--- /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