| /* |
| * Copyright 2015 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef SYSTEM_KEYMASTER_HKDF_H_ |
| #define SYSTEM_KEYMASTER_HKDF_H_ |
| |
| #include <hardware/keymaster_defs.h> |
| #include <keymaster/serializable.h> |
| |
| #include <UniquePtr.h> |
| |
| namespace keymaster { |
| |
| // Rfc5869HmacSha256Kdf implements the key derivation function specified in RFC 5869 (using |
| // SHA256) and outputs key material, as needed by ECIES. |
| // See https://tools.ietf.org/html/rfc5869 for details. |
| class Rfc5869HmacSha256Kdf { |
| public: |
| // |secret|: the input shared secret (or, from RFC 5869, the IKM). |
| // |salt|: an (optional) public salt / non-secret random value. While |
| // optional, callers are strongly recommended to provide a salt. There is no |
| // added security value in making this larger than the SHA-256 block size of |
| // 64 bytes. |
| // |info|: an (optional) label to distinguish different uses of HKDF. It is |
| // optional context and application specific information (can be a zero-length |
| // string). |
| // |key_bytes_to_generate|: the number of bytes of key material to generate. |
| Rfc5869HmacSha256Kdf(Buffer& secret, Buffer& salt, Buffer& info, size_t key_bytes_to_generate, |
| keymaster_error_t* error); |
| |
| Rfc5869HmacSha256Kdf(const uint8_t* secret, size_t secret_len, const uint8_t* salt, |
| size_t salt_len, const uint8_t* info, size_t info_len, |
| size_t key_bytes_to_generate, keymaster_error_t* error); |
| |
| bool secret_key(Buffer* buf) const { |
| return buf->Reinitialize(secret_key_.get(), secret_key_len_); |
| }; |
| |
| private: |
| UniquePtr<uint8_t[]> output_; |
| UniquePtr<uint8_t[]> secret_key_; |
| size_t secret_key_len_; |
| }; |
| |
| } // namespace keymaster |
| |
| #endif // SYSTEM_KEYMASTER_HKDF_H_ |