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93 lines
3.1 KiB
93 lines
3.1 KiB
// Minio Cloud Storage, (C) 2015, 2016, 2017, 2018 Minio, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package crypto
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import (
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"bytes"
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"context"
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"crypto/hmac"
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"crypto/rand"
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"encoding/binary"
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"errors"
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"io"
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"path/filepath"
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"github.com/minio/minio/cmd/logger"
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sha256 "github.com/minio/sha256-simd"
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"github.com/minio/sio"
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)
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// ObjectKey is a 256 bit secret key used to encrypt the object.
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// It must never be stored in plaintext.
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type ObjectKey [32]byte
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// GenerateKey generates a unique ObjectKey from a 256 bit external key
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// and a source of randomness. If random is nil the default PRNG of system
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// (crypto/rand) is used.
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func GenerateKey(extKey [32]byte, random io.Reader) (key ObjectKey) {
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if random == nil {
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random = rand.Reader
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}
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var nonce [32]byte
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if _, err := io.ReadFull(random, nonce[:]); err != nil {
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logger.CriticalIf(context.Background(), errors.New("Unable to read enough randomness from the system"))
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}
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sha := sha256.New()
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sha.Write(extKey[:])
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sha.Write(nonce[:])
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sha.Sum(key[:0])
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return
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}
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// Seal encrypts the ObjectKey using the 256 bit external key and IV. The sealed
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// key is also cryptographically bound to the object's path (bucket/object).
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func (key ObjectKey) Seal(extKey, iv [32]byte, bucket, object string) []byte {
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var sealedKey bytes.Buffer
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mac := hmac.New(sha256.New, extKey[:])
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mac.Write(iv[:])
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mac.Write([]byte(filepath.Join(bucket, object)))
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if n, err := sio.Encrypt(&sealedKey, bytes.NewReader(key[:]), sio.Config{Key: mac.Sum(nil)}); n != 64 || err != nil {
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logger.CriticalIf(context.Background(), errors.New("Unable to generate sealed key"))
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}
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return sealedKey.Bytes()
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}
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// Unseal decrypts a sealed key using the 256 bit external key and IV. Since the sealed key
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// is cryptographically bound to the object's path the same bucket/object as during sealing
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// must be provided. On success the ObjectKey contains the decrypted sealed key.
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func (key *ObjectKey) Unseal(sealedKey []byte, extKey, iv [32]byte, bucket, object string) error {
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var unsealedKey bytes.Buffer
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mac := hmac.New(sha256.New, extKey[:])
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mac.Write(iv[:])
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mac.Write([]byte(filepath.Join(bucket, object)))
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if n, err := sio.Decrypt(&unsealedKey, bytes.NewReader(sealedKey), sio.Config{Key: mac.Sum(nil)}); n != 32 || err != nil {
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return err // TODO(aead): upgrade sio to use sio.Error
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}
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copy(key[:], unsealedKey.Bytes())
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return nil
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}
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// DerivePartKey derives an unique 256 bit key from an ObjectKey and the part index.
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func (key ObjectKey) DerivePartKey(id uint32) (partKey [32]byte) {
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var bin [4]byte
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binary.LittleEndian.PutUint32(bin[:], id)
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mac := hmac.New(sha256.New, key[:])
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mac.Write(bin[:])
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mac.Sum(partKey[:0])
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return
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}
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