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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/base/status.h"
#include "mongo/crypto/sha1_block.h"
#include "mongo/db/logical_time.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
/**
* The TimeProofService holds the key used by mongod and mongos processes to verify cluster times
* and contains the logic to generate this key. As a performance optimization to avoid expensive
* signature generation the class also holds the cache.
*/
class TimeProofService {
public:
// This type must be synchronized with the library that generates SHA1 or other proof.
using TimeProof = SHA1Block;
using Key = SHA1Block;
TimeProofService() = default;
/**
* Generates a pseudorandom key to be used for HMAC authentication.
*/
static Key generateRandomKey();
/**
* Returns the proof matching the time argument.
*/
TimeProof getProof(LogicalTime time, const Key& key);
/**
* Verifies that the proof matches the time argument.
*/
Status checkProof(LogicalTime time, const TimeProof& proof, const Key& key);
/**
* Resets the cache.
*/
void resetCache();
private:
/**
* Nested class to cache TimeProof. It holds proof for the greatest time allowed.
*/
struct CacheEntry {
CacheEntry(TimeProof proof, LogicalTime time, const Key& key)
: _proof(std::move(proof)), _time(time), _key(key) {}
/**
* Returns true if it has proof for time greater or equal than the argument.
*/
bool hasProof(LogicalTime time, const Key& key) const {
return key == _key && time == _time;
}
TimeProof _proof;
LogicalTime _time;
Key _key;
};
// protects _cache
stdx::mutex _cacheMutex;
// one-entry cache
boost::optional<CacheEntry> _cache;
};
} // namespace mongo
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