79 lines
2.8 KiB
C++
79 lines
2.8 KiB
C++
/*
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* Copyright 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <keymaster/km_openssl/iso18033kdf.h>
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#include <openssl/evp.h>
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#include <keymaster/km_openssl/openssl_utils.h>
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namespace keymaster {
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inline size_t min(size_t a, size_t b) {
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return (a < b) ? a : b;
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}
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bool Iso18033Kdf::GenerateKey(const uint8_t* info, size_t info_len, uint8_t* output,
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size_t output_len) {
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if (!is_initialized_ || output == nullptr) return false;
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/* Check whether output length is too long as specified in ISO/IEC 18033-2. */
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if ((0xFFFFFFFFULL + start_counter_) * digest_size_ < (uint64_t)output_len) return false;
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EVP_MD_CTX ctx;
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EvpMdCtxCleaner ctxCleaner(&ctx);
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EVP_MD_CTX_init(&ctx);
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size_t num_blocks = (output_len + digest_size_ - 1) / digest_size_;
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UniquePtr<uint8_t[]> counter(new (std::nothrow) uint8_t[4]);
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UniquePtr<uint8_t[]> digest_result(new (std::nothrow) uint8_t[digest_size_]);
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if (!counter.get() || !digest_result.get()) return false;
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for (size_t block = 0; block < num_blocks; block++) {
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switch (digest_type_) {
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case KM_DIGEST_SHA1:
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if (!EVP_DigestInit_ex(&ctx, EVP_sha1(), nullptr /* default digest */)) return false;
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break;
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case KM_DIGEST_SHA_2_256:
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if (!EVP_DigestInit_ex(&ctx, EVP_sha256(), nullptr /* default digest */)) return false;
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break;
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default:
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return false;
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}
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if (!EVP_DigestUpdate(&ctx, secret_key_.get(), secret_key_len_) ||
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!Uint32ToBigEndianByteArray(block + start_counter_, counter.get()) ||
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!EVP_DigestUpdate(&ctx, counter.get(), 4))
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return false;
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if (info != nullptr && info_len > 0) {
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if (!EVP_DigestUpdate(&ctx, info, info_len)) return false;
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}
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/* OpenSSL does not accept size_t parameter. */
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uint32_t uint32_digest_size_ = digest_size_;
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if (!EVP_DigestFinal_ex(&ctx, digest_result.get(), &uint32_digest_size_) ||
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uint32_digest_size_ != digest_size_)
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return false;
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size_t block_start = digest_size_ * block;
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size_t block_length = min(digest_size_, output_len - block_start);
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memcpy(output + block_start, digest_result.get(), block_length);
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}
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return true;
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}
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} // namespace keymaster
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