Index: sandbox/win/src/policy_engine_opcodes.h |
diff --git a/sandbox/win/src/policy_engine_opcodes.h b/sandbox/win/src/policy_engine_opcodes.h |
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-// Copyright (c) 2010 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. |
- |
-#ifndef SANDBOX_WIN_SRC_POLICY_ENGINE_OPCODES_H_ |
-#define SANDBOX_WIN_SRC_POLICY_ENGINE_OPCODES_H_ |
- |
-#include <stddef.h> |
-#include <stdint.h> |
- |
-#include "base/macros.h" |
-#include "base/numerics/safe_conversions.h" |
-#include "sandbox/win/src/policy_engine_params.h" |
- |
-// The low-level policy is implemented using the concept of policy 'opcodes'. |
-// An opcode is a structure that contains enough information to perform one |
-// comparison against one single input parameter. For example, an opcode can |
-// encode just one of the following comparison: |
-// |
-// - Is input parameter 3 not equal to NULL? |
-// - Does input parameter 2 start with L"c:\\"? |
-// - Is input parameter 5, bit 3 is equal 1? |
-// |
-// Each opcode is in fact equivalent to a function invocation where all |
-// the parameters are known by the opcode except one. So say you have a |
-// function of this form: |
-// bool fn(a, b, c, d) with 4 arguments |
-// |
-// Then an opcode is: |
-// op(fn, b, c, d) |
-// Which stores the function to call and its 3 last arguments |
-// |
-// Then and opcode evaluation is: |
-// op.eval(a) ------------------------> fn(a,b,c,d) |
-// internally calls |
-// |
-// The idea is that complex policy rules can be split into streams of |
-// opcodes which are evaluated in sequence. The evaluation is done in |
-// groups of opcodes that have N comparison opcodes plus 1 action opcode: |
-// |
-// [comparison 1][comparison 2]...[comparison N][action][comparison 1]... |
-// ----- evaluation order-----------> |
-// |
-// Each opcode group encodes one high-level policy rule. The rule applies |
-// only if all the conditions on the group evaluate to true. The action |
-// opcode contains the policy outcome for that particular rule. |
-// |
-// Note that this header contains the main building blocks of low-level policy |
-// but not the low level policy class. |
-namespace sandbox { |
- |
-// These are the possible policy outcomes. Note that some of them might |
-// not apply and can be removed. Also note that The following values only |
-// specify what to do, not how to do it and it is acceptable given specific |
-// cases to ignore the policy outcome. |
-enum EvalResult { |
- // Comparison opcode values: |
- EVAL_TRUE, // Opcode condition evaluated true. |
- EVAL_FALSE, // Opcode condition evaluated false. |
- EVAL_ERROR, // Opcode condition generated an error while evaluating. |
- // Action opcode values: |
- ASK_BROKER, // The target must generate an IPC to the broker. On the broker |
- // side, this means grant access to the resource. |
- DENY_ACCESS, // No access granted to the resource. |
- GIVE_READONLY, // Give readonly access to the resource. |
- GIVE_ALLACCESS, // Give full access to the resource. |
- GIVE_CACHED, // IPC is not required. Target can return a cached handle. |
- GIVE_FIRST, // TODO(cpu) |
- SIGNAL_ALARM, // Unusual activity. Generate an alarm. |
- FAKE_SUCCESS, // Do not call original function. Just return 'success'. |
- FAKE_ACCESS_DENIED, // Do not call original function. Just return 'denied' |
- // and do not do IPC. |
- TERMINATE_PROCESS, // Destroy target process. Do IPC as well. |
-}; |
- |
-// The following are the implemented opcodes. |
-enum OpcodeID { |
- OP_ALWAYS_FALSE, // Evaluates to false (EVAL_FALSE). |
- OP_ALWAYS_TRUE, // Evaluates to true (EVAL_TRUE). |
- OP_NUMBER_MATCH, // Match a 32-bit integer as n == a. |
- OP_NUMBER_MATCH_RANGE, // Match a 32-bit integer as a <= n <= b. |
- OP_NUMBER_AND_MATCH, // Match using bitwise AND; as in: n & a != 0. |
- OP_WSTRING_MATCH, // Match a string for equality. |
- OP_ACTION // Evaluates to an action opcode. |
-}; |
- |
-// Options that apply to every opcode. They are specified when creating |
-// each opcode using OpcodeFactory::MakeOpXXXXX() family of functions |
-// Do nothing special. |
-const uint32_t kPolNone = 0; |
- |
-// Convert EVAL_TRUE into EVAL_FALSE and vice-versa. This allows to express |
-// negated conditions such as if ( a && !b). |
-const uint32_t kPolNegateEval = 1; |
- |
-// Zero the MatchContext context structure. This happens after the opcode |
-// is evaluated. |
-const uint32_t kPolClearContext = 2; |
- |
-// Use OR when evaluating this set of opcodes. The policy evaluator by default |
-// uses AND when evaluating. Very helpful when |
-// used with kPolNegateEval. For example if you have a condition best expressed |
-// as if(! (a && b && c)), the use of this flags allows it to be expressed as |
-// if ((!a) || (!b) || (!c)). |
-const uint32_t kPolUseOREval = 4; |
- |
-// Keeps the evaluation state between opcode evaluations. This is used |
-// for string matching where the next opcode needs to continue matching |
-// from the last character position from the current opcode. The match |
-// context is preserved across opcode evaluation unless an opcode specifies |
-// as an option kPolClearContext. |
-struct MatchContext { |
- size_t position; |
- uint32_t options; |
- |
- MatchContext() { |
- Clear(); |
- } |
- |
- void Clear() { |
- position = 0; |
- options = 0; |
- } |
-}; |
- |
-// Models a policy opcode; that is a condition evaluation were all the |
-// arguments but one are stored in objects of this class. Use OpcodeFactory |
-// to create objects of this type. |
-// This class is just an implementation artifact and not exposed to the |
-// API clients or visible in the intercepted service. Internally, an |
-// opcode is just: |
-// - An integer that identifies the actual opcode. |
-// - An index to indicate which one is the input argument |
-// - An array of arguments. |
-// While an OO hierarchy of objects would have been a natural choice, the fact |
-// that 1) this code can execute before the CRT is loaded, presents serious |
-// problems in terms of guarantees about the actual state of the vtables and |
-// 2) because the opcode objects are generated in the broker process, we need to |
-// use plain objects. To preserve some minimal type safety templates are used |
-// when possible. |
-class PolicyOpcode { |
- friend class OpcodeFactory; |
- public: |
- // Evaluates the opcode. For a typical comparison opcode the return value |
- // is EVAL_TRUE or EVAL_FALSE. If there was an error in the evaluation the |
- // the return is EVAL_ERROR. If the opcode is an action opcode then the |
- // return can take other values such as ASK_BROKER. |
- // parameters: An array of all input parameters. This argument is normally |
- // created by the macros POLPARAMS_BEGIN() POLPARAMS_END. |
- // count: The number of parameters passed as first argument. |
- // match: The match context that is persisted across the opcode evaluation |
- // sequence. |
- EvalResult Evaluate(const ParameterSet* parameters, size_t count, |
- MatchContext* match); |
- |
- // Retrieves a stored argument by index. Valid index values are |
- // from 0 to < kArgumentCount. |
- template <typename T> |
- void GetArgument(size_t index, T* argument) const { |
- static_assert(sizeof(T) <= sizeof(arguments_[0]), "invalid size"); |
- *argument = *reinterpret_cast<const T*>(&arguments_[index].mem); |
- } |
- |
- // Sets a stored argument by index. Valid index values are |
- // from 0 to < kArgumentCount. |
- template <typename T> |
- void SetArgument(size_t index, const T& argument) { |
- static_assert(sizeof(T) <= sizeof(arguments_[0]), "invalid size"); |
- *reinterpret_cast<T*>(&arguments_[index].mem) = argument; |
- } |
- |
- // Retrieves the actual address of an string argument. When using |
- // GetArgument() to retrieve an index that contains a string, the returned |
- // value is just an offset to the actual string. |
- // index: the stored string index. Valid values are from 0 |
- // to < kArgumentCount. |
- const wchar_t* GetRelativeString(size_t index) const { |
- ptrdiff_t str_delta = 0; |
- GetArgument(index, &str_delta); |
- const char* delta = reinterpret_cast<const char*>(this) + str_delta; |
- return reinterpret_cast<const wchar_t*>(delta); |
- } |
- |
- // Returns true if this opcode is an action opcode without actually |
- // evaluating it. Used to do a quick scan forward to the next opcode group. |
- bool IsAction() const { |
- return (OP_ACTION == opcode_id_); |
- }; |
- |
- // Returns the opcode type. |
- OpcodeID GetID() const { |
- return opcode_id_; |
- } |
- |
- // Returns the stored options such as kPolNegateEval and others. |
- uint32_t GetOptions() const { return options_; } |
- |
- // Sets the stored options such as kPolNegateEval. |
- void SetOptions(uint32_t options) { |
- options_ = base::checked_cast<uint16_t>(options); |
- } |
- |
- private: |
- |
- static const size_t kArgumentCount = 4; // The number of supported argument. |
- |
- struct OpcodeArgument { |
- UINT_PTR mem; |
- }; |
- |
- // Better define placement new in the class instead of relying on the |
- // global definition which seems to be fubared. |
- void* operator new(size_t, void* location) { |
- return location; |
- } |
- |
- // Helper function to evaluate the opcode. The parameters have the same |
- // meaning that in Evaluate(). |
- EvalResult EvaluateHelper(const ParameterSet* parameters, |
- MatchContext* match); |
- OpcodeID opcode_id_; |
- int16_t parameter_; |
- // TODO(cpu): Making |options_| a uint32_t would avoid casting, but causes |
- // test failures. Somewhere code is relying on the size of this struct. |
- // http://crbug.com/420296 |
- uint16_t options_; |
- OpcodeArgument arguments_[PolicyOpcode::kArgumentCount]; |
-}; |
- |
-enum StringMatchOptions { |
- CASE_SENSITIVE = 0, // Pay or Not attention to the case as defined by |
- CASE_INSENSITIVE = 1, // RtlCompareUnicodeString windows API. |
- EXACT_LENGHT = 2 // Don't do substring match. Do full string match. |
-}; |
- |
-// Opcodes that do string comparisons take a parameter that is the starting |
-// position to perform the comparison so we can do substring matching. There |
-// are two special values: |
-// |
-// Start from the current position and compare strings advancing forward until |
-// a match is found if any. Similar to CRT strstr(). |
-const int kSeekForward = -1; |
-// Perform a match with the end of the string. It only does a single comparison. |
-const int kSeekToEnd = 0xfffff; |
- |
- |
-// A PolicyBuffer is a variable size structure that contains all the opcodes |
-// that are to be created or evaluated in sequence. |
-struct PolicyBuffer { |
- size_t opcode_count; |
- PolicyOpcode opcodes[1]; |
-}; |
- |
-// Helper class to create any opcode sequence. This class is normally invoked |
-// only by the high level policy module or when you need to handcraft a special |
-// policy. |
-// The factory works by creating the opcodes using a chunk of memory given |
-// in the constructor. The opcodes themselves are allocated from the beginning |
-// (top) of the memory, while any string that an opcode needs is allocated from |
-// the end (bottom) of the memory. |
-// |
-// In essence: |
-// |
-// low address ---> [opcode 1] |
-// [opcode 2] |
-// [opcode 3] |
-// | | <--- memory_top_ |
-// | free | |
-// | | |
-// | | <--- memory_bottom_ |
-// [string 1] |
-// high address --> [string 2] |
-// |
-// Note that this class does not keep track of the number of opcodes made and |
-// it is designed to be a building block for low-level policy. |
-// |
-// Note that any of the MakeOpXXXXX member functions below can return NULL on |
-// failure. When that happens opcode sequence creation must be aborted. |
-class OpcodeFactory { |
- public: |
- // memory: base pointer to a chunk of memory where the opcodes are created. |
- // memory_size: the size in bytes of the memory chunk. |
- OpcodeFactory(char* memory, size_t memory_size) |
- : memory_top_(memory) { |
- memory_bottom_ = &memory_top_[memory_size]; |
- } |
- |
- // policy: contains the raw memory where the opcodes are created. |
- // memory_size: contains the actual size of the policy argument. |
- OpcodeFactory(PolicyBuffer* policy, size_t memory_size) { |
- memory_top_ = reinterpret_cast<char*>(&policy->opcodes[0]); |
- memory_bottom_ = &memory_top_[memory_size]; |
- } |
- |
- // Returns the available memory to make opcodes. |
- size_t memory_size() const { |
- return memory_bottom_ - memory_top_; |
- } |
- |
- // Creates an OpAlwaysFalse opcode. |
- PolicyOpcode* MakeOpAlwaysFalse(uint32_t options); |
- |
- // Creates an OpAlwaysFalse opcode. |
- PolicyOpcode* MakeOpAlwaysTrue(uint32_t options); |
- |
- // Creates an OpAction opcode. |
- // action: The action to return when Evaluate() is called. |
- PolicyOpcode* MakeOpAction(EvalResult action, uint32_t options); |
- |
- // Creates an OpNumberMatch opcode. |
- // selected_param: index of the input argument. It must be a uint32_t or the |
- // evaluation result will generate a EVAL_ERROR. |
- // match: the number to compare against the selected_param. |
- PolicyOpcode* MakeOpNumberMatch(int16_t selected_param, |
- uint32_t match, |
- uint32_t options); |
- |
- // Creates an OpNumberMatch opcode (void pointers are cast to numbers). |
- // selected_param: index of the input argument. It must be an void* or the |
- // evaluation result will generate a EVAL_ERROR. |
- // match: the pointer numeric value to compare against selected_param. |
- PolicyOpcode* MakeOpVoidPtrMatch(int16_t selected_param, |
- const void* match, |
- uint32_t options); |
- |
- // Creates an OpNumberMatchRange opcode using the memory passed in the ctor. |
- // selected_param: index of the input argument. It must be a uint32_t or the |
- // evaluation result will generate a EVAL_ERROR. |
- // lower_bound, upper_bound: the range to compare against selected_param. |
- PolicyOpcode* MakeOpNumberMatchRange(int16_t selected_param, |
- uint32_t lower_bound, |
- uint32_t upper_bound, |
- uint32_t options); |
- |
- // Creates an OpWStringMatch opcode using the raw memory passed in the ctor. |
- // selected_param: index of the input argument. It must be a wide string |
- // pointer or the evaluation result will generate a EVAL_ERROR. |
- // match_str: string to compare against selected_param. |
- // start_position: when its value is from 0 to < 0x7fff it indicates an |
- // offset from the selected_param string where to perform the comparison. If |
- // the value is SeekForward then a substring search is performed. If the |
- // value is SeekToEnd the comparison is performed against the last part of |
- // the selected_param string. |
- // Note that the range in the position (0 to 0x7fff) is dictated by the |
- // current implementation. |
- // match_opts: Indicates additional matching flags. Currently CaseInsensitive |
- // is supported. |
- PolicyOpcode* MakeOpWStringMatch(int16_t selected_param, |
- const wchar_t* match_str, |
- int start_position, |
- StringMatchOptions match_opts, |
- uint32_t options); |
- |
- // Creates an OpNumberAndMatch opcode using the raw memory passed in the ctor. |
- // selected_param: index of the input argument. It must be uint32_t or the |
- // evaluation result will generate a EVAL_ERROR. |
- // match: the value to bitwise AND against selected_param. |
- PolicyOpcode* MakeOpNumberAndMatch(int16_t selected_param, |
- uint32_t match, |
- uint32_t options); |
- |
- private: |
- // Constructs the common part of every opcode. selected_param is the index |
- // of the input param to use when evaluating the opcode. Pass -1 in |
- // selected_param to indicate that no input parameter is required. |
- PolicyOpcode* MakeBase(OpcodeID opcode_id, |
- uint32_t options, |
- int16_t selected_param); |
- |
- // Allocates (and copies) a string (of size length) inside the buffer and |
- // returns the displacement with respect to start. |
- ptrdiff_t AllocRelative(void* start, const wchar_t* str, size_t lenght); |
- |
- // Points to the lowest currently available address of the memory |
- // used to make the opcodes. This pointer increments as opcodes are made. |
- char* memory_top_; |
- |
- // Points to the highest currently available address of the memory |
- // used to make the opcodes. This pointer decrements as opcode strings are |
- // allocated. |
- char* memory_bottom_; |
- |
- DISALLOW_COPY_AND_ASSIGN(OpcodeFactory); |
-}; |
- |
-} // namespace sandbox |
- |
-#endif // SANDBOX_WIN_SRC_POLICY_ENGINE_OPCODES_H_ |