1 // 2 // Copyright (C) 2020 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 #pragma once 17 18 #include <keymaster/serializable.h> 19 20 #include "host/commands/secure_env/tpm_resource_manager.h" 21 22 /** 23 * A keymaster::Serializable that wraps another keymaster::Serializable, 24 * protecting it from tampering while it is stored elsewhere. This stores 25 * the serialized data of the other type together with a signature over that 26 * serialized data. When deserializing, it will attempt to make the same 27 * signature over the data. If the signature or data has been tampered with, 28 * the signatures won't match and it won't attempt to deserialize the wrapped 29 * type. 30 * 31 * The serialization format is: 32 * [uint32_t: wrapped_size] [wrapped_data] 33 * [uint32_t: signature_size] [signature_data] 34 * 35 * While this class currently assumes all signatures will use the same key 36 * and algorithm and therefore be the same size, the serialization format is 37 * future-proof to accommodate signature changes. 38 */ 39 class HmacSerializable : public keymaster::Serializable { 40 public: 41 HmacSerializable(TpmResourceManager*, 42 std::function<TpmObjectSlot(TpmResourceManager*)>, 43 uint32_t digest_size, 44 Serializable*); 45 46 size_t SerializedSize() const override; 47 uint8_t* Serialize(uint8_t* buf, const uint8_t* end) const override; 48 bool Deserialize(const uint8_t** buf_ptr, const uint8_t* end) override; 49 private: 50 TpmResourceManager* resource_manager_; 51 std::function<TpmObjectSlot(TpmResourceManager*)> signing_key_fn_; 52 uint32_t digest_size_; 53 keymaster::Serializable* wrapped_; 54 }; 55