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tar-split/archive/tar/reader.go
Derek McGowan 6b59e6942e archive/tar: fix writing too many raw bytes
When an EOF is read, only the part of the header buffer which
was read should be accounted for.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>
2016-09-26 14:01:48 -07:00

1064 lines
30 KiB
Go

// Copyright 2009 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
// TODO(dsymonds):
// - pax extensions
import (
"bytes"
"errors"
"io"
"io/ioutil"
"math"
"os"
"strconv"
"strings"
"time"
)
var (
ErrHeader = errors.New("archive/tar: invalid tar header")
)
const maxNanoSecondIntSize = 9
// A Reader provides sequential access to the contents of a tar archive.
// A tar archive consists of a sequence of files.
// 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
RawAccounting bool // Whether to enable the access needed to reassemble the tar from raw bytes. Some performance/memory hit for this.
rawBytes *bytes.Buffer // last raw bits
}
type parser struct {
err error // Last error seen
}
// RawBytes accesses the raw bytes of the archive, apart from the file payload itself.
// This includes the header and padding.
//
// This call resets the current rawbytes buffer
//
// Only when RawAccounting is enabled, otherwise this returns nil
func (tr *Reader) RawBytes() []byte {
if !tr.RawAccounting {
return nil
}
if tr.rawBytes == nil {
tr.rawBytes = bytes.NewBuffer(nil)
}
// if we've read them, then flush them.
defer tr.rawBytes.Reset()
return tr.rawBytes.Bytes()
}
// A numBytesReader is an io.Reader with a numBytes method, returning the number
// of bytes remaining in the underlying encoded data.
type numBytesReader interface {
io.Reader
numBytes() int64
}
// A regFileReader is a numBytesReader for reading file data from a tar archive.
type regFileReader struct {
r io.Reader // underlying reader
nb int64 // number of unread bytes for current file entry
}
// A sparseFileReader is a numBytesReader for reading sparse file data from a
// tar archive.
type sparseFileReader struct {
rfr numBytesReader // Reads the sparse-encoded file data
sp []sparseEntry // The sparse map for the file
pos int64 // Keeps track of file position
total int64 // Total size of the file
}
// A sparseEntry holds a single entry in a sparse file's sparse map.
//
// Sparse files are represented using a series of sparseEntrys.
// Despite the name, a sparseEntry represents an actual data fragment that
// references data found in the underlying archive stream. All regions not
// covered by a sparseEntry are logically filled with zeros.
//
// For example, if the underlying raw file contains the 10-byte data:
// var compactData = "abcdefgh"
//
// And the sparse map has the following entries:
// var sp = []sparseEntry{
// {offset: 2, numBytes: 5} // Data fragment for [2..7]
// {offset: 18, numBytes: 3} // Data fragment for [18..21]
// }
//
// Then the content of the resulting sparse file with a "real" size of 25 is:
// var sparseData = "\x00"*2 + "abcde" + "\x00"*11 + "fgh" + "\x00"*4
type sparseEntry struct {
offset int64 // Starting position of the fragment
numBytes int64 // Length of the fragment
}
// Keywords for GNU sparse files in a PAX extended header
const (
paxGNUSparseNumBlocks = "GNU.sparse.numblocks"
paxGNUSparseOffset = "GNU.sparse.offset"
paxGNUSparseNumBytes = "GNU.sparse.numbytes"
paxGNUSparseMap = "GNU.sparse.map"
paxGNUSparseName = "GNU.sparse.name"
paxGNUSparseMajor = "GNU.sparse.major"
paxGNUSparseMinor = "GNU.sparse.minor"
paxGNUSparseSize = "GNU.sparse.size"
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} }
// Next advances to the next entry in the tar archive.
//
// io.EOF is returned at the end of the input.
func (tr *Reader) Next() (*Header, error) {
if tr.RawAccounting {
if tr.rawBytes == nil {
tr.rawBytes = bytes.NewBuffer(nil)
} else {
tr.rawBytes.Reset()
}
}
if tr.err != nil {
return nil, tr.err
}
var hdr *Header
var extHdrs map[string]string
// Externally, Next iterates through the tar archive as if it is a series of
// files. Internally, the tar format often uses fake "files" to add meta
// data that describes the next file. These meta data "files" should not
// normally be visible to the outside. As such, this loop iterates through
// one or more "header files" until it finds a "normal file".
loop:
for {
tr.err = tr.skipUnread()
if tr.err != nil {
return nil, tr.err
}
hdr = tr.readHeader()
if tr.err != nil {
return nil, tr.err
}
// Check for PAX/GNU special headers and files.
switch hdr.Typeflag {
case TypeXHeader:
extHdrs, tr.err = parsePAX(tr)
if tr.err != nil {
return nil, tr.err
}
continue loop // This is a meta header affecting the next header
case TypeGNULongName, TypeGNULongLink:
var realname []byte
realname, tr.err = ioutil.ReadAll(tr)
if tr.err != nil {
return nil, tr.err
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(realname); tr.err != nil {
return nil, tr.err
}
}
// Convert GNU extensions to use PAX headers.
if extHdrs == nil {
extHdrs = make(map[string]string)
}
var p parser
switch hdr.Typeflag {
case TypeGNULongName:
extHdrs[paxPath] = p.parseString(realname)
case TypeGNULongLink:
extHdrs[paxLinkpath] = p.parseString(realname)
}
if p.err != nil {
tr.err = p.err
return nil, tr.err
}
continue loop // This is a meta header affecting the next header
default:
mergePAX(hdr, extHdrs)
// Check for a PAX format sparse file
sp, err := tr.checkForGNUSparsePAXHeaders(hdr, extHdrs)
if err != nil {
tr.err = err
return nil, err
}
if sp != nil {
// Current file is a PAX format GNU sparse file.
// Set the current file reader to a sparse file reader.
tr.curr, tr.err = newSparseFileReader(tr.curr, sp, hdr.Size)
if tr.err != nil {
return nil, tr.err
}
}
break loop // This is a file, so stop
}
}
return hdr, nil
}
// checkForGNUSparsePAXHeaders checks the PAX headers for GNU sparse headers. If they are found, then
// this function reads the sparse map and returns it. Unknown sparse formats are ignored, causing the file to
// be treated as a regular file.
func (tr *Reader) checkForGNUSparsePAXHeaders(hdr *Header, headers map[string]string) ([]sparseEntry, error) {
var sparseFormat string
// Check for sparse format indicators
major, majorOk := headers[paxGNUSparseMajor]
minor, minorOk := headers[paxGNUSparseMinor]
sparseName, sparseNameOk := headers[paxGNUSparseName]
_, sparseMapOk := headers[paxGNUSparseMap]
sparseSize, sparseSizeOk := headers[paxGNUSparseSize]
sparseRealSize, sparseRealSizeOk := headers[paxGNUSparseRealSize]
// Identify which, if any, sparse format applies from which PAX headers are set
if majorOk && minorOk {
sparseFormat = major + "." + minor
} else if sparseNameOk && sparseMapOk {
sparseFormat = "0.1"
} else if sparseSizeOk {
sparseFormat = "0.0"
} else {
// Not a PAX format GNU sparse file.
return nil, nil
}
// Check for unknown sparse format
if sparseFormat != "0.0" && sparseFormat != "0.1" && sparseFormat != "1.0" {
return nil, nil
}
// Update hdr from GNU sparse PAX headers
if sparseNameOk {
hdr.Name = sparseName
}
if sparseSizeOk {
realSize, err := strconv.ParseInt(sparseSize, 10, 0)
if err != nil {
return nil, ErrHeader
}
hdr.Size = realSize
} else if sparseRealSizeOk {
realSize, err := strconv.ParseInt(sparseRealSize, 10, 0)
if err != nil {
return nil, ErrHeader
}
hdr.Size = realSize
}
// Set up the sparse map, according to the particular sparse format in use
var sp []sparseEntry
var err error
switch sparseFormat {
case "0.0", "0.1":
sp, err = readGNUSparseMap0x1(headers)
case "1.0":
sp, err = readGNUSparseMap1x0(tr.curr)
}
return sp, err
}
// mergePAX merges well known headers according to PAX standard.
// In general headers with the same name as those found
// in the header struct overwrite those found in the header
// struct with higher precision or longer values. Esp. useful
// for name and linkname fields.
func mergePAX(hdr *Header, headers map[string]string) error {
for k, v := range headers {
switch k {
case paxPath:
hdr.Name = v
case paxLinkpath:
hdr.Linkname = v
case paxGname:
hdr.Gname = v
case paxUname:
hdr.Uname = v
case paxUid:
uid, err := strconv.ParseInt(v, 10, 0)
if err != nil {
return err
}
hdr.Uid = int(uid)
case paxGid:
gid, err := strconv.ParseInt(v, 10, 0)
if err != nil {
return err
}
hdr.Gid = int(gid)
case paxAtime:
t, err := parsePAXTime(v)
if err != nil {
return err
}
hdr.AccessTime = t
case paxMtime:
t, err := parsePAXTime(v)
if err != nil {
return err
}
hdr.ModTime = t
case paxCtime:
t, err := parsePAXTime(v)
if err != nil {
return err
}
hdr.ChangeTime = t
case paxSize:
size, err := strconv.ParseInt(v, 10, 0)
if err != nil {
return err
}
hdr.Size = int64(size)
default:
if strings.HasPrefix(k, paxXattr) {
if hdr.Xattrs == nil {
hdr.Xattrs = make(map[string]string)
}
hdr.Xattrs[k[len(paxXattr):]] = v
}
}
}
return nil
}
// parsePAXTime takes a string of the form %d.%d as described in
// the PAX specification.
func parsePAXTime(t string) (time.Time, error) {
buf := []byte(t)
pos := bytes.IndexByte(buf, '.')
var seconds, nanoseconds int64
var err error
if pos == -1 {
seconds, err = strconv.ParseInt(t, 10, 0)
if err != nil {
return time.Time{}, err
}
} else {
seconds, err = strconv.ParseInt(string(buf[:pos]), 10, 0)
if err != nil {
return time.Time{}, err
}
nano_buf := string(buf[pos+1:])
// Pad as needed before converting to a decimal.
// For example .030 -> .030000000 -> 30000000 nanoseconds
if len(nano_buf) < maxNanoSecondIntSize {
// Right pad
nano_buf += strings.Repeat("0", maxNanoSecondIntSize-len(nano_buf))
} else if len(nano_buf) > maxNanoSecondIntSize {
// Right truncate
nano_buf = nano_buf[:maxNanoSecondIntSize]
}
nanoseconds, err = strconv.ParseInt(string(nano_buf), 10, 0)
if err != nil {
return time.Time{}, err
}
}
ts := time.Unix(seconds, nanoseconds)
return ts, nil
}
// parsePAX parses PAX headers.
// If an extended header (type 'x') is invalid, ErrHeader is returned
func parsePAX(r io.Reader) (map[string]string, error) {
buf, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
}
// leaving this function for io.Reader makes it more testable
if tr, ok := r.(*Reader); ok && tr.RawAccounting {
if _, err = tr.rawBytes.Write(buf); err != nil {
return nil, err
}
}
sbuf := string(buf)
// For GNU PAX sparse format 0.0 support.
// This function transforms the sparse format 0.0 headers into sparse format 0.1 headers.
var sparseMap bytes.Buffer
headers := make(map[string]string)
// Each record is constructed as
// "%d %s=%s\n", length, keyword, value
for len(sbuf) > 0 {
key, value, residual, err := parsePAXRecord(sbuf)
if err != nil {
return nil, ErrHeader
}
sbuf = residual
keyStr := string(key)
if keyStr == paxGNUSparseOffset || keyStr == paxGNUSparseNumBytes {
// GNU sparse format 0.0 special key. Write to sparseMap instead of using the headers map.
sparseMap.WriteString(value)
sparseMap.Write([]byte{','})
} else {
// Normal key. Set the value in the headers map.
headers[keyStr] = string(value)
}
}
if sparseMap.Len() != 0 {
// Add sparse info to headers, chopping off the extra comma
sparseMap.Truncate(sparseMap.Len() - 1)
headers[paxGNUSparseMap] = sparseMap.String()
}
return headers, nil
}
// parsePAXRecord parses the input PAX record string into a key-value pair.
// If parsing is successful, it will slice off the currently read record and
// return the remainder as r.
//
// A PAX record is of the following form:
// "%d %s=%s\n" % (size, key, value)
func parsePAXRecord(s string) (k, v, r string, err error) {
// The size field ends at the first space.
sp := strings.IndexByte(s, ' ')
if sp == -1 {
return "", "", s, ErrHeader
}
// Parse the first token as a decimal integer.
n, perr := strconv.ParseInt(s[:sp], 10, 0) // Intentionally parse as native int
if perr != nil || n < 5 || int64(len(s)) < n {
return "", "", s, ErrHeader
}
// Extract everything between the space and the final newline.
rec, nl, rem := s[sp+1:n-1], s[n-1:n], s[n:]
if nl != "\n" {
return "", "", s, ErrHeader
}
// The first equals separates the key from the value.
eq := strings.IndexByte(rec, '=')
if eq == -1 {
return "", "", s, ErrHeader
}
return rec[:eq], rec[eq+1:], rem, nil
}
// parseString parses bytes as a NUL-terminated C-style string.
// If a NUL byte is not found then the whole slice is returned as a string.
func (*parser) parseString(b []byte) string {
n := 0
for n < len(b) && b[n] != 0 {
n++
}
return string(b[0:n])
}
// parseNumeric parses the input as being encoded in either base-256 or octal.
// This function may return negative numbers.
// If parsing fails or an integer overflow occurs, err will be set.
func (p *parser) parseNumeric(b []byte) int64 {
// Check for base-256 (binary) format first.
// If the first bit is set, then all following bits constitute a two's
// complement encoded number in big-endian byte order.
if len(b) > 0 && b[0]&0x80 != 0 {
// Handling negative numbers relies on the following identity:
// -a-1 == ^a
//
// If the number is negative, we use an inversion mask to invert the
// data bytes and treat the value as an unsigned number.
var inv byte // 0x00 if positive or zero, 0xff if negative
if b[0]&0x40 != 0 {
inv = 0xff
}
var x uint64
for i, c := range b {
c ^= inv // Inverts c only if inv is 0xff, otherwise does nothing
if i == 0 {
c &= 0x7f // Ignore signal bit in first byte
}
if (x >> 56) > 0 {
p.err = ErrHeader // Integer overflow
return 0
}
x = x<<8 | uint64(c)
}
if (x >> 63) > 0 {
p.err = ErrHeader // Integer overflow
return 0
}
if inv == 0xff {
return ^int64(x)
}
return int64(x)
}
// Normal case is base-8 (octal) format.
return p.parseOctal(b)
}
func (p *parser) parseOctal(b []byte) int64 {
// Because unused fields are filled with NULs, we need
// to skip leading NULs. Fields may also be padded with
// spaces or NULs.
// So we remove leading and trailing NULs and spaces to
// be sure.
b = bytes.Trim(b, " \x00")
if len(b) == 0 {
return 0
}
x, perr := strconv.ParseUint(p.parseString(b), 8, 64)
if perr != nil {
p.err = ErrHeader
}
return int64(x)
}
// skipUnread skips any unread bytes in the existing file entry, as well as any
// alignment padding. It returns io.ErrUnexpectedEOF if any io.EOF is
// encountered in the data portion; it is okay to hit io.EOF in the padding.
//
// Note that this function still works properly even when sparse files are being
// used since numBytes returns the bytes remaining in the underlying io.Reader.
func (tr *Reader) skipUnread() error {
dataSkip := tr.numBytes() // Number of data bytes to skip
totalSkip := dataSkip + tr.pad // Total number of bytes to skip
tr.curr, tr.pad = nil, 0
if tr.RawAccounting {
_, tr.err = io.CopyN(tr.rawBytes, tr.r, totalSkip)
return tr.err
}
// If possible, Seek to the last byte before the end of the data section.
// Do this because Seek is often lazy about reporting errors; this will mask
// the fact that the tar stream may be truncated. We can rely on the
// io.CopyN done shortly afterwards to trigger any IO errors.
var seekSkipped int64 // Number of bytes skipped via Seek
if sr, ok := tr.r.(io.Seeker); ok && dataSkip > 1 {
// Not all io.Seeker can actually Seek. For example, os.Stdin implements
// io.Seeker, but calling Seek always returns an error and performs
// no action. Thus, we try an innocent seek to the current position
// to see if Seek is really supported.
pos1, err := sr.Seek(0, os.SEEK_CUR)
if err == nil {
// Seek seems supported, so perform the real Seek.
pos2, err := sr.Seek(dataSkip-1, os.SEEK_CUR)
if err != nil {
tr.err = err
return tr.err
}
seekSkipped = pos2 - pos1
}
}
var copySkipped int64 // Number of bytes skipped via CopyN
copySkipped, tr.err = io.CopyN(ioutil.Discard, tr.r, totalSkip-seekSkipped)
if tr.err == io.EOF && seekSkipped+copySkipped < dataSkip {
tr.err = io.ErrUnexpectedEOF
}
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.
//
// The err will be set to io.EOF only when one of the following occurs:
// * Exactly 0 bytes are read and EOF is hit.
// * 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 n, err := io.ReadFull(tr.r, header); err != nil {
tr.err = err
// because it could read some of the block, but reach EOF first
if tr.err == io.EOF && tr.RawAccounting {
if _, err := tr.rawBytes.Write(header[:n]); err != nil {
tr.err = err
}
}
return nil // io.EOF is okay here
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(header); tr.err != nil {
return nil
}
}
// Two blocks of zero bytes marks the end of the archive.
if bytes.Equal(header, zeroBlock[0:blockSize]) {
if n, err := io.ReadFull(tr.r, header); err != nil {
tr.err = err
// because it could read some of the block, but reach EOF first
if tr.err == io.EOF && tr.RawAccounting {
if _, err := tr.rawBytes.Write(header[:n]); err != nil {
tr.err = err
}
}
return nil // io.EOF is okay here
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(header); tr.err != nil {
return nil
}
}
if bytes.Equal(header, zeroBlock[0:blockSize]) {
tr.err = io.EOF
} else {
tr.err = ErrHeader // zero block and then non-zero block
}
return nil
}
if !tr.verifyChecksum(header) {
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))
// 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)
if hdr.Typeflag == TypeChar || hdr.Typeflag == TypeBlock {
hdr.Devmajor = p.parseNumeric(devmajor)
hdr.Devminor = p.parseNumeric(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)
}
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
}
if nb < 0 {
tr.err = ErrHeader
return nil
}
// Set the current file reader.
tr.pad = -nb & (blockSize - 1) // blockSize is a power of two
tr.curr = &regFileReader{r: tr.r, nb: nb}
// 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])
if p.err != nil {
tr.err = p.err
return nil
}
// Read the sparse map.
sp := tr.readOldGNUSparseMap(header)
if tr.err != nil {
return nil
}
// Current file is a GNU sparse file. Update the current file reader.
tr.curr, tr.err = newSparseFileReader(tr.curr, sp, hdr.Size)
if tr.err != nil {
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 {
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))
if p.err != nil {
tr.err = p.err
return nil
}
if offset == 0 && numBytes == 0 {
break
}
sp = append(sp, sparseEntry{offset: offset, numBytes: numBytes})
}
for isExtended {
// 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 {
return nil
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(sparseHeader); 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))
if p.err != nil {
tr.err = p.err
return nil
}
if offset == 0 && numBytes == 0 {
break
}
sp = append(sp, sparseEntry{offset: offset, numBytes: numBytes})
}
}
return sp
}
// readGNUSparseMap1x0 reads the sparse map as stored in GNU's PAX sparse format
// version 1.0. The format of the sparse map consists of a series of
// newline-terminated numeric fields. The first field is the number of entries
// and is always present. Following this are the entries, consisting of two
// fields (offset, numBytes). This function must stop reading at the end
// boundary of the block containing the last newline.
//
// Note that the GNU manual says that numeric values should be encoded in octal
// format. However, the GNU tar utility itself outputs these values in decimal.
// As such, this library treats values as being encoded in decimal.
func readGNUSparseMap1x0(r io.Reader) ([]sparseEntry, error) {
var cntNewline int64
var buf bytes.Buffer
var blk = make([]byte, blockSize)
// feedTokens copies data in numBlock chunks from r into buf until there are
// at least cnt newlines in buf. It will not read more blocks than needed.
var feedTokens = func(cnt int64) error {
for cntNewline < cnt {
if _, err := io.ReadFull(r, blk); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
buf.Write(blk)
for _, c := range blk {
if c == '\n' {
cntNewline++
}
}
}
return nil
}
// nextToken gets the next token delimited by a newline. This assumes that
// at least one newline exists in the buffer.
var nextToken = func() string {
cntNewline--
tok, _ := buf.ReadString('\n')
return tok[:len(tok)-1] // Cut off newline
}
// Parse for the number of entries.
// Use integer overflow resistant math to check this.
if err := feedTokens(1); err != nil {
return nil, err
}
numEntries, err := strconv.ParseInt(nextToken(), 10, 0) // Intentionally parse as native int
if err != nil || numEntries < 0 || int(2*numEntries) < int(numEntries) {
return nil, ErrHeader
}
// Parse for all member entries.
// numEntries is trusted after this since a potential attacker must have
// committed resources proportional to what this library used.
if err := feedTokens(2 * numEntries); err != nil {
return nil, err
}
sp := make([]sparseEntry, 0, numEntries)
for i := int64(0); i < numEntries; i++ {
offset, err := strconv.ParseInt(nextToken(), 10, 64)
if err != nil {
return nil, ErrHeader
}
numBytes, err := strconv.ParseInt(nextToken(), 10, 64)
if err != nil {
return nil, ErrHeader
}
sp = append(sp, sparseEntry{offset: offset, numBytes: numBytes})
}
return sp, nil
}
// readGNUSparseMap0x1 reads the sparse map as stored in GNU's PAX sparse format
// version 0.1. The sparse map is stored in the PAX headers.
func readGNUSparseMap0x1(extHdrs map[string]string) ([]sparseEntry, error) {
// Get number of entries.
// Use integer overflow resistant math to check this.
numEntriesStr := extHdrs[paxGNUSparseNumBlocks]
numEntries, err := strconv.ParseInt(numEntriesStr, 10, 0) // Intentionally parse as native int
if err != nil || numEntries < 0 || int(2*numEntries) < int(numEntries) {
return nil, ErrHeader
}
// There should be two numbers in sparseMap for each entry.
sparseMap := strings.Split(extHdrs[paxGNUSparseMap], ",")
if int64(len(sparseMap)) != 2*numEntries {
return nil, ErrHeader
}
// Loop through the entries in the sparse map.
// numEntries is trusted now.
sp := make([]sparseEntry, 0, numEntries)
for i := int64(0); i < numEntries; i++ {
offset, err := strconv.ParseInt(sparseMap[2*i], 10, 64)
if err != nil {
return nil, ErrHeader
}
numBytes, err := strconv.ParseInt(sparseMap[2*i+1], 10, 64)
if err != nil {
return nil, ErrHeader
}
sp = append(sp, sparseEntry{offset: offset, numBytes: numBytes})
}
return sp, nil
}
// numBytes returns the number of bytes left to read in the current file's entry
// in the tar archive, or 0 if there is no current file.
func (tr *Reader) numBytes() int64 {
if tr.curr == nil {
// No current file, so no bytes
return 0
}
return tr.curr.numBytes()
}
// Read reads from the current entry in the tar archive.
// It returns 0, io.EOF when it reaches the end of that entry,
// until Next is called to advance to the next entry.
//
// Calling Read on special types like TypeLink, TypeSymLink, TypeChar,
// TypeBlock, TypeDir, and TypeFifo returns 0, io.EOF regardless of what
// the Header.Size claims.
func (tr *Reader) Read(b []byte) (n int, err error) {
if tr.err != nil {
return 0, tr.err
}
if tr.curr == nil {
return 0, io.EOF
}
n, err = tr.curr.Read(b)
if err != nil && err != io.EOF {
tr.err = err
}
return
}
func (rfr *regFileReader) Read(b []byte) (n int, err error) {
if rfr.nb == 0 {
// file consumed
return 0, io.EOF
}
if int64(len(b)) > rfr.nb {
b = b[0:rfr.nb]
}
n, err = rfr.r.Read(b)
rfr.nb -= int64(n)
if err == io.EOF && rfr.nb > 0 {
err = io.ErrUnexpectedEOF
}
return
}
// numBytes returns the number of bytes left to read in the file's data in the tar archive.
func (rfr *regFileReader) numBytes() int64 {
return rfr.nb
}
// newSparseFileReader creates a new sparseFileReader, but validates all of the
// sparse entries before doing so.
func newSparseFileReader(rfr numBytesReader, sp []sparseEntry, total int64) (*sparseFileReader, error) {
if total < 0 {
return nil, ErrHeader // Total size cannot be negative
}
// Validate all sparse entries. These are the same checks as performed by
// the BSD tar utility.
for i, s := range sp {
switch {
case s.offset < 0 || s.numBytes < 0:
return nil, ErrHeader // Negative values are never okay
case s.offset > math.MaxInt64-s.numBytes:
return nil, ErrHeader // Integer overflow with large length
case s.offset+s.numBytes > total:
return nil, ErrHeader // Region extends beyond the "real" size
case i > 0 && sp[i-1].offset+sp[i-1].numBytes > s.offset:
return nil, ErrHeader // Regions can't overlap and must be in order
}
}
return &sparseFileReader{rfr: rfr, sp: sp, total: total}, nil
}
// readHole reads a sparse hole ending at endOffset.
func (sfr *sparseFileReader) readHole(b []byte, endOffset int64) int {
n64 := endOffset - sfr.pos
if n64 > int64(len(b)) {
n64 = int64(len(b))
}
n := int(n64)
for i := 0; i < n; i++ {
b[i] = 0
}
sfr.pos += n64
return n
}
// Read reads the sparse file data in expanded form.
func (sfr *sparseFileReader) Read(b []byte) (n int, err error) {
// Skip past all empty fragments.
for len(sfr.sp) > 0 && sfr.sp[0].numBytes == 0 {
sfr.sp = sfr.sp[1:]
}
// If there are no more fragments, then it is possible that there
// is one last sparse hole.
if len(sfr.sp) == 0 {
// This behavior matches the BSD tar utility.
// However, GNU tar stops returning data even if sfr.total is unmet.
if sfr.pos < sfr.total {
return sfr.readHole(b, sfr.total), nil
}
return 0, io.EOF
}
// In front of a data fragment, so read a hole.
if sfr.pos < sfr.sp[0].offset {
return sfr.readHole(b, sfr.sp[0].offset), nil
}
// In a data fragment, so read from it.
// This math is overflow free since we verify that offset and numBytes can
// be safely added when creating the sparseFileReader.
endPos := sfr.sp[0].offset + sfr.sp[0].numBytes // End offset of fragment
bytesLeft := endPos - sfr.pos // Bytes left in fragment
if int64(len(b)) > bytesLeft {
b = b[:bytesLeft]
}
n, err = sfr.rfr.Read(b)
sfr.pos += int64(n)
if err == io.EOF {
if sfr.pos < endPos {
err = io.ErrUnexpectedEOF // There was supposed to be more data
} else if sfr.pos < sfr.total {
err = nil // There is still an implicit sparse hole at the end
}
}
if sfr.pos == endPos {
sfr.sp = sfr.sp[1:] // We are done with this fragment, so pop it
}
return n, err
}
// numBytes returns the number of bytes left to read in the sparse file's
// sparse-encoded data in the tar archive.
func (sfr *sparseFileReader) numBytes() int64 {
return sfr.rfr.numBytes()
}