mirror of
https://github.com/kidfromjupiter/nearby.git
synced 2026-09-14 22:56:12 -04:00
116 lines
4.7 KiB
C++
116 lines
4.7 KiB
C++
// Copyright 2022 Google LLC
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// https://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
#include "fastpair/crypto/fast_pair_decryption.h"
|
|
|
|
#include <algorithm>
|
|
#include <array>
|
|
#include <optional>
|
|
|
|
#ifdef NEARBY_CHROMIUM
|
|
#include "base/check.h"
|
|
#elif defined(NEARBY_SWIFTPM)
|
|
#include "internal/platform/logging.h"
|
|
#else
|
|
#include "absl/log/check.h" // nogncheck
|
|
#endif
|
|
|
|
#include "fastpair/common/constant.h"
|
|
#include "fastpair/crypto/decrypted_passkey.h"
|
|
#include "fastpair/crypto/decrypted_response.h"
|
|
#include <openssl/aes.h>
|
|
|
|
namespace nearby {
|
|
namespace fastpair {
|
|
|
|
std::array<uint8_t, kAesBlockByteSize> FastPairDecryption::DecryptBytes(
|
|
const std::array<uint8_t, kAesBlockByteSize>& aes_key_bytes,
|
|
const std::array<uint8_t, kAesBlockByteSize>& encrypted_bytes) {
|
|
AES_KEY aes_key;
|
|
int aes_key_was_set = AES_set_decrypt_key(aes_key_bytes.data(),
|
|
aes_key_bytes.size() * 8, &aes_key);
|
|
CHECK(aes_key_was_set == 0) << "Invalid AES key size.";
|
|
std::array<uint8_t, kAesBlockByteSize> decrypted_bytes;
|
|
// Encrypted_bytes is less than 16 bytes and can be guaranteed to be a
|
|
// single block, so we encrypt/decrypt it using AES ECB mode (Approved by:
|
|
// b/73360609)
|
|
AES_decrypt(encrypted_bytes.data(), decrypted_bytes.data(), &aes_key);
|
|
return decrypted_bytes;
|
|
}
|
|
|
|
// Decrypts the encrypted response
|
|
// (https://developers.google.com/nearby/fast-pair/specifications/characteristics#table1.4)
|
|
// and returns the parsed decrypted response
|
|
// (https://developers.google.com/nearby/fast-pair/specifications/characteristics#table1.3)
|
|
std::optional<DecryptedResponse> FastPairDecryption::ParseDecryptResponse(
|
|
const std::array<uint8_t, kAesBlockByteSize>& aes_key_bytes,
|
|
const std::array<uint8_t, kAesBlockByteSize>& encrypted_response_bytes) {
|
|
std::array<uint8_t, kAesBlockByteSize> decrypted_response_bytes =
|
|
DecryptBytes(aes_key_bytes, encrypted_response_bytes);
|
|
|
|
uint8_t message_type = decrypted_response_bytes[kMessageTypeIndex];
|
|
|
|
// If the message type index is not the expected fast pair message type, then
|
|
// this is not a valid fast pair response.
|
|
if (message_type != kKeybasedPairingResponseType) {
|
|
return std::nullopt;
|
|
}
|
|
|
|
std::array<uint8_t, kDecryptedResponseAddressByteSize> address_bytes;
|
|
std::copy(decrypted_response_bytes.begin() + kResponseAddressStartIndex,
|
|
decrypted_response_bytes.begin() + kResponseSaltStartIndex,
|
|
address_bytes.begin());
|
|
|
|
std::array<uint8_t, kDecryptedResponseSaltByteSize> salt;
|
|
std::copy(decrypted_response_bytes.begin() + kResponseSaltStartIndex,
|
|
decrypted_response_bytes.end(), salt.begin());
|
|
return DecryptedResponse(FastPairMessageType::kKeyBasedPairingResponse,
|
|
address_bytes, salt);
|
|
}
|
|
|
|
// Decrypts the encrypted passkey
|
|
// (https://developers.google.com/nearby/fast-pair/specifications/characteristics#table2.1)
|
|
// and returns the parsed decrypted passkey
|
|
// (https://developers.google.com/nearby/fast-pair/specifications/characteristics#table2.2)
|
|
// TODO(b/263400788) Add unit test to cover this function and fix all Mutants
|
|
// warning
|
|
std::optional<DecryptedPasskey> FastPairDecryption::ParseDecryptPasskey(
|
|
const std::array<uint8_t, kAesBlockByteSize>& aes_key_bytes,
|
|
const std::array<uint8_t, kAesBlockByteSize>& encrypted_passkey_bytes) {
|
|
std::array<uint8_t, kAesBlockByteSize> decrypted_passkey_bytes =
|
|
DecryptBytes(aes_key_bytes, encrypted_passkey_bytes);
|
|
|
|
FastPairMessageType message_type;
|
|
if (decrypted_passkey_bytes[kMessageTypeIndex] == kSeekerPasskeyType) {
|
|
message_type = FastPairMessageType::kSeekersPasskey;
|
|
} else if (decrypted_passkey_bytes[kMessageTypeIndex] ==
|
|
kProviderPasskeyType) {
|
|
message_type = FastPairMessageType::kProvidersPasskey;
|
|
} else {
|
|
return std::nullopt;
|
|
}
|
|
|
|
uint32_t passkey = decrypted_passkey_bytes[3];
|
|
passkey += decrypted_passkey_bytes[2] << 8;
|
|
passkey += decrypted_passkey_bytes[1] << 16;
|
|
|
|
std::array<uint8_t, kDecryptedPasskeySaltByteSize> salt;
|
|
std::copy(decrypted_passkey_bytes.begin() + kPasskeySaltStartIndex,
|
|
decrypted_passkey_bytes.end(), salt.begin());
|
|
return DecryptedPasskey(message_type, passkey, salt);
|
|
}
|
|
|
|
} // namespace fastpair
|
|
} // namespace nearby
|