From 720c192831a890d0a36b4c6720b60411fa4a0159 Mon Sep 17 00:00:00 2001 From: zeripath Date: Wed, 12 May 2021 21:42:07 +0100 Subject: [PATCH] plumbing: format/packfile, prevent large objects from being read into memory completely (#303) This PR adds code to prevent large objects from being read into memory from packfiles or the filesystem. Objects greater than 1Mb are now no longer directly stored in the cache or read completely into memory. Signed-off-by: Andrew Thornton --- plumbing/format/packfile/fsobject.go | 15 ++ plumbing/format/packfile/packfile.go | 73 ++++++++ plumbing/format/packfile/patch_delta.go | 210 ++++++++++++++++++++++++ plumbing/format/packfile/scanner.go | 15 ++ storage/filesystem/dotgit/reader.go | 79 +++++++++ storage/filesystem/object.go | 9 +- utils/ioutil/common.go | 22 +++ 7 files changed, 422 insertions(+), 1 deletion(-) create mode 100644 storage/filesystem/dotgit/reader.go diff --git a/plumbing/format/packfile/fsobject.go b/plumbing/format/packfile/fsobject.go index c5edaf52e..4aa3c8e01 100644 --- a/plumbing/format/packfile/fsobject.go +++ b/plumbing/format/packfile/fsobject.go @@ -7,6 +7,7 @@ import ( "github.com/go-git/go-git/v5/plumbing" "github.com/go-git/go-git/v5/plumbing/cache" "github.com/go-git/go-git/v5/plumbing/format/idxfile" + "github.com/go-git/go-git/v5/utils/ioutil" ) // FSObject is an object from the packfile on the filesystem. @@ -63,6 +64,20 @@ func (o *FSObject) Reader() (io.ReadCloser, error) { } p := NewPackfileWithCache(o.index, nil, f, o.cache) + if o.size > LargeObjectThreshold { + // We have a big object + h, err := p.objectHeaderAtOffset(o.offset) + if err != nil { + return nil, err + } + + r, err := p.getReaderDirect(h) + if err != nil { + _ = f.Close() + return nil, err + } + return ioutil.NewReadCloserWithCloser(r, f.Close), nil + } r, err := p.getObjectContent(o.offset) if err != nil { _ = f.Close() diff --git a/plumbing/format/packfile/packfile.go b/plumbing/format/packfile/packfile.go index ddd7f62fc..77861d257 100644 --- a/plumbing/format/packfile/packfile.go +++ b/plumbing/format/packfile/packfile.go @@ -32,6 +32,12 @@ var ( // wrapped in FSObject. const smallObjectThreshold = 16 * 1024 +// Conversely there are large objects that should not be cached and kept +// in memory as they're too large to be reasonably cached. Objects larger +// than this threshold are now always never read into memory to be stored +// in the cache +const LargeObjectThreshold = 1024 * 1024 + // Packfile allows retrieving information from inside a packfile. type Packfile struct { idxfile.Index @@ -282,6 +288,37 @@ func (p *Packfile) getObjectContent(offset int64) (io.ReadCloser, error) { return obj.Reader() } +func (p *Packfile) getReaderDirect(h *ObjectHeader) (io.ReadCloser, error) { + switch h.Type { + case plumbing.CommitObject, plumbing.TreeObject, plumbing.BlobObject, plumbing.TagObject: + return p.s.ReadObject() + case plumbing.REFDeltaObject: + deltaRC, err := p.s.ReadObject() + if err != nil { + return nil, err + } + r, err := p.readREFDeltaObjectContent(h, deltaRC) + if err != nil { + _ = deltaRC.Close() + return nil, err + } + return r, nil + case plumbing.OFSDeltaObject: + deltaRC, err := p.s.ReadObject() + if err != nil { + return nil, err + } + r, err := p.readOFSDeltaObjectContent(h, deltaRC) + if err != nil { + _ = deltaRC.Close() + return nil, err + } + return r, nil + default: + return nil, ErrInvalidObject.AddDetails("type %q", h.Type) + } +} + func (p *Packfile) getNextMemoryObject(h *ObjectHeader) (plumbing.EncodedObject, error) { var obj = new(plumbing.MemoryObject) obj.SetSize(h.Length) @@ -334,6 +371,20 @@ func (p *Packfile) fillREFDeltaObjectContent(obj plumbing.EncodedObject, ref plu return p.fillREFDeltaObjectContentWithBuffer(obj, ref, buf) } +func (p *Packfile) readREFDeltaObjectContent(h *ObjectHeader, deltaRC io.ReadCloser) (io.ReadCloser, error) { + var err error + + base, ok := p.cacheGet(h.Reference) + if !ok { + base, err = p.Get(h.Reference) + if err != nil { + return nil, err + } + } + + return ReaderFromDelta(h, base, deltaRC) +} + func (p *Packfile) fillREFDeltaObjectContentWithBuffer(obj plumbing.EncodedObject, ref plumbing.Hash, buf *bytes.Buffer) error { var err error @@ -364,6 +415,28 @@ func (p *Packfile) fillOFSDeltaObjectContent(obj plumbing.EncodedObject, offset return p.fillOFSDeltaObjectContentWithBuffer(obj, offset, buf) } +func (p *Packfile) readOFSDeltaObjectContent(h *ObjectHeader, deltaRC io.ReadCloser) (io.ReadCloser, error) { + hash, err := p.FindHash(h.OffsetReference) + if err != nil { + return nil, err + } + + base, err := p.objectAtOffset(h.OffsetReference, hash) + if err != nil { + return nil, err + } + + base, ok := p.cacheGet(h.Reference) + if !ok { + base, err = p.Get(h.Reference) + if err != nil { + return nil, err + } + } + + return ReaderFromDelta(h, base, deltaRC) +} + func (p *Packfile) fillOFSDeltaObjectContentWithBuffer(obj plumbing.EncodedObject, offset int64, buf *bytes.Buffer) error { hash, err := p.FindHash(offset) if err != nil { diff --git a/plumbing/format/packfile/patch_delta.go b/plumbing/format/packfile/patch_delta.go index 9e90f30a7..76fef4a13 100644 --- a/plumbing/format/packfile/patch_delta.go +++ b/plumbing/format/packfile/patch_delta.go @@ -1,9 +1,11 @@ package packfile import ( + "bufio" "bytes" "errors" "io" + "math" "github.com/go-git/go-git/v5/plumbing" "github.com/go-git/go-git/v5/utils/ioutil" @@ -73,6 +75,131 @@ func PatchDelta(src, delta []byte) ([]byte, error) { return b.Bytes(), nil } +func ReaderFromDelta(h *ObjectHeader, base plumbing.EncodedObject, deltaRC io.ReadCloser) (io.ReadCloser, error) { + deltaBuf := bufio.NewReaderSize(deltaRC, 1024) + srcSz, err := decodeLEB128ByteReader(deltaBuf) + if err != nil { + if err == io.EOF { + return nil, ErrInvalidDelta + } + return nil, err + } + if srcSz != uint(base.Size()) { + return nil, ErrInvalidDelta + } + + targetSz, err := decodeLEB128ByteReader(deltaBuf) + if err != nil { + if err == io.EOF { + return nil, ErrInvalidDelta + } + return nil, err + } + remainingTargetSz := targetSz + + dstRd, dstWr := io.Pipe() + + go func() { + baseRd, err := base.Reader() + if err != nil { + _ = dstWr.CloseWithError(ErrInvalidDelta) + return + } + defer baseRd.Close() + + baseBuf := bufio.NewReader(baseRd) + basePos := uint(0) + + for { + cmd, err := deltaBuf.ReadByte() + if err == io.EOF { + _ = dstWr.CloseWithError(ErrInvalidDelta) + return + } + if err != nil { + _ = dstWr.CloseWithError(err) + return + } + + if isCopyFromSrc(cmd) { + offset, err := decodeOffsetByteReader(cmd, deltaBuf) + if err != nil { + _ = dstWr.CloseWithError(err) + return + } + sz, err := decodeSizeByteReader(cmd, deltaBuf) + if err != nil { + _ = dstWr.CloseWithError(err) + return + } + + if invalidSize(sz, targetSz) || + invalidOffsetSize(offset, sz, srcSz) { + _ = dstWr.Close() + return + } + + discard := offset - basePos + if discard < 0 { + _ = baseRd.Close() + baseRd, err = base.Reader() + if err != nil { + _ = dstWr.CloseWithError(ErrInvalidDelta) + return + } + baseBuf.Reset(baseRd) + discard = offset + } + for discard > math.MaxInt32 { + n, err := baseBuf.Discard(math.MaxInt32) + if err != nil { + _ = dstWr.CloseWithError(err) + return + } + basePos += uint(n) + discard -= uint(n) + } + for discard > 0 { + n, err := baseBuf.Discard(int(discard)) + if err != nil { + _ = dstWr.CloseWithError(err) + return + } + basePos += uint(n) + discard -= uint(n) + } + if _, err := io.Copy(dstWr, io.LimitReader(baseBuf, int64(sz))); err != nil { + _ = dstWr.CloseWithError(err) + return + } + remainingTargetSz -= sz + basePos += sz + } else if isCopyFromDelta(cmd) { + sz := uint(cmd) // cmd is the size itself + if invalidSize(sz, targetSz) { + _ = dstWr.CloseWithError(ErrInvalidDelta) + return + } + if _, err := io.Copy(dstWr, io.LimitReader(deltaBuf, int64(sz))); err != nil { + _ = dstWr.CloseWithError(err) + return + } + + remainingTargetSz -= sz + } else { + _ = dstWr.CloseWithError(ErrDeltaCmd) + return + } + if remainingTargetSz <= 0 { + _ = dstWr.Close() + return + } + } + }() + + return dstRd, nil +} + func patchDelta(dst *bytes.Buffer, src, delta []byte) error { if len(delta) < deltaSizeMin { return ErrInvalidDelta @@ -161,6 +288,25 @@ func decodeLEB128(input []byte) (uint, []byte) { return num, input[sz:] } +func decodeLEB128ByteReader(input io.ByteReader) (uint, error) { + var num, sz uint + for { + b, err := input.ReadByte() + if err != nil { + return 0, err + } + + num |= (uint(b) & payload) << (sz * 7) // concats 7 bits chunks + sz++ + + if uint(b)&continuation == 0 { + break + } + } + + return num, nil +} + const ( payload = 0x7f // 0111 1111 continuation = 0x80 // 1000 0000 @@ -174,6 +320,40 @@ func isCopyFromDelta(cmd byte) bool { return (cmd&0x80) == 0 && cmd != 0 } +func decodeOffsetByteReader(cmd byte, delta io.ByteReader) (uint, error) { + var offset uint + if (cmd & 0x01) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + offset = uint(next) + } + if (cmd & 0x02) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + offset |= uint(next) << 8 + } + if (cmd & 0x04) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + offset |= uint(next) << 16 + } + if (cmd & 0x08) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + offset |= uint(next) << 24 + } + + return offset, nil +} + func decodeOffset(cmd byte, delta []byte) (uint, []byte, error) { var offset uint if (cmd & 0x01) != 0 { @@ -208,6 +388,36 @@ func decodeOffset(cmd byte, delta []byte) (uint, []byte, error) { return offset, delta, nil } +func decodeSizeByteReader(cmd byte, delta io.ByteReader) (uint, error) { + var sz uint + if (cmd & 0x10) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + sz = uint(next) + } + if (cmd & 0x20) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + sz |= uint(next) << 8 + } + if (cmd & 0x40) != 0 { + next, err := delta.ReadByte() + if err != nil { + return 0, err + } + sz |= uint(next) << 16 + } + if sz == 0 { + sz = 0x10000 + } + + return sz, nil +} + func decodeSize(cmd byte, delta []byte) (uint, []byte, error) { var sz uint if (cmd & 0x10) != 0 { diff --git a/plumbing/format/packfile/scanner.go b/plumbing/format/packfile/scanner.go index 6e6a68788..5d9e8fb65 100644 --- a/plumbing/format/packfile/scanner.go +++ b/plumbing/format/packfile/scanner.go @@ -320,6 +320,21 @@ func (s *Scanner) NextObject(w io.Writer) (written int64, crc32 uint32, err erro return } +// ReadObject returns a reader for the object content and an error +func (s *Scanner) ReadObject() (io.ReadCloser, error) { + s.pendingObject = nil + zr := zlibReaderPool.Get().(io.ReadCloser) + + if err := zr.(zlib.Resetter).Reset(s.r, nil); err != nil { + return nil, fmt.Errorf("zlib reset error: %s", err) + } + + return ioutil.NewReadCloserWithCloser(zr, func() error { + zlibReaderPool.Put(zr) + return nil + }), nil +} + // ReadRegularObject reads and write a non-deltified object // from it zlib stream in an object entry in the packfile. func (s *Scanner) copyObject(w io.Writer) (n int64, err error) { diff --git a/storage/filesystem/dotgit/reader.go b/storage/filesystem/dotgit/reader.go new file mode 100644 index 000000000..a82ac94eb --- /dev/null +++ b/storage/filesystem/dotgit/reader.go @@ -0,0 +1,79 @@ +package dotgit + +import ( + "fmt" + "io" + "os" + + "github.com/go-git/go-git/v5/plumbing" + "github.com/go-git/go-git/v5/plumbing/format/objfile" + "github.com/go-git/go-git/v5/utils/ioutil" +) + +var _ (plumbing.EncodedObject) = &EncodedObject{} + +type EncodedObject struct { + dir *DotGit + h plumbing.Hash + t plumbing.ObjectType + sz int64 +} + +func (e *EncodedObject) Hash() plumbing.Hash { + return e.h +} + +func (e *EncodedObject) Reader() (io.ReadCloser, error) { + f, err := e.dir.Object(e.h) + if err != nil { + if os.IsNotExist(err) { + return nil, plumbing.ErrObjectNotFound + } + + return nil, err + } + r, err := objfile.NewReader(f) + if err != nil { + return nil, err + } + + t, size, err := r.Header() + if err != nil { + _ = r.Close() + return nil, err + } + if t != e.t { + _ = r.Close() + return nil, objfile.ErrHeader + } + if size != e.sz { + _ = r.Close() + return nil, objfile.ErrHeader + } + return ioutil.NewReadCloserWithCloser(r, f.Close), nil +} + +func (e *EncodedObject) SetType(plumbing.ObjectType) {} + +func (e *EncodedObject) Type() plumbing.ObjectType { + return e.t +} + +func (e *EncodedObject) Size() int64 { + return e.sz +} + +func (e *EncodedObject) SetSize(int64) {} + +func (e *EncodedObject) Writer() (io.WriteCloser, error) { + return nil, fmt.Errorf("Not supported") +} + +func NewEncodedObject(dir *DotGit, h plumbing.Hash, t plumbing.ObjectType, size int64) *EncodedObject { + return &EncodedObject{ + dir: dir, + h: h, + t: t, + sz: size, + } +} diff --git a/storage/filesystem/object.go b/storage/filesystem/object.go index 0c25dad61..4862362fc 100644 --- a/storage/filesystem/object.go +++ b/storage/filesystem/object.go @@ -389,7 +389,6 @@ func (s *ObjectStorage) getFromUnpacked(h plumbing.Hash) (obj plumbing.EncodedOb return cacheObj, nil } - obj = s.NewEncodedObject() r, err := objfile.NewReader(f) if err != nil { return nil, err @@ -402,6 +401,14 @@ func (s *ObjectStorage) getFromUnpacked(h plumbing.Hash) (obj plumbing.EncodedOb return nil, err } + if size > packfile.LargeObjectThreshold { + obj = dotgit.NewEncodedObject(s.dir, h, t, size) + s.objectCache.Put(obj) + return obj, nil + } + + obj = s.NewEncodedObject() + obj.SetType(t) obj.SetSize(size) w, err := obj.Writer() diff --git a/utils/ioutil/common.go b/utils/ioutil/common.go index b52e85a38..a0e79a2e2 100644 --- a/utils/ioutil/common.go +++ b/utils/ioutil/common.go @@ -55,6 +55,28 @@ func NewReadCloser(r io.Reader, c io.Closer) io.ReadCloser { return &readCloser{Reader: r, closer: c} } +type readCloserCloser struct { + io.ReadCloser + closer func() error +} + +func (r *readCloserCloser) Close() (err error) { + defer func() { + if err == nil { + err = r.closer() + return + } + _ = r.closer() + }() + return r.ReadCloser.Close() +} + +// NewReadCloserWithCloser creates an `io.ReadCloser` with the given `io.ReaderCloser` and +// `io.Closer` that ensures that the closer is closed on close +func NewReadCloserWithCloser(r io.ReadCloser, c func() error) io.ReadCloser { + return &readCloserCloser{ReadCloser: r, closer: c} +} + type writeCloser struct { io.Writer closer io.Closer