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111 lines
2.0 KiB
Go
111 lines
2.0 KiB
Go
package crypto
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"fmt"
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"io"
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"sync"
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)
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type encryptWriter struct {
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iv iv
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wroteIV bool
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data *bytes.Buffer
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key *Key
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s cipher.Stream
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w io.Writer
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origWr io.Writer
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err error // remember error writing iv
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}
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func (e *encryptWriter) Close() error {
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// write mac
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mac := poly1305Sign(e.data.Bytes()[ivSize:], e.data.Bytes()[:ivSize], &e.key.Sign)
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_, err := e.origWr.Write(mac)
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if err != nil {
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return err
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}
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// return buffer
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bufPool.Put(e.data.Bytes())
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return nil
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}
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const encryptWriterChunkSize = 512 * 1024 // 512 KiB
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var encryptWriterBufPool = sync.Pool{
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New: func() interface{} {
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return make([]byte, encryptWriterChunkSize)
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},
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}
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func (e *encryptWriter) Write(p []byte) (int, error) {
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// write iv first
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if !e.wroteIV {
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_, e.err = e.origWr.Write(e.iv[:])
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e.wroteIV = true
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}
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if e.err != nil {
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return 0, e.err
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}
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buf := encryptWriterBufPool.Get().([]byte)
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defer encryptWriterBufPool.Put(buf)
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written := 0
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for len(p) > 0 {
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max := len(p)
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if max > encryptWriterChunkSize {
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max = encryptWriterChunkSize
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}
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e.s.XORKeyStream(buf, p[:max])
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n, err := e.w.Write(buf[:max])
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if n != max {
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if err == nil { // should never happen
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err = io.ErrShortWrite
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}
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}
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written += n
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p = p[n:]
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if err != nil {
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e.err = err
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return written, err
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}
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}
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return written, nil
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}
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// EncryptTo buffers data written to the returned io.WriteCloser. When Close()
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// is called, the data is encrypted an written to the underlying writer.
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func EncryptTo(ks *Key, wr io.Writer) io.WriteCloser {
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ew := &encryptWriter{
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iv: newIV(),
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data: bytes.NewBuffer(getBuffer()[:0]),
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key: ks,
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origWr: wr,
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}
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// buffer iv for mac
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_, err := ew.data.Write(ew.iv[:])
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if err != nil {
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panic(err)
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}
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c, err := aes.NewCipher(ks.Encrypt[:])
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if err != nil {
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panic(fmt.Sprintf("unable to create cipher: %v", err))
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}
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ew.s = cipher.NewCTR(c, ew.iv[:])
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ew.w = io.MultiWriter(ew.data, wr)
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return ew
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}
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