1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "adb/pairing/aes_128_gcm.h" 18 19 #include <android-base/endian.h> 20 #include <android-base/logging.h> 21 22 #include <openssl/evp.h> 23 #include <openssl/hkdf.h> 24 #include <openssl/rand.h> 25 26 namespace adb { 27 namespace pairing { 28 29 namespace { 30 // Size of AES-128-GCM key, in bytes 31 static constexpr size_t kHkdfKeyLength = 16; 32 33 } // namespace 34 35 Aes128Gcm::Aes128Gcm(const uint8_t* key_material, size_t key_material_len) { 36 CHECK(key_material); 37 CHECK_NE(key_material_len, 0ul); 38 39 uint8_t key[kHkdfKeyLength]; 40 uint8_t info[] = "adb pairing_auth aes-128-gcm key"; 41 CHECK_EQ(HKDF(key, sizeof(key), EVP_sha256(), key_material, key_material_len, nullptr, 0, info, 42 sizeof(info) - 1), 43 1); 44 CHECK(EVP_AEAD_CTX_init(context_.get(), EVP_aead_aes_128_gcm(), key, sizeof(key), 45 EVP_AEAD_DEFAULT_TAG_LENGTH, nullptr)); 46 } 47 48 std::optional<size_t> Aes128Gcm::Encrypt(const uint8_t* in, size_t in_len, uint8_t* out, 49 size_t out_len) { 50 std::vector<uint8_t> nonce(EVP_AEAD_nonce_length(EVP_AEAD_CTX_aead(context_.get())), 0); 51 memcpy(nonce.data(), &enc_sequence_, sizeof(enc_sequence_)); 52 size_t written_sz; 53 if (!EVP_AEAD_CTX_seal(context_.get(), out, &written_sz, out_len, nonce.data(), nonce.size(), 54 in, in_len, nullptr, 0)) { 55 LOG(ERROR) << "Failed to encrypt (in_len=" << in_len << ", out_len=" << out_len 56 << ", out_len_needed=" << EncryptedSize(in_len) << ")"; 57 return std::nullopt; 58 } 59 60 ++enc_sequence_; 61 return written_sz; 62 } 63 64 std::optional<size_t> Aes128Gcm::Decrypt(const uint8_t* in, size_t in_len, uint8_t* out, 65 size_t out_len) { 66 std::vector<uint8_t> nonce(EVP_AEAD_nonce_length(EVP_AEAD_CTX_aead(context_.get())), 0); 67 memcpy(nonce.data(), &dec_sequence_, sizeof(dec_sequence_)); 68 size_t written_sz; 69 if (!EVP_AEAD_CTX_open(context_.get(), out, &written_sz, out_len, nonce.data(), nonce.size(), 70 in, in_len, nullptr, 0)) { 71 LOG(ERROR) << "Failed to decrypt (in_len=" << in_len << ", out_len=" << out_len 72 << ", out_len_needed=" << DecryptedSize(in_len) << ")"; 73 return std::nullopt; 74 } 75 76 ++dec_sequence_; 77 return written_sz; 78 } 79 80 size_t Aes128Gcm::EncryptedSize(size_t size) { 81 // https://commondatastorage.googleapis.com/chromium-boringssl-docs/aead.h.html#EVP_AEAD_CTX_seal 82 return size + EVP_AEAD_max_overhead(EVP_AEAD_CTX_aead(context_.get())); 83 } 84 85 size_t Aes128Gcm::DecryptedSize(size_t size) { 86 // https://commondatastorage.googleapis.com/chromium-boringssl-docs/aead.h.html#EVP_AEAD_CTX_open 87 return size; 88 } 89 90 } // namespace pairing 91 } // namespace adb 92