[docker plugin] Refactor pipeline reader for data safety #14375
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,114 @@ | ||
| // Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
| // or more contributor license agreements. Licensed under the Elastic License; | ||
| // you may not use this file except in compliance with the Elastic License. | ||
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| package pipereader | ||
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| import ( | ||
| "context" | ||
| "encoding/binary" | ||
| "io" | ||
| "syscall" | ||
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| "github.com/containerd/fifo" | ||
| "github.com/docker/engine/api/types/plugins/logdriver" | ||
| "github.com/gogo/protobuf/proto" | ||
| "github.com/pkg/errors" | ||
| ) | ||
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| // PipeReader reads from the FIFO pipe we get from the docker container | ||
| type PipeReader struct { | ||
| fifoPipe io.ReadCloser | ||
| byteOrder binary.ByteOrder | ||
| lenFrameBuf []byte | ||
| bodyBuf []byte | ||
| maxSize int | ||
| } | ||
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| // NewReaderFromPath creates a new FIFO pipe reader from a docker log pipe location | ||
| func NewReaderFromPath(file string) (*PipeReader, error) { | ||
| inputFile, err := fifo.OpenFifo(context.Background(), file, syscall.O_RDONLY, 0700) | ||
| if err != nil { | ||
| return nil, errors.Wrapf(err, "error opening logger fifo: %q", file) | ||
| } | ||
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| return &PipeReader{fifoPipe: inputFile, byteOrder: binary.BigEndian, lenFrameBuf: make([]byte, 4), bodyBuf: nil, maxSize: 2e6}, nil | ||
| } | ||
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| // NewReaderFromReadCloser creates a new FIFO pipe reader from an existing ReadCloser | ||
| func NewReaderFromReadCloser(pipe io.ReadCloser) (*PipeReader, error) { | ||
| return &PipeReader{fifoPipe: pipe, byteOrder: binary.BigEndian, lenFrameBuf: make([]byte, 4), bodyBuf: nil, maxSize: 2e6}, nil | ||
| } | ||
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| // ReadMessage reads a log message from the pipe | ||
| // The message stream consists of a 4-byte length frame and a message body | ||
| // There's three logical paths for this code to take: | ||
| // 1) If length <0, we have bad data, and we cycle through the frames until we get a valid length. | ||
| // 2) If length is valid but larger than the max buffer size, we disregard length bytes and continue | ||
| // 3) If length is valid and we can consume everything into the buffer, continue. | ||
| func (reader *PipeReader) ReadMessage(log *logdriver.LogEntry) error { | ||
| // loop until we're at a valid state and ready to read a message body | ||
| var lenFrame int | ||
| var err error | ||
| for { | ||
| lenFrame, err = reader.getValidLengthFrame() | ||
| if err != nil { | ||
| return errors.Wrap(err, "error getting length frame") | ||
| } | ||
| if lenFrame <= reader.maxSize { | ||
| break | ||
| } | ||
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| // 2) we have a too-large message. Disregard length bytes | ||
| _, err = io.CopyBuffer(nil, io.LimitReader(reader.fifoPipe, int64(lenFrame)), reader.bodyBuf) | ||
| if err != nil { | ||
| return errors.Wrap(err, "error emptying buffer") | ||
| } | ||
| } | ||
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| //proceed with 3) | ||
| readBuf := reader.setBuffer(lenFrame) | ||
| _, err = io.ReadFull(reader.fifoPipe, readBuf[:lenFrame]) | ||
| if err != nil { | ||
| return errors.Wrap(err, "error reading buffer") | ||
| } | ||
| return proto.Unmarshal(readBuf[:lenFrame], log) | ||
|
There was a problem hiding this comment. nit: given |
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| } | ||
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| // setBuffer checks the needed size, and returns a buffer, allocating a new buffer if needed | ||
| func (reader *PipeReader) setBuffer(sz int) []byte { | ||
| const minSz = 1024 | ||
| const maxSz = minSz * 32 | ||
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| // return only the portion of the buffer we need | ||
| if len(reader.bodyBuf) >= sz { | ||
| return reader.bodyBuf[:sz] | ||
| } | ||
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| // if we have an abnormally large buffer, don't set it to bodyBuf so GC can clean it up | ||
| if sz > maxSz { | ||
| return make([]byte, sz) | ||
| } | ||
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| reader.bodyBuf = make([]byte, sz) | ||
| return reader.bodyBuf | ||
| } | ||
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| // getValidLengthFrame scrolls through the buffer until we get a valid length | ||
| func (reader *PipeReader) getValidLengthFrame() (int, error) { | ||
| for { | ||
| if _, err := io.ReadFull(reader.fifoPipe, reader.lenFrameBuf); err != nil { | ||
| return 0, err | ||
| } | ||
| bodyLen := int(reader.byteOrder.Uint32(reader.lenFrameBuf)) | ||
| if bodyLen > 0 { | ||
| return bodyLen, nil | ||
| } | ||
| } | ||
| } | ||
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| // Close closes the reader and underlying pipe | ||
| func (reader *PipeReader) Close() error { | ||
| return reader.fifoPipe.Close() | ||
| } | ||
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consider calling
NewReaderFromReadCloser