187 lines · cpp
1//== ObjCContainersChecker.cpp - Path sensitive checker for CFArray *- C++ -*=//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// Performs path sensitive checks of Core Foundation static containers like10// CFArray.11// 1) Check for buffer overflows:12// In CFArrayGetArrayAtIndex( myArray, index), if the index is outside the13// index space of theArray (0 to N-1 inclusive (where N is the count of14// theArray), the behavior is undefined.15//16//===----------------------------------------------------------------------===//17 18#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"19#include "clang/AST/ParentMap.h"20#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"21#include "clang/StaticAnalyzer/Core/Checker.h"22#include "clang/StaticAnalyzer/Core/CheckerManager.h"23#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"24#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"25 26using namespace clang;27using namespace ento;28 29namespace {30class ObjCContainersChecker : public Checker< check::PreStmt<CallExpr>,31 check::PostStmt<CallExpr>,32 check::PointerEscape> {33 const BugType BT{this, "CFArray API", categories::CoreFoundationObjectiveC};34 35 inline SymbolRef getArraySym(const Expr *E, CheckerContext &C) const {36 SVal ArrayRef = C.getSVal(E);37 SymbolRef ArraySym = ArrayRef.getAsSymbol();38 return ArraySym;39 }40 41 void addSizeInfo(const Expr *Array, const Expr *Size,42 CheckerContext &C) const;43 44public:45 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;46 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;47 ProgramStateRef checkPointerEscape(ProgramStateRef State,48 const InvalidatedSymbols &Escaped,49 const CallEvent *Call,50 PointerEscapeKind Kind) const;51 52 void printState(raw_ostream &OS, ProgramStateRef State,53 const char *NL, const char *Sep) const override;54};55} // end anonymous namespace56 57// ProgramState trait - a map from array symbol to its state.58REGISTER_MAP_WITH_PROGRAMSTATE(ArraySizeMap, SymbolRef, DefinedSVal)59 60void ObjCContainersChecker::addSizeInfo(const Expr *Array, const Expr *Size,61 CheckerContext &C) const {62 ProgramStateRef State = C.getState();63 SVal SizeV = C.getSVal(Size);64 // Undefined is reported by another checker.65 if (SizeV.isUnknownOrUndef())66 return;67 68 // Get the ArrayRef symbol.69 SVal ArrayRef = C.getSVal(Array);70 SymbolRef ArraySym = ArrayRef.getAsSymbol();71 if (!ArraySym)72 return;73 74 C.addTransition(75 State->set<ArraySizeMap>(ArraySym, SizeV.castAs<DefinedSVal>()));76}77 78void ObjCContainersChecker::checkPostStmt(const CallExpr *CE,79 CheckerContext &C) const {80 StringRef Name = C.getCalleeName(CE);81 if (Name.empty() || CE->getNumArgs() < 1)82 return;83 84 // Add array size information to the state.85 if (Name == "CFArrayCreate") {86 if (CE->getNumArgs() < 3)87 return;88 // Note, we can visit the Create method in the post-visit because89 // the CFIndex parameter is passed in by value and will not be invalidated90 // by the call.91 addSizeInfo(CE, CE->getArg(2), C);92 return;93 }94 95 if (Name == "CFArrayGetCount") {96 addSizeInfo(CE->getArg(0), CE, C);97 return;98 }99}100 101void ObjCContainersChecker::checkPreStmt(const CallExpr *CE,102 CheckerContext &C) const {103 StringRef Name = C.getCalleeName(CE);104 if (Name.empty() || CE->getNumArgs() < 2)105 return;106 107 // Check the array access.108 if (Name == "CFArrayGetValueAtIndex") {109 ProgramStateRef State = C.getState();110 // Retrieve the size.111 // Find out if we saw this array symbol before and have information about112 // it.113 const Expr *ArrayExpr = CE->getArg(0);114 SymbolRef ArraySym = getArraySym(ArrayExpr, C);115 if (!ArraySym)116 return;117 118 const DefinedSVal *Size = State->get<ArraySizeMap>(ArraySym);119 120 if (!Size)121 return;122 123 // Get the index.124 const Expr *IdxExpr = CE->getArg(1);125 SVal IdxVal = C.getSVal(IdxExpr);126 if (IdxVal.isUnknownOrUndef())127 return;128 DefinedSVal Idx = IdxVal.castAs<DefinedSVal>();129 130 // Now, check if 'Idx in [0, Size-1]'.131 const QualType T = IdxExpr->getType();132 ProgramStateRef StInBound, StOutBound;133 std::tie(StInBound, StOutBound) = State->assumeInBoundDual(Idx, *Size, T);134 if (StOutBound && !StInBound) {135 ExplodedNode *N = C.generateErrorNode(StOutBound);136 if (!N)137 return;138 139 auto R = std::make_unique<PathSensitiveBugReport>(140 BT, "Index is out of bounds", N);141 R->addRange(IdxExpr->getSourceRange());142 bugreporter::trackExpressionValue(N, IdxExpr, *R,143 {bugreporter::TrackingKind::Thorough,144 /*EnableNullFPSuppression=*/false});145 C.emitReport(std::move(R));146 return;147 }148 }149}150 151ProgramStateRef152ObjCContainersChecker::checkPointerEscape(ProgramStateRef State,153 const InvalidatedSymbols &Escaped,154 const CallEvent *Call,155 PointerEscapeKind Kind) const {156 for (const auto &Sym : Escaped) {157 // When a symbol for a mutable array escapes, we can't reason precisely158 // about its size any more -- so remove it from the map.159 // Note that we aren't notified here when a CFMutableArrayRef escapes as a160 // CFArrayRef. This is because CFArrayRef is typedef'd as a pointer to a161 // const-qualified type.162 State = State->remove<ArraySizeMap>(Sym);163 }164 return State;165}166 167void ObjCContainersChecker::printState(raw_ostream &OS, ProgramStateRef State,168 const char *NL, const char *Sep) const {169 ArraySizeMapTy Map = State->get<ArraySizeMap>();170 if (Map.isEmpty())171 return;172 173 OS << Sep << "ObjC container sizes :" << NL;174 for (auto I : Map) {175 OS << I.first << " : " << I.second << NL;176 }177}178 179/// Register checker.180void ento::registerObjCContainersChecker(CheckerManager &mgr) {181 mgr.registerChecker<ObjCContainersChecker>();182}183 184bool ento::shouldRegisterObjCContainersChecker(const CheckerManager &mgr) {185 return true;186}187