sandbox/src/policy_low_level.h

   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 #ifndef SANDBOX_SRC_POLICY_LOW_LEVEL_H__
   6 #define SANDBOX_SRC_POLICY_LOW_LEVEL_H__
   7
   8 #include <list>
   9
  10 #include "base/basictypes.h"
  11 #include "sandbox/src/ipc_tags.h"
  12 #include "sandbox/src/policy_engine_params.h"
  13 #include "sandbox/src/policy_engine_opcodes.h"
  14
  15 // Low level policy classes.
  16 // Built on top of the PolicyOpcode and OpcodeFatory, the low level policy
  17 // provides a way to define rules on strings and numbers but it is unaware
  18 // of Windows specific details or how the Interceptions must be set up.
  19 // To use these classes you construct one or more rules and add them to the
  20 // LowLevelPolicy object like this:
  21 //
  22 //   PolicyRule rule1(ASK_BROKER);
  23 //   rule1.AddStringMatch(IF, 0, L"\\\\/?/?\\c:\\*Microsoft*\\*.exe", true);
  24 //   rule1.AddNumberMatch(IF_NOT, 1, CREATE_ALWAYS, EQUAL);
  25 //   rule1.AddNumberMatch(IF, 2, FILE_ATTRIBUTE_NORMAL, EQUAL);
  26 //
  27 //   PolicyRule rule2(FAKE_SUCCESS);
  28 //   rule2.AddStringMatch(IF, 0, L"\\\\/?/?\\Pipe\\Chrome.*", false));
  29 //   rule2.AddNumberMatch(IF, 1, OPEN_EXISTING, EQUAL));
  30 //
  31 //   LowLevelPolicy policyGen(*policy_memory);
  32 //   policyGen.AddRule(kNtCreateFileSvc, &rule1);
  33 //   policyGen.AddRule(kNtCreateFileSvc, &rule2);
  34 //   policyGen.Done();
  35 //
  36 // At this point (error checking omitted) the policy_memory can be copied
  37 // to the target process where it can be evaluated.
  38
  39 namespace sandbox {
  40
  41 // TODO(cpu): Move this constant to crosscall_client.h.
  42 const size_t kMaxServiceCount = 32;
  43 COMPILE_ASSERT(IPC_LAST_TAG <= kMaxServiceCount, kMaxServiceCount_is_too_low);
  44
  45 // Defines the memory layout of the policy. This memory is filled by
  46 // LowLevelPolicy object.
  47 // For example:
  48 //
  49 //  [Service 0] --points to---\
  50 //  [Service 1] --------------|-----\
  51 //   ......                   |     |
  52 //  [Service N]               |     |
  53 //  [data_size]               |     |
  54 //  [Policy Buffer 0] <-------/     |
  55 //  [opcodes of]                    |
  56 //  .......                         |
  57 //  [Policy Buffer 1] <-------------/
  58 //  [opcodes]
  59 //  .......
  60 //  .......
  61 //  [Policy Buffer N]
  62 //  [opcodes]
  63 //  .......
  64 //   <possibly unused space here>
  65 //  .......
  66 //  [opcode string ]
  67 //  [opcode string ]
  68 //  .......
  69 //  [opcode string ]
  70 struct PolicyGlobal {
  71   PolicyBuffer* entry[kMaxServiceCount];
  72   size_t data_size;
  73   PolicyBuffer data[1];
  74 };
  75
  76 class PolicyRule;
  77
  78 // Provides the means to collect rules into a policy store (memory)
  79 class LowLevelPolicy {
  80  public:
  81   // policy_store: must contain allocated memory and the internal
  82   // size fields set to correct values.
  83   explicit LowLevelPolicy(PolicyGlobal* policy_store)
  84       : policy_store_(policy_store) {
  85   }
  86
  87   // Destroys all the policy rules.
  88   ~LowLevelPolicy();
  89
  90   // Adds a rule to be generated when Done() is called.
  91   // service: The id of the service that this rule is associated with,
  92   // for example the 'Open Thread' service or the "Create File" service.
  93   // returns false on error.
  94   bool AddRule(int service, PolicyRule* rule);
  95
  96   // Generates all the rules added with AddRule() into the memory area
  97   // passed on the constructor. Returns false on error.
  98   bool Done();
  99
 100  private:
 101   struct RuleNode {
 102     const PolicyRule* rule;
 103     int service;
 104   };
 105   std::list<RuleNode> rules_;
 106   PolicyGlobal* policy_store_;
 107   DISALLOW_IMPLICIT_CONSTRUCTORS(LowLevelPolicy);
 108 };
 109
 110 // There are 'if' rules and 'if not' comparisons
 111 enum RuleType {
 112   IF = 0,
 113   IF_NOT = 1,
 114 };
 115
 116 // Possible comparisons for numbers
 117 enum RuleOp {
 118   EQUAL,
 119   AND,
 120   RANGE   // TODO(cpu): Implement this option.
 121 };
 122
 123 // Provides the means to collect a set of comparisons into a single
 124 // rule and its associated action.
 125 class PolicyRule {
 126   friend class LowLevelPolicy;
 127
 128  public:
 129   explicit PolicyRule(EvalResult action);
 130   PolicyRule(const PolicyRule& other);
 131   ~PolicyRule();
 132
 133   // Adds a string comparison to the rule.
 134   // rule_type: possible values are IF and IF_NOT.
 135   // parameter: the expected index of the argument for this rule. For example
 136   // in a 'create file' service the file name argument can be at index 0.
 137   // string: is the desired matching pattern.
 138   // match_opts: if the pattern matching is case sensitive or not.
 139   bool AddStringMatch(RuleType rule_type, int16 parameter,
 140                       const wchar_t* string, StringMatchOptions match_opts);
 141
 142   // Adds a number match comparison to the rule.
 143   // rule_type: possible values are IF and IF_NOT.
 144   // parameter: the expected index of the argument for this rule.
 145   // number: the value to compare the input to.
 146   // comparison_op: the comparison kind (equal, logical and, etc).
 147   bool AddNumberMatch(RuleType rule_type, int16 parameter,
 148                       unsigned long number, RuleOp comparison_op);
 149
 150   // Returns the number of opcodes generated so far.
 151   size_t GetOpcodeCount() const {
 152     return buffer_->opcode_count;
 153   }
 154
 155   // Called when there is no more comparisons to add. Internally it generates
 156   // the last opcode (the action opcode). Returns false if this operation fails.
 157   bool Done();
 158
 159  private:
 160   void operator=(const PolicyRule&);
 161   // Called in a loop from AddStringMatch to generate the required string
 162   // match opcodes. rule_type, match_opts and parameter are the same as
 163   // in AddStringMatch.
 164   bool GenStringOpcode(RuleType rule_type, StringMatchOptions match_opts,
 165                        uint16 parameter, int state, bool last_call,
 166                        int* skip_count, std::wstring* fragment);
 167
 168   // Loop over all generated opcodes and copy them to increasing memory
 169   // addresses from opcode_start and copy the extra data (strings usually) into
 170   // decreasing addresses from data_start. Extra data is only present in the
 171   // string evaluation opcodes.
 172   bool RebindCopy(PolicyOpcode* opcode_start, size_t opcode_size,
 173                   char* data_start, size_t* data_size) const;
 174   PolicyBuffer* buffer_;
 175   OpcodeFactory* opcode_factory_;
 176   EvalResult action_;
 177   bool done_;
 178 };
 179
 180 }  // namespace sandbox
 181
 182 #endif  // SANDBOX_SRC_POLICY_LOW_LEVEL_H__