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 "iso18033kdf.h" 18 #include "openssl_utils.h" 19 20 #include <algorithm> 21 22 #include <openssl/evp.h> 23 24 namespace keymaster { 25 26 inline size_t min(size_t a, size_t b) { 27 return (a < b) ? a : b; 28 } 29 30 bool Iso18033Kdf::GenerateKey(const uint8_t* info, size_t info_len, uint8_t* output, 31 size_t output_len) { 32 if (!is_initialized_ || output == nullptr) 33 return false; 34 35 /* Check whether output length is too long as specified in ISO/IEC 18033-2. */ 36 if ((0xFFFFFFFFULL + start_counter_) * digest_size_ < (uint64_t)output_len) 37 return false; 38 39 EVP_MD_CTX ctx; 40 EvpMdCtxCleaner ctxCleaner(&ctx); 41 EVP_MD_CTX_init(&ctx); 42 43 size_t num_blocks = (output_len + digest_size_ - 1) / digest_size_; 44 UniquePtr<uint8_t[]> counter(new uint8_t[4]); 45 UniquePtr<uint8_t[]> digest_result(new uint8_t[digest_size_]); 46 if (counter.get() == nullptr || digest_result.get() == nullptr) 47 return false; 48 for (size_t block = 0; block < num_blocks; block++) { 49 switch (digest_type_) { 50 case KM_DIGEST_SHA1: 51 if (!EVP_DigestInit_ex(&ctx, EVP_sha1(), nullptr /* default digest */)) 52 return false; 53 break; 54 case KM_DIGEST_SHA_2_256: 55 if (!EVP_DigestInit_ex(&ctx, EVP_sha256(), nullptr /* default digest */)) 56 return false; 57 break; 58 default: 59 return false; 60 } 61 62 if (!EVP_DigestUpdate(&ctx, secret_key_.get(), secret_key_len_) || 63 !Uint32ToBigEndianByteArray(block + start_counter_, counter.get()) || 64 !EVP_DigestUpdate(&ctx, counter.get(), 4)) 65 return false; 66 67 if (info != nullptr && info_len > 0) { 68 if (!EVP_DigestUpdate(&ctx, info, info_len)) 69 return false; 70 } 71 72 /* OpenSSL does not accept size_t parameter. */ 73 uint32_t uint32_digest_size_ = digest_size_; 74 if (!EVP_DigestFinal_ex(&ctx, digest_result.get(), &uint32_digest_size_) || 75 uint32_digest_size_ != digest_size_) 76 return false; 77 78 size_t block_start = digest_size_ * block; 79 size_t block_length = min(digest_size_, output_len - block_start); 80 memcpy(output + block_start, digest_result.get(), block_length); 81 } 82 return true; 83 } 84 85 } // namespace keymaster 86
