gecko-dev/ipc/mscom/ProcessRuntime.cpp

/* -*- 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 http://mozilla.org/MPL/2.0/. */

#include "mozilla/mscom/ProcessRuntime.h"

#if defined(ACCESSIBILITY) && \
    (defined(MOZILLA_INTERNAL_API) || defined(MOZ_HAS_MOZGLUE))
#  include "mozilla/mscom/ActCtxResource.h"
#endif  // defined(ACCESSIBILITY) && (defined(MOZILLA_INTERNAL_API) ||
        // defined(MOZ_HAS_MOZGLUE))
#include "mozilla/Assertions.h"
#include "mozilla/DynamicallyLinkedFunctionPtr.h"
#include "mozilla/mscom/COMWrappers.h"
#include "mozilla/mscom/ProcessRuntimeShared.h"
#include "mozilla/RefPtr.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
#include "mozilla/Vector.h"
#include "mozilla/WindowsProcessMitigations.h"
#include "mozilla/WindowsVersion.h"

#if defined(MOZILLA_INTERNAL_API)
#  include "mozilla/mscom/EnsureMTA.h"
#  if defined(MOZ_SANDBOX)
#    include "mozilla/sandboxTarget.h"
#  endif  // defined(MOZ_SANDBOX)
#endif    // defined(MOZILLA_INTERNAL_API)

#include <accctrl.h>
#include <aclapi.h>
#include <objbase.h>
#include <objidl.h>

// This API from oleaut32.dll is not declared in Windows SDK headers
extern "C" void __cdecl SetOaNoCache(void);

using namespace mozilla::mscom::detail;

namespace mozilla {
namespace mscom {

#if defined(MOZILLA_INTERNAL_API)
ProcessRuntime* ProcessRuntime::sInstance = nullptr;

ProcessRuntime::ProcessRuntime() : ProcessRuntime(XRE_GetProcessType()) {}

ProcessRuntime::ProcessRuntime(const GeckoProcessType aProcessType)
    : ProcessRuntime(aProcessType == GeckoProcessType_Default
                         ? ProcessCategory::GeckoBrowserParent
                         : ProcessCategory::GeckoChild) {}
#endif  // defined(MOZILLA_INTERNAL_API)

ProcessRuntime::ProcessRuntime(const ProcessCategory aProcessCategory)
    : mInitResult(CO_E_NOTINITIALIZED), mProcessCategory(aProcessCategory) {
#if defined(ACCESSIBILITY)
#  if defined(MOZILLA_INTERNAL_API)
  // If we're inside XUL, and we're the parent process, then we trust that
  // this has already been initialized for us prior to XUL being loaded.
  // Only required in the child if the Resource ID has been passed down.
  if (aProcessCategory != ProcessCategory::GeckoBrowserParent &&
      ActCtxResource::GetAccessibilityResourceId()) {
    mActCtxRgn.emplace(ActCtxResource::GetAccessibilityResource());
  }
#  elif defined(MOZ_HAS_MOZGLUE)
  // If we're here, then we're in mozglue and initializing this for the parent
  // process.
  MOZ_ASSERT(aProcessCategory == ProcessCategory::GeckoBrowserParent);
  mActCtxRgn.emplace(ActCtxResource::GetAccessibilityResource());
#  endif
#endif  // defined(ACCESSIBILITY)

#if defined(MOZILLA_INTERNAL_API)
  MOZ_DIAGNOSTIC_ASSERT(!sInstance);
  sInstance = this;

  EnsureMTA();
  /**
   * From this point forward, all threads in this process are implicitly
   * members of the multi-threaded apartment, with the following exceptions:
   * 1. If any Win32 GUI APIs were called on the current thread prior to
   *    executing this constructor, then this thread has already been implicitly
   *    initialized as the process's main STA thread; or
   * 2. A thread explicitly and successfully calls CoInitialize(Ex) to specify
   *    otherwise.
   */

  const bool isCurThreadImplicitMTA = IsCurrentThreadImplicitMTA();
  // We only assert that the implicit MTA precondition holds when not running
  // as the Gecko parent process.
  MOZ_DIAGNOSTIC_ASSERT(aProcessCategory ==
                            ProcessCategory::GeckoBrowserParent ||
                        isCurThreadImplicitMTA);

#  if defined(MOZ_SANDBOX)
  const bool isLockedDownChildProcess =
      mProcessCategory == ProcessCategory::GeckoChild && IsWin32kLockedDown();
  // If our process is running under Win32k lockdown, we cannot initialize
  // COM with a single-threaded apartment. This is because STAs create a hidden
  // window, which implicitly requires user32 and Win32k, which are blocked.
  // Instead we start the multi-threaded apartment and conduct our process-wide
  // COM initialization there.
  if (isLockedDownChildProcess) {
    // Make sure we're still running with the sandbox's privileged impersonation
    // token.
    HANDLE rawCurThreadImpToken;
    if (!::OpenThreadToken(::GetCurrentThread(), TOKEN_DUPLICATE | TOKEN_QUERY,
                           FALSE, &rawCurThreadImpToken)) {
      mInitResult = HRESULT_FROM_WIN32(::GetLastError());
      return;
    }
    nsAutoHandle curThreadImpToken(rawCurThreadImpToken);

    // Ensure that our current token is still an impersonation token (ie, we
    // have not yet called RevertToSelf() on this thread).
    DWORD len;
    TOKEN_TYPE tokenType;
    MOZ_RELEASE_ASSERT(
        ::GetTokenInformation(rawCurThreadImpToken, TokenType, &tokenType,
                              sizeof(tokenType), &len) &&
        len == sizeof(tokenType) && tokenType == TokenImpersonation);

    // Ideally we want our current thread to be running implicitly inside the
    // MTA, but if for some wacky reason we did not end up with that, we may
    // compensate by completing initialization via EnsureMTA's persistent
    // thread.
    if (!isCurThreadImplicitMTA) {
      InitUsingPersistentMTAThread(curThreadImpToken);
      return;
    }
  }
#  endif  // defined(MOZ_SANDBOX)
#endif    // defined(MOZILLA_INTERNAL_API)

  mAptRegion.Init(GetDesiredApartmentType(mProcessCategory));

  // It can happen that we are not the outermost COM initialization on this
  // thread. In fact it should regularly be the case that the outermost
  // initialization occurs from outside of XUL, before we show the skeleton UI,
  // at which point we still need to run some things here from within XUL.
  if (!mAptRegion.IsValidOutermost()) {
    mInitResult = mAptRegion.GetHResult();
#if defined(MOZILLA_INTERNAL_API)
    MOZ_ASSERT(mProcessCategory == ProcessCategory::GeckoBrowserParent);
    if (mProcessCategory != ProcessCategory::GeckoBrowserParent) {
      // This is unexpected unless we're GeckoBrowserParent
      return;
    }

    ProcessInitLock lock;

    // Is another instance of ProcessRuntime responsible for the outer
    // initialization?
    const bool prevInit =
        lock.GetInitState() == ProcessInitState::FullyInitialized;
    MOZ_ASSERT(prevInit);
    if (prevInit) {
      PostInit();
    }
#endif  // defined(MOZILLA_INTERNAL_API)
    return;
  }

  InitInsideApartment();
  if (FAILED(mInitResult)) {
    return;
  }

#if defined(MOZILLA_INTERNAL_API)
#  if defined(MOZ_SANDBOX)
  if (isLockedDownChildProcess) {
    // In locked-down child processes, defer PostInit until priv drop
    SandboxTarget::Instance()->RegisterSandboxStartCallback([self = this]() {
      // Ensure that we're still live and the init was successful before
      // calling PostInit()
      if (self == sInstance && SUCCEEDED(self->mInitResult)) {
        PostInit();
      }
    });
    return;
  }
#  endif  // defined(MOZ_SANDBOX)

  PostInit();
#endif  // defined(MOZILLA_INTERNAL_API)
}

#if defined(MOZILLA_INTERNAL_API)
ProcessRuntime::~ProcessRuntime() {
  MOZ_DIAGNOSTIC_ASSERT(sInstance == this);
  sInstance = nullptr;
}

#  if defined(MOZ_SANDBOX)
void ProcessRuntime::InitUsingPersistentMTAThread(
    const nsAutoHandle& aCurThreadToken) {
  // Create an impersonation token based on the current thread's token
  HANDLE rawMtaThreadImpToken = nullptr;
  if (!::DuplicateToken(aCurThreadToken, SecurityImpersonation,
                        &rawMtaThreadImpToken)) {
    mInitResult = HRESULT_FROM_WIN32(::GetLastError());
    return;
  }
  nsAutoHandle mtaThreadImpToken(rawMtaThreadImpToken);

  // Impersonate and initialize.
  bool tokenSet = false;
  EnsureMTA(
      [this, rawMtaThreadImpToken, &tokenSet]() -> void {
        if (!::SetThreadToken(nullptr, rawMtaThreadImpToken)) {
          mInitResult = HRESULT_FROM_WIN32(::GetLastError());
          return;
        }

        tokenSet = true;
        InitInsideApartment();
      },
      EnsureMTA::Option::ForceDispatchToPersistentThread);

  if (!tokenSet) {
    return;
  }

  SandboxTarget::Instance()->RegisterSandboxStartCallback(
      [self = this]() -> void {
        EnsureMTA(
            []() -> void {
              // This is a security risk if it fails, so we release assert
              MOZ_RELEASE_ASSERT(::RevertToSelf(),
                                 "mscom::ProcessRuntime RevertToSelf failed");
            },
            EnsureMTA::Option::ForceDispatchToPersistentThread);

        // Ensure that we're still live and the init was successful before
        // calling PostInit()
        if (self == sInstance && SUCCEEDED(self->mInitResult)) {
          PostInit();
        }
      });
}
#  endif  // defined(MOZ_SANDBOX)
#endif    // defined(MOZILLA_INTERNAL_API)

/* static */
COINIT ProcessRuntime::GetDesiredApartmentType(
    const ProcessRuntime::ProcessCategory aProcessCategory) {
  switch (aProcessCategory) {
    case ProcessCategory::GeckoBrowserParent:
      return COINIT_APARTMENTTHREADED;
    case ProcessCategory::GeckoChild:
      if (!IsWin32kLockedDown()) {
        // If Win32k is not locked down then we probably still need STA.
        // We disable DDE since that is not usable from child processes.
        return static_cast<COINIT>(COINIT_APARTMENTTHREADED |
                                   COINIT_DISABLE_OLE1DDE);
      }

      [[fallthrough]];
    default:
      return COINIT_MULTITHREADED;
  }
}

void ProcessRuntime::InitInsideApartment() {
  ProcessInitLock lock;
  const ProcessInitState prevInitState = lock.GetInitState();
  if (prevInitState == ProcessInitState::FullyInitialized) {
    // COM has already been initialized by a previous ProcessRuntime instance
    mInitResult = S_OK;
    return;
  }

  if (prevInitState < ProcessInitState::PartialSecurityInitialized) {
    // We are required to initialize security prior to configuring global
    // options.
    mInitResult = InitializeSecurity(mProcessCategory);
    MOZ_DIAGNOSTIC_ASSERT(SUCCEEDED(mInitResult));

    // Even though this isn't great, we should try to proceed even when
    // CoInitializeSecurity has previously been called: the additional settings
    // we want to change are important enough that we don't want to skip them.
    if (FAILED(mInitResult) && mInitResult != RPC_E_TOO_LATE) {
      return;
    }

    lock.SetInitState(ProcessInitState::PartialSecurityInitialized);
  }

  if (prevInitState < ProcessInitState::PartialGlobalOptions) {
    RefPtr<IGlobalOptions> globalOpts;
    mInitResult = wrapped::CoCreateInstance(
        CLSID_GlobalOptions, nullptr, CLSCTX_INPROC_SERVER, IID_IGlobalOptions,
        getter_AddRefs(globalOpts));
    MOZ_ASSERT(SUCCEEDED(mInitResult));
    if (FAILED(mInitResult)) {
      return;
    }

    // Disable COM's catch-all exception handler
    mInitResult = globalOpts->Set(COMGLB_EXCEPTION_HANDLING,
                                  COMGLB_EXCEPTION_DONOT_HANDLE_ANY);
    MOZ_ASSERT(SUCCEEDED(mInitResult));
    if (FAILED(mInitResult)) {
      return;
    }

    lock.SetInitState(ProcessInitState::PartialGlobalOptions);
  }

  // Disable the BSTR cache (as it never invalidates, thus leaking memory)
  // (This function is itself idempotent, so we do not concern ourselves with
  // tracking whether or not we've already called it.)
  ::SetOaNoCache();

  lock.SetInitState(ProcessInitState::FullyInitialized);
}

#if defined(MOZILLA_INTERNAL_API)
/**
 * Guaranteed to run *after* the COM (and possible sandboxing) initialization
 * has successfully completed and stabilized. This method MUST BE IDEMPOTENT!
 */
/* static */ void ProcessRuntime::PostInit() {
  // Currently "roughed-in" but unused.
}
#endif  // defined(MOZILLA_INTERNAL_API)

/* static */
DWORD
ProcessRuntime::GetClientThreadId() {
  DWORD callerTid;
  HRESULT hr = ::CoGetCallerTID(&callerTid);
  // Don't return callerTid unless the call succeeded and returned S_FALSE,
  // indicating that the caller originates from a different process.
  if (hr != S_FALSE) {
    return 0;
  }

  return callerTid;
}

/* static */
HRESULT
ProcessRuntime::InitializeSecurity(const ProcessCategory aProcessCategory) {
  HANDLE rawToken = nullptr;
  BOOL ok = ::OpenProcessToken(::GetCurrentProcess(), TOKEN_QUERY, &rawToken);
  if (!ok) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }
  nsAutoHandle token(rawToken);

  DWORD len = 0;
  ok = ::GetTokenInformation(token, TokenUser, nullptr, len, &len);
  DWORD win32Error = ::GetLastError();
  if (!ok && win32Error != ERROR_INSUFFICIENT_BUFFER) {
    return HRESULT_FROM_WIN32(win32Error);
  }

  auto tokenUserBuf = MakeUnique<BYTE[]>(len);
  TOKEN_USER& tokenUser = *reinterpret_cast<TOKEN_USER*>(tokenUserBuf.get());
  ok = ::GetTokenInformation(token, TokenUser, tokenUserBuf.get(), len, &len);
  if (!ok) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  len = 0;
  ok = ::GetTokenInformation(token, TokenPrimaryGroup, nullptr, len, &len);
  win32Error = ::GetLastError();
  if (!ok && win32Error != ERROR_INSUFFICIENT_BUFFER) {
    return HRESULT_FROM_WIN32(win32Error);
  }

  auto tokenPrimaryGroupBuf = MakeUnique<BYTE[]>(len);
  TOKEN_PRIMARY_GROUP& tokenPrimaryGroup =
      *reinterpret_cast<TOKEN_PRIMARY_GROUP*>(tokenPrimaryGroupBuf.get());
  ok = ::GetTokenInformation(token, TokenPrimaryGroup,
                             tokenPrimaryGroupBuf.get(), len, &len);
  if (!ok) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  SECURITY_DESCRIPTOR sd;
  if (!::InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION)) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  BYTE systemSid[SECURITY_MAX_SID_SIZE];
  DWORD systemSidSize = sizeof(systemSid);
  if (!::CreateWellKnownSid(WinLocalSystemSid, nullptr, systemSid,
                            &systemSidSize)) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  BYTE adminSid[SECURITY_MAX_SID_SIZE];
  DWORD adminSidSize = sizeof(adminSid);
  if (!::CreateWellKnownSid(WinBuiltinAdministratorsSid, nullptr, adminSid,
                            &adminSidSize)) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  const bool allowAppContainers =
      aProcessCategory == ProcessCategory::GeckoBrowserParent &&
      IsWin8OrLater();

  BYTE appContainersSid[SECURITY_MAX_SID_SIZE];
  DWORD appContainersSidSize = sizeof(appContainersSid);
  if (allowAppContainers) {
    if (!::CreateWellKnownSid(WinBuiltinAnyPackageSid, nullptr,
                              appContainersSid, &appContainersSidSize)) {
      return HRESULT_FROM_WIN32(::GetLastError());
    }
  }

  // Grant access to SYSTEM, Administrators, the user, and when running as the
  // browser process on Windows 8+, all app containers.
  const size_t kMaxInlineEntries = 4;
  mozilla::Vector<EXPLICIT_ACCESS_W, kMaxInlineEntries> entries;

  Unused << entries.append(EXPLICIT_ACCESS_W{
      COM_RIGHTS_EXECUTE,
      GRANT_ACCESS,
      NO_INHERITANCE,
      {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID, TRUSTEE_IS_USER,
       reinterpret_cast<LPWSTR>(systemSid)}});

  Unused << entries.append(EXPLICIT_ACCESS_W{
      COM_RIGHTS_EXECUTE,
      GRANT_ACCESS,
      NO_INHERITANCE,
      {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID,
       TRUSTEE_IS_WELL_KNOWN_GROUP, reinterpret_cast<LPWSTR>(adminSid)}});

  Unused << entries.append(EXPLICIT_ACCESS_W{
      COM_RIGHTS_EXECUTE,
      GRANT_ACCESS,
      NO_INHERITANCE,
      {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID, TRUSTEE_IS_USER,
       reinterpret_cast<LPWSTR>(tokenUser.User.Sid)}});

  if (allowAppContainers) {
    Unused << entries.append(
        EXPLICIT_ACCESS_W{COM_RIGHTS_EXECUTE,
                          GRANT_ACCESS,
                          NO_INHERITANCE,
                          {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID,
                           TRUSTEE_IS_WELL_KNOWN_GROUP,
                           reinterpret_cast<LPWSTR>(appContainersSid)}});
  }

  PACL rawDacl = nullptr;
  win32Error =
      ::SetEntriesInAclW(entries.length(), entries.begin(), nullptr, &rawDacl);
  if (win32Error != ERROR_SUCCESS) {
    return HRESULT_FROM_WIN32(win32Error);
  }

  UniquePtr<ACL, LocalFreeDeleter> dacl(rawDacl);

  if (!::SetSecurityDescriptorDacl(&sd, TRUE, dacl.get(), FALSE)) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  if (!::SetSecurityDescriptorOwner(&sd, tokenUser.User.Sid, FALSE)) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  if (!::SetSecurityDescriptorGroup(&sd, tokenPrimaryGroup.PrimaryGroup,
                                    FALSE)) {
    return HRESULT_FROM_WIN32(::GetLastError());
  }

  return wrapped::CoInitializeSecurity(
      &sd, -1, nullptr, nullptr, RPC_C_AUTHN_LEVEL_DEFAULT,
      RPC_C_IMP_LEVEL_IDENTIFY, nullptr, EOAC_NONE, nullptr);
}

}  // namespace mscom
}  // namespace mozilla