/archive/tar/writer.go
View File

@ -36,10 +36,10 @@ type Writer struct {
nb int64 // number of unwritten bytes for current file entry
pad int64 // amount of padding to write after current file entry
closed bool
usedBinary bool // whether the binary numeric field extension was used
preferPax bool // use pax header instead of binary numeric header
hdrBuff [blockSize]byte // buffer to use in writeHeader when writing a regular header
paxHdrBuff [blockSize]byte // buffer to use in writeHeader when writing a pax header
usedBinary bool // whether the binary numeric field extension was used
preferPax bool // use PAX header instead of binary numeric header
hdrBuff block // buffer to use in writeHeader when writing a regular header
paxHdrBuff block // buffer to use in writeHeader when writing a PAX header
}
type formatter struct {
@ -153,27 +153,24 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
// a map to hold pax header records, if any are needed
paxHeaders := make(map[string]string)
// TODO(shanemhansen): we might want to use PAX headers for
// TODO(dsnet): we might want to use PAX headers for
// subsecond time resolution, but for now let's just capture
// too long fields or non ascii characters
var f formatter
var header []byte
// We need to select which scratch buffer to use carefully,
// since this method is called recursively to write PAX headers.
// If allowPax is true, this is the non-recursive call, and we will use hdrBuff.
// If allowPax is false, we are being called by writePAXHeader, and hdrBuff is
// already being used by the non-recursive call, so we must use paxHdrBuff.
header = tw.hdrBuff[:]
header := &tw.hdrBuff
if !allowPax {
header = tw.paxHdrBuff[:]
header = &tw.paxHdrBuff
}
copy(header, zeroBlock)
s := slicer(header)
copy(header[:], zeroBlock[:])
// Wrappers around formatter that automatically sets paxHeaders if the
// argument extends beyond the capacity of the input byte slice.
var f formatter
var formatString = func(b []byte, s string, paxKeyword string) {
needsPaxHeader := paxKeyword != paxNone && len(s) > len(b) || !isASCII(s)
if needsPaxHeader {
@ -202,44 +199,33 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
f.formatNumeric(b, x)
}
// keep a reference to the filename to allow to overwrite it later if we detect that we can use ustar longnames instead of pax
pathHeaderBytes := s.next(fileNameSize)
formatString(pathHeaderBytes, hdr.Name, paxPath)
// Handle out of range ModTime carefully.
var modTime int64
if !hdr.ModTime.Before(minTime) && !hdr.ModTime.After(maxTime) {
modTime = hdr.ModTime.Unix()
}
f.formatOctal(s.next(8), hdr.Mode) // 100:108
formatNumeric(s.next(8), int64(hdr.Uid), paxUid) // 108:116
formatNumeric(s.next(8), int64(hdr.Gid), paxGid) // 116:124
formatNumeric(s.next(12), hdr.Size, paxSize) // 124:136
formatNumeric(s.next(12), modTime, paxNone) // 136:148 --- consider using pax for finer granularity
s.next(8) // chksum (148:156)
s.next(1)[0] = hdr.Typeflag // 156:157
v7 := header.V7()
formatString(v7.Name(), hdr.Name, paxPath)
// TODO(dsnet): The GNU format permits the mode field to be encoded in
// base-256 format. Thus, we can use formatNumeric instead of formatOctal.
f.formatOctal(v7.Mode(), hdr.Mode)
formatNumeric(v7.UID(), int64(hdr.Uid), paxUid)
formatNumeric(v7.GID(), int64(hdr.Gid), paxGid)
formatNumeric(v7.Size(), hdr.Size, paxSize)
// TODO(dsnet): Consider using PAX for finer time granularity.
formatNumeric(v7.ModTime(), modTime, paxNone)
v7.TypeFlag()[0] = hdr.Typeflag
formatString(v7.LinkName(), hdr.Linkname, paxLinkpath)
formatString(s.next(100), hdr.Linkname, paxLinkpath)
ustar := header.USTAR()
formatString(ustar.UserName(), hdr.Uname, paxUname)
formatString(ustar.GroupName(), hdr.Gname, paxGname)
formatNumeric(ustar.DevMajor(), hdr.Devmajor, paxNone)
formatNumeric(ustar.DevMinor(), hdr.Devminor, paxNone)
copy(s.next(8), []byte("ustar\x0000")) // 257:265
formatString(s.next(32), hdr.Uname, paxUname) // 265:297
formatString(s.next(32), hdr.Gname, paxGname) // 297:329
formatNumeric(s.next(8), hdr.Devmajor, paxNone) // 329:337
formatNumeric(s.next(8), hdr.Devminor, paxNone) // 337:345
// keep a reference to the prefix to allow to overwrite it later if we detect that we can use ustar longnames instead of pax
prefixHeaderBytes := s.next(155)
formatString(prefixHeaderBytes, "", paxNone) // 345:500 prefix
// Use the GNU magic instead of POSIX magic if we used any GNU extensions.
if tw.usedBinary {
copy(header[257:265], []byte("ustar \x00"))
}
_, paxPathUsed := paxHeaders[paxPath]
// try to use a ustar header when only the name is too long
_, paxPathUsed := paxHeaders[paxPath]
if !tw.preferPax && len(paxHeaders) == 1 && paxPathUsed {
prefix, suffix, ok := splitUSTARPath(hdr.Name)
if ok {
@ -247,16 +233,16 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
delete(paxHeaders, paxPath)
// Update the path fields
formatString(pathHeaderBytes, suffix, paxNone)
formatString(prefixHeaderBytes, prefix, paxNone)
formatString(v7.Name(), suffix, paxNone)
formatString(ustar.Prefix(), prefix, paxNone)
}
}
// The chksum field is terminated by a NUL and a space.
// This is different from the other octal fields.
chksum, _ := checksum(header)
f.formatOctal(header[148:155], chksum) // Never fails
header[155] = ' '
if tw.usedBinary {
header.SetFormat(formatGNU)
} else {
header.SetFormat(formatUSTAR)
}
// Check if there were any formatting errors.
if f.err != nil {
@ -281,7 +267,7 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
tw.nb = hdr.Size
tw.pad = (blockSize - (tw.nb % blockSize)) % blockSize
_, tw.err = tw.w.Write(header)
_, tw.err = tw.w.Write(header[:])
return tw.err
}
@ -289,10 +275,10 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
// If the path is not splittable, then it will return ("", "", false).
func splitUSTARPath(name string) (prefix, suffix string, ok bool) {
length := len(name)
if length <= fileNameSize || !isASCII(name) {
if length <= nameSize || !isASCII(name) {
return "", "", false
} else if length > fileNamePrefixSize+1 {
length = fileNamePrefixSize + 1
} else if length > prefixSize+1 {
length = prefixSize + 1
} else if name[length-1] == '/' {
length--
}
@ -300,7 +286,7 @@ func splitUSTARPath(name string) (prefix, suffix string, ok bool) {
i := strings.LastIndex(name[:length], "/")
nlen := len(name) - i - 1 // nlen is length of suffix
plen := i // plen is length of prefix
if i <= 0 || nlen > fileNameSize || nlen == 0 || plen > fileNamePrefixSize {
if i <= 0 || nlen > nameSize || nlen == 0 || plen > prefixSize {
return "", "", false
}
return name[:i], name[i+1:], true
@ -323,8 +309,8 @@ func (tw *Writer) writePAXHeader(hdr *Header, paxHeaders map[string]string) erro
fullName := path.Join(dir, "PaxHeaders.0", file)
ascii := toASCII(fullName)
if len(ascii) > 100 {
ascii = ascii[:100]
if len(ascii) > nameSize {
ascii = ascii[:nameSize]
}
ext.Name = ascii
// Construct the body
@ -407,7 +393,7 @@ func (tw *Writer) Close() error {
// trailer: two zero blocks
for i := 0; i < 2; i++ {
_, tw.err = tw.w.Write(zeroBlock)
_, tw.err = tw.w.Write(zeroBlock[:])
if tw.err != nil {
break
}

22
src/archive/tar/writer_test.go
View File

@ -587,17 +587,17 @@ func TestSplitUSTARPath(t *testing.T) {
{"", "", "", false},
{"abc", "", "", false},
{"用戶名", "", "", false},
{sr("a", fileNameSize), "", "", false},
{sr("a", fileNameSize) + "/", "", "", false},
{sr("a", fileNameSize) + "/a", sr("a", fileNameSize), "a", true},
{sr("a", fileNamePrefixSize) + "/", "", "", false},
{sr("a", fileNamePrefixSize) + "/a", sr("a", fileNamePrefixSize), "a", true},
{sr("a", fileNameSize+1), "", "", false},
{sr("/", fileNameSize+1), sr("/", fileNameSize-1), "/", true},
{sr("a", fileNamePrefixSize) + "/" + sr("b", fileNameSize),
sr("a", fileNamePrefixSize), sr("b", fileNameSize), true},
{sr("a", fileNamePrefixSize) + "//" + sr("b", fileNameSize), "", "", false},
{sr("a/", fileNameSize), sr("a/", 77) + "a", sr("a/", 22), true},
{sr("a", nameSize), "", "", false},
{sr("a", nameSize) + "/", "", "", false},
{sr("a", nameSize) + "/a", sr("a", nameSize), "a", true},
{sr("a", prefixSize) + "/", "", "", false},
{sr("a", prefixSize) + "/a", sr("a", prefixSize), "a", true},
{sr("a", nameSize+1), "", "", false},
{sr("/", nameSize+1), sr("/", nameSize-1), "/", true},
{sr("a", prefixSize) + "/" + sr("b", nameSize),
sr("a", prefixSize), sr("b", nameSize), true},
{sr("a", prefixSize) + "//" + sr("b", nameSize), "", "", false},
{sr("a/", nameSize), sr("a/", 77) + "a", sr("a/", 22), true},
}
for _, v := range vectors {