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      1 /*
      2  **
      3  ** Copyright 2017, The Android Open Source Project
      4  **
      5  ** Licensed under the Apache License, Version 2.0 (the "License");
      6  ** you may not use this file except in compliance with the License.
      7  ** You may obtain a copy of the License at
      8  **
      9  **     http://www.apache.org/licenses/LICENSE-2.0
     10  **
     11  ** Unless required by applicable law or agreed to in writing, software
     12  ** distributed under the License is distributed on an "AS IS" BASIS,
     13  ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  ** See the License for the specific language governing permissions and
     15  ** limitations under the License.
     16  */
     17 
     18 #ifndef HARDWARE_INTERFACES_KEYMASTER_40_SUPPORT_KEYMASTER_H_
     19 #define HARDWARE_INTERFACES_KEYMASTER_40_SUPPORT_KEYMASTER_H_
     20 
     21 #include <android/hardware/keymaster/4.0/IKeymasterDevice.h>
     22 
     23 namespace android {
     24 namespace hardware {
     25 namespace keymaster {
     26 namespace V4_0 {
     27 namespace support {
     28 
     29 /**
     30  * Keymaster abstracts the underlying V4_0::IKeymasterDevice.  There is one implementation
     31  * (Keymaster4) which is a trivial passthrough and one that wraps a V3_0::IKeymasterDevice.
     32  *
     33  * The reason for adding this additional layer, rather than simply using the latest HAL directly and
     34  * subclassing it to wrap any older HAL, is because this provides a place to put additional methods
     35  * which clients can use when they need to distinguish between different underlying HAL versions,
     36  * while still having to use only the latest interface.
     37  */
     38 class Keymaster : public IKeymasterDevice {
     39    public:
     40     using KeymasterSet = std::vector<std::unique_ptr<Keymaster>>;
     41 
     42     Keymaster(const hidl_string& descriptor, const hidl_string& instanceName)
     43         : descriptor_(descriptor), instanceName_(instanceName) {}
     44     virtual ~Keymaster() {}
     45 
     46     struct VersionResult {
     47         hidl_string keymasterName;
     48         hidl_string authorName;
     49         uint8_t majorVersion;
     50         SecurityLevel securityLevel;
     51         bool supportsEc;
     52 
     53         bool operator>(const VersionResult& other) const {
     54             auto lhs = std::tie(securityLevel, majorVersion, supportsEc);
     55             auto rhs = std::tie(other.securityLevel, other.majorVersion, other.supportsEc);
     56             return lhs > rhs;
     57         }
     58     };
     59 
     60     virtual const VersionResult& halVersion() const = 0;
     61     const hidl_string& descriptor() const { return descriptor_; }
     62     const hidl_string& instanceName() const { return instanceName_; }
     63 
     64     /**
     65      * Returns all available Keymaster3 and Keymaster4 instances, in order of most secure to least
     66      * secure (as defined by VersionResult::operator<).
     67      */
     68     static KeymasterSet enumerateAvailableDevices();
     69 
     70     /**
     71      * Ask provided Keymaster instances to compute a shared HMAC key using
     72      * getHmacSharingParameters() and computeSharedHmac().  This computation is idempotent as long
     73      * as the same set of Keymaster instances is used each time (and if all of the instances work
     74      * correctly).  It must be performed once per boot, but should do no harm to be repeated.
     75      *
     76      * If key agreement fails, this method will crash the process (with CHECK).
     77      */
     78     static void performHmacKeyAgreement(const KeymasterSet& keymasters);
     79 
     80    private:
     81     hidl_string descriptor_;
     82     hidl_string instanceName_;
     83 };
     84 
     85 std::ostream& operator<<(std::ostream& os, const Keymaster& keymaster);
     86 
     87 }  // namespace support
     88 }  // namespace V4_0
     89 }  // namespace keymaster
     90 }  // namespace hardware
     91 }  // namespace android
     92 
     93 #endif  // HARDWARE_INTERFACES_KEYMASTER_40_SUPPORT_KEYMASTER_H_
     94