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archive/tar: fix bugs with sparseFileReader
The sparseFileReader is prone to two different forms of denial-of-service attacks: * A malicious tar file can cause an infinite loop * A malicious tar file can cause arbitrary panics This results because of poor error checking/handling, which this CL fixes. While we are at it, add a plethora of unit tests to test for possible malicious inputs. Change-Id: I2f9446539d189f3c1738a1608b0ad4859c1be929 Reviewed-on: https://go-review.googlesource.com/15115 Reviewed-by: Andrew Gerrand <adg@golang.org> Run-TryBot: Andrew Gerrand <adg@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joe Tsai
parent
440ba9e519
commit
af15385a0d
2 changed files with 258 additions and 127 deletions
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@ -12,6 +12,7 @@ import (
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"errors"
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"io"
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"io/ioutil"
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"math"
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"os"
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"strconv"
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"strings"
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@ -70,12 +71,36 @@ type regFileReader struct {
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nb int64 // number of unread bytes for current file entry
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}
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// A sparseFileReader is a numBytesReader for reading sparse file data from a tar archive.
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// A sparseFileReader is a numBytesReader for reading sparse file data from a
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// tar archive.
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type sparseFileReader struct {
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rfr *regFileReader // reads the sparse-encoded file data
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sp []sparseEntry // the sparse map for the file
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pos int64 // keeps track of file position
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tot int64 // total size of the file
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rfr numBytesReader // Reads the sparse-encoded file data
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sp []sparseEntry // The sparse map for the file
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pos int64 // Keeps track of file position
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total int64 // Total size of the file
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}
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// A sparseEntry holds a single entry in a sparse file's sparse map.
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//
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// Sparse files are represented using a series of sparseEntrys.
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// Despite the name, a sparseEntry represents an actual data fragment that
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// references data found in the underlying archive stream. All regions not
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// covered by a sparseEntry are logically filled with zeros.
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//
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// For example, if the underlying raw file contains the 10-byte data:
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// var compactData = "abcdefgh"
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//
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// And the sparse map has the following entries:
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// var sp = []sparseEntry{
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// {offset: 2, numBytes: 5} // Data fragment for [2..7]
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// {offset: 18, numBytes: 3} // Data fragment for [18..21]
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// }
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//
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// Then the content of the resulting sparse file with a "real" size of 25 is:
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// var sparseData = "\x00"*2 + "abcde" + "\x00"*11 + "fgh" + "\x00"*4
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type sparseEntry struct {
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offset int64 // Starting position of the fragment
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numBytes int64 // Length of the fragment
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}
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// Keywords for GNU sparse files in a PAX extended header
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@ -156,7 +181,10 @@ func (tr *Reader) Next() (*Header, error) {
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if sp != nil {
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// Current file is a PAX format GNU sparse file.
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// Set the current file reader to a sparse file reader.
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tr.curr = &sparseFileReader{rfr: tr.curr.(*regFileReader), sp: sp, tot: hdr.Size}
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tr.curr, tr.err = newSparseFileReader(tr.curr, sp, hdr.Size)
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if tr.err != nil {
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return nil, tr.err
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}
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}
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return hdr, nil
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case TypeGNULongName:
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@ -631,21 +659,17 @@ func (tr *Reader) readHeader() *Header {
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if tr.err != nil {
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return nil
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}
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// Current file is a GNU sparse file. Update the current file reader.
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tr.curr = &sparseFileReader{rfr: tr.curr.(*regFileReader), sp: sp, tot: hdr.Size}
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tr.curr, tr.err = newSparseFileReader(tr.curr, sp, hdr.Size)
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if tr.err != nil {
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return nil
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}
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}
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return hdr
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}
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// A sparseEntry holds a single entry in a sparse file's sparse map.
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// A sparse entry indicates the offset and size in a sparse file of a
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// block of data.
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type sparseEntry struct {
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offset int64
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numBytes int64
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}
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// readOldGNUSparseMap reads the sparse map as stored in the old GNU sparse format.
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// The sparse map is stored in the tar header if it's small enough. If it's larger than four entries,
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// then one or more extension headers are used to store the rest of the sparse map.
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@ -879,9 +903,33 @@ func (rfr *regFileReader) numBytes() int64 {
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return rfr.nb
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}
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// readHole reads a sparse file hole ending at offset toOffset
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func (sfr *sparseFileReader) readHole(b []byte, toOffset int64) int {
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n64 := toOffset - sfr.pos
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// newSparseFileReader creates a new sparseFileReader, but validates all of the
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// sparse entries before doing so.
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func newSparseFileReader(rfr numBytesReader, sp []sparseEntry, total int64) (*sparseFileReader, error) {
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if total < 0 {
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return nil, ErrHeader // Total size cannot be negative
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}
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// Validate all sparse entries. These are the same checks as performed by
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// the BSD tar utility.
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for i, s := range sp {
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switch {
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case s.offset < 0 || s.numBytes < 0:
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return nil, ErrHeader // Negative values are never okay
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case s.offset > math.MaxInt64-s.numBytes:
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return nil, ErrHeader // Integer overflow with large length
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case s.offset+s.numBytes > total:
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return nil, ErrHeader // Region extends beyond the "real" size
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case i > 0 && sp[i-1].offset+sp[i-1].numBytes > s.offset:
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return nil, ErrHeader // Regions can't overlap and must be in order
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}
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}
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return &sparseFileReader{rfr: rfr, sp: sp, total: total}, nil
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}
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// readHole reads a sparse hole ending at endOffset.
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func (sfr *sparseFileReader) readHole(b []byte, endOffset int64) int {
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n64 := endOffset - sfr.pos
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if n64 > int64(len(b)) {
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n64 = int64(len(b))
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}
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@ -895,49 +943,54 @@ func (sfr *sparseFileReader) readHole(b []byte, toOffset int64) int {
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// Read reads the sparse file data in expanded form.
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func (sfr *sparseFileReader) Read(b []byte) (n int, err error) {
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if len(sfr.sp) == 0 {
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// No more data fragments to read from.
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if sfr.pos < sfr.tot {
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// We're in the last hole
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n = sfr.readHole(b, sfr.tot)
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return
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}
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// Otherwise, we're at the end of the file
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return 0, io.EOF
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}
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if sfr.tot < sfr.sp[0].offset {
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return 0, io.ErrUnexpectedEOF
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}
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if sfr.pos < sfr.sp[0].offset {
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// We're in a hole
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n = sfr.readHole(b, sfr.sp[0].offset)
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return
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// Skip past all empty fragments.
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for len(sfr.sp) > 0 && sfr.sp[0].numBytes == 0 {
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sfr.sp = sfr.sp[1:]
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}
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// We're not in a hole, so we'll read from the next data fragment
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posInFragment := sfr.pos - sfr.sp[0].offset
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bytesLeft := sfr.sp[0].numBytes - posInFragment
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// If there are no more fragments, then it is possible that there
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// is one last sparse hole.
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if len(sfr.sp) == 0 {
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// This behavior matches the BSD tar utility.
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// However, GNU tar stops returning data even if sfr.total is unmet.
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if sfr.pos < sfr.total {
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return sfr.readHole(b, sfr.total), nil
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}
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return 0, io.EOF
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}
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// In front of a data fragment, so read a hole.
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if sfr.pos < sfr.sp[0].offset {
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return sfr.readHole(b, sfr.sp[0].offset), nil
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}
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// In a data fragment, so read from it.
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// This math is overflow free since we verify that offset and numBytes can
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// be safely added when creating the sparseFileReader.
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endPos := sfr.sp[0].offset + sfr.sp[0].numBytes // End offset of fragment
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bytesLeft := endPos - sfr.pos // Bytes left in fragment
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if int64(len(b)) > bytesLeft {
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b = b[0:bytesLeft]
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b = b[:bytesLeft]
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}
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n, err = sfr.rfr.Read(b)
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sfr.pos += int64(n)
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if int64(n) == bytesLeft {
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// We're done with this fragment
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sfr.sp = sfr.sp[1:]
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if err == io.EOF {
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if sfr.pos < endPos {
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err = io.ErrUnexpectedEOF // There was supposed to be more data
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} else if sfr.pos < sfr.total {
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err = nil // There is still an implicit sparse hole at the end
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}
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}
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if err == io.EOF && sfr.pos < sfr.tot {
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// We reached the end of the last fragment's data, but there's a final hole
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err = nil
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if sfr.pos == endPos {
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sfr.sp = sfr.sp[1:] // We are done with this fragment, so pop it
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}
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return
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return n, err
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}
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// numBytes returns the number of bytes left to read in the sparse file's
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// sparse-encoded data in the tar archive.
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func (sfr *sparseFileReader) numBytes() int64 {
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return sfr.rfr.nb
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return sfr.rfr.numBytes()
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}
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@ -10,6 +10,7 @@ import (
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"fmt"
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"io"
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"io/ioutil"
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"math"
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"os"
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"reflect"
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"strings"
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@ -560,80 +561,155 @@ func TestSparseEndToEnd(t *testing.T) {
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}
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}
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type sparseFileReadTest struct {
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sparseData []byte
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sparseMap []sparseEntry
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realSize int64
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expected []byte
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}
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var sparseFileReadTests = []sparseFileReadTest{
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{
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sparseData: []byte("abcde"),
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sparseMap: []sparseEntry{
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{offset: 0, numBytes: 2},
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{offset: 5, numBytes: 3},
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},
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realSize: 8,
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expected: []byte("ab\x00\x00\x00cde"),
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},
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{
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sparseData: []byte("abcde"),
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sparseMap: []sparseEntry{
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{offset: 0, numBytes: 2},
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{offset: 5, numBytes: 3},
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},
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realSize: 10,
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expected: []byte("ab\x00\x00\x00cde\x00\x00"),
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},
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{
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sparseData: []byte("abcde"),
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 2},
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},
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realSize: 8,
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expected: []byte("\x00abc\x00\x00de"),
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},
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{
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sparseData: []byte("abcde"),
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 2},
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},
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realSize: 10,
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expected: []byte("\x00abc\x00\x00de\x00\x00"),
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},
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{
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sparseData: []byte(""),
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sparseMap: nil,
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realSize: 2,
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expected: []byte("\x00\x00"),
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},
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}
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func TestSparseFileReader(t *testing.T) {
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for i, test := range sparseFileReadTests {
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r := bytes.NewReader(test.sparseData)
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nb := int64(r.Len())
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sfr := &sparseFileReader{
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rfr: ®FileReader{r: r, nb: nb},
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sp: test.sparseMap,
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pos: 0,
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tot: test.realSize,
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}
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if sfr.numBytes() != nb {
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t.Errorf("test %d: Before reading, sfr.numBytes() = %d, want %d", i, sfr.numBytes(), nb)
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}
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buf, err := ioutil.ReadAll(sfr)
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var vectors = []struct {
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realSize int64 // Real size of the output file
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sparseMap []sparseEntry // Input sparse map
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sparseData string // Input compact data
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expected string // Expected output data
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err error // Expected error outcome
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}{{
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realSize: 8,
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sparseMap: []sparseEntry{
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{offset: 0, numBytes: 2},
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{offset: 5, numBytes: 3},
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},
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sparseData: "abcde",
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expected: "ab\x00\x00\x00cde",
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}, {
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realSize: 10,
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sparseMap: []sparseEntry{
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{offset: 0, numBytes: 2},
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{offset: 5, numBytes: 3},
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},
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sparseData: "abcde",
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expected: "ab\x00\x00\x00cde\x00\x00",
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}, {
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realSize: 8,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 2},
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},
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sparseData: "abcde",
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expected: "\x00abc\x00\x00de",
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}, {
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realSize: 8,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 0},
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{offset: 6, numBytes: 0},
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{offset: 6, numBytes: 2},
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},
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sparseData: "abcde",
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expected: "\x00abc\x00\x00de",
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}, {
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realSize: 10,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 2},
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},
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sparseData: "abcde",
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expected: "\x00abc\x00\x00de\x00\x00",
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}, {
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realSize: 10,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 2},
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{offset: 8, numBytes: 0},
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{offset: 8, numBytes: 0},
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{offset: 8, numBytes: 0},
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{offset: 8, numBytes: 0},
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},
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sparseData: "abcde",
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expected: "\x00abc\x00\x00de\x00\x00",
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}, {
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realSize: 2,
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sparseMap: []sparseEntry{},
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sparseData: "",
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expected: "\x00\x00",
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}, {
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realSize: -2,
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sparseMap: []sparseEntry{},
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err: ErrHeader,
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}, {
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realSize: -10,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 2},
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},
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sparseData: "abcde",
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err: ErrHeader,
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}, {
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realSize: 10,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 5},
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},
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sparseData: "abcde",
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err: ErrHeader,
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}, {
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realSize: 35,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: 5},
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},
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sparseData: "abcde",
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err: io.ErrUnexpectedEOF,
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}, {
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realSize: 35,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 6, numBytes: -5},
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},
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sparseData: "abcde",
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err: ErrHeader,
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}, {
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realSize: 35,
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sparseMap: []sparseEntry{
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{offset: math.MaxInt64, numBytes: 3},
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{offset: 6, numBytes: -5},
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},
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sparseData: "abcde",
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err: ErrHeader,
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}, {
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realSize: 10,
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sparseMap: []sparseEntry{
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{offset: 1, numBytes: 3},
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{offset: 2, numBytes: 2},
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},
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sparseData: "abcde",
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err: ErrHeader,
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}}
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for i, v := range vectors {
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r := bytes.NewReader([]byte(v.sparseData))
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rfr := ®FileReader{r: r, nb: int64(len(v.sparseData))}
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var sfr *sparseFileReader
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var err error
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var buf []byte
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sfr, err = newSparseFileReader(rfr, v.sparseMap, v.realSize)
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if err != nil {
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t.Errorf("test %d: Unexpected error: %v", i, err)
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goto fail
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}
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if e := test.expected; !bytes.Equal(buf, e) {
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t.Errorf("test %d: Contents = %v, want %v", i, buf, e)
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if sfr.numBytes() != int64(len(v.sparseData)) {
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t.Errorf("test %d, numBytes() before reading: got %d, want %d", i, sfr.numBytes(), len(v.sparseData))
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}
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buf, err = ioutil.ReadAll(sfr)
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if err != nil {
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goto fail
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}
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if string(buf) != v.expected {
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t.Errorf("test %d, ReadAll(): got %q, want %q", i, string(buf), v.expected)
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}
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if sfr.numBytes() != 0 {
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t.Errorf("test %d: After draining the reader, numBytes() was nonzero", i)
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t.Errorf("test %d, numBytes() after reading: got %d, want %d", i, sfr.numBytes(), 0)
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}
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fail:
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if err != v.err {
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t.Errorf("test %d, unexpected error: got %v, want %v", i, err, v.err)
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}
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}
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}
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@ -646,10 +722,10 @@ func TestSparseIncrementalRead(t *testing.T) {
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r := bytes.NewReader(sparseData)
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nb := int64(r.Len())
|
||||
sfr := &sparseFileReader{
|
||||
rfr: ®FileReader{r: r, nb: nb},
|
||||
sp: sparseMap,
|
||||
pos: 0,
|
||||
tot: int64(len(expected)),
|
||||
rfr: ®FileReader{r: r, nb: nb},
|
||||
sp: sparseMap,
|
||||
pos: 0,
|
||||
total: int64(len(expected)),
|
||||
}
|
||||
|
||||
// We'll read the data 6 bytes at a time, with a hole of size 10 at
|
||||
|
|
@ -747,6 +823,11 @@ func TestUninitializedRead(t *testing.T) {
|
|||
|
||||
}
|
||||
|
||||
// TODO(dsnet): TestNegativeHdrSize, TestIssue10968, and TestIssue11169 tests
|
||||
// that Reader properly handles corrupted tar files. Given the increasing number
|
||||
// of invalid/malicious that can crash Reader, we should modify TestReader to
|
||||
// be able to test that intentionally corrupt tar files don't succeed or crash.
|
||||
|
||||
// Negative header size should not cause panic.
|
||||
// Issues 10959 and 10960.
|
||||
func TestNegativeHdrSize(t *testing.T) {
|
||||
|
|
@ -771,14 +852,11 @@ func TestIssue10968(t *testing.T) {
|
|||
t.Fatal(err)
|
||||
}
|
||||
defer f.Close()
|
||||
|
||||
r := NewReader(f)
|
||||
_, err = r.Next()
|
||||
if err != nil {
|
||||
t.Fatal(err)
|
||||
}
|
||||
_, err = io.Copy(ioutil.Discard, r)
|
||||
if err != io.ErrUnexpectedEOF {
|
||||
t.Fatalf("expected %q, got %q", io.ErrUnexpectedEOF, err)
|
||||
if err == nil {
|
||||
t.Fatal("Unexpected success")
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in a new issue