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archive/tar: fix numeric overflow issues in readGNUSparseMap0x1

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Motivation:
* The logic to verify the numEntries can overflow and incorrectly
pass, allowing a malicious file to allocate arbitrary memory.
* The use of strconv.ParseInt does not set the integer precision
to 64bit, causing this code to work incorrectly on 32bit machines.

Change-Id: I1b1571a750a84f2dde97cc329ed04fe2342aaa60
Reviewed-on: https://go-review.googlesource.com/15173
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joe Tsai 2015-10-01 01:04:24 -07:00 committed by Vincent Batts
parent cb423795eb
commit cf83c95de8
2 changed files with 173 additions and 40 deletions
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57
archive/tar/reader.go
View file

@ -504,20 +504,48 @@ func (tr *Reader) octal(b []byte) int64 {
return int64(x)
}
// skipUnread skips any unread bytes in the existing file entry, as well as any alignment padding.
func (tr *Reader) skipUnread() {
nr := tr.numBytes() + tr.pad // number of bytes to skip
// 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, nr)
return
_, tr.err = io.CopyN(tr.rawBytes, tr.r, totalSkip)
return tr.err
}
if sr, ok := tr.r.(io.Seeker); ok {
if _, err := sr.Seek(nr, os.SEEK_CUR); err == nil {
return
// 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
}
}
_, tr.err = io.CopyN(ioutil.Discard, tr.r, nr)
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 {
@ -530,6 +558,13 @@ func (tr *Reader) verifyChecksum(header []byte) bool {
return 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)
@ -541,7 +576,7 @@ func (tr *Reader) readHeader() *Header {
return nil
}
}
return nil
return nil // io.EOF is okay here
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(header); tr.err != nil {
@ -558,7 +593,7 @@ func (tr *Reader) readHeader() *Header {
return nil
}
}
return nil
return nil // io.EOF is okay here
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(header); tr.err != nil {

156
archive/tar/reader_test.go
View file

@ -414,35 +414,6 @@ func TestPartialRead(t *testing.T) {
}
}
func TestNonSeekable(t *testing.T) {
test := gnuTarTest
f, err := os.Open(test.file)
if err != nil {
t.Fatalf("Unexpected error: %v", err)
}
defer f.Close()
type readerOnly struct {
io.Reader
}
tr := NewReader(readerOnly{f})
nread := 0
for ; ; nread++ {
_, err := tr.Next()
if err == io.EOF {
break
}
if err != nil {
t.Fatalf("Unexpected error: %v", err)
}
}
if nread != len(test.headers) {
t.Errorf("Didn't process all files\nexpected: %d\nprocessed %d\n", len(test.headers), nread)
}
}
func TestParsePAXHeader(t *testing.T) {
paxTests := [][3]string{
{"a", "a=name", "10 a=name\n"}, // Test case involving multiple acceptable lengths
@ -795,3 +766,130 @@ func TestUninitializedRead(t *testing.T) {
}
}
type reader struct{ io.Reader }
type readSeeker struct{ io.ReadSeeker }
type readBadSeeker struct{ io.ReadSeeker }
func (rbs *readBadSeeker) Seek(int64, int) (int64, error) { return 0, fmt.Errorf("illegal seek") }
// TestReadTruncation test the ending condition on various truncated files and
// that truncated files are still detected even if the underlying io.Reader
// satisfies io.Seeker.
func TestReadTruncation(t *testing.T) {
var ss []string
for _, p := range []string{
"testdata/gnu.tar",
"testdata/ustar-file-reg.tar",
"testdata/pax-path-hdr.tar",
"testdata/sparse-formats.tar",
} {
buf, err := ioutil.ReadFile(p)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
ss = append(ss, string(buf))
}
data1, data2, pax, sparse := ss[0], ss[1], ss[2], ss[3]
data2 += strings.Repeat("\x00", 10*512)
trash := strings.Repeat("garbage ", 64) // Exactly 512 bytes
var vectors = []struct {
input string // Input stream
cnt int // Expected number of headers read
err error // Expected error outcome
}{
{"", 0, io.EOF}, // Empty file is a "valid" tar file
{data1[:511], 0, io.ErrUnexpectedEOF},
{data1[:512], 1, io.ErrUnexpectedEOF},
{data1[:1024], 1, io.EOF},
{data1[:1536], 2, io.ErrUnexpectedEOF},
{data1[:2048], 2, io.EOF},
{data1, 2, io.EOF},
{data1[:2048] + data2[:1536], 3, io.EOF},
{data2[:511], 0, io.ErrUnexpectedEOF},
{data2[:512], 1, io.ErrUnexpectedEOF},
{data2[:1195], 1, io.ErrUnexpectedEOF},
{data2[:1196], 1, io.EOF}, // Exact end of data and start of padding
{data2[:1200], 1, io.EOF},
{data2[:1535], 1, io.EOF},
{data2[:1536], 1, io.EOF}, // Exact end of padding
{data2[:1536] + trash[:1], 1, io.ErrUnexpectedEOF},
{data2[:1536] + trash[:511], 1, io.ErrUnexpectedEOF},
{data2[:1536] + trash, 1, ErrHeader},
{data2[:2048], 1, io.EOF}, // Exactly 1 empty block
{data2[:2048] + trash[:1], 1, io.ErrUnexpectedEOF},
{data2[:2048] + trash[:511], 1, io.ErrUnexpectedEOF},
{data2[:2048] + trash, 1, ErrHeader},
{data2[:2560], 1, io.EOF}, // Exactly 2 empty blocks (normal end-of-stream)
{data2[:2560] + trash[:1], 1, io.EOF},
{data2[:2560] + trash[:511], 1, io.EOF},
{data2[:2560] + trash, 1, io.EOF},
{data2[:3072], 1, io.EOF},
{pax, 0, io.EOF}, // PAX header without data is a "valid" tar file
{pax + trash[:1], 0, io.ErrUnexpectedEOF},
{pax + trash[:511], 0, io.ErrUnexpectedEOF},
{sparse[:511], 0, io.ErrUnexpectedEOF},
// TODO(dsnet): This should pass, but currently fails.
// {sparse[:512], 0, io.ErrUnexpectedEOF},
{sparse[:3584], 1, io.EOF},
{sparse[:9200], 1, io.EOF}, // Terminate in padding of sparse header
{sparse[:9216], 1, io.EOF},
{sparse[:9728], 2, io.ErrUnexpectedEOF},
{sparse[:10240], 2, io.EOF},
{sparse[:11264], 2, io.ErrUnexpectedEOF},
{sparse, 5, io.EOF},
{sparse + trash, 5, io.EOF},
}
for i, v := range vectors {
for j := 0; j < 6; j++ {
var tr *Reader
var s1, s2 string
switch j {
case 0:
tr = NewReader(&reader{strings.NewReader(v.input)})
s1, s2 = "io.Reader", "auto"
case 1:
tr = NewReader(&reader{strings.NewReader(v.input)})
s1, s2 = "io.Reader", "manual"
case 2:
tr = NewReader(&readSeeker{strings.NewReader(v.input)})
s1, s2 = "io.ReadSeeker", "auto"
case 3:
tr = NewReader(&readSeeker{strings.NewReader(v.input)})
s1, s2 = "io.ReadSeeker", "manual"
case 4:
tr = NewReader(&readBadSeeker{strings.NewReader(v.input)})
s1, s2 = "ReadBadSeeker", "auto"
case 5:
tr = NewReader(&readBadSeeker{strings.NewReader(v.input)})
s1, s2 = "ReadBadSeeker", "manual"
}
var cnt int
var err error
for {
if _, err = tr.Next(); err != nil {
break
}
cnt++
if s2 == "manual" {
if _, err = io.Copy(ioutil.Discard, tr); err != nil {
break
}
}
}
if err != v.err {
t.Errorf("test %d, NewReader(%s(...)) with %s discard: got %v, want %v",
i, s1, s2, err, v.err)
}
if cnt != v.cnt {
t.Errorf("test %d, NewReader(%s(...)) with %s discard: got %d headers, want %d headers",
i, s1, s2, cnt, v.cnt)
}
}
}
}