DXR will be turned off on Tuesday, December 29th. It will redirect to Searchfox.
See the announcement on Discourse.

DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (b66b287a2650)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/iat_patch.h"
#include "base/logging.h"

namespace iat_patch {

struct InterceptFunctionInformation {
  bool finished_operation;
  const char* imported_from_module;
  const char* function_name;
  void* new_function;
  void** old_function;
  IMAGE_THUNK_DATA** iat_thunk;
  DWORD return_code;
};

static void* GetIATFunction(IMAGE_THUNK_DATA* iat_thunk) {
  if (NULL == iat_thunk) {
    NOTREACHED();
    return NULL;
  }

  // Works around the 64 bit portability warning:
  // The Function member inside IMAGE_THUNK_DATA is really a pointer
  // to the IAT function. IMAGE_THUNK_DATA correctly maps to IMAGE_THUNK_DATA32
  // or IMAGE_THUNK_DATA64 for correct pointer size.
  union FunctionThunk {
    IMAGE_THUNK_DATA thunk;
    void* pointer;
  } iat_function;

  iat_function.thunk = *iat_thunk;
  return iat_function.pointer;
}

static bool InterceptEnumCallback(const PEImage &image, const char* module,
                                  DWORD ordinal, const char* name, DWORD hint,
                                  IMAGE_THUNK_DATA* iat, void* cookie) {
  InterceptFunctionInformation* intercept_information =
    reinterpret_cast<InterceptFunctionInformation*>(cookie);

  if (NULL == intercept_information) {
    NOTREACHED();
    return false;
  }

  DCHECK(module);

  if ((0 == lstrcmpiA(module, intercept_information->imported_from_module)) &&
     (NULL != name) &&
     (0 == lstrcmpiA(name, intercept_information->function_name))) {
    // Save the old pointer.
    if (NULL != intercept_information->old_function) {
      *(intercept_information->old_function) = GetIATFunction(iat);
    }

    if (NULL != intercept_information->iat_thunk) {
      *(intercept_information->iat_thunk) = iat;
    }

    // portability check
    COMPILE_ASSERT(sizeof(iat->u1.Function) ==
      sizeof(intercept_information->new_function), unknown_IAT_thunk_format);

    // Patch the function.
    intercept_information->return_code =
      ModifyCode(&(iat->u1.Function),
                 &(intercept_information->new_function),
                 sizeof(intercept_information->new_function));

    // Terminate further enumeration.
    intercept_information->finished_operation = true;
    return false;
  }

  return true;
}

DWORD InterceptImportedFunction(HMODULE module_handle,
                                const char* imported_from_module,
                                const char* function_name, void* new_function,
                                void** old_function,
                                IMAGE_THUNK_DATA** iat_thunk) {
  if ((NULL == module_handle) || (NULL == imported_from_module) ||
     (NULL == function_name) || (NULL == new_function)) {
    NOTREACHED();
    return ERROR_INVALID_PARAMETER;
  }

  PEImage target_image(module_handle);
  if (!target_image.VerifyMagic()) {
    NOTREACHED();
    return ERROR_INVALID_PARAMETER;
  }

  InterceptFunctionInformation intercept_information = {
    false,
    imported_from_module,
    function_name,
    new_function,
    old_function,
    iat_thunk,
    ERROR_GEN_FAILURE};

  // First go through the IAT. If we don't find the import we are looking
  // for in IAT, search delay import table.
  target_image.EnumAllImports(InterceptEnumCallback, &intercept_information);
  if (!intercept_information.finished_operation) {
    target_image.EnumAllDelayImports(InterceptEnumCallback,
                                     &intercept_information);
  }

  return intercept_information.return_code;
}

DWORD RestoreImportedFunction(void* intercept_function,
                              void* original_function,
                              IMAGE_THUNK_DATA* iat_thunk) {
  if ((NULL == intercept_function) || (NULL == original_function) ||
      (NULL == iat_thunk)) {
    NOTREACHED();
    return ERROR_INVALID_PARAMETER;
  }

  if (GetIATFunction(iat_thunk) != intercept_function) {
    // Check if someone else has intercepted on top of us.
    // We cannot unpatch in this case, just raise a red flag.
    NOTREACHED();
    return ERROR_INVALID_FUNCTION;
  }

  return ModifyCode(&(iat_thunk->u1.Function),
                    &original_function,
                    sizeof(original_function));
}

DWORD ModifyCode(void* old_code, void* new_code, int length) {
  if ((NULL == old_code) || (NULL == new_code) || (0 == length)) {
    NOTREACHED();
    return ERROR_INVALID_PARAMETER;
  }

  // Change the page protection so that we can write.
  DWORD error = NO_ERROR;
  DWORD old_page_protection = 0;
  if (VirtualProtect(old_code,
                     length,
                     PAGE_READWRITE,
                     &old_page_protection)) {

    // Write the data.
    CopyMemory(old_code, new_code, length);

    // Restore the old page protection.
    error = ERROR_SUCCESS;
    VirtualProtect(old_code,
                  length,
                  old_page_protection,
                  &old_page_protection);
  } else {
    error = GetLastError();
    NOTREACHED();
  }

  return error;
}

IATPatchFunction::IATPatchFunction()
    : module_handle_(NULL),
      original_function_(NULL),
      iat_thunk_(NULL),
      intercept_function_(NULL) {
}

IATPatchFunction::~IATPatchFunction() {
  if (NULL != intercept_function_) {
    DWORD error = Unpatch();
    DCHECK_EQ(NO_ERROR, error);
  }
}

DWORD IATPatchFunction::Patch(const wchar_t* module,
                              const char* imported_from_module,
                              const char* function_name,
                              void* new_function) {
  DCHECK_EQ(static_cast<void*>(NULL), original_function_);
  DCHECK_EQ(static_cast<IMAGE_THUNK_DATA*>(NULL), iat_thunk_);
  DCHECK_EQ(static_cast<void*>(NULL), intercept_function_);

  HMODULE module_handle = LoadLibraryW(module);

  if (module_handle == NULL) {
    NOTREACHED();
    return GetLastError();
  }

  DWORD error = InterceptImportedFunction(module_handle,
                                          imported_from_module,
                                          function_name,
                                          new_function,
                                          &original_function_,
                                          &iat_thunk_);

  if (NO_ERROR == error) {
    DCHECK_NE(original_function_, intercept_function_);
    module_handle_ = module_handle;
    intercept_function_ = new_function;
  } else {
    FreeLibrary(module_handle);
  }

  return error;
}

DWORD IATPatchFunction::Unpatch() {
  DWORD error = RestoreImportedFunction(intercept_function_,
                                        original_function_,
                                        iat_thunk_);
  DCHECK(NO_ERROR == error);

  // Hands off the intercept if we fail to unpatch.
  // If IATPatchFunction::Unpatch fails during RestoreImportedFunction
  // it means that we cannot safely unpatch the import address table
  // patch. In this case its better to be hands off the intercept as
  // trying to unpatch again in the destructor of IATPatchFunction is
  // not going to be any safer
  if (module_handle_)
    FreeLibrary(module_handle_);
  module_handle_ = NULL;
  intercept_function_ = NULL;
  original_function_ = NULL;
  iat_thunk_ = NULL;

  return error;
}

}  // namespace iat_patch