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// 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.
#ifndef SANDBOX_SRC_POLICY_ENGINE_PARAMS_H__
#define SANDBOX_SRC_POLICY_ENGINE_PARAMS_H__
#include <stdint.h>
#include "sandbox/win/src/internal_types.h"
#include "sandbox/win/src/nt_internals.h"
#include "sandbox/win/src/sandbox_nt_util.h"
// This header defines the classes that allow the low level policy to select
// the input parameters. In order to better make sense of this header is
// recommended that you check policy_engine_opcodes.h first.
namespace sandbox {
// Models the set of interesting parameters of an intercepted system call
// normally you don't create objects of this class directly, instead you
// use the POLPARAMS_XXX macros.
// For example, if an intercepted function has the following signature:
//
// NTSTATUS NtOpenFileFunction (PHANDLE FileHandle,
// ACCESS_MASK DesiredAccess,
// POBJECT_ATTRIBUTES ObjectAttributes,
// PIO_STATUS_BLOCK IoStatusBlock,
// ULONG ShareAccess,
// ULONG OpenOptions);
//
// You could say that the following parameters are of interest to policy:
//
// POLPARAMS_BEGIN(open_params)
// POLPARAM(DESIRED_ACCESS)
// POLPARAM(OBJECT_NAME)
// POLPARAM(SECURITY_DESCRIPTOR)
// POLPARAM(IO_STATUS)
// POLPARAM(OPEN_OPTIONS)
// POLPARAMS_END;
//
// and the actual code will use this for defining the parameters:
//
// CountedParameterSet<open_params> p;
// p[open_params::DESIRED_ACCESS] = ParamPickerMake(DesiredAccess);
// p[open_params::OBJECT_NAME] =
// ParamPickerMake(ObjectAttributes->ObjectName);
// p[open_params::SECURITY_DESCRIPTOR] =
// ParamPickerMake(ObjectAttributes->SecurityDescriptor);
// p[open_params::IO_STATUS] = ParamPickerMake(IoStatusBlock);
// p[open_params::OPEN_OPTIONS] = ParamPickerMake(OpenOptions);
//
// These will create an stack-allocated array of ParameterSet objects which
// have each 1) the address of the parameter 2) a numeric id that encodes the
// original C++ type. This allows the policy to treat any set of supported
// argument types uniformily and with some type safety.
//
// TODO(cpu): support not fully implemented yet for unicode string and will
// probably add other types as well.
class ParameterSet {
public:
ParameterSet() : real_type_(INVALID_TYPE), address_(nullptr) {}
// Retrieve the stored parameter. If the type does not match ulong fail.
bool Get(uint32_t* destination) const {
if (real_type_ != UINT32_TYPE) {
return false;
}
*destination = Void2TypePointerCopy<uint32_t>();
return true;
}
// Retrieve the stored parameter. If the type does not match void* fail.
bool Get(const void** destination) const {
if (real_type_ != VOIDPTR_TYPE) {
return false;
}
*destination = Void2TypePointerCopy<void*>();
return true;
}
// Retrieve the stored parameter. If the type does not match wchar_t* fail.
bool Get(const wchar_t** destination) const {
if (real_type_ != WCHAR_TYPE) {
return false;
}
*destination = Void2TypePointerCopy<const wchar_t*>();
return true;
}
// False if the parameter is not properly initialized.
bool IsValid() const { return real_type_ != INVALID_TYPE; }
protected:
// The constructor can only be called by derived types, which should
// safely provide the real_type and the address of the argument.
ParameterSet(ArgType real_type, const void* address)
: real_type_(real_type), address_(address) {}
private:
// This template provides the same functionality as bits_cast but
// it works with pointer while the former works only with references.
template <typename T>
T Void2TypePointerCopy() const {
return *(reinterpret_cast<const T*>(address_));
}
ArgType real_type_;
const void* address_;
};
// To safely infer the type, we use a set of template specializations
// in ParameterSetEx with a template function ParamPickerMake to do the
// parameter type deduction.
// Base template class. Not implemented so using unsupported types should
// fail to compile.
template <typename T>
class ParameterSetEx : public ParameterSet {
public:
ParameterSetEx(const void* address);
};
template <>
class ParameterSetEx<void const*> : public ParameterSet {
public:
ParameterSetEx(const void* address) : ParameterSet(VOIDPTR_TYPE, address) {}
};
template <>
class ParameterSetEx<void*> : public ParameterSet {
public:
ParameterSetEx(const void* address) : ParameterSet(VOIDPTR_TYPE, address) {}
};
template <>
class ParameterSetEx<wchar_t*> : public ParameterSet {
public:
ParameterSetEx(const void* address) : ParameterSet(WCHAR_TYPE, address) {}
};
template <>
class ParameterSetEx<wchar_t const*> : public ParameterSet {
public:
ParameterSetEx(const void* address) : ParameterSet(WCHAR_TYPE, address) {}
};
template <>
class ParameterSetEx<uint32_t> : public ParameterSet {
public:
ParameterSetEx(const void* address) : ParameterSet(UINT32_TYPE, address) {}
};
template <>
class ParameterSetEx<UNICODE_STRING> : public ParameterSet {
public:
ParameterSetEx(const void* address) : ParameterSet(UNISTR_TYPE, address) {}
};
template <typename T>
ParameterSet ParamPickerMake(T& parameter) {
return ParameterSetEx<T>(¶meter);
}
struct CountedParameterSetBase {
size_t count;
ParameterSet parameters[1];
};
// This template defines the actual list of policy parameters for a given
// interception.
// Warning: This template stores the address to the actual variables, in
// other words, the values are not copied.
template <typename T>
struct CountedParameterSet {
CountedParameterSet() : count(T::PolParamLast) {}
ParameterSet& operator[](typename T::Args n) { return parameters[n]; }
CountedParameterSetBase* GetBase() {
return reinterpret_cast<CountedParameterSetBase*>(this);
}
size_t count;
ParameterSet parameters[T::PolParamLast];
};
} // namespace sandbox
#endif // SANDBOX_SRC_POLICY_ENGINE_PARAMS_H__
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