| //== 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/BugReporterVisitors.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/DynamicExtent.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()); |
| |
| // We assume that the location after the last element in the array is used as |
| // end() iterator. Reporting on these would return too many false positives. |
| if (Idx == ElementCount) |
| return; |
| |
| 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, "Buffer overflow", |
| "Returned pointer value points outside the original object " |
| "(potential buffer overflow)")); |
| |
| // Generate a report for this bug. |
| auto Report = |
| std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N); |
| Report->addRange(RetE->getSourceRange()); |
| |
| const auto ConcreteElementCount = ElementCount.getAs<nonloc::ConcreteInt>(); |
| const auto ConcreteIdx = Idx.getAs<nonloc::ConcreteInt>(); |
| |
| const auto *DeclR = ER->getSuperRegion()->getAs<DeclRegion>(); |
| |
| if (DeclR) |
| Report->addNote("Original object declared here", |
| {DeclR->getDecl(), C.getSourceManager()}); |
| |
| if (ConcreteElementCount) { |
| SmallString<128> SBuf; |
| llvm::raw_svector_ostream OS(SBuf); |
| OS << "Original object "; |
| if (DeclR) { |
| OS << "'"; |
| DeclR->getDecl()->printName(OS); |
| OS << "' "; |
| } |
| OS << "is an array of " << ConcreteElementCount->getValue() << " '"; |
| ER->getValueType().print(OS, |
| PrintingPolicy(C.getASTContext().getLangOpts())); |
| OS << "' objects"; |
| if (ConcreteIdx) { |
| OS << ", returned pointer points at index " << ConcreteIdx->getValue(); |
| } |
| |
| Report->addNote(SBuf, |
| {RetE, C.getSourceManager(), C.getLocationContext()}); |
| } |
| |
| bugreporter::trackExpressionValue(N, RetE, *Report); |
| |
| C.emitReport(std::move(Report)); |
| } |
| } |
| |
| void ento::registerReturnPointerRangeChecker(CheckerManager &mgr) { |
| mgr.registerChecker<ReturnPointerRangeChecker>(); |
| } |
| |
| bool ento::shouldRegisterReturnPointerRangeChecker(const CheckerManager &mgr) { |
| return true; |
| } |