chrome_elf/ntdll_cache.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome_elf/ntdll_cache.h"
   6
   7 #include <stdint.h>
   8 #include <windows.h>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/win/pe_image.h"
  13 #include "chrome_elf/thunk_getter.h"
  14 #include "sandbox/win/src/interception_internal.h"
  15 #include "sandbox/win/src/internal_types.h"
  16 #include "sandbox/win/src/service_resolver.h"
  17
  18 FunctionLookupTable g_ntdll_lookup;
  19
  20 // Allocate storage for thunks in a page of this module to save on doing
  21 // an extra allocation at run time.
  22 #pragma section(".crthunk",read,execute)
  23 __declspec(allocate(".crthunk")) sandbox::ThunkData g_nt_thunk_storage;
  24
  25
  26
  27 namespace {
  28
  29 bool EnumExportsCallback(const base::win::PEImage& image,
  30                          DWORD ordinal,
  31                          DWORD hint,
  32                          LPCSTR name,
  33                          PVOID function_addr,
  34                          LPCSTR forward,
  35                          PVOID cookie) {
  36   // Our lookup only cares about named functions that are in ntdll, so skip
  37   // unnamed or forwarded exports.
  38   if (name && function_addr)
  39     g_ntdll_lookup[std::string(name)] = function_addr;
  40
  41   return true;
  42 }
  43
  44 }  // namespace
  45
  46 void InitCache() {
  47   HMODULE ntdll_handle = ::GetModuleHandle(L"ntdll.dll");
  48
  49   base::win::PEImage ntdll_image(ntdll_handle);
  50
  51   ntdll_image.EnumExports(EnumExportsCallback, NULL);
  52
  53   // If ntdll has already been patched, don't copy it.
  54   const bool kRelaxed = false;
  55
  56   // Create a thunk via the appropriate ServiceResolver instance.
  57   scoped_ptr<sandbox::ServiceResolverThunk> thunk(GetThunk(kRelaxed));
  58
  59   if (thunk.get()) {
  60     BYTE* thunk_storage = reinterpret_cast<BYTE*>(&g_nt_thunk_storage);
  61
  62     // Mark the thunk storage as readable and writeable, since we
  63     // are ready to write to it.
  64     DWORD old_protect = 0;
  65     if (!::VirtualProtect(&g_nt_thunk_storage,
  66                           sizeof(g_nt_thunk_storage),
  67                           PAGE_EXECUTE_READWRITE,
  68                           &old_protect)) {
  69       return;
  70     }
  71
  72     size_t storage_used = 0;
  73     NTSTATUS ret = thunk->CopyThunk(::GetModuleHandle(sandbox::kNtdllName),
  74                                     "NtCreateFile",
  75                                     thunk_storage,
  76                                     sizeof(sandbox::ThunkData),
  77                                     &storage_used);
  78
  79     if (!NT_SUCCESS(ret)) {
  80       memset(&g_nt_thunk_storage, 0, sizeof(g_nt_thunk_storage));
  81     }
  82
  83     // Ensure that the pointer to the old function can't be changed.
  84     ::VirtualProtect(&g_nt_thunk_storage,
  85                      sizeof(g_nt_thunk_storage),
  86                      PAGE_EXECUTE_READ,
  87                      &old_protect);
  88   }
  89 }