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117 lines
3.6 KiB
Go
117 lines
3.6 KiB
Go
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/*
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*
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* Copyright 2018 gRPC authors.
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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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*
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*/
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package conn
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import (
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"crypto/cipher"
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core "google.golang.org/grpc/credentials/alts/internal"
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)
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const (
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// Overflow length n in bytes, never encrypt more than 2^(n*8) frames (in
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// each direction).
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overflowLenAES128GCMRekey = 8
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nonceLen = 12
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aeadKeyLen = 16
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kdfKeyLen = 32
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kdfCounterOffset = 2
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kdfCounterLen = 6
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sizeUint64 = 8
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)
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// aes128gcmRekey is the struct that holds necessary information for ALTS record.
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// The counter value is NOT included in the payload during the encryption and
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// decryption operations.
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type aes128gcmRekey struct {
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// inCounter is used in ALTS record to check that incoming counters are
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// as expected, since ALTS record guarantees that messages are unwrapped
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// in the same order that the peer wrapped them.
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inCounter Counter
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outCounter Counter
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inAEAD cipher.AEAD
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outAEAD cipher.AEAD
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}
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// NewAES128GCMRekey creates an instance that uses aes128gcm with rekeying
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// for ALTS record. The key argument should be 44 bytes, the first 32 bytes
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// are used as a key for HKDF-expand and the remainining 12 bytes are used
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// as a random mask for the counter.
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func NewAES128GCMRekey(side core.Side, key []byte) (ALTSRecordCrypto, error) {
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inCounter := NewInCounter(side, overflowLenAES128GCMRekey)
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outCounter := NewOutCounter(side, overflowLenAES128GCMRekey)
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inAEAD, err := newRekeyAEAD(key)
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if err != nil {
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return nil, err
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}
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outAEAD, err := newRekeyAEAD(key)
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if err != nil {
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return nil, err
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}
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return &aes128gcmRekey{
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inCounter,
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outCounter,
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inAEAD,
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outAEAD,
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}, nil
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}
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// Encrypt is the encryption function. dst can contain bytes at the beginning of
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// the ciphertext that will not be encrypted but will be authenticated. If dst
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// has enough capacity to hold these bytes, the ciphertext and the tag, no
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// allocation and copy operations will be performed. dst and plaintext do not
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// overlap.
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func (s *aes128gcmRekey) Encrypt(dst, plaintext []byte) ([]byte, error) {
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// If we need to allocate an output buffer, we want to include space for
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// GCM tag to avoid forcing ALTS record to reallocate as well.
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dlen := len(dst)
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dst, out := SliceForAppend(dst, len(plaintext)+GcmTagSize)
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seq, err := s.outCounter.Value()
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if err != nil {
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return nil, err
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}
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data := out[:len(plaintext)]
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copy(data, plaintext) // data may alias plaintext
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// Seal appends the ciphertext and the tag to its first argument and
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// returns the updated slice. However, SliceForAppend above ensures that
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// dst has enough capacity to avoid a reallocation and copy due to the
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// append.
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dst = s.outAEAD.Seal(dst[:dlen], seq, data, nil)
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s.outCounter.Inc()
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return dst, nil
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}
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func (s *aes128gcmRekey) EncryptionOverhead() int {
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return GcmTagSize
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}
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func (s *aes128gcmRekey) Decrypt(dst, ciphertext []byte) ([]byte, error) {
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seq, err := s.inCounter.Value()
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if err != nil {
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return nil, err
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}
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plaintext, err := s.inAEAD.Open(dst, seq, ciphertext, nil)
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if err != nil {
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return nil, ErrAuth
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}
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s.inCounter.Inc()
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return plaintext, nil
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}
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