fix incorrect header size assumption

Author: ngicks

copied_std.go

@@ -0,0 +1,371 @@
+// 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 tarfs
+
+import (
+	"archive/tar"
+	"bytes"
+	"io"
+	"strconv"
+	"strings"
+)
+
+// start -- common.go
+
+const (
+	// Keywords for GNU sparse files in a PAX extended header.
+	paxGNUSparse          = "GNU.sparse."
+	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"
+)
+
+type sparseEntry struct{ Offset, Length int64 }
+
+func (s sparseEntry) endOffset() int64 { return s.Offset + s.Length }
+
+// A sparse file can be represented as either a sparseDatas or a sparseHoles.
+// As long as the total size is known, they are equivalent and one can be
+// converted to the other form and back. The various tar formats with sparse
+// file support represent sparse files in the sparseDatas form. That is, they
+// specify the fragments in the file that has data, and treat everything else as
+// having zero bytes. As such, the encoding and decoding logic in this package
+// deals with sparseDatas.
+//
+// However, the external API uses sparseHoles instead of sparseDatas because the
+// zero value of sparseHoles logically represents a normal file (i.e., there are
+// no holes in it). On the other hand, the zero value of sparseDatas implies
+// that the file has no data in it, which is rather odd.
+//
+// As an example, if the underlying raw file contains the 10-byte data:
+//
+//	var compactFile = "abcdefgh"
+//
+// And the sparse map has the following entries:
+//
+//	var spd sparseDatas = []sparseEntry{
+//		{Offset: 2,  Length: 5},  // Data fragment for 2..6
+//		{Offset: 18, Length: 3},  // Data fragment for 18..20
+//	}
+//	var sph sparseHoles = []sparseEntry{
+//		{Offset: 0,  Length: 2},  // Hole fragment for 0..1
+//		{Offset: 7,  Length: 11}, // Hole fragment for 7..17
+//		{Offset: 21, Length: 4},  // Hole fragment for 21..24
+//	}
+//
+// Then the content of the resulting sparse file with a Header.Size of 25 is:
+//
+//	var sparseFile = "\x00"*2 + "abcde" + "\x00"*11 + "fgh" + "\x00"*4
+type (
+	sparseDatas []sparseEntry
+	sparseHoles []sparseEntry
+)
+
+func invertSparseEntries(src []sparseEntry, size int64) []sparseEntry {
+	dst := src[:0]
+	var pre sparseEntry
+	for _, cur := range src {
+		if cur.Length == 0 {
+			continue // Skip empty fragments
+		}
+		pre.Length = cur.Offset - pre.Offset
+		if pre.Length > 0 {
+			dst = append(dst, pre) // Only add non-empty fragments
+		}
+		pre.Offset = cur.endOffset()
+	}
+	pre.Length = size - pre.Offset // Possibly the only empty fragment
+	return append(dst, pre)
+}
+
+// end -- common.go
+
+// start -- format.go
+
+// 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
+)
+
+type block [blockSize]byte
+
+type headerV7 [blockSize]byte
+
+// Convert block to any number of formats.
+func (b *block) toV7() *headerV7   { return (*headerV7)(b) }
+func (b *block) toGNU() *headerGNU { return (*headerGNU)(b) }
+
+// func (b *block) toSTAR() *headerSTAR   { return (*headerSTAR)(b) }
+// func (b *block) toUSTAR() *headerUSTAR { return (*headerUSTAR)(b) }
+func (b *block) toSparse() sparseArray { return sparseArray(b[:]) }
+
+// 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) sparseElem { return sparseElem(s[i*24:]) }
+func (s sparseArray) isExtended() []byte     { return s[24*s.maxEntries():][:1] }
+func (s sparseArray) maxEntries() int        { return len(s) / 24 }
+
+type sparseElem []byte
+
+func (s sparseElem) offset() []byte { return s[0o0:][:12] }
+func (s sparseElem) length() []byte { return s[12:][:12] }
+
+// end -- format.go
+
+// start -- reader.go
+
+func mustReadFull(r io.Reader, b []byte) (int, error) {
+	n, err := tryReadFull(r, b)
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return n, err
+}
+
+func tryReadFull(r io.Reader, b []byte) (n int, err error) {
+	for len(b) > n && err == nil {
+		var nn int
+		nn, err = r.Read(b[n:])
+		n += nn
+	}
+	if len(b) == n && err == io.EOF {
+		err = nil
+	}
+	return n, err
+}
+
+func readGNUSparseMap1x0(r io.Reader) (sparseDatas, error) {
+	var (
+		cntNewline int64
+		buf        bytes.Buffer
+		blk        block
+	)
+
+	// feedTokens copies data in blocks from r into buf until there are
+	// at least cnt newlines in buf. It will not read more blocks than needed.
+	feedTokens := func(n int64) error {
+		for cntNewline < n {
+			if _, err := mustReadFull(r, blk[:]); err != nil {
+				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.
+	nextToken := func() string {
+		cntNewline--
+		tok, _ := buf.ReadString('\n')
+		return strings.TrimRight(tok, "\n")
+	}
+
+	// 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, tar.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
+	}
+	spd := make(sparseDatas, 0, numEntries)
+	for i := int64(0); i < numEntries; i++ {
+		offset, err1 := strconv.ParseInt(nextToken(), 10, 64)
+		length, err2 := strconv.ParseInt(nextToken(), 10, 64)
+		if err1 != nil || err2 != nil {
+			return nil, tar.ErrHeader
+		}
+		spd = append(spd, sparseEntry{Offset: offset, Length: length})
+	}
+	return spd, nil
+}
+
+func readGNUSparseMap0x1(paxHdrs map[string]string) (sparseDatas, error) {
+	// Get number of entries.
+	// Use integer overflow resistant math to check this.
+	numEntriesStr := paxHdrs[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, tar.ErrHeader
+	}
+
+	// There should be two numbers in sparseMap for each entry.
+	sparseMap := strings.Split(paxHdrs[paxGNUSparseMap], ",")
+	if len(sparseMap) == 1 && sparseMap[0] == "" {
+		sparseMap = sparseMap[:0]
+	}
+	if int64(len(sparseMap)) != 2*numEntries {
+		return nil, tar.ErrHeader
+	}
+
+	// Loop through the entries in the sparse map.
+	// numEntries is trusted now.
+	spd := make(sparseDatas, 0, numEntries)
+	for len(sparseMap) >= 2 {
+		offset, err1 := strconv.ParseInt(sparseMap[0], 10, 64)
+		length, err2 := strconv.ParseInt(sparseMap[1], 10, 64)
+		if err1 != nil || err2 != nil {
+			return nil, tar.ErrHeader
+		}
+		spd = append(spd, sparseEntry{Offset: offset, Length: length})
+		sparseMap = sparseMap[2:]
+	}
+	return spd, nil
+}
+
+// end -- reader.go
+
+// start -- strconv.go
+
+type parser struct {
+	err error // Last error seen
+}
+
+// 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 {
+	if i := bytes.IndexByte(b, 0); i >= 0 {
+		return string(b[:i])
+	}
+	return string(b)
+}
+
+// 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 = tar.ErrHeader // Integer overflow
+				return 0
+			}
+			x = x<<8 | uint64(c)
+		}
+		if (x >> 63) > 0 {
+			p.err = tar.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 = tar.ErrHeader
+	}
+	return int64(x)
+}
+
+// end -- strconv.go