// NewUnpacker returns a pointer to Unpacker which can be used to read
// individual Blobs from a pack.
func NewUnpacker(k *crypto.Key, rd io.ReadSeeker) (*Unpacker, error) {
var err error
ls := binary.Size(uint32(0))
// reset to the end to read header length
_, err = rd.Seek(-int64(ls), 2)
if err != nil {
return nil, fmt.Errorf("seeking to read header length failed: %v", err)
}
var length uint32
err = binary.Read(rd, binary.LittleEndian, &length)
if err != nil {
return nil, fmt.Errorf("reading header length failed: %v", err)
}
// reset to the beginning of the header
_, err = rd.Seek(-int64(ls)-int64(length), 2)
if err != nil {
return nil, fmt.Errorf("seeking to read header length failed: %v", err)
}
// read header
hrd, err := crypto.DecryptFrom(k, io.LimitReader(rd, int64(length)))
if err != nil {
return nil, err
}
var entries []Blob
pos := uint(0)
for {
e := headerEntry{}
err = binary.Read(hrd, binary.LittleEndian, &e)
if err == io.EOF {
break
}
if err != nil {
return nil, err
}
entries = append(entries, Blob{
Type: e.Type,
Length: uint(e.Length),
ID: e.ID,
Offset: pos,
})
pos += uint(e.Length)
}
p := &Unpacker{
rd: rd,
k: k,
Entries: entries,
}
return p, nil
}
func TestDecryptStreamReader(t *testing.T) {
k := crypto.NewRandomKey()
tests := []int{5, 23, 2<<18 + 23, 1 << 20}
if testLargeCrypto {
tests = append(tests, 7<<20+123)
}
for _, size := range tests {
data := Random(42, size)
var err error
ciphertext := make([]byte, size+crypto.Extension)
// encrypt with default function
ciphertext, err = crypto.Encrypt(k, ciphertext, data)
OK(t, err)
Assert(t, len(ciphertext) == len(data)+crypto.Extension,
"wrong number of bytes returned after encryption: expected %d, got %d",
len(data)+crypto.Extension, len(ciphertext))
rd, err := crypto.DecryptFrom(k, bytes.NewReader(ciphertext))
OK(t, err)
plaintext, err := ioutil.ReadAll(rd)
OK(t, err)
Assert(t, bytes.Equal(data, plaintext),
"wrong plaintext after decryption: expected %02x, got %02x",
data, plaintext)
}
}
func BenchmarkDecryptReader(b *testing.B) {
size := 8 << 20 // 8MiB
buf := Random(23, size)
k := crypto.NewRandomKey()
ciphertext := make([]byte, len(buf)+crypto.Extension)
_, err := crypto.Encrypt(k, ciphertext, buf)
OK(b, err)
rd := bytes.NewReader(ciphertext)
b.ResetTimer()
b.SetBytes(int64(size))
for i := 0; i < b.N; i++ {
rd.Seek(0, 0)
decRd, err := crypto.DecryptFrom(k, rd)
OK(b, err)
_, err = io.Copy(ioutil.Discard, decRd)
OK(b, err)
}
}
func BenchmarkEncryptDecryptReader(b *testing.B) {
k := crypto.NewRandomKey()
size := 8 << 20 // 8MiB
b.ResetTimer()
b.SetBytes(int64(size))
buf := bytes.NewBuffer(nil)
for i := 0; i < b.N; i++ {
rd := RandomLimitReader(23, size)
buf.Reset()
wr := crypto.EncryptTo(k, buf)
_, err := io.Copy(wr, rd)
OK(b, err)
OK(b, wr.Close())
r, err := crypto.DecryptFrom(k, buf)
OK(b, err)
_, err = io.Copy(ioutil.Discard, r)
OK(b, err)
}
}