diff options
| -rw-r--r-- | src/archive/tar/writer.go | 253 |
1 files changed, 11 insertions, 242 deletions
diff --git a/src/archive/tar/writer.go b/src/archive/tar/writer.go index c4d908c4ea..be600895d5 100644 --- a/src/archive/tar/writer.go +++ b/src/archive/tar/writer.go @@ -14,7 +14,6 @@ import ( "io" "path" "sort" - "strconv" "strings" "time" ) @@ -31,15 +30,11 @@ var ( // Call WriteHeader to begin a new file, and then call Write to supply that file's data, // writing at most hdr.Size bytes in total. type Writer struct { - w io.Writer - err error - nb int64 // number of unwritten bytes for current file entry - pad int64 // amount of padding to write after current file entry - closed bool - usedBinary bool // whether the binary numeric field extension was used - preferPax bool // use PAX header instead of binary numeric header - hdrBuff block // buffer to use in writeHeader when writing a regular header - paxHdrBuff block // buffer to use in writeHeader when writing a PAX header + w io.Writer + err error + nb int64 // number of unwritten bytes for current file entry + pad int64 // amount of padding to write after current file entry + closed bool blk block // Buffer to use as temporary local storage } @@ -57,28 +52,21 @@ func (tw *Writer) Flush() error { tw.err = fmt.Errorf("archive/tar: missed writing %d bytes", tw.nb) return tw.err } - tw.err = tw.writePadding() - return tw.err -} - -func (tw *Writer) writePadding() error { - if _, err := tw.w.Write(zeroBlock[:tw.pad]); err != nil { - return err + if _, tw.err = tw.w.Write(zeroBlock[:tw.pad]); tw.err != nil { + return tw.err } tw.pad = 0 return nil } -var ( - minTime = time.Unix(0, 0) - // There is room for 11 octal digits (33 bits) of mtime. - maxTime = minTime.Add((1<<33 - 1) * time.Second) -) - // WriteHeader writes hdr and prepares to accept the file's contents. // WriteHeader calls Flush if it is not the first header. // Calling after a Close will return ErrWriteAfterClose. func (tw *Writer) WriteHeader(hdr *Header) error { + if err := tw.Flush(); err != nil { + return err + } + // TODO(dsnet): Add PAX timestamps with nanosecond support. hdrCpy := *hdr hdrCpy.ModTime = hdrCpy.ModTime.Truncate(time.Second) @@ -254,176 +242,6 @@ func (tw *Writer) writeRawHeader(blk *block, size int64) error { return nil } -// WriteHeader writes hdr and prepares to accept the file's contents. -// WriteHeader calls Flush if it is not the first header. -// Calling after a Close will return ErrWriteAfterClose. -// As this method is called internally by writePax header to allow it to -// suppress writing the pax header. -func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error { - if tw.closed { - return ErrWriteAfterClose - } - if tw.err == nil { - tw.Flush() - } - if tw.err != nil { - return tw.err - } - - // a map to hold pax header records, if any are needed - paxHeaders := make(map[string]string) - - // TODO(dsnet): we might want to use PAX headers for - // subsecond time resolution, but for now let's just capture - // too long fields or non ascii characters - - // We need to select which scratch buffer to use carefully, - // since this method is called recursively to write PAX headers. - // If allowPax is true, this is the non-recursive call, and we will use hdrBuff. - // If allowPax is false, we are being called by writePAXHeaderLegacy, and hdrBuff is - // already being used by the non-recursive call, so we must use paxHdrBuff. - header := &tw.hdrBuff - if !allowPax { - header = &tw.paxHdrBuff - } - copy(header[:], zeroBlock[:]) - - // Wrappers around formatter that automatically sets paxHeaders if the - // argument extends beyond the capacity of the input byte slice. - var f formatter - var formatString = func(b []byte, s string, paxKeyword string) { - needsPaxHeader := paxKeyword != paxNone && len(s) > len(b) || !isASCII(s) - if needsPaxHeader { - paxHeaders[paxKeyword] = s - } - - // Write string in a best-effort manner to satisfy readers that expect - // the field to be non-empty. - s = toASCII(s) - if len(s) > len(b) { - s = s[:len(b)] - } - f.formatString(b, s) // Should never error - } - var formatNumeric = func(b []byte, x int64, paxKeyword string) { - if !fitsInOctal(len(b), x) { - if paxKeyword != paxNone && tw.preferPax { - // Use PAX format. - f.formatOctal(b, 0) - paxHeaders[paxKeyword] = strconv.FormatInt(x, 10) - return - } else { - // Use GNU format. - tw.usedBinary = true - } - } - f.formatNumeric(b, x) - } - - // Handle out of range ModTime carefully. - var modTime int64 - if !hdr.ModTime.Before(minTime) && !hdr.ModTime.After(maxTime) { - modTime = hdr.ModTime.Unix() - } - - v7 := header.V7() - formatString(v7.Name(), hdr.Name, paxPath) - // TODO(dsnet): The GNU format permits the mode field to be encoded in - // base-256 format. Thus, we can use formatNumeric instead of formatOctal. - f.formatOctal(v7.Mode(), hdr.Mode) - formatNumeric(v7.UID(), int64(hdr.Uid), paxUid) - formatNumeric(v7.GID(), int64(hdr.Gid), paxGid) - formatNumeric(v7.Size(), hdr.Size, paxSize) - // TODO(dsnet): Consider using PAX for finer time granularity. - formatNumeric(v7.ModTime(), modTime, paxNone) - v7.TypeFlag()[0] = hdr.Typeflag - formatString(v7.LinkName(), hdr.Linkname, paxLinkpath) - - ustar := header.USTAR() - formatString(ustar.UserName(), hdr.Uname, paxUname) - formatString(ustar.GroupName(), hdr.Gname, paxGname) - formatNumeric(ustar.DevMajor(), hdr.Devmajor, paxNone) - formatNumeric(ustar.DevMinor(), hdr.Devminor, paxNone) - - // TODO(dsnet): The logic surrounding the prefix field is broken when trying - // to encode the header as GNU format. The challenge with the current logic - // is that we are unsure what format we are using at any given moment until - // we have processed *all* of the fields. The problem is that by the time - // all fields have been processed, some work has already been done to handle - // each field under the assumption that it is for one given format or - // another. In some situations, this causes the Writer to be confused and - // encode a prefix field when the format being used is GNU. Thus, producing - // an invalid tar file. - // - // As a short-term fix, we disable the logic to use the prefix field, which - // will force the badly generated GNU files to become encoded as being - // the PAX format. - // - // As an alternative fix, we could hard-code preferPax to be true. However, - // this is problematic for the following reasons: - // * The preferPax functionality is not tested at all. - // * This can result in headers that try to use both the GNU and PAX - // features at the same time, which is also wrong. - // - // The proper fix for this is to use a two-pass method: - // * The first pass simply determines what set of formats can possibly - // encode the given header. - // * The second pass actually encodes the header as that given format - // without worrying about violating the format. - // - // See the following: - // https://golang.org/issue/12594 - // https://golang.org/issue/17630 - // https://golang.org/issue/9683 - const usePrefix = false - - // try to use a ustar header when only the name is too long - _, paxPathUsed := paxHeaders[paxPath] - if usePrefix && !tw.preferPax && len(paxHeaders) == 1 && paxPathUsed { - prefix, suffix, ok := splitUSTARPath(hdr.Name) - if ok { - // Since we can encode in USTAR format, disable PAX header. - delete(paxHeaders, paxPath) - - // Update the path fields - formatString(v7.Name(), suffix, paxNone) - formatString(ustar.Prefix(), prefix, paxNone) - } - } - - if tw.usedBinary { - header.SetFormat(formatGNU) - } else { - header.SetFormat(formatUSTAR) - } - - // Check if there were any formatting errors. - if f.err != nil { - tw.err = f.err - return tw.err - } - - if allowPax { - for k, v := range hdr.Xattrs { - paxHeaders[paxXattr+k] = v - } - } - - if len(paxHeaders) > 0 { - if !allowPax { - return errInvalidHeader - } - if err := tw.writePAXHeaderLegacy(hdr, paxHeaders); err != nil { - return err - } - } - tw.nb = hdr.Size - tw.pad = (blockSize - (tw.nb % blockSize)) % blockSize - - _, tw.err = tw.w.Write(header[:]) - return tw.err -} - // splitUSTARPath splits a path according to USTAR prefix and suffix rules. // If the path is not splittable, then it will return ("", "", false). func splitUSTARPath(name string) (prefix, suffix string, ok bool) { @@ -445,55 +263,6 @@ func splitUSTARPath(name string) (prefix, suffix string, ok bool) { return name[:i], name[i+1:], true } -// writePAXHeaderLegacy writes an extended pax header to the -// archive. -func (tw *Writer) writePAXHeaderLegacy(hdr *Header, paxHeaders map[string]string) error { - // Prepare extended header - ext := new(Header) - ext.Typeflag = TypeXHeader - // Setting ModTime is required for reader parsing to - // succeed, and seems harmless enough. - ext.ModTime = hdr.ModTime - // The spec asks that we namespace our pseudo files - // with the current pid. However, this results in differing outputs - // for identical inputs. As such, the constant 0 is now used instead. - // golang.org/issue/12358 - dir, file := path.Split(hdr.Name) - fullName := path.Join(dir, "PaxHeaders.0", file) - - ascii := toASCII(fullName) - if len(ascii) > nameSize { - ascii = ascii[:nameSize] - } - ext.Name = ascii - // Construct the body - var buf bytes.Buffer - - // Keys are sorted before writing to body to allow deterministic output. - keys := make([]string, 0, len(paxHeaders)) - for k := range paxHeaders { - keys = append(keys, k) - } - sort.Strings(keys) - - for _, k := range keys { - rec, err := formatPAXRecord(k, paxHeaders[k]) - if err != nil { - return err - } - fmt.Fprint(&buf, rec) - } - - ext.Size = int64(len(buf.Bytes())) - if err := tw.writeHeader(ext, false); err != nil { - return err - } - if _, err := tw.Write(buf.Bytes()); err != nil { - return err - } - return tw.writePadding() -} - // Write writes to the current entry in the tar archive. // Write returns the error ErrWriteTooLong if more than // hdr.Size bytes are written after WriteHeader. |