sandbox/win/src/crosscall_params.h

   1 // Copyright (c) 2012 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_CROSSCALL_PARAMS_H__
   6 #define SANDBOX_SRC_CROSSCALL_PARAMS_H__
   7
   8 #include <windows.h>
   9 #include <lmaccess.h>
  10
  11 #include <memory>
  12
  13 #include "base/basictypes.h"
  14 #include "sandbox/win/src/internal_types.h"
  15 #include "sandbox/win/src/sandbox_types.h"
  16
  17 namespace {
  18
  19 // Increases |value| until there is no need for padding given an int64
  20 // alignment. Returns the increased value.
  21 uint32 Align(uint32 value) {
  22   uint32 alignment = sizeof(int64);
  23   return ((value + alignment - 1) / alignment) * alignment;
  24 }
  25
  26 }
  27 // This header is part of CrossCall: the sandbox inter-process communication.
  28 // This header defines the basic types used both in the client IPC and in the
  29 // server IPC code. CrossCallParams and ActualCallParams model the input
  30 // parameters of an IPC call and CrossCallReturn models the output params and
  31 // the return value.
  32 //
  33 // An IPC call is defined by its 'tag' which is a (uint32) unique identifier
  34 // that is used to route the IPC call to the proper server. Every tag implies
  35 // a complete call signature including the order and type of each parameter.
  36 //
  37 // Like most IPC systems. CrossCall is designed to take as inputs 'simple'
  38 // types such as integers and strings. Classes, generic arrays or pointers to
  39 // them are not supported.
  40 //
  41 // Another limitation of CrossCall is that the return value and output
  42 // parameters can only be uint32 integers. Returning complex structures or
  43 // strings is not supported.
  44
  45 namespace sandbox {
  46
  47 // max number of extended return parameters. See CrossCallReturn
  48 const size_t kExtendedReturnCount = 8;
  49
  50 // Union of multiple types to be used as extended results
  51 // in the CrossCallReturn.
  52 union MultiType {
  53   uint32 unsigned_int;
  54   void* pointer;
  55   HANDLE handle;
  56   ULONG_PTR ulong_ptr;
  57 };
  58
  59 // Maximum number of IPC parameters currently supported.
  60 // To increase this value, we have to:
  61 //  - Add another Callback typedef to Dispatcher.
  62 //  - Add another case to the switch on SharedMemIPCServer::InvokeCallback.
  63 //  - Add another case to the switch in GetActualAndMaxBufferSize
  64 const int kMaxIpcParams = 9;
  65
  66 // Contains the information about a parameter in the ipc buffer.
  67 struct ParamInfo {
  68   ArgType type_;
  69   uint32 offset_;
  70   uint32 size_;
  71 };
  72
  73 // Models the return value and the return parameters of an IPC call
  74 // currently limited to one status code and eight generic return values
  75 // which cannot be pointers to other data. For x64 ports this structure
  76 // might have to use other integer types.
  77 struct CrossCallReturn {
  78   // the IPC tag. It should match the original IPC tag.
  79   uint32 tag;
  80   // The result of the IPC operation itself.
  81   ResultCode call_outcome;
  82   // the result of the IPC call as executed in the server. The interpretation
  83   // of this value depends on the specific service.
  84   union {
  85     NTSTATUS nt_status;
  86     DWORD    win32_result;
  87   };
  88   // Number of extended return values.
  89   uint32 extended_count;
  90   // for calls that should return a windows handle. It is found here.
  91   HANDLE handle;
  92   // The array of extended values.
  93   MultiType extended[kExtendedReturnCount];
  94 };
  95
  96 // CrossCallParams base class that models the input params all packed in a
  97 // single compact memory blob. The representation can vary but in general a
  98 // given child of this class is meant to represent all input parameters
  99 // necessary to make a IPC call.
 100 //
 101 // This class cannot have virtual members because its assumed the IPC
 102 // parameters start from the 'this' pointer to the end, which is defined by
 103 // one of the subclasses
 104 //
 105 // Objects of this class cannot be constructed directly. Only derived
 106 // classes have the proper knowledge to construct it.
 107 class CrossCallParams {
 108  public:
 109   // Returns the tag (ipc unique id) associated with this IPC.
 110   uint32 GetTag() const {
 111     return tag_;
 112   }
 113
 114   // Returns the beggining of the buffer where the IPC params can be stored.
 115   // prior to an IPC call
 116   const void* GetBuffer() const {
 117     return this;
 118   }
 119
 120   // Returns how many parameter this IPC call should have.
 121   const uint32 GetParamsCount() const {
 122     return params_count_;
 123   }
 124
 125   // Returns a pointer to the CrossCallReturn structure.
 126   CrossCallReturn* GetCallReturn() {
 127     return &call_return;
 128   }
 129
 130   // Returns TRUE if this call contains InOut parameters.
 131   const bool IsInOut() const {
 132     return (1 == is_in_out_);
 133   }
 134
 135   // Tells the CrossCall object if it contains InOut parameters.
 136   void SetIsInOut(bool value) {
 137     if (value)
 138       is_in_out_ = 1;
 139     else
 140       is_in_out_ = 0;
 141   }
 142
 143  protected:
 144   // constructs the IPC call params. Called only from the derived classes
 145   CrossCallParams(uint32 tag, uint32 params_count)
 146       : tag_(tag), is_in_out_(0), params_count_(params_count) {}
 147
 148  private:
 149   uint32 tag_;
 150   uint32 is_in_out_;
 151   CrossCallReturn call_return;
 152   const uint32 params_count_;
 153   DISALLOW_COPY_AND_ASSIGN(CrossCallParams);
 154 };
 155
 156 // ActualCallParams models an specific IPC call parameters with respect to the
 157 // storage allocation that the packed parameters should need.
 158 // NUMBER_PARAMS: the number of parameters, valid from 1 to N
 159 // BLOCK_SIZE: the total storage that the NUMBER_PARAMS parameters can take,
 160 // typically the block size is defined by the channel size of the underlying
 161 // ipc mechanism.
 162 // In practice this class is used to levergage C++ capacity to properly
 163 // calculate sizes and displacements given the possibility of the packed params
 164 // blob to be complex.
 165 //
 166 // As is, this class assumes that the layout of the blob is as follows. Assume
 167 // that NUMBER_PARAMS = 2 and a 32-bit build:
 168 //
 169 // [ tag                4 bytes]
 170 // [ IsOnOut            4 bytes]
 171 // [ call return       52 bytes]
 172 // [ params count       4 bytes]
 173 // [ parameter 0 type   4 bytes]
 174 // [ parameter 0 offset 4 bytes] ---delta to ---\
 175 // [ parameter 0 size   4 bytes]                |
 176 // [ parameter 1 type   4 bytes]                |
 177 // [ parameter 1 offset 4 bytes] ---------------|--\
 178 // [ parameter 1 size   4 bytes]                |  |
 179 // [ parameter 2 type   4 bytes]                |  |
 180 // [ parameter 2 offset 4 bytes] ----------------------\
 181 // [ parameter 2 size   4 bytes]                |  |   |
 182 // |---------------------------|                |  |   |
 183 // | value 0     (x bytes)     | <--------------/  |   |
 184 // | value 1     (y bytes)     | <-----------------/   |
 185 // |                           |                       |
 186 // | end of buffer             | <---------------------/
 187 // |---------------------------|
 188 //
 189 // Note that the actual number of params is NUMBER_PARAMS + 1
 190 // so that the size of each actual param can be computed from the difference
 191 // between one parameter and the next down. The offset of the last param
 192 // points to the end of the buffer and the type and size are undefined.
 193 //
 194 template <size_t NUMBER_PARAMS, size_t BLOCK_SIZE>
 195 class ActualCallParams : public CrossCallParams {
 196  public:
 197   // constructor. Pass the ipc unique tag as input
 198   explicit ActualCallParams(uint32 tag)
 199       : CrossCallParams(tag, NUMBER_PARAMS) {
 200     param_info_[0].offset_ =
 201         static_cast<uint32>(parameters_ - reinterpret_cast<char*>(this));
 202   }
 203
 204   // Testing-only constructor. Allows setting the |number_params| to a
 205   // wrong value.
 206   ActualCallParams(uint32 tag, uint32 number_params)
 207       : CrossCallParams(tag, number_params) {
 208     param_info_[0].offset_ =
 209         static_cast<uint32>(parameters_ - reinterpret_cast<char*>(this));
 210   }
 211
 212   // Testing-only method. Allows setting the apparent size to a wrong value.
 213   // returns the previous size.
 214   uint32 OverrideSize(uint32 new_size) {
 215     uint32 previous_size = param_info_[NUMBER_PARAMS].offset_;
 216     param_info_[NUMBER_PARAMS].offset_ = new_size;
 217     return previous_size;
 218   }
 219
 220   // Copies each paramter into the internal buffer. For each you must supply:
 221   // index: 0 for the first param, 1 for the next an so on
 222   bool CopyParamIn(uint32 index, const void* parameter_address, uint32 size,
 223                    bool is_in_out, ArgType type) {
 224     if (index >= NUMBER_PARAMS) {
 225       return false;
 226     }
 227
 228     if (kuint32max == size) {
 229       // Memory error while getting the size.
 230       return false;
 231     }
 232
 233     if (size && !parameter_address) {
 234       return false;
 235     }
 236
 237     if ((size > sizeof(*this)) ||
 238         (param_info_[index].offset_ > (sizeof(*this) - size))) {
 239       // It does not fit, abort copy.
 240       return false;
 241     }
 242
 243     char* dest = reinterpret_cast<char*>(this) +  param_info_[index].offset_;
 244
 245     // We might be touching user memory, this has to be done from inside a try
 246     // except.
 247     __try {
 248       memcpy(dest, parameter_address, size);
 249     }
 250     __except(EXCEPTION_EXECUTE_HANDLER) {
 251       return false;
 252     }
 253
 254     // Set the flag to tell the broker to update the buffer once the call is
 255     // made.
 256     if (is_in_out)
 257       SetIsInOut(true);
 258
 259     param_info_[index + 1].offset_ = Align(param_info_[index].offset_ +
 260                                                 size);
 261     param_info_[index].size_ = size;
 262     param_info_[index].type_ = type;
 263     return true;
 264   }
 265
 266   // Returns a pointer to a parameter in the memory section.
 267   void* GetParamPtr(size_t index) {
 268     return reinterpret_cast<char*>(this) + param_info_[index].offset_;
 269   }
 270
 271   // Returns the total size of the buffer. Only valid once all the paramters
 272   // have been copied in with CopyParamIn.
 273   uint32 GetSize() const {
 274     return param_info_[NUMBER_PARAMS].offset_;
 275   }
 276
 277  protected:
 278   ActualCallParams() : CrossCallParams(0, NUMBER_PARAMS) { }
 279
 280  private:
 281   ParamInfo param_info_[NUMBER_PARAMS + 1];
 282   char parameters_[BLOCK_SIZE - sizeof(CrossCallParams)
 283                    - sizeof(ParamInfo) * (NUMBER_PARAMS + 1)];
 284   DISALLOW_COPY_AND_ASSIGN(ActualCallParams);
 285 };
 286
 287 static_assert(sizeof(ActualCallParams<1, 1024>) == 1024, "bad size buffer");
 288 static_assert(sizeof(ActualCallParams<2, 1024>) == 1024, "bad size buffer");
 289 static_assert(sizeof(ActualCallParams<3, 1024>) == 1024, "bad size buffer");
 290
 291 }  // namespace sandbox
 292
 293 #endif  // SANDBOX_SRC_CROSSCALL_PARAMS_H__