1 files changed, 146 insertions, 0 deletions
diff --git a/mfbt/RandomNum.cpp b/mfbt/RandomNum.cpp
new file mode 100644
index 0000000000..96de5d4055
--- /dev/null
+++ b/mfbt/RandomNum.cpp
@@ -0,0 +1,146 @@
+/* -*- 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__) || \
+    defined(__wasi__)
+#  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 {
+
+MFBT_API bool GenerateRandomBytesFromOS(void* aBuffer, size_t aLength) {
+  MOZ_ASSERT(aBuffer);
+  MOZ_ASSERT(aLength > 0);
+
+#if defined(XP_WIN)
+  return !!RtlGenRandom(aBuffer, aLength);
+
+#elif defined(USE_ARC4RANDOM)  // defined(XP_WIN)
+
+  arc4random_buf(aBuffer, aLength);
+  return true;
+
+#elif defined(XP_UNIX)  // defined(USE_ARC4RANDOM)
+
+#  if defined(__linux__)
+
+  long bytesGenerated = syscall(SYS_getrandom, aBuffer, aLength, GRND_NONBLOCK);
+
+  if (static_cast<unsigned long>(bytesGenerated) == aLength) {
+    return true;
+  }
+
+  // Fall-through to UNIX behavior if failed
+
+#  endif  // defined(__linux__)
+
+  int fd = open("/dev/urandom", O_RDONLY);
+  if (fd < 0) {
+    return false;
+  }
+
+  ssize_t bytesRead = read(fd, aBuffer, aLength);
+
+  close(fd);
+
+  return (static_cast<size_t>(bytesRead) == aLength);
+
+#else  // defined(XP_UNIX)
+#  error "Platform needs to implement GenerateRandomBytesFromOS()"
+#endif
+}
+
+MFBT_API Maybe<uint64_t> RandomUint64() {
+  uint64_t randomNum;
+  if (!GenerateRandomBytesFromOS(&randomNum, sizeof(randomNum))) {
+    return Nothing();
+  }
+
+  return Some(randomNum);
+}
+
+MFBT_API uint64_t RandomUint64OrDie() {
+  uint64_t randomNum;
+  MOZ_RELEASE_ASSERT(GenerateRandomBytesFromOS(&randomNum, sizeof(randomNum)));
+  return randomNum;
+}
+
+}  // namespace mozilla