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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 "sandbox/src/policy_engine_processor.h"
namespace sandbox {
void PolicyProcessor::SetInternalState(size_t index, EvalResult result) {
state_.current_index_ = index;
state_.current_result_ = result;
}
EvalResult PolicyProcessor::GetAction() const {
return state_.current_result_;
}
// Decides if an opcode can be skipped (not evaluated) or not. The function
// takes as inputs the opcode and the current evaluation context and returns
// true if the opcode should be skipped or not and also can set keep_skipping
// to false to signal that the current instruction should be skipped but not
// the next after the current one.
bool SkipOpcode(PolicyOpcode& opcode, MatchContext* context,
bool* keep_skipping) {
if (opcode.IsAction()) {
uint32 options = context->options;
context->Clear();
*keep_skipping = false;
return (kPolUseOREval == options)? false : true;
}
*keep_skipping = true;
return true;
}
PolicyResult PolicyProcessor::Evaluate(uint32 options,
ParameterSet* parameters,
size_t param_count) {
if (NULL == policy_) {
return NO_POLICY_MATCH;
}
if (0 == policy_->opcode_count) {
return NO_POLICY_MATCH;
}
if (!(kShortEval & options)) {
return POLICY_ERROR;
}
MatchContext context;
bool evaluation = false;
bool skip_group = false;
SetInternalState(0, EVAL_FALSE);
size_t count = policy_->opcode_count;
// Loop over all the opcodes Evaluating in sequence. Since we only support
// short circuit evaluation, we stop as soon as we find an 'action' opcode
// and the current evaluation is true.
//
// Skipping opcodes can happen when we are in AND mode (!kPolUseOREval) and
// have got EVAL_FALSE or when we are in OR mode (kPolUseOREval) and got
// EVAL_TRUE. Skipping will stop at the next action opcode or at the opcode
// after the action depending on kPolUseOREval.
for (size_t ix = 0; ix != count; ++ix) {
PolicyOpcode& opcode = policy_->opcodes[ix];
// Skipping block.
if (skip_group) {
if (SkipOpcode(opcode, &context, &skip_group)) {
continue;
}
}
// Evaluation block.
EvalResult result = opcode.Evaluate(parameters, param_count, &context);
switch (result) {
case EVAL_FALSE:
evaluation = false;
if (kPolUseOREval != context.options) {
skip_group = true;
}
break;
case EVAL_ERROR:
if (kStopOnErrors & options) {
return POLICY_ERROR;
}
break;
case EVAL_TRUE:
evaluation = true;
if (kPolUseOREval == context.options) {
skip_group = true;
}
break;
default:
// We have evaluated an action.
SetInternalState(ix, result);
return POLICY_MATCH;
}
}
if (evaluation) {
// Reaching the end of the policy with a positive evaluation is probably
// an error: we did not find a final action opcode?
return POLICY_ERROR;
}
return NO_POLICY_MATCH;
}
} // namespace sandbox
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