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s2: Add ReaderMaxBlockSize #311

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Jan 13, 2021
Merged

s2: Add ReaderMaxBlockSize #311

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118 changes: 98 additions & 20 deletions s2/decode.go
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Original file line number Diff line number Diff line change
Expand Up @@ -77,10 +77,38 @@ func Decode(dst, src []byte) ([]byte, error) {
// NewReader returns a new Reader that decompresses from r, using the framing
// format described at
// https://github.com/google/snappy/blob/master/framing_format.txt with S2 changes.
func NewReader(r io.Reader) *Reader {
return &Reader{
r: r,
buf: make([]byte, MaxEncodedLen(maxBlockSize)+checksumSize),
func NewReader(r io.Reader, opts ...ReaderOption) *Reader {
nr := Reader{
r: r,
maxBlock: maxBlockSize,
}
for _, opt := range opts {
if err := opt(&nr); err != nil {
nr.err = err
return &nr
}
}
nr.buf = make([]byte, MaxEncodedLen(nr.maxBlock)+checksumSize)
nr.paramsOK = true
return &nr
}

// ReaderOption is an option for creating a decoder.
type ReaderOption func(*Reader) error

// ReaderMaxBlockSize allows to control allocations if the stream
// has been compressed with a smaller WriterBlockSize, or with the default 1MB.
// Blocks must be this size or smaller to decompress,
// otherwise the decoder will return ErrUnsupported.
//
// Default is the maximum limit of 4MB.
func ReaderMaxBlockSize(n int) ReaderOption {
return func(r *Reader) error {
if n > maxBlockSize || n <= 0 {
return errors.New("s2: block size too large. Must be <= 4MB and > 0")
}
r.maxBlock = n
return nil
}
}

Expand All @@ -92,13 +120,18 @@ type Reader struct {
buf []byte
// decoded[i:j] contains decoded bytes that have not yet been passed on.
i, j int
maxBlock int
readHeader bool
paramsOK bool
}

// Reset discards any buffered data, resets all state, and switches the Snappy
// reader to read from r. This permits reusing a Reader rather than allocating
// a new one.
func (r *Reader) Reset(reader io.Reader) {
if !r.paramsOK {
return
}
r.r = reader
r.err = nil
r.i = 0
Expand All @@ -116,6 +149,36 @@ func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
return true
}

// skipN will skip n bytes.
// If the supplied reader supports seeking that is used.
// tmp is used as a temporary buffer for reading.
// The supplied slice does not need to be the size of the read.
func (r *Reader) skipN(tmp []byte, n int, allowEOF bool) (ok bool) {
if rs, ok := r.r.(io.ReadSeeker); ok {
_, err := rs.Seek(int64(n), io.SeekCurrent)
if err == nil {
return true
}
if err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
r.err = ErrCorrupt
return false
}
}
for n > 0 {
if n < len(tmp) {
tmp = tmp[:n]
}
if _, r.err = io.ReadFull(r.r, tmp); r.err != nil {
if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
r.err = ErrCorrupt
}
return false
}
n -= len(tmp)
}
return true
}

// Read satisfies the io.Reader interface.
func (r *Reader) Read(p []byte) (int, error) {
if r.err != nil {
Expand All @@ -139,10 +202,6 @@ func (r *Reader) Read(p []byte) (int, error) {
r.readHeader = true
}
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
if chunkLen > len(r.buf) {
r.err = ErrUnsupported
return 0, r.err
}

// The chunk types are specified at
// https://github.com/google/snappy/blob/master/framing_format.txt
Expand All @@ -153,6 +212,10 @@ func (r *Reader) Read(p []byte) (int, error) {
r.err = ErrCorrupt
return 0, r.err
}
if chunkLen > len(r.buf) {
r.err = ErrUnsupported
return 0, r.err
}
buf := r.buf[:chunkLen]
if !r.readFull(buf, false) {
return 0, r.err
Expand All @@ -166,7 +229,7 @@ func (r *Reader) Read(p []byte) (int, error) {
return 0, r.err
}
if n > len(r.decoded) {
if n > maxBlockSize {
if n > r.maxBlock {
r.err = ErrCorrupt
return 0, r.err
}
Expand All @@ -189,6 +252,10 @@ func (r *Reader) Read(p []byte) (int, error) {
r.err = ErrCorrupt
return 0, r.err
}
if chunkLen > len(r.buf) {
r.err = ErrUnsupported
return 0, r.err
}
buf := r.buf[:checksumSize]
if !r.readFull(buf, false) {
return 0, r.err
Expand All @@ -197,7 +264,7 @@ func (r *Reader) Read(p []byte) (int, error) {
// Read directly into r.decoded instead of via r.buf.
n := chunkLen - checksumSize
if n > len(r.decoded) {
if n > maxBlockSize {
if n > r.maxBlock {
r.err = ErrCorrupt
return 0, r.err
}
Expand Down Expand Up @@ -238,7 +305,12 @@ func (r *Reader) Read(p []byte) (int, error) {
}
// Section 4.4 Padding (chunk type 0xfe).
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
if !r.readFull(r.buf[:chunkLen], false) {
if chunkLen > maxBlockSize {
r.err = ErrUnsupported
return 0, r.err
}

if !r.skipN(r.buf, chunkLen, false) {
return 0, r.err
}
}
Expand Down Expand Up @@ -286,10 +358,6 @@ func (r *Reader) Skip(n int64) error {
r.readHeader = true
}
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
if chunkLen > len(r.buf) {
r.err = ErrUnsupported
return r.err
}

// The chunk types are specified at
// https://github.com/google/snappy/blob/master/framing_format.txt
Expand All @@ -300,6 +368,10 @@ func (r *Reader) Skip(n int64) error {
r.err = ErrCorrupt
return r.err
}
if chunkLen > len(r.buf) {
r.err = ErrUnsupported
return r.err
}
buf := r.buf[:chunkLen]
if !r.readFull(buf, false) {
return r.err
Expand All @@ -312,7 +384,7 @@ func (r *Reader) Skip(n int64) error {
r.err = err
return r.err
}
if dLen > maxBlockSize {
if dLen > r.maxBlock {
r.err = ErrCorrupt
return r.err
}
Expand Down Expand Up @@ -342,6 +414,10 @@ func (r *Reader) Skip(n int64) error {
r.err = ErrCorrupt
return r.err
}
if chunkLen > len(r.buf) {
r.err = ErrUnsupported
return r.err
}
buf := r.buf[:checksumSize]
if !r.readFull(buf, false) {
return r.err
Expand All @@ -350,7 +426,7 @@ func (r *Reader) Skip(n int64) error {
// Read directly into r.decoded instead of via r.buf.
n2 := chunkLen - checksumSize
if n2 > len(r.decoded) {
if n2 > maxBlockSize {
if n2 > r.maxBlock {
r.err = ErrCorrupt
return r.err
}
Expand Down Expand Up @@ -391,13 +467,15 @@ func (r *Reader) Skip(n int64) error {
r.err = ErrUnsupported
return r.err
}
if chunkLen > maxBlockSize {
r.err = ErrUnsupported
return r.err
}
// Section 4.4 Padding (chunk type 0xfe).
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
if !r.readFull(r.buf[:chunkLen], false) {
if !r.skipN(r.buf, chunkLen, false) {
return r.err
}

return io.ErrUnexpectedEOF
}
return nil
}
118 changes: 118 additions & 0 deletions s2/decode_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ package s2

import (
"bytes"
"fmt"
"io/ioutil"
"strings"
"testing"
Expand Down Expand Up @@ -41,3 +42,120 @@ func TestDecodeRegression(t *testing.T) {
})
}
}

func TestDecoderMaxBlockSize(t *testing.T) {
data, err := ioutil.ReadFile("testdata/enc_regressions.zip")
if err != nil {
t.Fatal(err)
}
zr, err := zip.NewReader(bytes.NewReader(data), int64(len(data)))
if err != nil {
t.Fatal(err)
}
sizes := []int{4 << 10, 10 << 10, 1 << 20, 4 << 20}
test := func(t *testing.T, data []byte) {
for _, size := range sizes {
t.Run(fmt.Sprintf("%d", size), func(t *testing.T) {
var buf bytes.Buffer
dec := NewReader(nil, ReaderMaxBlockSize(size))
enc := NewWriter(&buf, WriterBlockSize(size), WriterPadding(16<<10), WriterPaddingSrc(zeroReader{}))

// Test writer.
n, err := enc.Write(data)
if err != nil {
t.Error(err)
return
}
if n != len(data) {
t.Error(fmt.Errorf("Write: Short write, want %d, got %d", len(data), n))
return
}
err = enc.Close()
if err != nil {
t.Error(err)
return
}
// Calling close twice should not affect anything.
err = enc.Close()
if err != nil {
t.Error(err)
return
}

dec.Reset(&buf)
got, err := ioutil.ReadAll(dec)
if err != nil {
t.Error(err)
return
}
if !bytes.Equal(data, got) {
t.Error("block (reset) decoder mismatch")
return
}

// Test Reset on both and use ReadFrom instead.
buf.Reset()
enc.Reset(&buf)
n2, err := enc.ReadFrom(bytes.NewBuffer(data))
if err != nil {
t.Error(err)
return
}
if n2 != int64(len(data)) {
t.Error(fmt.Errorf("ReadFrom: Short read, want %d, got %d", len(data), n2))
return
}
// Encode twice...
n2, err = enc.ReadFrom(bytes.NewBuffer(data))
if err != nil {
t.Error(err)
return
}
if n2 != int64(len(data)) {
t.Error(fmt.Errorf("ReadFrom: Short read, want %d, got %d", len(data), n2))
return
}

err = enc.Close()
if err != nil {
t.Error(err)
return
}
if enc.pad > 0 && buf.Len()%enc.pad != 0 {
t.Error(fmt.Errorf("wanted size to be mutiple of %d, got size %d with remainder %d", enc.pad, buf.Len(), buf.Len()%enc.pad))
return
}
dec.Reset(&buf)
// Skip first...
dec.Skip(int64(len(data)))
got, err = ioutil.ReadAll(dec)
if err != nil {
t.Error(err)
return
}
if !bytes.Equal(data, got) {
t.Error("frame (reset) decoder mismatch")
return
}
})
}
}
for _, tt := range zr.File {
if !strings.HasSuffix(t.Name(), "") {
continue
}
t.Run(tt.Name, func(t *testing.T) {
r, err := tt.Open()
if err != nil {
t.Error(err)
return
}
b, err := ioutil.ReadAll(r)
if err != nil {
t.Error(err)
return
}
test(t, b[:len(b):len(b)])
})
}
}
2 changes: 1 addition & 1 deletion s2/encode.go
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Original file line number Diff line number Diff line change
Expand Up @@ -907,7 +907,7 @@ func WriterUncompressed() WriterOption {
// Default block size is 1MB.
func WriterBlockSize(n int) WriterOption {
return func(w *Writer) error {
if w.blockSize > maxBlockSize || w.blockSize < minBlockSize {
if n > maxBlockSize || n < minBlockSize {
return errors.New("s2: block size too large. Must be <= 4MB and >=4KB")
}
w.blockSize = n
Expand Down
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