1 //== ObjCContainersChecker.cpp - Path sensitive checker for CFArray *- C++ -*=// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // Performs path sensitive checks of Core Foundation static containers like 11 // CFArray. 12 // 1) Check for buffer overflows: 13 // In CFArrayGetArrayAtIndex( myArray, index), if the index is outside the 14 // index space of theArray (0 to N-1 inclusive (where N is the count of 15 // theArray), the behavior is undefined. 16 // 17 //===----------------------------------------------------------------------===// 18 19 #include "ClangSACheckers.h" 20 #include "clang/StaticAnalyzer/Core/Checker.h" 21 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 23 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" 24 #include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h" 25 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 26 #include "clang/AST/ParentMap.h" 27 28 using namespace clang; 29 using namespace ento; 30 31 namespace { 32 class ObjCContainersChecker : public Checker< check::PreStmt<CallExpr>, 33 check::PostStmt<CallExpr> > { 34 mutable OwningPtr<BugType> BT; 35 inline void initBugType() const { 36 if (!BT) 37 BT.reset(new BugType("CFArray API", 38 categories::CoreFoundationObjectiveC)); 39 } 40 41 inline SymbolRef getArraySym(const Expr *E, CheckerContext &C) const { 42 SVal ArrayRef = C.getState()->getSVal(E, C.getLocationContext()); 43 SymbolRef ArraySym = ArrayRef.getAsSymbol(); 44 return ArraySym; 45 } 46 47 void addSizeInfo(const Expr *Array, const Expr *Size, 48 CheckerContext &C) const; 49 50 public: 51 /// A tag to id this checker. 52 static void *getTag() { static int Tag; return &Tag; } 53 54 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const; 55 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 56 }; 57 } // end anonymous namespace 58 59 // ProgramState trait - a map from array symbol to it's state. 60 typedef llvm::ImmutableMap<SymbolRef, DefinedSVal> ArraySizeM; 61 62 namespace { struct ArraySizeMap {}; } 63 namespace clang { namespace ento { 64 template<> struct ProgramStateTrait<ArraySizeMap> 65 : public ProgramStatePartialTrait<ArraySizeM > { 66 static void *GDMIndex() { return ObjCContainersChecker::getTag(); } 67 }; 68 }} 69 70 void ObjCContainersChecker::addSizeInfo(const Expr *Array, const Expr *Size, 71 CheckerContext &C) const { 72 ProgramStateRef State = C.getState(); 73 SVal SizeV = State->getSVal(Size, C.getLocationContext()); 74 // Undefined is reported by another checker. 75 if (SizeV.isUnknownOrUndef()) 76 return; 77 78 // Get the ArrayRef symbol. 79 SVal ArrayRef = State->getSVal(Array, C.getLocationContext()); 80 SymbolRef ArraySym = ArrayRef.getAsSymbol(); 81 if (!ArraySym) 82 return; 83 84 C.addTransition(State->set<ArraySizeMap>(ArraySym, cast<DefinedSVal>(SizeV))); 85 return; 86 } 87 88 void ObjCContainersChecker::checkPostStmt(const CallExpr *CE, 89 CheckerContext &C) const { 90 StringRef Name = C.getCalleeName(CE); 91 if (Name.empty() || CE->getNumArgs() < 1) 92 return; 93 94 // Add array size information to the state. 95 if (Name.equals("CFArrayCreate")) { 96 if (CE->getNumArgs() < 3) 97 return; 98 // Note, we can visit the Create method in the post-visit because 99 // the CFIndex parameter is passed in by value and will not be invalidated 100 // by the call. 101 addSizeInfo(CE, CE->getArg(2), C); 102 return; 103 } 104 105 if (Name.equals("CFArrayGetCount")) { 106 addSizeInfo(CE->getArg(0), CE, C); 107 return; 108 } 109 } 110 111 void ObjCContainersChecker::checkPreStmt(const CallExpr *CE, 112 CheckerContext &C) const { 113 StringRef Name = C.getCalleeName(CE); 114 if (Name.empty() || CE->getNumArgs() < 2) 115 return; 116 117 // Check the array access. 118 if (Name.equals("CFArrayGetValueAtIndex")) { 119 ProgramStateRef State = C.getState(); 120 // Retrieve the size. 121 // Find out if we saw this array symbol before and have information about it. 122 const Expr *ArrayExpr = CE->getArg(0); 123 SymbolRef ArraySym = getArraySym(ArrayExpr, C); 124 if (!ArraySym) 125 return; 126 127 const DefinedSVal *Size = State->get<ArraySizeMap>(ArraySym); 128 129 if (!Size) 130 return; 131 132 // Get the index. 133 const Expr *IdxExpr = CE->getArg(1); 134 SVal IdxVal = State->getSVal(IdxExpr, C.getLocationContext()); 135 if (IdxVal.isUnknownOrUndef()) 136 return; 137 DefinedSVal Idx = cast<DefinedSVal>(IdxVal); 138 139 // Now, check if 'Idx in [0, Size-1]'. 140 const QualType T = IdxExpr->getType(); 141 ProgramStateRef StInBound = State->assumeInBound(Idx, *Size, true, T); 142 ProgramStateRef StOutBound = State->assumeInBound(Idx, *Size, false, T); 143 if (StOutBound && !StInBound) { 144 ExplodedNode *N = C.generateSink(StOutBound); 145 if (!N) 146 return; 147 initBugType(); 148 BugReport *R = new BugReport(*BT, "Index is out of bounds", N); 149 R->addRange(IdxExpr->getSourceRange()); 150 C.EmitReport(R); 151 return; 152 } 153 } 154 } 155 156 /// Register checker. 157 void ento::registerObjCContainersChecker(CheckerManager &mgr) { 158 mgr.registerChecker<ObjCContainersChecker>(); 159 } 160