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
Aes128Gcm(const uint8_t * key_material,size_t key_material_len)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
Encrypt(const uint8_t * in,size_t in_len,uint8_t * out,size_t out_len)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
Decrypt(const uint8_t * in,size_t in_len,uint8_t * out,size_t out_len)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
EncryptedSize(size_t size)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
DecryptedSize(size_t size)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