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crypto.go
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crypto.go
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package xcp
import (
"bytes"
"compress/zlib"
"crypto/cipher"
"crypto/rand"
"io"
)
type Writer struct {
aead cipher.AEAD
dst io.Writer
buf bytes.Buffer
nonce []byte
zWriter *zlib.Writer
}
// NewEncryptingWriter returns a new io.WriteCloser that encrypts data with the cipher and writes to dst.
func (cipher *SymmetricCipher) NewEncryptingWriter(dst io.Writer, compress bool) (io.WriteCloser, error) {
nonce := make([]byte, nonceLength)
if _, err := rand.Read(nonce); err != nil {
return nil, err
}
if _, err := dst.Write(nonce); err != nil {
return nil, err
}
return cipher.newWriter(nonce, dst, compress)
}
func (cipher *SymmetricCipher) newWriter(nonce []byte, dst io.Writer, compress bool) (*Writer, error) {
ciphWriter := &Writer{
aead: *cipher.aead,
dst: dst,
buf: bytes.Buffer{},
nonce: nonce,
}
if compress {
if _, err := dst.Write([]byte{1}); err != nil {
return nil, err
}
zWriter, err := zlib.NewWriterLevel(&ciphWriter.buf, zlib.BestCompression)
if err != nil {
return nil, err
}
ciphWriter.zWriter = zWriter
} else {
if _, err := dst.Write([]byte{0}); err != nil {
return nil, err
}
}
return ciphWriter, nil
}
func (w *Writer) Write(p []byte) (n int, err error) {
if w.zWriter == nil {
n, err = w.buf.Write(p)
} else {
n, err = w.zWriter.Write(p)
}
if err != nil {
return n, err
}
return n, w.flush(ptBlockSize)
}
func (w *Writer) flush(minBufSize int) error {
for w.buf.Len() >= minBufSize {
block := w.buf.Next(ptBlockSize)
ct := w.aead.Seal(nil, w.nonce, block, nil)
if _, err := w.dst.Write(ct); err != nil {
return err
}
}
return nil
}
// Close flushes the last chunk. It does not close the underlying Writer.
func (w *Writer) Close() error {
if w.zWriter != nil {
if err := w.zWriter.Close(); err != nil {
return err
}
}
return w.flush(1)
}
type Reader struct {
aead cipher.AEAD
src io.Reader
buf bytes.Buffer
nonce []byte
}
// NewDecryptingReader returns a new io.ReadCloser that decrypts src with the cipher
func (cipher *SymmetricCipher) NewDecryptingReader(src io.Reader) (io.ReadCloser, error) {
nonce := make([]byte, nonceLength)
if _, err := io.ReadFull(src, nonce); err != nil {
return nil, err
}
return cipher.newReader(nonce, src)
}
func (cipher *SymmetricCipher) newReader(nonce []byte, src io.Reader) (io.ReadCloser, error) {
ciphReader := &Reader{
aead: *cipher.aead,
src: src,
buf: bytes.Buffer{},
nonce: nonce,
}
compressFlag := make([]byte, 1)
if _, err := io.ReadFull(src, compressFlag); err != nil {
return nil, err
}
if compressFlag[0] == 0 {
return io.NopCloser(ciphReader), nil
}
zReader, err := zlib.NewReader(ciphReader)
if err != nil {
return nil, err
}
return zReader, nil
}
func (r *Reader) Read(p []byte) (int, error) {
if r.buf.Len() > len(p) {
return r.buf.Read(p)
}
var block [ctBlockSize]byte
n, err := io.ReadFull(r.src, block[:])
if err == nil || err == io.ErrUnexpectedEOF {
pt, err := r.aead.Open(nil, r.nonce, block[:n], nil)
if err != nil {
return 0, err
}
r.buf.Write(pt)
return r.buf.Read(p)
} else if err == io.EOF {
return r.buf.Read(p)
} else {
return 0, err
}
}