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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.

 #include <string>

 #include <map>

 #include "sandbox/win/src/policy_low_level.h"

 #include "base/basictypes.h"

 namespace {

   // A single rule can use at most this amount of memory.

   const size_t kRuleBufferSize = 1024*4;

   // The possible states of the string matching opcode generator.

   enum {

     PENDING_NONE,

     PENDING_ASTERISK,    // Have seen an '*' but have not generated an opcode.

     PENDING_QMARK,       // Have seen an '?' but have not generated an opcode.

   };

   // The category of the last character seen by the string matching opcode

   // generator.

   const uint32 kLastCharIsNone = 0;

   const uint32 kLastCharIsAlpha = 1;

   const uint32 kLastCharIsWild = 2;

   const uint32 kLastCharIsAsterisk = kLastCharIsWild + 4;

   const uint32 kLastCharIsQuestionM = kLastCharIsWild + 8;

 }

 namespace sandbox {

 // Adding a rule is nothing more than pushing it into an stl container. Done()

 // is called for the rule in case the code that made the rule in the first

 // place has not done it.

 bool LowLevelPolicy::AddRule(int service, PolicyRule* rule) {

   if (!rule->Done()) {

     return false;

   }

   PolicyRule* local_rule = new PolicyRule(*rule);

   RuleNode node = {local_rule, service};

   rules_.push_back(node);

   return true;

 }

 LowLevelPolicy::~LowLevelPolicy() {

   // Delete all the rules.

   typedef std::list<RuleNode> RuleNodes;

   for (RuleNodes::iterator it = rules_.begin(); it != rules_.end(); ++it) {

     delete it->rule;

   }

 }

 // Here is where the heavy byte shuffling is done. We take all the rules and

 // 'compile' them into a single memory region. Now, the rules are in random

 // order so the first step is to reorganize them into a stl map that is keyed

 // by the service id and as a value contains a list with all the rules that

 // belong to that service. Then we enter the big for-loop where we carve a

 // memory zone for the opcodes and the data and call RebindCopy on each rule

 // so they all end up nicely packed in the policy_store_.

 bool LowLevelPolicy::Done() {

   typedef std::list<RuleNode> RuleNodes;

   typedef std::list<const PolicyRule*> RuleList;

   typedef std::map<uint32, RuleList> Mmap;

   Mmap mmap;

   for (RuleNodes::iterator it = rules_.begin(); it != rules_.end(); ++it) {

     mmap[it->service].push_back(it->rule);

   }

   PolicyBuffer* current_buffer = &policy_store_->data[0];

   char* buffer_end = reinterpret_cast<char*>(current_buffer) +

     policy_store_->data_size;

   size_t avail_size =  policy_store_->data_size;

   for (Mmap::iterator it = mmap.begin(); it != mmap.end(); ++it) {

     uint32 service = (*it).first;

     if (service >= kMaxServiceCount) {

       return false;

     }

     policy_store_->entry[service] = current_buffer;

     RuleList::iterator rules_it = (*it).second.begin();

     RuleList::iterator rules_it_end = (*it).second.end();

     size_t svc_opcode_count = 0;

     for (; rules_it != rules_it_end; ++rules_it) {

       const PolicyRule* rule = (*rules_it);

       size_t op_count = rule->GetOpcodeCount();

       size_t opcodes_size = op_count * sizeof(PolicyOpcode);

       if (avail_size < opcodes_size) {

         return false;

       }

       size_t data_size = avail_size - opcodes_size;

       PolicyOpcode* opcodes_start = &current_buffer->opcodes[svc_opcode_count];

       if (!rule->RebindCopy(opcodes_start, opcodes_size,

                             buffer_end, &data_size)) {

         return false;

       }

       size_t used = avail_size - data_size;

       buffer_end -= used;

       avail_size -= used;

       svc_opcode_count += op_count;

     }

     current_buffer->opcode_count += svc_opcode_count;

     size_t policy_byte_count = (svc_opcode_count * sizeof(PolicyOpcode))

                                 / sizeof(current_buffer[0]);

     current_buffer = &current_buffer[policy_byte_count + 1];

   }

   return true;

 }

 PolicyRule::PolicyRule(EvalResult action)

     : action_(action), done_(false) {

   char* memory = new char[sizeof(PolicyBuffer) + kRuleBufferSize];

   buffer_ = reinterpret_cast<PolicyBuffer*>(memory);

   buffer_->opcode_count = 0;

   opcode_factory_ = new OpcodeFactory(buffer_,

                                       kRuleBufferSize + sizeof(PolicyOpcode));

 }

 PolicyRule::PolicyRule(const PolicyRule& other) {

   if (this == &other)

     return;

   action_ = other.action_;

   done_ = other.done_;

   size_t buffer_size = sizeof(PolicyBuffer) + kRuleBufferSize;

   char* memory = new char[buffer_size];

   buffer_ = reinterpret_cast<PolicyBuffer*>(memory);

   memcpy(buffer_, other.buffer_, buffer_size);

   char* opcode_buffer = reinterpret_cast<char*>(&buffer_->opcodes[0]);

   char* next_opcode = &opcode_buffer[GetOpcodeCount() * sizeof(PolicyOpcode)];

   opcode_factory_ =

       new OpcodeFactory(next_opcode, other.opcode_factory_->memory_size());

 }

 // This function get called from a simple state machine implemented in

 // AddStringMatch() which passes the current state (in state) and it passes

 // true in last_call if AddStringMatch() has finished processing the input

 // pattern string and this would be the last call to generate any pending

 // opcode. The skip_count is the currently accumulated number of '?' seen so

 // far and once the associated opcode is generated this function sets it back

 // to zero.

 bool PolicyRule::GenStringOpcode(RuleType rule_type,

                                  StringMatchOptions match_opts,

                                  uint16 parameter, int state, bool last_call,

                                  int* skip_count, std::wstring* fragment) {

   // The last opcode must:

   //   1) Always clear the context.

   //   2) Preserve the negation.

   //   3) Remove the 'OR' mode flag.

   uint32 options = kPolNone;

   if (last_call) {

     if (IF_NOT == rule_type) {

       options = kPolClearContext | kPolNegateEval;

     } else {

       options = kPolClearContext;

     }

   } else if (IF_NOT == rule_type) {

     options = kPolUseOREval | kPolNegateEval;

   }

   PolicyOpcode* op = NULL;

   // The fragment string contains the accumulated characters to match with, it

   // never contains wildcards (unless they have been escaped) and while there

   // is no fragment there is no new string match opcode to generate.

   if (fragment->empty()) {

     // There is no new opcode to generate but in the last call we have to fix

     // the previous opcode because it was really the last but we did not know

     // it at that time.

     if (last_call && (buffer_->opcode_count > 0)) {

       op = &buffer_->opcodes[buffer_->opcode_count - 1];

       op->SetOptions(options);

     }

     return true;

   }

   if (PENDING_ASTERISK == state) {

     if (last_call) {

       op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(),

                                                kSeekToEnd, match_opts,

                                                options);

     } else {

       op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(),

                                                kSeekForward, match_opts,

                                                options);

     }

   } else if (PENDING_QMARK == state) {

     op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(),

                                              *skip_count, match_opts, options);

     *skip_count = 0;

   } else {

     if (last_call) {

       match_opts = static_cast<StringMatchOptions>(EXACT_LENGHT | match_opts);

     }

     op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(), 0,

                                              match_opts, options);

   }

   if (NULL == op) {

     return false;

   }

   ++buffer_->opcode_count;

   fragment->clear();

   return true;

 }

 bool PolicyRule::AddStringMatch(RuleType rule_type, int16 parameter,

                                 const wchar_t* string,

                                 StringMatchOptions match_opts) {

   if (done_) {

     // Do not allow to add more rules after generating the action opcode.

     return false;

   }

   const wchar_t* current_char = string;

   uint32 last_char = kLastCharIsNone;

   int state = PENDING_NONE;

   int skip_count = 0;       // counts how many '?' we have seen in a row.

   std::wstring fragment;    // accumulates the non-wildcard part of the string.

   while (L'\0' != *current_char) {

     switch (*current_char) {

       case L'*':

         if (kLastCharIsWild & last_char) {

           // '**' and '&*' is an error.

           return false;

         }

         if (!GenStringOpcode(rule_type, match_opts, parameter,

                              state, false, &skip_count, &fragment)) {

           return false;

         }

         last_char = kLastCharIsAsterisk;

         state = PENDING_ASTERISK;

         break;

       case L'?':

         if (kLastCharIsAsterisk == last_char) {

           // '*?' is an error.

           return false;

         }

         if (!GenStringOpcode(rule_type, match_opts, parameter,

                              state, false, &skip_count, &fragment)) {

           return false;

         }

         ++skip_count;

         last_char = kLastCharIsQuestionM;

         state = PENDING_QMARK;

         break;

       case L'/':

         // Note: "/?" is an escaped '?'. Eat the slash and fall through.

         if (L'?' == current_char[1]) {

           ++current_char;

         }

       default:

         fragment += *current_char;

         last_char = kLastCharIsAlpha;

     }

     ++current_char;

   }

   if (!GenStringOpcode(rule_type, match_opts, parameter,

                        state, true, &skip_count, &fragment)) {

     return false;

   }

   return true;

 }

 bool PolicyRule::AddNumberMatch(RuleType rule_type, int16 parameter,

                                 unsigned long number, RuleOp comparison_op) {

   if (done_) {

     // Do not allow to add more rules after generating the action opcode.

     return false;

   }

   uint32 opts = (rule_type == IF_NOT)? kPolNegateEval : kPolNone;

   if (EQUAL == comparison_op) {

     if (NULL == opcode_factory_->MakeOpNumberMatch(parameter, number, opts)) {

       return false;

     }

   } else if (AND == comparison_op) {

     if (NULL == opcode_factory_->MakeOpUlongAndMatch(parameter, number, opts)) {

       return false;

     }

   }

   ++buffer_->opcode_count;

   return true;

 }

 bool PolicyRule::Done() {

   if (done_) {

     return true;

   }

   if (NULL == opcode_factory_->MakeOpAction(action_, kPolNone)) {

     return false;

   }

   ++buffer_->opcode_count;

   done_ = true;

   return true;

 }

 bool PolicyRule::RebindCopy(PolicyOpcode* opcode_start, size_t opcode_size,

                             char* data_start, size_t* data_size) const {

   size_t count = buffer_->opcode_count;

   for (size_t ix = 0; ix != count; ++ix) {

     if (opcode_size < sizeof(PolicyOpcode)) {

       return false;

     }

     PolicyOpcode& opcode = buffer_->opcodes[ix];

     *opcode_start = opcode;

     if (OP_WSTRING_MATCH == opcode.GetID()) {

       // For this opcode argument 0 is a delta to the string and argument 1

       // is the length (in chars) of the string.

       const wchar_t* str = opcode.GetRelativeString(0);

       size_t str_len;

       opcode.GetArgument(1, &str_len);

       str_len = str_len * sizeof(wchar_t);

       if ((*data_size) < str_len) {

         return false;

       }

       *data_size -= str_len;

       data_start -= str_len;

       memcpy(data_start, str, str_len);

       // Recompute the string displacement

       ptrdiff_t delta = data_start - reinterpret_cast<char*>(opcode_start);

       opcode_start->SetArgument(0, delta);

     }

     ++opcode_start;

     opcode_size -= sizeof(PolicyOpcode);

   }

   return true;

 }

 PolicyRule::~PolicyRule() {

   delete [] reinterpret_cast<char*>(buffer_);

   delete opcode_factory_;

 }

 }  // namespace sandbox