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crypto_common.go
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crypto_common.go
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// Copyright 2016 Keybase Inc. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.
package libkbfs
import (
"crypto/rand"
"encoding/binary"
"io"
"github.com/keybase/client/go/kbfs/kbfsblock"
"github.com/keybase/client/go/kbfs/kbfscodec"
"github.com/keybase/client/go/kbfs/kbfscrypto"
"github.com/keybase/client/go/kbfs/kbfsmd"
"github.com/keybase/client/go/kbfs/tlf"
"github.com/pkg/errors"
"golang.org/x/crypto/nacl/box"
)
// CryptoCommon contains many of the function implementations need for
// the Crypto interface, which can be reused by other implementations.
type CryptoCommon struct {
codec kbfscodec.Codec
blockCryptVersioner blockCryptVersioner
}
var _ cryptoPure = (*CryptoCommon)(nil)
// MakeCryptoCommon returns a default CryptoCommon object.
func MakeCryptoCommon(
codec kbfscodec.Codec,
blockCryptVersioner blockCryptVersioner) CryptoCommon {
return CryptoCommon{codec, blockCryptVersioner}
}
// MakeRandomTlfID implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) MakeRandomTlfID(t tlf.Type) (tlf.ID, error) {
return tlf.MakeRandomID(t)
}
// MakeRandomBranchID implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) MakeRandomBranchID() (kbfsmd.BranchID, error) {
return kbfsmd.MakeRandomBranchID()
}
// MakeTemporaryBlockID implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) MakeTemporaryBlockID() (kbfsblock.ID, error) {
return kbfsblock.MakeTemporaryID()
}
// MakeBlockRefNonce implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) MakeBlockRefNonce() (nonce kbfsblock.RefNonce, err error) {
return kbfsblock.MakeRefNonce()
}
// MakeRandomBlockCryptKeyServerHalf implements the Crypto interface
// for CryptoCommon.
func (c CryptoCommon) MakeRandomBlockCryptKeyServerHalf() (
kbfscrypto.BlockCryptKeyServerHalf, error) {
return kbfscrypto.MakeRandomBlockCryptKeyServerHalf()
}
// MakeRandomTLFEphemeralKeys implements the Crypto interface for
// CryptoCommon.
func (c CryptoCommon) MakeRandomTLFEphemeralKeys() (
kbfscrypto.TLFEphemeralPublicKey, kbfscrypto.TLFEphemeralPrivateKey,
error) {
return kbfscrypto.MakeRandomTLFEphemeralKeys()
}
// MakeRandomTLFKeys implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) MakeRandomTLFKeys() (kbfscrypto.TLFPublicKey,
kbfscrypto.TLFPrivateKey, kbfscrypto.TLFCryptKey, error) {
publicKey, privateKey, err := box.GenerateKey(rand.Reader)
if err != nil {
return kbfscrypto.TLFPublicKey{}, kbfscrypto.TLFPrivateKey{},
kbfscrypto.TLFCryptKey{}, errors.WithStack(err)
}
pubKey := kbfscrypto.MakeTLFPublicKey(*publicKey)
privKey := kbfscrypto.MakeTLFPrivateKey(*privateKey)
cryptKey, err := kbfscrypto.MakeRandomTLFCryptKey()
if err != nil {
return kbfscrypto.TLFPublicKey{}, kbfscrypto.TLFPrivateKey{},
kbfscrypto.TLFCryptKey{}, err
}
return pubKey, privKey, cryptKey, nil
}
// EncryptPrivateMetadata implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) EncryptPrivateMetadata(
pmd PrivateMetadata, key kbfscrypto.TLFCryptKey) (
encryptedPmd kbfscrypto.EncryptedPrivateMetadata, err error) {
encodedPmd, err := c.codec.Encode(pmd)
if err != nil {
return kbfscrypto.EncryptedPrivateMetadata{}, err
}
return kbfscrypto.EncryptEncodedPrivateMetadata(encodedPmd, key)
}
// DecryptPrivateMetadata implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) DecryptPrivateMetadata(
encryptedPmd kbfscrypto.EncryptedPrivateMetadata, key kbfscrypto.TLFCryptKey) (
PrivateMetadata, error) {
encodedPrivateMetadata, err := kbfscrypto.DecryptPrivateMetadata(
encryptedPmd, key)
if err != nil {
return PrivateMetadata{}, err
}
var pmd PrivateMetadata
err = c.codec.Decode(encodedPrivateMetadata, &pmd)
if err != nil {
return PrivateMetadata{}, err
}
return pmd, nil
}
const minBlockSize = 256
// powerOfTwoEqualOrGreater returns smallest power of 2 greater than or equal
// to the input n.
// https://en.wikipedia.org/wiki/Power_of_two#Algorithm_to_round_up_to_power_of_two
func powerOfTwoEqualOrGreater(n int) int {
if n <= minBlockSize {
return minBlockSize
}
if n&(n-1) == 0 {
// if n is already power of 2, return it
return n
}
n--
n = n | (n >> 1)
n = n | (n >> 2)
n = n | (n >> 4)
n = n | (n >> 8)
n = n | (n >> 16)
n = n | (n >> 16 >> 16) // make it work with 64 bit int; no effect on 32bit.
n++
return n
}
const padPrefixSize = 4
// padBlock adds zero padding to an encoded block.
func (c CryptoCommon) padBlock(block []byte) ([]byte, error) {
totalLen := powerOfTwoEqualOrGreater(len(block))
buf := make([]byte, padPrefixSize+totalLen)
binary.LittleEndian.PutUint32(buf, uint32(len(block)))
copy(buf[padPrefixSize:], block)
return buf, nil
}
// depadBlock extracts the actual block data from a padded block.
func (c CryptoCommon) depadBlock(paddedBlock []byte) ([]byte, error) {
totalLen := len(paddedBlock)
if totalLen < padPrefixSize {
return nil, errors.WithStack(io.ErrUnexpectedEOF)
}
blockLen := binary.LittleEndian.Uint32(paddedBlock)
blockEndPos := int(blockLen + padPrefixSize)
if totalLen < blockEndPos {
return nil, errors.WithStack(
PaddedBlockReadError{
ActualLen: totalLen,
ExpectedLen: blockEndPos,
})
}
return paddedBlock[padPrefixSize:blockEndPos], nil
}
// EncryptBlock implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) EncryptBlock(
block Block, tlfCryptKey kbfscrypto.TLFCryptKey,
blockServerHalf kbfscrypto.BlockCryptKeyServerHalf) (
plainSize int, encryptedBlock kbfscrypto.EncryptedBlock, err error) {
encodedBlock, err := c.codec.Encode(block)
if err != nil {
return -1, kbfscrypto.EncryptedBlock{}, err
}
paddedBlock, err := c.padBlock(encodedBlock)
if err != nil {
return -1, kbfscrypto.EncryptedBlock{}, err
}
encryptedBlock, err =
kbfscrypto.EncryptPaddedEncodedBlock(
paddedBlock, tlfCryptKey, blockServerHalf,
c.blockCryptVersioner.BlockCryptVersion())
if err != nil {
return -1, kbfscrypto.EncryptedBlock{}, err
}
plainSize = len(encodedBlock)
return plainSize, encryptedBlock, nil
}
// DecryptBlock implements the Crypto interface for CryptoCommon.
func (c CryptoCommon) DecryptBlock(
encryptedBlock kbfscrypto.EncryptedBlock,
tlfCryptKey kbfscrypto.TLFCryptKey,
blockServerHalf kbfscrypto.BlockCryptKeyServerHalf, block Block) error {
var paddedBlock []byte
paddedBlock, err := kbfscrypto.DecryptBlock(
encryptedBlock, tlfCryptKey, blockServerHalf)
if err != nil {
return err
}
encodedBlock, err := c.depadBlock(paddedBlock)
if err != nil {
return err
}
err = c.codec.Decode(encodedBlock, &block)
if err != nil {
return errors.WithStack(BlockDecodeError{err})
}
return nil
}