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// Copyright 2021 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/common/pseudonymization_salt.h"
#include <atomic>
#include "base/check_op.h"
#include "base/dcheck_is_on.h"
#include "base/rand_util.h"
#if DCHECK_IS_ON()
#include "sandbox/policy/sandbox.h"
#endif
namespace content {
namespace {
std::atomic<uint32_t> g_salt(0);
uint32_t InitializeSalt() {
uint32_t salt;
do {
salt = base::RandUint64();
} while (salt == 0);
// If `g_salt` is still uninitialized (has a value of 0), then put `salt` into
// `g_salt`. Otherwise, use the current `value` of `g_salt`.
uint32_t value = 0;
if (!g_salt.compare_exchange_strong(value, salt))
salt = value;
return salt;
}
} // namespace
uint32_t GetPseudonymizationSalt() {
uint32_t salt = g_salt.load();
if (salt == 0) {
#if DCHECK_IS_ON()
// Only the Browser process needs to initialize the `salt` on demand.
// Other processes (identified via the IsProcessSandboxed heuristic) should
// receive the salt from their parent processes.
DCHECK(!sandbox::policy::Sandbox::IsProcessSandboxed());
#endif
salt = InitializeSalt();
}
return salt;
}
void SetPseudonymizationSalt(uint32_t salt) {
DCHECK_NE(0u, salt);
// TODO(lukasza): Ideally we would DCHECK that `g_salt` is not set twice (e.g.
// that DCHECK_EQ(0u, g_salt.load(std::memory_order_acquire))), but this is
// made rather difficult by tests that run in single-process-mode, or
// construct ChildProcessHostImpl directly (e.g. RenderThreadImplBrowserTest).
g_salt.store(salt);
}
} // namespace content
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