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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
#include "mozilla/RandomNum.h"
#include <fcntl.h>
#ifdef XP_UNIX
# include <unistd.h>
#endif
#if defined(XP_WIN)
// Microsoft doesn't "officially" support using RtlGenRandom() directly
// anymore, and the Windows headers assume that __stdcall is
// the default calling convention (which is true when Microsoft uses this
// function to build their own CRT libraries).
// We will explicitly declare it with the proper calling convention.
# include "minwindef.h"
# define RtlGenRandom SystemFunction036
extern "C" BOOLEAN NTAPI RtlGenRandom(PVOID RandomBuffer,
ULONG RandomBufferLength);
#endif
#if defined(ANDROID) || defined(XP_DARWIN) || defined(__DragonFly__) || \
defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
# include <stdlib.h>
# define USE_ARC4RANDOM
#endif
#if defined(__linux__)
# include <linux/random.h> // For GRND_NONBLOCK.
# include <sys/syscall.h> // For SYS_getrandom.
// Older glibc versions don't define SYS_getrandom, so we define it here if
// it's not available. See bug 995069.
# if defined(__x86_64__)
# define GETRANDOM_NR 318
# elif defined(__i386__)
# define GETRANDOM_NR 355
# elif defined(__aarch64__)
# define GETRANDOM_NR 278
# elif defined(__arm__)
# define GETRANDOM_NR 384
# elif defined(__powerpc__)
# define GETRANDOM_NR 359
# elif defined(__s390__)
# define GETRANDOM_NR 349
# elif defined(__mips__)
# include <sgidefs.h>
# if _MIPS_SIM == _MIPS_SIM_ABI32
# define GETRANDOM_NR 4353
# elif _MIPS_SIM == _MIPS_SIM_ABI64
# define GETRANDOM_NR 5313
# elif _MIPS_SIM == _MIPS_SIM_NABI32
# define GETRANDOM_NR 6317
# endif
# endif
# if defined(SYS_getrandom)
// We have SYS_getrandom. Use it to check GETRANDOM_NR. Only do this if we set
// GETRANDOM_NR so tier 3 platforms with recent glibc are not forced to define
// it for no good reason.
# if defined(GETRANDOM_NR)
static_assert(GETRANDOM_NR == SYS_getrandom,
"GETRANDOM_NR should match the actual SYS_getrandom value");
# endif
# else
# define SYS_getrandom GETRANDOM_NR
# endif
# if defined(GRND_NONBLOCK)
static_assert(GRND_NONBLOCK == 1,
"If GRND_NONBLOCK is not 1 the #define below is wrong");
# else
# define GRND_NONBLOCK 1
# endif
#endif // defined(__linux__)
namespace mozilla {
/*
* Note - Bug 1500115 has been opened to discuss simplifying or improving
* this function in the future; however, the function is secure as-is right
* now. Further improvements may be made to reduce complexity, improve
* robustness, or take advantage of OS-specific API improvements as they
* become available.
*
*/
MFBT_API Maybe<uint64_t> RandomUint64() {
#if defined(XP_WIN)
uint64_t result = 0;
if (!RtlGenRandom(&result, sizeof(result))) {
return Nothing();
}
return Some(result);
#elif defined(USE_ARC4RANDOM) // defined(XP_WIN)
return Some((static_cast<uint64_t>(arc4random()) << 32) | arc4random());
#elif defined(XP_UNIX) // defined(USE_ARC4RANDOM)
uint64_t result = 0;
# if defined(__linux__)
long bytesGenerated =
syscall(SYS_getrandom, &result, sizeof(result), GRND_NONBLOCK);
if ((bytesGenerated > 0) &&
(static_cast<unsigned long>(bytesGenerated) == sizeof(result))) {
return Some(result);
}
// Fall-through to UNIX behavior if failed
# endif // defined(__linux__)
int fd = open("/dev/urandom", O_RDONLY);
if (fd < 0) {
return Nothing();
}
ssize_t bytesRead = read(fd, &result, sizeof(result));
close(fd);
if (bytesRead < 0) {
return Nothing();
}
if (static_cast<size_t>(bytesRead) != sizeof(result)) {
return Nothing();
}
return Some(result);
#else // defined(XP_UNIX)
# error "Platform needs to implement RandomUint64()"
#endif
}
MFBT_API uint64_t RandomUint64OrDie() {
Maybe<uint64_t> maybeRandomNum = RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandomNum.isSome());
return maybeRandomNum.value();
}
} // namespace mozilla