sandbox/win/src/policy_engine_params.h

   1 // Copyright (c) 2006-2008 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 #ifndef SANDBOX_SRC_POLICY_ENGINE_PARAMS_H__
   6 #define SANDBOX_SRC_POLICY_ENGINE_PARAMS_H__
   7
   8 #include "base/basictypes.h"
   9 #include "sandbox/win/src/internal_types.h"
  10 #include "sandbox/win/src/nt_internals.h"
  11 #include "sandbox/win/src/sandbox_nt_util.h"
  12
  13 // This header defines the classes that allow the low level policy to select
  14 // the input parameters. In order to better make sense of this header is
  15 // recommended that you check policy_engine_opcodes.h first.
  16
  17 namespace sandbox {
  18
  19 // Models the set of interesting parameters of an intercepted system call
  20 // normally you don't create objects of this class directly, instead you
  21 // use the POLPARAMS_XXX macros.
  22 // For example, if an intercepted function has the following signature:
  23 //
  24 // NTSTATUS NtOpenFileFunction (PHANDLE FileHandle,
  25 //                              ACCESS_MASK DesiredAccess,
  26 //                              POBJECT_ATTRIBUTES ObjectAttributes,
  27 //                              PIO_STATUS_BLOCK IoStatusBlock,
  28 //                              ULONG ShareAccess,
  29 //                              ULONG OpenOptions);
  30 //
  31 // You could say that the following parameters are of interest to policy:
  32 //
  33 //   POLPARAMS_BEGIN(open_params)
  34 //      POLPARAM(DESIRED_ACCESS)
  35 //      POLPARAM(OBJECT_NAME)
  36 //      POLPARAM(SECURITY_DESCRIPTOR)
  37 //      POLPARAM(IO_STATUS)
  38 //      POLPARAM(OPEN_OPTIONS)
  39 //   POLPARAMS_END;
  40 //
  41 // and the actual code will use this for defining the parameters:
  42 //
  43 //   CountedParameterSet<open_params> p;
  44 //   p[open_params::DESIRED_ACCESS] = ParamPickerMake(DesiredAccess);
  45 //   p[open_params::OBJECT_NAME] =
  46 //       ParamPickerMake(ObjectAttributes->ObjectName);
  47 //   p[open_params::SECURITY_DESCRIPTOR] =
  48 //       ParamPickerMake(ObjectAttributes->SecurityDescriptor);
  49 //   p[open_params::IO_STATUS] = ParamPickerMake(IoStatusBlock);
  50 //   p[open_params::OPEN_OPTIONS] = ParamPickerMake(OpenOptions);
  51 //
  52 //  These will create an stack-allocated array of ParameterSet objects which
  53 //  have each 1) the address of the parameter 2) a numeric id that encodes the
  54 //  original C++ type. This allows the policy to treat any set of supported
  55 //  argument types uniformily and with some type safety.
  56 //
  57 //  TODO(cpu): support not fully implemented yet for unicode string and will
  58 //  probably add other types as well.
  59 class ParameterSet {
  60  public:
  61   ParameterSet() : real_type_(INVALID_TYPE), address_(NULL) {}
  62
  63   // Retrieve the stored parameter. If the type does not match ulong fail.
  64   bool Get(unsigned long* destination) const {
  65     if (ULONG_TYPE != real_type_) {
  66       return false;
  67     }
  68     *destination = Void2TypePointerCopy<unsigned long>();
  69     return true;
  70   }
  71
  72   // Retrieve the stored parameter. If the type does not match void* fail.
  73   bool Get(const void** destination) const {
  74     if (VOIDPTR_TYPE != real_type_) {
  75       return false;
  76     }
  77     *destination = Void2TypePointerCopy<void*>();
  78     return true;
  79   }
  80
  81   // Retrieve the stored parameter. If the type does not match wchar_t* fail.
  82   bool Get(const wchar_t** destination) const {
  83     if (WCHAR_TYPE != real_type_) {
  84       return false;
  85     }
  86     *destination = Void2TypePointerCopy<const wchar_t*>();
  87     return true;
  88   }
  89
  90   // False if the parameter is not properly initialized.
  91   bool IsValid() const {
  92     return INVALID_TYPE != real_type_;
  93   }
  94
  95  protected:
  96   // The constructor can only be called by derived types, which should
  97   // safely provide the real_type and the address of the argument.
  98   ParameterSet(ArgType real_type, const void* address)
  99       : real_type_(real_type), address_(address) {
 100   }
 101
 102  private:
 103   // This template provides the same functionality as bits_cast but
 104   // it works with pointer while the former works only with references.
 105   template <typename T>
 106   T Void2TypePointerCopy() const {
 107     return *(reinterpret_cast<const T*>(address_));
 108   }
 109
 110   ArgType real_type_;
 111   const void* address_;
 112 };
 113
 114 // To safely infer the type, we use a set of template specializations
 115 // in ParameterSetEx with a template function ParamPickerMake to do the
 116 // parameter type deduction.
 117
 118 // Base template class. Not implemented so using unsupported types should
 119 // fail to compile.
 120 template <typename T>
 121 class ParameterSetEx : public ParameterSet {
 122  public:
 123   ParameterSetEx(const void* address);
 124 };
 125
 126 template<>
 127 class ParameterSetEx<void const*> : public ParameterSet {
 128  public:
 129   ParameterSetEx(const void* address)
 130       : ParameterSet(VOIDPTR_TYPE, address) {}
 131 };
 132
 133 template<>
 134 class ParameterSetEx<void*> : public ParameterSet {
 135  public:
 136   ParameterSetEx(const void* address)
 137       : ParameterSet(VOIDPTR_TYPE, address) {}
 138 };
 139
 140
 141 template<>
 142 class ParameterSetEx<wchar_t*> : public ParameterSet {
 143  public:
 144   ParameterSetEx(const void* address)
 145       : ParameterSet(WCHAR_TYPE, address) {}
 146 };
 147
 148 template<>
 149 class ParameterSetEx<wchar_t const*> : public ParameterSet {
 150  public:
 151   ParameterSetEx(const void* address)
 152       : ParameterSet(WCHAR_TYPE, address) {}
 153 };
 154
 155
 156 template<>
 157 class ParameterSetEx<unsigned long> : public ParameterSet {
 158  public:
 159   ParameterSetEx(const void* address)
 160       : ParameterSet(ULONG_TYPE, address) {}
 161 };
 162
 163 template<>
 164 class ParameterSetEx<UNICODE_STRING> : public ParameterSet {
 165  public:
 166   ParameterSetEx(const void* address)
 167       : ParameterSet(UNISTR_TYPE, address) {}
 168 };
 169
 170 template <typename T>
 171 ParameterSet ParamPickerMake(T& parameter) {
 172   return ParameterSetEx<T>(&parameter);
 173 };
 174
 175 struct CountedParameterSetBase {
 176   int count;
 177   ParameterSet parameters[1];
 178 };
 179
 180 // This template defines the actual list of policy parameters for a given
 181 // interception.
 182 // Warning: This template stores the address to the actual variables, in
 183 // other words, the values are not copied.
 184 template <typename T>
 185 struct CountedParameterSet {
 186   CountedParameterSet() : count(T::PolParamLast) {}
 187
 188   ParameterSet& operator[](typename T::Args n) {
 189     return parameters[n];
 190   }
 191
 192   CountedParameterSetBase* GetBase() {
 193     return reinterpret_cast<CountedParameterSetBase*>(this);
 194   }
 195
 196   int count;
 197   ParameterSet parameters[T::PolParamLast];
 198 };
 199
 200 }  // namespace sandbox
 201
 202 #endif  // SANDBOX_SRC_POLICY_ENGINE_PARAMS_H__