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89 lines
2.5 KiB
89 lines
2.5 KiB
// |
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// Copyright (C) 2014 The Android Open Source Project |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// |
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#include "update_engine/update_manager/real_random_provider.h" |
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#include <stdio.h> |
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#include <unistd.h> |
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#include <string> |
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#include <base/files/file_path.h> |
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#include <base/files/scoped_file.h> |
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#include <base/strings/stringprintf.h> |
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#include "update_engine/update_manager/variable.h" |
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using std::string; |
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namespace { |
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// The device providing randomness. |
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const char* kRandomDevice = "/dev/urandom"; |
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} // namespace |
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namespace chromeos_update_manager { |
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// A random seed variable. |
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class RandomSeedVariable : public Variable<uint64_t> { |
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public: |
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// RandomSeedVariable is initialized as kVariableModeConst to let the |
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// EvaluationContext cache the value between different evaluations of the same |
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// policy request. |
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RandomSeedVariable(const string& name, FILE* fp) |
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: Variable<uint64_t>(name, kVariableModeConst), fp_(fp) {} |
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~RandomSeedVariable() override {} |
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protected: |
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const uint64_t* GetValue(base::TimeDelta /* timeout */, |
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string* errmsg) override { |
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uint64_t result; |
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// Aliasing via char pointer abides by the C/C++ strict-aliasing rules. |
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char* const buf = reinterpret_cast<char*>(&result); |
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unsigned int buf_rd = 0; |
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while (buf_rd < sizeof(result)) { |
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int rd = fread(buf + buf_rd, 1, sizeof(result) - buf_rd, fp_.get()); |
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if (rd == 0 || ferror(fp_.get())) { |
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// Either EOF on fp or read failed. |
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if (errmsg) { |
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*errmsg = base::StringPrintf( |
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"Error reading from the random device: %s", kRandomDevice); |
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} |
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return nullptr; |
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} |
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buf_rd += rd; |
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} |
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return new uint64_t(result); |
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} |
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private: |
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base::ScopedFILE fp_; |
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DISALLOW_COPY_AND_ASSIGN(RandomSeedVariable); |
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}; |
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bool RealRandomProvider::Init(void) { |
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FILE* fp = fopen(kRandomDevice, "r"); |
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if (!fp) |
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return false; |
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var_seed_.reset(new RandomSeedVariable("seed", fp)); |
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return true; |
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} |
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} // namespace chromeos_update_manager
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