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 25 inline size_t min(size_t a, size_t b) { 26 return (a < b) ? a : b; 27 } 28 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