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/*
* Copyright (C) 2020 The Android Open Source Project
*
* 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
*
* http://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 "adb/pairing/aes_128_gcm.h"
#include <android-base/endian.h>
#include <android-base/logging.h>
#include <openssl/evp.h>
#include <openssl/hkdf.h>
#include <openssl/rand.h>
namespace adb {
namespace pairing {
namespace {
// Size of AES-128-GCM key, in bytes
static constexpr size_t kHkdfKeyLength = 16;
} // namespace
Aes128Gcm::Aes128Gcm(const uint8_t* key_material, size_t key_material_len) {
CHECK(key_material);
CHECK_NE(key_material_len, 0ul);
uint8_t key[kHkdfKeyLength];
uint8_t info[] = "adb pairing_auth aes-128-gcm key";
CHECK_EQ(HKDF(key, sizeof(key), EVP_sha256(), key_material, key_material_len, nullptr, 0, info,
sizeof(info) - 1),
1);
CHECK(EVP_AEAD_CTX_init(context_.get(), EVP_aead_aes_128_gcm(), key, sizeof(key),
EVP_AEAD_DEFAULT_TAG_LENGTH, nullptr));
}
std::optional<size_t> Aes128Gcm::Encrypt(const uint8_t* in, size_t in_len, uint8_t* out,
size_t out_len) {
std::vector<uint8_t> nonce(EVP_AEAD_nonce_length(EVP_AEAD_CTX_aead(context_.get())), 0);
memcpy(nonce.data(), &enc_sequence_, sizeof(enc_sequence_));
size_t written_sz;
if (!EVP_AEAD_CTX_seal(context_.get(), out, &written_sz, out_len, nonce.data(), nonce.size(),
in, in_len, nullptr, 0)) {
LOG(ERROR) << "Failed to encrypt (in_len=" << in_len << ", out_len=" << out_len
<< ", out_len_needed=" << EncryptedSize(in_len) << ")";
return std::nullopt;
}
++enc_sequence_;
return written_sz;
}
std::optional<size_t> Aes128Gcm::Decrypt(const uint8_t* in, size_t in_len, uint8_t* out,
size_t out_len) {
std::vector<uint8_t> nonce(EVP_AEAD_nonce_length(EVP_AEAD_CTX_aead(context_.get())), 0);
memcpy(nonce.data(), &dec_sequence_, sizeof(dec_sequence_));
size_t written_sz;
if (!EVP_AEAD_CTX_open(context_.get(), out, &written_sz, out_len, nonce.data(), nonce.size(),
in, in_len, nullptr, 0)) {
LOG(ERROR) << "Failed to decrypt (in_len=" << in_len << ", out_len=" << out_len
<< ", out_len_needed=" << DecryptedSize(in_len) << ")";
return std::nullopt;
}
++dec_sequence_;
return written_sz;
}
size_t Aes128Gcm::EncryptedSize(size_t size) {
// https://commondatastorage.googleapis.com/chromium-boringssl-docs/aead.h.html#EVP_AEAD_CTX_seal
return size + EVP_AEAD_max_overhead(EVP_AEAD_CTX_aead(context_.get()));
}
size_t Aes128Gcm::DecryptedSize(size_t size) {
// https://commondatastorage.googleapis.com/chromium-boringssl-docs/aead.h.html#EVP_AEAD_CTX_open
return size;
}
} // namespace pairing
} // namespace adb
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