1 /*
2 * Copyright 2015 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 <keymaster/km_openssl/iso18033kdf.h>
18
19 #include <openssl/evp.h>
20
21 #include <keymaster/km_openssl/openssl_utils.h>
22
23 namespace keymaster {
24
min(size_t a,size_t b)25 inline size_t min(size_t a, size_t b) {
26 return (a < b) ? a : b;
27 }
28
GenerateKey(const uint8_t * info,size_t info_len,uint8_t * output,size_t output_len)29 bool Iso18033Kdf::GenerateKey(const uint8_t* info, size_t info_len, uint8_t* output,
30 size_t output_len) {
31 if (!is_initialized_ || output == nullptr) return false;
32
33 /* Check whether output length is too long as specified in ISO/IEC 18033-2. */
34 if ((0xFFFFFFFFULL + start_counter_) * digest_size_ < (uint64_t)output_len) return false;
35
36 EVP_MD_CTX ctx;
37 EvpMdCtxCleaner ctxCleaner(&ctx);
38 EVP_MD_CTX_init(&ctx);
39
40 size_t num_blocks = (output_len + digest_size_ - 1) / digest_size_;
41 UniquePtr<uint8_t[]> counter(new (std::nothrow) uint8_t[4]);
42 UniquePtr<uint8_t[]> digest_result(new (std::nothrow) uint8_t[digest_size_]);
43 if (!counter.get() || !digest_result.get()) return false;
44 for (size_t block = 0; block < num_blocks; block++) {
45 switch (digest_type_) {
46 case KM_DIGEST_SHA1:
47 if (!EVP_DigestInit_ex(&ctx, EVP_sha1(), nullptr /* default digest */)) return false;
48 break;
49 case KM_DIGEST_SHA_2_256:
50 if (!EVP_DigestInit_ex(&ctx, EVP_sha256(), nullptr /* default digest */)) return false;
51 break;
52 default:
53 return false;
54 }
55
56 if (!EVP_DigestUpdate(&ctx, secret_key_.get(), secret_key_len_) ||
57 !Uint32ToBigEndianByteArray(block + start_counter_, counter.get()) ||
58 !EVP_DigestUpdate(&ctx, counter.get(), 4))
59 return false;
60
61 if (info != nullptr && info_len > 0) {
62 if (!EVP_DigestUpdate(&ctx, info, info_len)) return false;
63 }
64
65 /* OpenSSL does not accept size_t parameter. */
66 uint32_t uint32_digest_size_ = digest_size_;
67 if (!EVP_DigestFinal_ex(&ctx, digest_result.get(), &uint32_digest_size_) ||
68 uint32_digest_size_ != digest_size_)
69 return false;
70
71 size_t block_start = digest_size_ * block;
72 size_t block_length = min(digest_size_, output_len - block_start);
73 memcpy(output + block_start, digest_result.get(), block_length);
74 }
75 return true;
76 }
77
78 } // namespace keymaster
79