//== ObjCContainersChecker.cpp - Path sensitive checker for CFArray *- 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 // //===----------------------------------------------------------------------===// // // Performs path sensitive checks of Core Foundation static containers like // CFArray. // 1) Check for buffer overflows: // In CFArrayGetArrayAtIndex( myArray, index), if the index is outside the // index space of theArray (0 to N-1 inclusive (where N is the count of // theArray), the behavior is undefined. // //===----------------------------------------------------------------------===// #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" #include "clang/AST/ParentMap.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/ProgramStateTrait.h" using namespace clang; using namespace ento; namespace { class ObjCContainersChecker : public Checker< check::PreStmt<CallExpr>, check::PostStmt<CallExpr>, check::PointerEscape> { mutable std::unique_ptr<BugType> BT; inline void initBugType() const { if (!BT) BT.reset(new BugType(this, "CFArray API", categories::CoreFoundationObjectiveC)); } inline SymbolRef getArraySym(const Expr *E, CheckerContext &C) const { SVal ArrayRef = C.getSVal(E); SymbolRef ArraySym = ArrayRef.getAsSymbol(); return ArraySym; } void addSizeInfo(const Expr *Array, const Expr *Size, CheckerContext &C) const; public: void checkPostStmt(const CallExpr *CE, CheckerContext &C) const; void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; ProgramStateRef checkPointerEscape(ProgramStateRef State, const InvalidatedSymbols &Escaped, const CallEvent *Call, PointerEscapeKind Kind) const; void printState(raw_ostream &OS, ProgramStateRef State, const char *NL, const char *Sep) const override; }; } // end anonymous namespace // ProgramState trait - a map from array symbol to its state. REGISTER_MAP_WITH_PROGRAMSTATE(ArraySizeMap, SymbolRef, DefinedSVal) void ObjCContainersChecker::addSizeInfo(const Expr *Array, const Expr *Size, CheckerContext &C) const { ProgramStateRef State = C.getState(); SVal SizeV = C.getSVal(Size); // Undefined is reported by another checker. if (SizeV.isUnknownOrUndef()) return; // Get the ArrayRef symbol. SVal ArrayRef = C.getSVal(Array); SymbolRef ArraySym = ArrayRef.getAsSymbol(); if (!ArraySym) return; C.addTransition( State->set<ArraySizeMap>(ArraySym, SizeV.castAs<DefinedSVal>())); } void ObjCContainersChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const { StringRef Name = C.getCalleeName(CE); if (Name.empty() || CE->getNumArgs() < 1) return; // Add array size information to the state. if (Name.equals("CFArrayCreate")) { if (CE->getNumArgs() < 3) return; // Note, we can visit the Create method in the post-visit because // the CFIndex parameter is passed in by value and will not be invalidated // by the call. addSizeInfo(CE, CE->getArg(2), C); return; } if (Name.equals("CFArrayGetCount")) { addSizeInfo(CE->getArg(0), CE, C); return; } } void ObjCContainersChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const { StringRef Name = C.getCalleeName(CE); if (Name.empty() || CE->getNumArgs() < 2) return; // Check the array access. if (Name.equals("CFArrayGetValueAtIndex")) { ProgramStateRef State = C.getState(); // Retrieve the size. // Find out if we saw this array symbol before and have information about // it. const Expr *ArrayExpr = CE->getArg(0); SymbolRef ArraySym = getArraySym(ArrayExpr, C); if (!ArraySym) return; const DefinedSVal *Size = State->get<ArraySizeMap>(ArraySym); if (!Size) return; // Get the index. const Expr *IdxExpr = CE->getArg(1); SVal IdxVal = C.getSVal(IdxExpr); if (IdxVal.isUnknownOrUndef()) return; DefinedSVal Idx = IdxVal.castAs<DefinedSVal>(); // Now, check if 'Idx in [0, Size-1]'. const QualType T = IdxExpr->getType(); ProgramStateRef StInBound, StOutBound; std::tie(StInBound, StOutBound) = State->assumeInBoundDual(Idx, *Size, T); if (StOutBound && !StInBound) { ExplodedNode *N = C.generateErrorNode(StOutBound); if (!N) return; initBugType(); auto R = std::make_unique<PathSensitiveBugReport>( *BT, "Index is out of bounds", N); R->addRange(IdxExpr->getSourceRange()); bugreporter::trackExpressionValue(N, IdxExpr, *R, {bugreporter::TrackingKind::Thorough, /*EnableNullFPSuppression=*/false}); C.emitReport(std::move(R)); return; } } } ProgramStateRef ObjCContainersChecker::checkPointerEscape(ProgramStateRef State, const InvalidatedSymbols &Escaped, const CallEvent *Call, PointerEscapeKind Kind) const { for (const auto &Sym : Escaped) { // When a symbol for a mutable array escapes, we can't reason precisely // about its size any more -- so remove it from the map. // Note that we aren't notified here when a CFMutableArrayRef escapes as a // CFArrayRef. This is because CFArrayRef is typedef'd as a pointer to a // const-qualified type. State = State->remove<ArraySizeMap>(Sym); } return State; } void ObjCContainersChecker::printState(raw_ostream &OS, ProgramStateRef State, const char *NL, const char *Sep) const { ArraySizeMapTy Map = State->get<ArraySizeMap>(); if (Map.isEmpty()) return; OS << Sep << "ObjC container sizes :" << NL; for (auto I : Map) { OS << I.first << " : " << I.second << NL; } } /// Register checker. void ento::registerObjCContainersChecker(CheckerManager &mgr) { mgr.registerChecker<ObjCContainersChecker>(); } bool ento::shouldRegisterObjCContainersChecker(const CheckerManager &mgr) { return true; }