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
23namespace keymaster {
24
25inline size_t min(size_t a, size_t b) {
26    return (a < b) ? a : b;
27}
28
29bool 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