Brian Gitonga Marete
690e22b80a
This patch implements the facilities needed to compress data before encryption as allowed (and recommended) by RFC 4880. The new functionality is then used to add support for compressing data during symmetric encryption (openpgp.SymmetricallyEncrypt()). For now, compression defaults to off. Also, only the ZIP and ZLIB compression schemes are supported by this patch. Resulting output tested/verified using GPG. https://gist.github.com/marete/6189760 is a small program that can be used to test that the output of various compression/encryption settings can be read by GPG or other RFC 4880 programs. Upon review, I will follow this patch with 2 others: a) Add support for compression during public key encryption (openpgp.Encrypt()) b) Enable compression by default (subject to the restrictions of the "Compression Preferences" section in RFC 4880). R=golang-dev, agl CC=golang-dev https://golang.org/cl/12685044
124 lines
3.2 KiB
Go
124 lines
3.2 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package packet
|
|
|
|
import (
|
|
"code.google.com/p/go.crypto/openpgp/errors"
|
|
"compress/bzip2"
|
|
"compress/flate"
|
|
"compress/zlib"
|
|
"io"
|
|
"strconv"
|
|
)
|
|
|
|
// Compressed represents a compressed OpenPGP packet. The decompressed contents
|
|
// will contain more OpenPGP packets. See RFC 4880, section 5.6.
|
|
type Compressed struct {
|
|
Body io.Reader
|
|
}
|
|
|
|
const (
|
|
NoCompression = flate.NoCompression
|
|
BestSpeed = flate.BestSpeed
|
|
BestCompression = flate.BestCompression
|
|
DefaultCompression = flate.DefaultCompression
|
|
)
|
|
|
|
// CompressionConfig contains compressor configuration settings.
|
|
type CompressionConfig struct {
|
|
// Level is the compression level to use. It must be set to
|
|
// between -1 and 9, with -1 causing the compressor to use the
|
|
// default compression level, 0 causing the compressor to use
|
|
// no compression and 1 to 9 representing increasing (better,
|
|
// slower) compression levels. If Level is less than -1 or
|
|
// more then 9, a non-nil error will be returned during
|
|
// encryption. See the constants above for convenient common
|
|
// settings for Level.
|
|
Level int
|
|
}
|
|
|
|
func (c *Compressed) parse(r io.Reader) error {
|
|
var buf [1]byte
|
|
_, err := readFull(r, buf[:])
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
switch buf[0] {
|
|
case 1:
|
|
c.Body = flate.NewReader(r)
|
|
case 2:
|
|
c.Body, err = zlib.NewReader(r)
|
|
case 3:
|
|
c.Body = bzip2.NewReader(r)
|
|
default:
|
|
err = errors.UnsupportedError("unknown compression algorithm: " + strconv.Itoa(int(buf[0])))
|
|
}
|
|
|
|
return err
|
|
}
|
|
|
|
// compressedWriterCloser represents the serialized compression stream
|
|
// header and the compressor. Its Close() method ensures that both the
|
|
// compressor and serialized stream header are closed. Its Write()
|
|
// method writes to the compressor.
|
|
type compressedWriteCloser struct {
|
|
sh io.Closer // Stream Header
|
|
c io.WriteCloser // Compressor
|
|
}
|
|
|
|
func (cwc compressedWriteCloser) Write(p []byte) (int, error) {
|
|
return cwc.c.Write(p)
|
|
}
|
|
|
|
func (cwc compressedWriteCloser) Close() (err error) {
|
|
err = cwc.c.Close()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
return cwc.sh.Close()
|
|
}
|
|
|
|
// SerializeCompressed serializes a compressed data packet to w and
|
|
// returns a WriteCloser to which the literal data packets themselves
|
|
// can be written and which MUST be closed on completion. If cc is
|
|
// nil, sensible defaults will be used to configure the compression
|
|
// algorithm.
|
|
func SerializeCompressed(w io.WriteCloser, algo CompressionAlgo, cc *CompressionConfig) (literaldata io.WriteCloser, err error) {
|
|
compressed, err := serializeStreamHeader(w, packetTypeCompressed)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
_, err = compressed.Write([]byte{uint8(algo)})
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
level := DefaultCompression
|
|
if cc != nil {
|
|
level = cc.Level
|
|
}
|
|
|
|
var compressor io.WriteCloser
|
|
switch algo {
|
|
case CompressionZIP:
|
|
compressor, err = flate.NewWriter(compressed, level)
|
|
case CompressionZLIB:
|
|
compressor, err = zlib.NewWriterLevel(compressed, level)
|
|
default:
|
|
s := strconv.Itoa(int(algo))
|
|
err = errors.UnsupportedError("Unsupported compression algorithm: " + s)
|
|
}
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
literaldata = compressedWriteCloser{compressed, compressor}
|
|
|
|
return
|
|
}
|