mfbt/RandomNum.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
   6
   7 /* Routines for generating random numbers */
   8
   9 #ifndef mozilla_RandomNum_h_
  10 #define mozilla_RandomNum_h_
  11
  12 #include "mozilla/Maybe.h"
  13 #include "mozilla/Types.h"
  14
  15 namespace mozilla {
  16
  17 /**
  18  *  Generate cryptographically secure random bytes using the best facilities
  19  *  available on the current OS.
  20  *
  21  *  Return value: true if random bytes were copied into `aBuffer` or false on
  22  *  error.
  23  *
  24  *  Useful whenever a secure random number is needed and NSS isn't available.
  25  *  (Perhaps because it hasn't been initialized yet)
  26  *
  27  *  Current mechanisms:
  28  *    Windows: RtlGenRandom()
  29  *    Android, Darwin, DragonFly, FreeBSD, OpenBSD, NetBSD: arc4random()
  30  *    Linux: getrandom() if available, "/dev/urandom" otherwise
  31  *    Other Unix: "/dev/urandom"
  32  *
  33  */
  34 [[nodiscard]] MFBT_API bool GenerateRandomBytesFromOS(void* aBuffer,
  35                                                       size_t aLength);
  36
  37 /**
  38  *  Generate a cryptographically secure random 64-bit unsigned number using the
  39  *  best facilities available on the current OS.
  40  */
  41 MFBT_API Maybe<uint64_t> RandomUint64();
  42
  43 /**
  44  *  Like RandomUint64, but always returns a uint64_t or crashes with an assert
  45  *  if the underlying RandomUint64 call failed.
  46  */
  47 MFBT_API uint64_t RandomUint64OrDie();
  48
  49 }  // namespace mozilla
  50
  51 #endif  // mozilla_RandomNum_h_