restic/crypto/reader.go

98 lines
1.7 KiB
Go

package crypto
import (
"io"
"io/ioutil"
)
type decryptReader struct {
buf []byte
pos int
}
func (d *decryptReader) Read(dst []byte) (int, error) {
if d.buf == nil {
return 0, io.EOF
}
if len(dst) == 0 {
return 0, nil
}
remaining := len(d.buf) - d.pos
if len(dst) >= remaining {
n := copy(dst, d.buf[d.pos:])
d.Close()
return n, io.EOF
}
n := copy(dst, d.buf[d.pos:d.pos+len(dst)])
d.pos += n
return n, nil
}
func (d *decryptReader) ReadByte() (c byte, err error) {
if d.buf == nil {
return 0, io.EOF
}
remaining := len(d.buf) - d.pos
if remaining == 1 {
c = d.buf[d.pos]
d.Close()
return c, io.EOF
}
c = d.buf[d.pos]
d.pos++
return
}
func (d *decryptReader) Close() error {
if d.buf == nil {
return nil
}
freeBuffer(d.buf)
d.buf = nil
return nil
}
// DecryptFrom verifies and decrypts the ciphertext read from rd with ks and
// makes it available on the returned Reader. Ciphertext must be in the form IV
// || Ciphertext || MAC. In order to correctly verify the ciphertext, rd is
// drained, locally buffered and made available on the returned Reader
// afterwards. If a MAC verification failure is observed, it is returned
// immediately.
func DecryptFrom(ks *Key, rd io.Reader) (io.ReadCloser, error) {
ciphertext := getBuffer()
ciphertext = ciphertext[0:cap(ciphertext)]
n, err := io.ReadFull(rd, ciphertext)
if err != io.ErrUnexpectedEOF {
// read remaining data
buf, e := ioutil.ReadAll(rd)
ciphertext = append(ciphertext, buf...)
n += len(buf)
err = e
} else {
err = nil
}
if err != nil {
return nil, err
}
ciphertext = ciphertext[:n]
// decrypt
ciphertext, err = Decrypt(ks, ciphertext, ciphertext)
if err != nil {
return nil, err
}
return &decryptReader{buf: ciphertext}, nil
}