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      1 /*
      2  * Copyright (C) 2016 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 #ifndef ANDROID_VOLD_KEYMASTER_H
     18 #define ANDROID_VOLD_KEYMASTER_H
     19 
     20 #include <memory>
     21 #include <string>
     22 #include <utility>
     23 
     24 #include <keymaster/authorization_set.h>
     25 
     26 namespace android {
     27 namespace vold {
     28 
     29 using namespace keymaster;
     30 
     31 // C++ wrappers to the Keymaster C interface.
     32 // This is tailored to the needs of KeyStorage, but could be extended to be
     33 // a more general interface.
     34 
     35 // Class that wraps a keymaster1_device_t or keymaster2_device_t and provides methods
     36 // they have in common. Also closes the device on destruction.
     37 class IKeymasterDevice;
     38 
     39 // Wrapper for a keymaster_operation_handle_t representing an
     40 // ongoing Keymaster operation.  Aborts the operation
     41 // in the destructor if it is unfinished. Methods log failures
     42 // to LOG(ERROR).
     43 class KeymasterOperation {
     44   public:
     45     ~KeymasterOperation();
     46     // Is this instance valid? This is false if creation fails, and becomes
     47     // false on finish or if an update fails.
     48     explicit operator bool() { return mDevice != nullptr; }
     49     // Call "update" repeatedly until all of the input is consumed, and
     50     // concatenate the output. Return true on success.
     51     bool updateCompletely(const std::string& input, std::string* output);
     52     // Finish; pass nullptr for the "output" param.
     53     bool finish();
     54     // Finish and write the output to this string.
     55     bool finishWithOutput(std::string* output);
     56     // Move constructor
     57     KeymasterOperation(KeymasterOperation&& rhs) {
     58         mOpHandle = std::move(rhs.mOpHandle);
     59         mDevice = std::move(rhs.mDevice);
     60     }
     61 
     62   private:
     63     KeymasterOperation(std::shared_ptr<IKeymasterDevice> d, keymaster_operation_handle_t h)
     64         : mDevice{d}, mOpHandle{h} {}
     65     std::shared_ptr<IKeymasterDevice> mDevice;
     66     keymaster_operation_handle_t mOpHandle;
     67     DISALLOW_COPY_AND_ASSIGN(KeymasterOperation);
     68     friend class Keymaster;
     69 };
     70 
     71 // Wrapper for a Keymaster device for methods that start a KeymasterOperation or are not
     72 // part of one.
     73 class Keymaster {
     74   public:
     75     Keymaster();
     76     // false if we failed to open the keymaster device.
     77     explicit operator bool() { return mDevice != nullptr; }
     78     // Generate a key in the keymaster from the given params.
     79     bool generateKey(const AuthorizationSet& inParams, std::string* key);
     80     // If the keymaster supports it, permanently delete a key.
     81     bool deleteKey(const std::string& key);
     82     // Begin a new cryptographic operation, collecting output parameters.
     83     KeymasterOperation begin(keymaster_purpose_t purpose, const std::string& key,
     84                              const AuthorizationSet& inParams, AuthorizationSet* outParams);
     85     // Begin a new cryptographic operation; don't collect output parameters.
     86     KeymasterOperation begin(keymaster_purpose_t purpose, const std::string& key,
     87                              const AuthorizationSet& inParams);
     88 
     89   private:
     90     std::shared_ptr<IKeymasterDevice> mDevice;
     91     DISALLOW_COPY_AND_ASSIGN(Keymaster);
     92 };
     93 
     94 template <keymaster_tag_t Tag>
     95 inline AuthorizationSetBuilder& addStringParam(AuthorizationSetBuilder&& params,
     96                                                TypedTag<KM_BYTES, Tag> tag,
     97                                                const std::string& val) {
     98     return params.Authorization(tag, val.data(), val.size());
     99 }
    100 
    101 template <keymaster_tag_t Tag>
    102 inline void addStringParam(AuthorizationSetBuilder* params, TypedTag<KM_BYTES, Tag> tag,
    103                            const std::string& val) {
    104     params->Authorization(tag, val.data(), val.size());
    105 }
    106 
    107 }  // namespace vold
    108 }  // namespace android
    109 
    110 #endif
    111