michael@0: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #include <string>
michael@0: #include <vector>
michael@0: 
michael@0: #include "sandbox/win/src/crosscall_server.h"
michael@0: #include "sandbox/win/src/crosscall_params.h"
michael@0: #include "sandbox/win/src/crosscall_client.h"
michael@0: #include "base/logging.h"
michael@0: 
michael@0: // This code performs the ipc message validation. Potential security flaws
michael@0: // on the ipc are likelier to be found in this code than in the rest of
michael@0: // the ipc code.
michael@0: 
michael@0: namespace {
michael@0: 
michael@0: // The buffer for a message must match the max channel size.
michael@0: const size_t kMaxBufferSize = sandbox::kIPCChannelSize;
michael@0: 
michael@0: }
michael@0: 
michael@0: namespace sandbox {
michael@0: 
michael@0: // Returns the actual size for the parameters in an IPC buffer. Returns
michael@0: // zero if the |param_count| is zero or too big.
michael@0: uint32 GetActualBufferSize(uint32 param_count, void* buffer_base) {
michael@0:   // The template types are used to calculate the maximum expected size.
michael@0:   typedef ActualCallParams<1, kMaxBufferSize> ActualCP1;
michael@0:   typedef ActualCallParams<2, kMaxBufferSize> ActualCP2;
michael@0:   typedef ActualCallParams<3, kMaxBufferSize> ActualCP3;
michael@0:   typedef ActualCallParams<4, kMaxBufferSize> ActualCP4;
michael@0:   typedef ActualCallParams<5, kMaxBufferSize> ActualCP5;
michael@0:   typedef ActualCallParams<6, kMaxBufferSize> ActualCP6;
michael@0:   typedef ActualCallParams<7, kMaxBufferSize> ActualCP7;
michael@0:   typedef ActualCallParams<8, kMaxBufferSize> ActualCP8;
michael@0:   typedef ActualCallParams<9, kMaxBufferSize> ActualCP9;
michael@0: 
michael@0:   // Retrieve the actual size and the maximum size of the params buffer.
michael@0:   switch (param_count) {
michael@0:     case 0:
michael@0:       return 0;
michael@0:     case 1:
michael@0:       return reinterpret_cast<ActualCP1*>(buffer_base)->GetSize();
michael@0:     case 2:
michael@0:       return reinterpret_cast<ActualCP2*>(buffer_base)->GetSize();
michael@0:     case 3:
michael@0:       return reinterpret_cast<ActualCP3*>(buffer_base)->GetSize();
michael@0:     case 4:
michael@0:       return reinterpret_cast<ActualCP4*>(buffer_base)->GetSize();
michael@0:     case 5:
michael@0:       return reinterpret_cast<ActualCP5*>(buffer_base)->GetSize();
michael@0:     case 6:
michael@0:       return reinterpret_cast<ActualCP6*>(buffer_base)->GetSize();
michael@0:     case 7:
michael@0:       return reinterpret_cast<ActualCP7*>(buffer_base)->GetSize();
michael@0:     case 8:
michael@0:       return reinterpret_cast<ActualCP8*>(buffer_base)->GetSize();
michael@0:     case 9:
michael@0:       return reinterpret_cast<ActualCP9*>(buffer_base)->GetSize();
michael@0:     default:
michael@0:       NOTREACHED();
michael@0:       return 0;
michael@0:   }
michael@0: }
michael@0: 
michael@0: // Verifies that the declared sizes of an IPC buffer are within range.
michael@0: bool IsSizeWithinRange(uint32 buffer_size, uint32 min_declared_size,
michael@0:                        uint32 declared_size) {
michael@0:   if ((buffer_size < min_declared_size) ||
michael@0:       (sizeof(CrossCallParamsEx) > min_declared_size)) {
michael@0:     // Minimal computed size bigger than existing buffer or param_count
michael@0:     // integer overflow.
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   if ((declared_size > buffer_size) || (declared_size < min_declared_size)) {
michael@0:     // Declared size is bigger than buffer or smaller than computed size
michael@0:     // or param_count is equal to 0 or bigger than 9.
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: CrossCallParamsEx::CrossCallParamsEx()
michael@0:   :CrossCallParams(0, 0) {
michael@0: }
michael@0: 
michael@0: // We override the delete operator because the object's backing memory
michael@0: // is hand allocated in CreateFromBuffer. We don't override the new operator
michael@0: // because the constructors are private so there is no way to mismatch
michael@0: // new & delete.
michael@0: void CrossCallParamsEx::operator delete(void* raw_memory) throw() {
michael@0:   if (NULL == raw_memory) {
michael@0:     // C++ standard allows 'delete 0' behavior.
michael@0:     return;
michael@0:   }
michael@0:   delete[] reinterpret_cast<char*>(raw_memory);
michael@0: }
michael@0: 
michael@0: // This function uses a SEH try block so cannot use C++ objects that
michael@0: // have destructors or else you get Compiler Error C2712. So no DCHECKs
michael@0: // inside this function.
michael@0: CrossCallParamsEx* CrossCallParamsEx::CreateFromBuffer(void* buffer_base,
michael@0:                                                        uint32 buffer_size,
michael@0:                                                        uint32* output_size) {
michael@0:   // IMPORTANT: Everything inside buffer_base and derived from it such
michael@0:   // as param_count and declared_size is untrusted.
michael@0:   if (NULL == buffer_base) {
michael@0:     return NULL;
michael@0:   }
michael@0:   if (buffer_size < sizeof(CrossCallParams)) {
michael@0:     return NULL;
michael@0:   }
michael@0:   if (buffer_size > kMaxBufferSize) {
michael@0:     return NULL;
michael@0:   }
michael@0: 
michael@0:   char* backing_mem = NULL;
michael@0:   uint32 param_count = 0;
michael@0:   uint32 declared_size;
michael@0:   uint32 min_declared_size;
michael@0:   CrossCallParamsEx* copied_params = NULL;
michael@0: 
michael@0:   // Touching the untrusted buffer is done under a SEH try block. This
michael@0:   // will catch memory access violations so we don't crash.
michael@0:   __try {
michael@0:     CrossCallParams* call_params =
michael@0:         reinterpret_cast<CrossCallParams*>(buffer_base);
michael@0: 
michael@0:     // Check against the minimum size given the number of stated params
michael@0:     // if too small we bail out.
michael@0:     param_count = call_params->GetParamsCount();
michael@0:     min_declared_size = sizeof(CrossCallParams) +
michael@0:                         ((param_count + 1) * sizeof(ParamInfo));
michael@0: 
michael@0:     // Retrieve the declared size which if it fails returns 0.
michael@0:     declared_size = GetActualBufferSize(param_count, buffer_base);
michael@0: 
michael@0:     if (!IsSizeWithinRange(buffer_size, min_declared_size, declared_size))
michael@0:       return NULL;
michael@0: 
michael@0:     // Now we copy the actual amount of the message.
michael@0:     *output_size = declared_size;
michael@0:     backing_mem = new char[declared_size];
michael@0:     copied_params = reinterpret_cast<CrossCallParamsEx*>(backing_mem);
michael@0:     memcpy(backing_mem, call_params, declared_size);
michael@0: 
michael@0:     // Avoid compiler optimizations across this point. Any value stored in
michael@0:     // memory should be stored for real, and values previously read from memory
michael@0:     // should be actually read.
michael@0:     _ReadWriteBarrier();
michael@0: 
michael@0:     min_declared_size = sizeof(CrossCallParams) +
michael@0:                         ((param_count + 1) * sizeof(ParamInfo));
michael@0: 
michael@0:     // Check that the copied buffer is still valid.
michael@0:     if (copied_params->GetParamsCount() != param_count ||
michael@0:         GetActualBufferSize(param_count, backing_mem) != declared_size ||
michael@0:         !IsSizeWithinRange(buffer_size, min_declared_size, declared_size)) {
michael@0:       delete [] backing_mem;
michael@0:       return NULL;
michael@0:     }
michael@0: 
michael@0:   } __except(EXCEPTION_EXECUTE_HANDLER) {
michael@0:     // In case of a windows exception we know it occurred while touching the
michael@0:     // untrusted buffer so we bail out as is.
michael@0:     delete [] backing_mem;
michael@0:     return NULL;
michael@0:   }
michael@0: 
michael@0:   const char* last_byte = &backing_mem[declared_size];
michael@0:   const char* first_byte = &backing_mem[min_declared_size];
michael@0: 
michael@0:   // Verify here that all and each parameters make sense. This is done in the
michael@0:   // local copy.
michael@0:   for (uint32 ix =0; ix != param_count; ++ix) {
michael@0:     uint32 size = 0;
michael@0:     ArgType type;
michael@0:     char* address = reinterpret_cast<char*>(
michael@0:                         copied_params->GetRawParameter(ix, &size, &type));
michael@0:     if ((NULL == address) ||               // No null params.
michael@0:         (INVALID_TYPE >= type) || (LAST_TYPE <= type) ||  // Unknown type.
michael@0:         (address < backing_mem) ||         // Start cannot point before buffer.
michael@0:         (address < first_byte) ||          // Start cannot point too low.
michael@0:         (address > last_byte) ||           // Start cannot point past buffer.
michael@0:         ((address + size) < address) ||    // Invalid size.
michael@0:         ((address + size) > last_byte)) {  // End cannot point past buffer.
michael@0:       // Malformed.
michael@0:       delete[] backing_mem;
michael@0:       return NULL;
michael@0:     }
michael@0:   }
michael@0:   // The parameter buffer looks good.
michael@0:   return copied_params;
michael@0: }
michael@0: 
michael@0: // Accessors to the parameters in the raw buffer.
michael@0: void* CrossCallParamsEx::GetRawParameter(uint32 index, uint32* size,
michael@0:                                          ArgType* type) {
michael@0:   if (index >= GetParamsCount()) {
michael@0:     return NULL;
michael@0:   }
michael@0:   // The size is always computed from the parameter minus the next
michael@0:   // parameter, this works because the message has an extra parameter slot
michael@0:   *size = param_info_[index].size_;
michael@0:   *type = param_info_[index].type_;
michael@0: 
michael@0:   return param_info_[index].offset_ + reinterpret_cast<char*>(this);
michael@0: }
michael@0: 
michael@0: // Covers common case for 32 bit integers.
michael@0: bool CrossCallParamsEx::GetParameter32(uint32 index, uint32* param) {
michael@0:   uint32 size = 0;
michael@0:   ArgType type;
michael@0:   void* start = GetRawParameter(index, &size, &type);
michael@0:   if ((NULL == start) || (4 != size) || (ULONG_TYPE != type)) {
michael@0:     return false;
michael@0:   }
michael@0:   // Copy the 4 bytes.
michael@0:   *(reinterpret_cast<uint32*>(param)) = *(reinterpret_cast<uint32*>(start));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool CrossCallParamsEx::GetParameterVoidPtr(uint32 index, void** param) {
michael@0:   uint32 size = 0;
michael@0:   ArgType type;
michael@0:   void* start = GetRawParameter(index, &size, &type);
michael@0:   if ((NULL == start) || (sizeof(void*) != size) || (VOIDPTR_TYPE != type)) {
michael@0:     return false;
michael@0:   }
michael@0:   *param = *(reinterpret_cast<void**>(start));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // Covers the common case of reading a string. Note that the string is not
michael@0: // scanned for invalid characters.
michael@0: bool CrossCallParamsEx::GetParameterStr(uint32 index, std::wstring* string) {
michael@0:   uint32 size = 0;
michael@0:   ArgType type;
michael@0:   void* start = GetRawParameter(index, &size, &type);
michael@0:   if (WCHAR_TYPE != type) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   // Check if this is an empty string.
michael@0:   if (size == 0) {
michael@0:     *string = L"";
michael@0:     return true;
michael@0:   }
michael@0: 
michael@0:   if ((NULL == start) || ((size % sizeof(wchar_t)) != 0)) {
michael@0:     return false;
michael@0:   }
michael@0:   string->append(reinterpret_cast<wchar_t*>(start), size/(sizeof(wchar_t)));
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool CrossCallParamsEx::GetParameterPtr(uint32 index, uint32 expected_size,
michael@0:                                         void** pointer) {
michael@0:   uint32 size = 0;
michael@0:   ArgType type;
michael@0:   void* start = GetRawParameter(index, &size, &type);
michael@0: 
michael@0:   if ((size != expected_size) || (INOUTPTR_TYPE != type)) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   if (NULL == start) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   *pointer = start;
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: void SetCallError(ResultCode error, CrossCallReturn* call_return) {
michael@0:   call_return->call_outcome = error;
michael@0:   call_return->extended_count = 0;
michael@0: }
michael@0: 
michael@0: void SetCallSuccess(CrossCallReturn* call_return) {
michael@0:   call_return->call_outcome = SBOX_ALL_OK;
michael@0: }
michael@0: 
michael@0: Dispatcher* Dispatcher::OnMessageReady(IPCParams* ipc,
michael@0:                                       CallbackGeneric* callback) {
michael@0:   DCHECK(callback);
michael@0:   std::vector<IPCCall>::iterator it = ipc_calls_.begin();
michael@0:   for (; it != ipc_calls_.end(); ++it) {
michael@0:     if (it->params.Matches(ipc)) {
michael@0:       *callback = it->callback;
michael@0:       return this;
michael@0:     }
michael@0:   }
michael@0:   return NULL;
michael@0: }
michael@0: 
michael@0: }  // namespace sandbox