package tarsum import ( "bytes" "compress/gzip" "crypto/sha256" "encoding/hex" "hash" "io" "sort" "strconv" "strings" "github.com/docker/docker/vendor/src/code.google.com/p/go/src/pkg/archive/tar" "github.com/docker/docker/pkg/log" ) const ( buf8K = 8 * 1024 buf16K = 16 * 1024 buf32K = 32 * 1024 ) // NewTarSum creates a new interface for calculating a fixed time checksum of a // tar archive. // // This is used for calculating checksums of layers of an image, in some cases // including the byte payload of the image's json metadata as well, and for // calculating the checksums for buildcache. func NewTarSum(r io.Reader, dc bool, v Version) (TarSum, error) { if _, ok := tarSumVersions[v]; !ok { return nil, ErrVersionNotImplemented } return &tarSum{Reader: r, DisableCompression: dc, tarSumVersion: v}, nil } // TarSum is the generic interface for calculating fixed time // checksums of a tar archive type TarSum interface { io.Reader GetSums() FileInfoSums Sum([]byte) string Version() Version } // tarSum struct is the structure for a Version0 checksum calculation type tarSum struct { io.Reader tarR *tar.Reader tarW *tar.Writer gz writeCloseFlusher bufTar *bytes.Buffer bufGz *bytes.Buffer bufData []byte h hash.Hash sums FileInfoSums fileCounter int64 currentFile string finished bool first bool DisableCompression bool // false by default. When false, the output gzip compressed. tarSumVersion Version // this field is not exported so it can not be mutated during use } func (ts tarSum) Version() Version { return ts.tarSumVersion } func (ts tarSum) selectHeaders(h *tar.Header, v Version) (set [][2]string) { for _, elem := range [][2]string{ {"name", h.Name}, {"mode", strconv.Itoa(int(h.Mode))}, {"uid", strconv.Itoa(h.Uid)}, {"gid", strconv.Itoa(h.Gid)}, {"size", strconv.Itoa(int(h.Size))}, {"mtime", strconv.Itoa(int(h.ModTime.UTC().Unix()))}, {"typeflag", string([]byte{h.Typeflag})}, {"linkname", h.Linkname}, {"uname", h.Uname}, {"gname", h.Gname}, {"devmajor", strconv.Itoa(int(h.Devmajor))}, {"devminor", strconv.Itoa(int(h.Devminor))}, } { if v >= VersionDev && elem[0] == "mtime" { continue } set = append(set, elem) } return } func (ts *tarSum) encodeHeader(h *tar.Header) error { for _, elem := range ts.selectHeaders(h, ts.Version()) { if _, err := ts.h.Write([]byte(elem[0] + elem[1])); err != nil { return err } } // include the additional pax headers, from an ordered list if ts.Version() >= VersionDev { var keys []string for k := range h.Xattrs { keys = append(keys, k) } sort.Strings(keys) for _, k := range keys { if _, err := ts.h.Write([]byte(k + h.Xattrs[k])); err != nil { return err } } } return nil } func (ts *tarSum) Read(buf []byte) (int, error) { if ts.gz == nil { ts.bufTar = bytes.NewBuffer([]byte{}) ts.bufGz = bytes.NewBuffer([]byte{}) ts.tarR = tar.NewReader(ts.Reader) ts.tarW = tar.NewWriter(ts.bufTar) if !ts.DisableCompression { ts.gz = gzip.NewWriter(ts.bufGz) } else { ts.gz = &nopCloseFlusher{Writer: ts.bufGz} } ts.h = sha256.New() ts.h.Reset() ts.first = true ts.sums = FileInfoSums{} } if ts.finished { return ts.bufGz.Read(buf) } if ts.bufData == nil { switch { case len(buf) <= buf8K: ts.bufData = make([]byte, buf8K) case len(buf) <= buf16K: ts.bufData = make([]byte, buf16K) case len(buf) <= buf32K: ts.bufData = make([]byte, buf32K) default: ts.bufData = make([]byte, len(buf)) } } buf2 := ts.bufData[:len(buf)-1] n, err := ts.tarR.Read(buf2) if err != nil { if err == io.EOF { if _, err := ts.h.Write(buf2[:n]); err != nil { return 0, err } if !ts.first { ts.sums = append(ts.sums, fileInfoSum{name: ts.currentFile, sum: hex.EncodeToString(ts.h.Sum(nil)), pos: ts.fileCounter}) ts.fileCounter++ ts.h.Reset() } else { ts.first = false } currentHeader, err := ts.tarR.Next() if err != nil { if err == io.EOF { if err := ts.tarW.Close(); err != nil { return 0, err } if _, err := io.Copy(ts.gz, ts.bufTar); err != nil { return 0, err } if err := ts.gz.Close(); err != nil { return 0, err } ts.finished = true return n, nil } return n, err } ts.currentFile = strings.TrimSuffix(strings.TrimPrefix(currentHeader.Name, "./"), "/") if err := ts.encodeHeader(currentHeader); err != nil { return 0, err } if err := ts.tarW.WriteHeader(currentHeader); err != nil { return 0, err } if _, err := ts.tarW.Write(buf2[:n]); err != nil { return 0, err } ts.tarW.Flush() if _, err := io.Copy(ts.gz, ts.bufTar); err != nil { return 0, err } ts.gz.Flush() return ts.bufGz.Read(buf) } return n, err } // Filling the hash buffer if _, err = ts.h.Write(buf2[:n]); err != nil { return 0, err } // Filling the tar writter if _, err = ts.tarW.Write(buf2[:n]); err != nil { return 0, err } ts.tarW.Flush() // Filling the gz writter if _, err = io.Copy(ts.gz, ts.bufTar); err != nil { return 0, err } ts.gz.Flush() return ts.bufGz.Read(buf) } func (ts *tarSum) Sum(extra []byte) string { ts.sums.SortBySums() h := sha256.New() if extra != nil { h.Write(extra) } for _, fis := range ts.sums { log.Debugf("-->%s<--", fis.Sum()) h.Write([]byte(fis.Sum())) } checksum := ts.Version().String() + "+sha256:" + hex.EncodeToString(h.Sum(nil)) log.Debugf("checksum processed: %s", checksum) return checksum } func (ts *tarSum) GetSums() FileInfoSums { return ts.sums }