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6929e31dcb
In bug 1788004, we started hooking BCryptGenRandom on the machines where calling it for the first time fails. This was useful to mitigate Rust panics linked to RNG function failures in the Rust stdlib and in the getrandom crate. Both now have proper fallbacks again, so we can remove our hook. Differential Revision: https://phabricator.services.mozilla.com/D174966
147 lines
3.9 KiB
C++
147 lines
3.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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#include "mozilla/RandomNum.h"
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#include <fcntl.h>
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#ifdef XP_UNIX
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# include <unistd.h>
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#endif
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#if defined(XP_WIN)
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// Microsoft doesn't "officially" support using RtlGenRandom() directly
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// anymore, and the Windows headers assume that __stdcall is
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// the default calling convention (which is true when Microsoft uses this
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// function to build their own CRT libraries).
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// We will explicitly declare it with the proper calling convention.
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# include "minwindef.h"
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# define RtlGenRandom SystemFunction036
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extern "C" BOOLEAN NTAPI RtlGenRandom(PVOID RandomBuffer,
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ULONG RandomBufferLength);
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#endif
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#if defined(ANDROID) || defined(XP_DARWIN) || defined(__DragonFly__) || \
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defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \
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defined(__wasi__)
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# include <stdlib.h>
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# define USE_ARC4RANDOM
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#endif
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#if defined(__linux__)
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# include <linux/random.h> // For GRND_NONBLOCK.
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# include <sys/syscall.h> // For SYS_getrandom.
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// Older glibc versions don't define SYS_getrandom, so we define it here if
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// it's not available. See bug 995069.
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# if defined(__x86_64__)
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# define GETRANDOM_NR 318
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# elif defined(__i386__)
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# define GETRANDOM_NR 355
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# elif defined(__aarch64__)
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# define GETRANDOM_NR 278
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# elif defined(__arm__)
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# define GETRANDOM_NR 384
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# elif defined(__powerpc__)
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# define GETRANDOM_NR 359
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# elif defined(__s390__)
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# define GETRANDOM_NR 349
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# elif defined(__mips__)
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# include <sgidefs.h>
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# if _MIPS_SIM == _MIPS_SIM_ABI32
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# define GETRANDOM_NR 4353
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# elif _MIPS_SIM == _MIPS_SIM_ABI64
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# define GETRANDOM_NR 5313
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# elif _MIPS_SIM == _MIPS_SIM_NABI32
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# define GETRANDOM_NR 6317
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# endif
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# endif
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# if defined(SYS_getrandom)
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// We have SYS_getrandom. Use it to check GETRANDOM_NR. Only do this if we set
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// GETRANDOM_NR so tier 3 platforms with recent glibc are not forced to define
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// it for no good reason.
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# if defined(GETRANDOM_NR)
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static_assert(GETRANDOM_NR == SYS_getrandom,
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"GETRANDOM_NR should match the actual SYS_getrandom value");
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# endif
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# else
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# define SYS_getrandom GETRANDOM_NR
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# endif
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# if defined(GRND_NONBLOCK)
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static_assert(GRND_NONBLOCK == 1,
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"If GRND_NONBLOCK is not 1 the #define below is wrong");
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# else
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# define GRND_NONBLOCK 1
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# endif
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#endif // defined(__linux__)
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namespace mozilla {
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MFBT_API bool GenerateRandomBytesFromOS(void* aBuffer, size_t aLength) {
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MOZ_ASSERT(aBuffer);
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MOZ_ASSERT(aLength > 0);
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#if defined(XP_WIN)
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return !!RtlGenRandom(aBuffer, aLength);
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#elif defined(USE_ARC4RANDOM) // defined(XP_WIN)
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arc4random_buf(aBuffer, aLength);
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return true;
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#elif defined(XP_UNIX) // defined(USE_ARC4RANDOM)
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# if defined(__linux__)
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long bytesGenerated = syscall(SYS_getrandom, aBuffer, aLength, GRND_NONBLOCK);
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if (static_cast<unsigned long>(bytesGenerated) == aLength) {
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return true;
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}
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// Fall-through to UNIX behavior if failed
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# endif // defined(__linux__)
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int fd = open("/dev/urandom", O_RDONLY);
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if (fd < 0) {
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return false;
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}
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ssize_t bytesRead = read(fd, aBuffer, aLength);
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close(fd);
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return (static_cast<size_t>(bytesRead) == aLength);
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#else // defined(XP_UNIX)
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# error "Platform needs to implement GenerateRandomBytesFromOS()"
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#endif
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}
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MFBT_API Maybe<uint64_t> RandomUint64() {
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uint64_t randomNum;
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if (!GenerateRandomBytesFromOS(&randomNum, sizeof(randomNum))) {
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return Nothing();
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}
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return Some(randomNum);
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}
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MFBT_API uint64_t RandomUint64OrDie() {
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uint64_t randomNum;
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MOZ_RELEASE_ASSERT(GenerateRandomBytesFromOS(&randomNum, sizeof(randomNum)));
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return randomNum;
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}
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} // namespace mozilla
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