+++ /dev/null
-// Copyright (c) 2016 Ryan Prichard
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to
-// deal in the Software without restriction, including without limitation the
-// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
-// sell copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in
-// all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
-// IN THE SOFTWARE.
-
-#include "GenRandom.h"
-
-#include <stdint.h>
-#include <string.h>
-
-#include "DebugClient.h"
-#include "StringBuilder.h"
-
-static volatile LONG g_pipeCounter;
-
-GenRandom::GenRandom() : m_advapi32(L"advapi32.dll") {
- // First try to use the pseudo-documented RtlGenRandom function from
- // advapi32.dll. Creating a CryptoAPI context is slow, and RtlGenRandom
- // avoids the overhead. It's documented in this blog post[1] and on
- // MSDN[2] with a disclaimer about future breakage. This technique is
- // apparently built-in into the MSVC CRT, though, for the rand_s function,
- // so perhaps it is stable enough.
- //
- // [1] http://blogs.msdn.com/b/michael_howard/archive/2005/01/14/353379.aspx
- // [2] https://msdn.microsoft.com/en-us/library/windows/desktop/aa387694(v=vs.85).aspx
- //
- // Both RtlGenRandom and the Crypto API functions exist in XP and up.
- m_rtlGenRandom = reinterpret_cast<RtlGenRandom_t*>(
- m_advapi32.proc("SystemFunction036"));
- // The OsModule class logs an error message if the proc is nullptr.
- if (m_rtlGenRandom != nullptr) {
- return;
- }
-
- // Fall back to the crypto API.
- m_cryptProvIsValid =
- CryptAcquireContext(&m_cryptProv, nullptr, nullptr,
- PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) != 0;
- if (!m_cryptProvIsValid) {
- trace("GenRandom: CryptAcquireContext failed: %u",
- static_cast<unsigned>(GetLastError()));
- }
-}
-
-GenRandom::~GenRandom() {
- if (m_cryptProvIsValid) {
- CryptReleaseContext(m_cryptProv, 0);
- }
-}
-
-// Returns false if the context is invalid or the generation fails.
-bool GenRandom::fillBuffer(void *buffer, size_t size) {
- memset(buffer, 0, size);
- bool success = false;
- if (m_rtlGenRandom != nullptr) {
- success = m_rtlGenRandom(buffer, size) != 0;
- if (!success) {
- trace("GenRandom: RtlGenRandom/SystemFunction036 failed: %u",
- static_cast<unsigned>(GetLastError()));
- }
- } else if (m_cryptProvIsValid) {
- success =
- CryptGenRandom(m_cryptProv, size,
- reinterpret_cast<BYTE*>(buffer)) != 0;
- if (!success) {
- trace("GenRandom: CryptGenRandom failed, size=%d, lasterror=%u",
- static_cast<int>(size),
- static_cast<unsigned>(GetLastError()));
- }
- }
- return success;
-}
-
-// Returns an empty string if either of CryptAcquireContext or CryptGenRandom
-// fail.
-std::string GenRandom::randomBytes(size_t numBytes) {
- std::string ret(numBytes, '\0');
- if (!fillBuffer(&ret[0], numBytes)) {
- return std::string();
- }
- return ret;
-}
-
-std::wstring GenRandom::randomHexString(size_t numBytes) {
- const std::string bytes = randomBytes(numBytes);
- std::wstring ret(bytes.size() * 2, L'\0');
- for (size_t i = 0; i < bytes.size(); ++i) {
- static const wchar_t hex[] = L"0123456789abcdef";
- ret[i * 2] = hex[static_cast<uint8_t>(bytes[i]) >> 4];
- ret[i * 2 + 1] = hex[static_cast<uint8_t>(bytes[i]) & 0xF];
- }
- return ret;
-}
-
-// Returns a 64-bit value representing the number of 100-nanosecond intervals
-// since January 1, 1601.
-static uint64_t systemTimeAsUInt64() {
- FILETIME monotonicTime = {};
- GetSystemTimeAsFileTime(&monotonicTime);
- return (static_cast<uint64_t>(monotonicTime.dwHighDateTime) << 32) |
- static_cast<uint64_t>(monotonicTime.dwLowDateTime);
-}
-
-// Generates a unique and hard-to-guess case-insensitive string suitable for
-// use in a pipe filename or a Windows object name.
-std::wstring GenRandom::uniqueName() {
- // First include enough information to avoid collisions assuming
- // cooperative software. This code assumes that a process won't die and
- // be replaced with a recycled PID within a single GetSystemTimeAsFileTime
- // interval.
- WStringBuilder sb(64);
- sb << GetCurrentProcessId()
- << L'-' << InterlockedIncrement(&g_pipeCounter)
- << L'-' << whexOfInt(systemTimeAsUInt64());
- // It isn't clear to me how the crypto APIs would fail. It *probably*
- // doesn't matter that much anyway? In principle, a predictable pipe name
- // is subject to a local denial-of-service attack.
- auto random = randomHexString(16);
- if (!random.empty()) {
- sb << L'-' << random;
- }
- return sb.str_moved();
-}
projects / VSoRC / .git / blobdiff