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//== ReturnPointerRangeChecker.cpp ------------------------------*- C++ -*--==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines ReturnPointerRangeChecker, which is a path-sensitive check
// which looks for an out-of-bound pointer being returned to callers.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicSize.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
using namespace clang;
using namespace ento;
namespace {
class ReturnPointerRangeChecker :
public Checker< check::PreStmt<ReturnStmt> > {
mutable std::unique_ptr<BuiltinBug> BT;
public:
void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
};
}
void ReturnPointerRangeChecker::checkPreStmt(const ReturnStmt *RS,
CheckerContext &C) const {
ProgramStateRef state = C.getState();
const Expr *RetE = RS->getRetValue();
if (!RetE)
return;
SVal V = C.getSVal(RetE);
const MemRegion *R = V.getAsRegion();
const ElementRegion *ER = dyn_cast_or_null<ElementRegion>(R);
if (!ER)
return;
DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
// Zero index is always in bound, this also passes ElementRegions created for
// pointer casts.
if (Idx.isZeroConstant())
return;
// FIXME: All of this out-of-bounds checking should eventually be refactored
// into a common place.
DefinedOrUnknownSVal ElementCount = getDynamicElementCount(
state, ER->getSuperRegion(), C.getSValBuilder(), ER->getValueType());
ProgramStateRef StInBound = state->assumeInBound(Idx, ElementCount, true);
ProgramStateRef StOutBound = state->assumeInBound(Idx, ElementCount, false);
if (StOutBound && !StInBound) {
ExplodedNode *N = C.generateErrorNode(StOutBound);
if (!N)
return;
// FIXME: This bug correspond to CWE-466. Eventually we should have bug
// types explicitly reference such exploit categories (when applicable).
if (!BT)
BT.reset(new BuiltinBug(
this, "Return of pointer value outside of expected range",
"Returned pointer value points outside the original object "
"(potential buffer overflow)"));
// FIXME: It would be nice to eventually make this diagnostic more clear,
// e.g., by referencing the original declaration or by saying *why* this
// reference is outside the range.
// Generate a report for this bug.
auto report =
std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
report->addRange(RetE->getSourceRange());
C.emitReport(std::move(report));
}
}
void ento::registerReturnPointerRangeChecker(CheckerManager &mgr) {
mgr.registerChecker<ReturnPointerRangeChecker>();
}
bool ento::shouldRegisterReturnPointerRangeChecker(const CheckerManager &mgr) {
return true;
}
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