sandbox/src/policy_low_level.cc

   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 #include <string>
   6 #include <map>
   7
   8 #include "sandbox/src/policy_low_level.h"
   9 #include "base/basictypes.h"
  10
  11 namespace {
  12
  13   // A single rule can use at most this amount of memory.
  14   const size_t kRuleBufferSize = 1024*4;
  15
  16   // The possible states of the string matching opcode generator.
  17   enum {
  18     PENDING_NONE,
  19     PENDING_ASTERISK,    // Have seen an '*' but have not generated an opcode.
  20     PENDING_QMARK,       // Have seen an '?' but have not generated an opcode.
  21   };
  22
  23   // The category of the last character seen by the string matching opcode
  24   // generator.
  25   const uint32 kLastCharIsNone = 0;
  26   const uint32 kLastCharIsAlpha = 1;
  27   const uint32 kLastCharIsWild = 2;
  28   const uint32 kLastCharIsAsterisk = kLastCharIsWild + 4;
  29   const uint32 kLastCharIsQuestionM = kLastCharIsWild + 8;
  30 }
  31
  32 namespace sandbox {
  33
  34 // Adding a rule is nothing more than pushing it into an stl container. Done()
  35 // is called for the rule in case the code that made the rule in the first
  36 // place has not done it.
  37 bool LowLevelPolicy::AddRule(int service, PolicyRule* rule) {
  38   if (!rule->Done()) {
  39     return false;
  40   }
  41
  42   PolicyRule* local_rule = new PolicyRule(*rule);
  43   RuleNode node = {local_rule, service};
  44   rules_.push_back(node);
  45   return true;
  46 }
  47
  48 LowLevelPolicy::~LowLevelPolicy() {
  49   // Delete all the rules.
  50   typedef std::list<RuleNode> RuleNodes;
  51   for (RuleNodes::iterator it = rules_.begin(); it != rules_.end(); ++it) {
  52     delete it->rule;
  53   }
  54 }
  55
  56 // Here is where the heavy byte shuffling is done. We take all the rules and
  57 // 'compile' them into a single memory region. Now, the rules are in random
  58 // order so the first step is to reorganize them into a stl map that is keyed
  59 // by the service id and as a value contains a list with all the rules that
  60 // belong to that service. Then we enter the big for-loop where we carve a
  61 // memory zone for the opcodes and the data and call RebindCopy on each rule
  62 // so they all end up nicely packed in the policy_store_.
  63 bool LowLevelPolicy::Done() {
  64   typedef std::list<RuleNode> RuleNodes;
  65   typedef std::list<const PolicyRule*> RuleList;
  66   typedef std::map<uint32, RuleList> Mmap;
  67   Mmap mmap;
  68
  69   for (RuleNodes::iterator it = rules_.begin(); it != rules_.end(); ++it) {
  70     mmap[it->service].push_back(it->rule);
  71   }
  72
  73   PolicyBuffer* current_buffer = &policy_store_->data[0];
  74   char* buffer_end = reinterpret_cast<char*>(current_buffer) +
  75     policy_store_->data_size;
  76   size_t avail_size =  policy_store_->data_size;
  77
  78   for (Mmap::iterator it = mmap.begin(); it != mmap.end(); ++it) {
  79     uint32 service = (*it).first;
  80     if (service >= kMaxServiceCount) {
  81       return false;
  82     }
  83     policy_store_->entry[service] = current_buffer;
  84
  85     RuleList::iterator rules_it = (*it).second.begin();
  86     RuleList::iterator rules_it_end = (*it).second.end();
  87
  88     size_t svc_opcode_count = 0;
  89
  90     for (; rules_it != rules_it_end; ++rules_it) {
  91       const PolicyRule* rule = (*rules_it);
  92       size_t op_count = rule->GetOpcodeCount();
  93
  94       size_t opcodes_size = op_count * sizeof(PolicyOpcode);
  95       if (avail_size < opcodes_size) {
  96         return false;
  97       }
  98       size_t data_size = avail_size - opcodes_size;
  99       PolicyOpcode* opcodes_start = &current_buffer->opcodes[svc_opcode_count];
 100       if (!rule->RebindCopy(opcodes_start, opcodes_size,
 101                             buffer_end, &data_size)) {
 102         return false;
 103       }
 104       size_t used = avail_size - data_size;
 105       buffer_end -= used;
 106       avail_size -= used;
 107       svc_opcode_count += op_count;
 108     }
 109
 110     current_buffer->opcode_count += svc_opcode_count;
 111     size_t policy_byte_count = (svc_opcode_count * sizeof(PolicyOpcode))
 112                                 / sizeof(current_buffer[0]);
 113     current_buffer = &current_buffer[policy_byte_count + 1];
 114   }
 115
 116   return true;
 117 }
 118
 119 PolicyRule::PolicyRule(EvalResult action)
 120     : action_(action), done_(false) {
 121   char* memory = new char[sizeof(PolicyBuffer) + kRuleBufferSize];
 122   buffer_ = reinterpret_cast<PolicyBuffer*>(memory);
 123   buffer_->opcode_count = 0;
 124   opcode_factory_ = new OpcodeFactory(buffer_,
 125                                       kRuleBufferSize + sizeof(PolicyOpcode));
 126 }
 127
 128 PolicyRule::PolicyRule(const PolicyRule& other) {
 129   if (this == &other)
 130     return;
 131   action_ = other.action_;
 132   done_ = other.done_;
 133   size_t buffer_size = sizeof(PolicyBuffer) + kRuleBufferSize;
 134   char* memory = new char[buffer_size];
 135   buffer_ = reinterpret_cast<PolicyBuffer*>(memory);
 136   memcpy(buffer_, other.buffer_, buffer_size);
 137
 138   char* opcode_buffer = reinterpret_cast<char*>(&buffer_->opcodes[0]);
 139   char* buffer_end = &opcode_buffer[kRuleBufferSize + sizeof(PolicyOpcode)];
 140   char* next_opcode = &opcode_buffer[GetOpcodeCount() * sizeof(PolicyOpcode)];
 141   opcode_factory_ = new OpcodeFactory(next_opcode, buffer_end - next_opcode);
 142 }
 143
 144 // This function get called from a simple state machine implemented in
 145 // AddStringMatch() which passes the current state (in state) and it passes
 146 // true in last_call if AddStringMatch() has finished processing the input
 147 // pattern string and this would be the last call to generate any pending
 148 // opcode. The skip_count is the currently accumulated number of '?' seen so
 149 // far and once the associated opcode is generated this function sets it back
 150 // to zero.
 151 bool PolicyRule::GenStringOpcode(RuleType rule_type,
 152                                  StringMatchOptions match_opts,
 153                                  uint16 parameter, int state, bool last_call,
 154                                  int* skip_count, std::wstring* fragment) {
 155
 156   // The last opcode must:
 157   //   1) Always clear the context.
 158   //   2) Preserve the negation.
 159   //   3) Remove the 'OR' mode flag.
 160   uint32 options = kPolNone;
 161   if (last_call) {
 162     if (IF_NOT == rule_type) {
 163       options = kPolClearContext | kPolNegateEval;
 164     } else {
 165       options = kPolClearContext;
 166     }
 167   } else if (IF_NOT == rule_type) {
 168     options = kPolUseOREval | kPolNegateEval;
 169   }
 170
 171   PolicyOpcode* op = NULL;
 172
 173   // The fragment string contains the accumulated characters to match with, it
 174   // never contains wildcards (unless they have been escaped) and while there
 175   // is no fragment there is no new string match opcode to generate.
 176   if (fragment->empty()) {
 177     // There is no new opcode to generate but in the last call we have to fix
 178     // the previous opcode because it was really the last but we did not know
 179     // it at that time.
 180     if (last_call && (buffer_->opcode_count > 0)) {
 181       op = &buffer_->opcodes[buffer_->opcode_count - 1];
 182       op->SetOptions(options);
 183     }
 184     return true;
 185   }
 186
 187   if (PENDING_ASTERISK == state) {
 188     if (last_call) {
 189       op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(),
 190                                                kSeekToEnd, match_opts,
 191                                                options);
 192     } else {
 193       op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(),
 194                                                kSeekForward, match_opts,
 195                                                options);
 196     }
 197
 198   } else if (PENDING_QMARK == state) {
 199     op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(),
 200                                              *skip_count, match_opts, options);
 201     *skip_count = 0;
 202   } else {
 203     if (last_call) {
 204       match_opts = static_cast<StringMatchOptions>(EXACT_LENGHT | match_opts);
 205     }
 206     op = opcode_factory_->MakeOpWStringMatch(parameter, fragment->c_str(), 0,
 207                                              match_opts, options);
 208   }
 209   if (NULL == op) {
 210     return false;
 211   }
 212   ++buffer_->opcode_count;
 213   fragment->clear();
 214   return true;
 215 }
 216
 217 bool PolicyRule::AddStringMatch(RuleType rule_type, int16 parameter,
 218                                 const wchar_t* string,
 219                                 StringMatchOptions match_opts) {
 220   if (done_) {
 221     // Do not allow to add more rules after generating the action opcode.
 222     return false;
 223   }
 224
 225   const wchar_t* current_char = string;
 226   uint32 last_char = kLastCharIsNone;
 227   int state = PENDING_NONE;
 228   int skip_count = 0;       // counts how many '?' we have seen in a row.
 229   std::wstring fragment;    // accumulates the non-wildcard part of the string.
 230
 231   while (L'\0' != *current_char) {
 232     switch (*current_char) {
 233       case L'*':
 234         if (kLastCharIsWild & last_char) {
 235           // '**' and '&*' is an error.
 236           return false;
 237         }
 238         if (!GenStringOpcode(rule_type, match_opts, parameter,
 239                              state, false, &skip_count, &fragment)) {
 240           return false;
 241         }
 242         last_char = kLastCharIsAsterisk;
 243         state = PENDING_ASTERISK;
 244         break;
 245       case L'?':
 246         if (kLastCharIsAsterisk == last_char) {
 247           // '*?' is an error.
 248           return false;
 249         }
 250         if (!GenStringOpcode(rule_type, match_opts, parameter,
 251                              state, false, &skip_count, &fragment)) {
 252           return false;
 253         }
 254         ++skip_count;
 255         last_char = kLastCharIsQuestionM;
 256         state = PENDING_QMARK;
 257         break;
 258       case L'/':
 259         // Note: "/?" is an escaped '?'. Eat the slash and fall through.
 260         if (L'?' == current_char[1]) {
 261           ++current_char;
 262         }
 263       default:
 264         fragment += *current_char;
 265         last_char = kLastCharIsAlpha;
 266     }
 267     ++current_char;
 268   }
 269
 270   if (!GenStringOpcode(rule_type, match_opts, parameter,
 271                        state, true, &skip_count, &fragment)) {
 272     return false;
 273   }
 274   return true;
 275 }
 276
 277 bool PolicyRule::AddNumberMatch(RuleType rule_type, int16 parameter,
 278                                 unsigned long number, RuleOp comparison_op) {
 279   if (done_) {
 280     // Do not allow to add more rules after generating the action opcode.
 281     return false;
 282   }
 283   uint32 opts = (rule_type == IF_NOT)? kPolNegateEval : kPolNone;
 284
 285   if (EQUAL == comparison_op) {
 286     if (NULL == opcode_factory_->MakeOpNumberMatch(parameter, number, opts)) {
 287       return false;
 288     }
 289   } else if (AND == comparison_op) {
 290     if (NULL == opcode_factory_->MakeOpUlongAndMatch(parameter, number, opts)) {
 291       return false;
 292     }
 293   }
 294   ++buffer_->opcode_count;
 295   return true;
 296 }
 297
 298 bool PolicyRule::Done() {
 299   if (done_) {
 300     return true;
 301   }
 302   if (NULL == opcode_factory_->MakeOpAction(action_, kPolNone)) {
 303     return false;
 304   }
 305   ++buffer_->opcode_count;
 306   done_ = true;
 307   return true;
 308 }
 309
 310 bool PolicyRule::RebindCopy(PolicyOpcode* opcode_start, size_t opcode_size,
 311                             char* data_start, size_t* data_size) const {
 312   size_t count = buffer_->opcode_count;
 313   for (size_t ix = 0; ix != count; ++ix) {
 314     if (opcode_size < sizeof(PolicyOpcode)) {
 315       return false;
 316     }
 317     PolicyOpcode& opcode = buffer_->opcodes[ix];
 318     *opcode_start = opcode;
 319     if (OP_WSTRING_MATCH == opcode.GetID()) {
 320       // For this opcode argument 0 is a delta to the string and argument 1
 321       // is the length (in chars) of the string.
 322       const wchar_t* str = opcode.GetRelativeString(0);
 323       size_t str_len;
 324       opcode.GetArgument(1, &str_len);
 325       str_len = str_len * sizeof(wchar_t);
 326       if ((*data_size) < str_len) {
 327         return false;
 328       }
 329       *data_size -= str_len;
 330       data_start -= str_len;
 331       memcpy(data_start, str, str_len);
 332       // Recompute the string displacement
 333       ptrdiff_t delta = data_start - reinterpret_cast<char*>(opcode_start);
 334       opcode_start->SetArgument(0, delta);
 335     }
 336     ++opcode_start;
 337     opcode_size -= sizeof(PolicyOpcode);
 338   }
 339
 340   return true;
 341 }
 342
 343 PolicyRule::~PolicyRule() {
 344   delete [] reinterpret_cast<char*>(buffer_);
 345   delete opcode_factory_;
 346 }
 347
 348 }  // namespace sandbox