// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/rand_util.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <unistd.h>
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#include "base/files/file_util.h"
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#include "base/lazy_instance.h"
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#include "base/logging.h"
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#include "base/posix/eintr_wrapper.h"
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namespace {
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// We keep the file descriptor for /dev/urandom around so we don't need to
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// reopen it (which is expensive), and since we may not even be able to reopen
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// it if we are later put in a sandbox. This class wraps the file descriptor so
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// we can use LazyInstance to handle opening it on the first access.
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class URandomFd {
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public:
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#if defined(OS_AIX)
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// AIX has no 64-bit support for open falgs such as -
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// O_CLOEXEC, O_NOFOLLOW and O_TTY_INIT
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URandomFd() : fd_(HANDLE_EINTR(open("/dev/urandom", O_RDONLY))) {
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DCHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
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}
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#else
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URandomFd() : fd_(HANDLE_EINTR(open("/dev/urandom", O_RDONLY | O_CLOEXEC))) {
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DCHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
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}
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#endif
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~URandomFd() { close(fd_); }
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int fd() const { return fd_; }
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private:
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const int fd_;
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};
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base::LazyInstance<URandomFd>::Leaky g_urandom_fd = LAZY_INSTANCE_INITIALIZER;
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} // namespace
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namespace base {
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void RandBytes(void* output, size_t output_length) {
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const int urandom_fd = g_urandom_fd.Pointer()->fd();
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const bool success =
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ReadFromFD(urandom_fd, static_cast<char*>(output), output_length);
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CHECK(success);
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}
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int GetUrandomFD(void) {
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return g_urandom_fd.Pointer()->fd();
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}
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} // namespace base
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