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Current File : //compat/linux/proc/68247/root/usr/src/contrib/llvm/tools/clang/lib/StaticAnalyzer/Checkers/MacOSKeychainAPIChecker.cpp |
//==--- MacOSKeychainAPIChecker.cpp ------------------------------*- C++ -*-==// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // This checker flags misuses of KeyChainAPI. In particular, the password data // allocated/returned by SecKeychainItemCopyContent, // SecKeychainFindGenericPassword, SecKeychainFindInternetPassword functions has // to be freed using a call to SecKeychainItemFreeContent. //===----------------------------------------------------------------------===// #include "ClangSACheckers.h" #include "clang/StaticAnalyzer/Core/Checker.h" #include "clang/StaticAnalyzer/Core/CheckerManager.h" #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" #include "llvm/ADT/SmallString.h" using namespace clang; using namespace ento; namespace { class MacOSKeychainAPIChecker : public Checker<check::PreStmt<CallExpr>, check::PreStmt<ReturnStmt>, check::PostStmt<CallExpr>, check::EndPath, check::DeadSymbols> { mutable OwningPtr<BugType> BT; public: /// AllocationState is a part of the checker specific state together with the /// MemRegion corresponding to the allocated data. struct AllocationState { /// The index of the allocator function. unsigned int AllocatorIdx; SymbolRef Region; AllocationState(const Expr *E, unsigned int Idx, SymbolRef R) : AllocatorIdx(Idx), Region(R) {} bool operator==(const AllocationState &X) const { return (AllocatorIdx == X.AllocatorIdx && Region == X.Region); } void Profile(llvm::FoldingSetNodeID &ID) const { ID.AddInteger(AllocatorIdx); ID.AddPointer(Region); } }; void checkPreStmt(const CallExpr *S, CheckerContext &C) const; void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const; void checkPostStmt(const CallExpr *S, CheckerContext &C) const; void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const; void checkEndPath(CheckerContext &C) const; private: typedef std::pair<SymbolRef, const AllocationState*> AllocationPair; typedef llvm::SmallVector<AllocationPair, 2> AllocationPairVec; enum APIKind { /// Denotes functions tracked by this checker. ValidAPI = 0, /// The functions commonly/mistakenly used in place of the given API. ErrorAPI = 1, /// The functions which may allocate the data. These are tracked to reduce /// the false alarm rate. PossibleAPI = 2 }; /// Stores the information about the allocator and deallocator functions - /// these are the functions the checker is tracking. struct ADFunctionInfo { const char* Name; unsigned int Param; unsigned int DeallocatorIdx; APIKind Kind; }; static const unsigned InvalidIdx = 100000; static const unsigned FunctionsToTrackSize = 8; static const ADFunctionInfo FunctionsToTrack[FunctionsToTrackSize]; /// The value, which represents no error return value for allocator functions. static const unsigned NoErr = 0; /// Given the function name, returns the index of the allocator/deallocator /// function. static unsigned getTrackedFunctionIndex(StringRef Name, bool IsAllocator); inline void initBugType() const { if (!BT) BT.reset(new BugType("Improper use of SecKeychain API", "Mac OS API")); } void generateDeallocatorMismatchReport(const AllocationPair &AP, const Expr *ArgExpr, CheckerContext &C) const; /// Find the allocation site for Sym on the path leading to the node N. const Stmt *getAllocationSite(const ExplodedNode *N, SymbolRef Sym, CheckerContext &C) const; BugReport *generateAllocatedDataNotReleasedReport(const AllocationPair &AP, ExplodedNode *N, CheckerContext &C) const; /// Check if RetSym evaluates to an error value in the current state. bool definitelyReturnedError(SymbolRef RetSym, ProgramStateRef State, SValBuilder &Builder, bool noError = false) const; /// Check if RetSym evaluates to a NoErr value in the current state. bool definitelyDidnotReturnError(SymbolRef RetSym, ProgramStateRef State, SValBuilder &Builder) const { return definitelyReturnedError(RetSym, State, Builder, true); } /// Mark an AllocationPair interesting for diagnostic reporting. void markInteresting(BugReport *R, const AllocationPair &AP) const { R->markInteresting(AP.first); R->markInteresting(AP.second->Region); } /// The bug visitor which allows us to print extra diagnostics along the /// BugReport path. For example, showing the allocation site of the leaked /// region. class SecKeychainBugVisitor : public BugReporterVisitorImpl<SecKeychainBugVisitor> { protected: // The allocated region symbol tracked by the main analysis. SymbolRef Sym; public: SecKeychainBugVisitor(SymbolRef S) : Sym(S) {} virtual ~SecKeychainBugVisitor() {} void Profile(llvm::FoldingSetNodeID &ID) const { static int X = 0; ID.AddPointer(&X); ID.AddPointer(Sym); } PathDiagnosticPiece *VisitNode(const ExplodedNode *N, const ExplodedNode *PrevN, BugReporterContext &BRC, BugReport &BR); }; }; } /// ProgramState traits to store the currently allocated (and not yet freed) /// symbols. This is a map from the allocated content symbol to the /// corresponding AllocationState. typedef llvm::ImmutableMap<SymbolRef, MacOSKeychainAPIChecker::AllocationState> AllocatedSetTy; namespace { struct AllocatedData {}; } namespace clang { namespace ento { template<> struct ProgramStateTrait<AllocatedData> : public ProgramStatePartialTrait<AllocatedSetTy > { static void *GDMIndex() { static int index = 0; return &index; } }; }} static bool isEnclosingFunctionParam(const Expr *E) { E = E->IgnoreParenCasts(); if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) { const ValueDecl *VD = DRE->getDecl(); if (isa<ImplicitParamDecl>(VD) || isa<ParmVarDecl>(VD)) return true; } return false; } const MacOSKeychainAPIChecker::ADFunctionInfo MacOSKeychainAPIChecker::FunctionsToTrack[FunctionsToTrackSize] = { {"SecKeychainItemCopyContent", 4, 3, ValidAPI}, // 0 {"SecKeychainFindGenericPassword", 6, 3, ValidAPI}, // 1 {"SecKeychainFindInternetPassword", 13, 3, ValidAPI}, // 2 {"SecKeychainItemFreeContent", 1, InvalidIdx, ValidAPI}, // 3 {"SecKeychainItemCopyAttributesAndData", 5, 5, ValidAPI}, // 4 {"SecKeychainItemFreeAttributesAndData", 1, InvalidIdx, ValidAPI}, // 5 {"free", 0, InvalidIdx, ErrorAPI}, // 6 {"CFStringCreateWithBytesNoCopy", 1, InvalidIdx, PossibleAPI}, // 7 }; unsigned MacOSKeychainAPIChecker::getTrackedFunctionIndex(StringRef Name, bool IsAllocator) { for (unsigned I = 0; I < FunctionsToTrackSize; ++I) { ADFunctionInfo FI = FunctionsToTrack[I]; if (FI.Name != Name) continue; // Make sure the function is of the right type (allocator vs deallocator). if (IsAllocator && (FI.DeallocatorIdx == InvalidIdx)) return InvalidIdx; if (!IsAllocator && (FI.DeallocatorIdx != InvalidIdx)) return InvalidIdx; return I; } // The function is not tracked. return InvalidIdx; } static bool isBadDeallocationArgument(const MemRegion *Arg) { if (!Arg) return false; if (isa<AllocaRegion>(Arg) || isa<BlockDataRegion>(Arg) || isa<TypedRegion>(Arg)) { return true; } return false; } /// Given the address expression, retrieve the value it's pointing to. Assume /// that value is itself an address, and return the corresponding symbol. static SymbolRef getAsPointeeSymbol(const Expr *Expr, CheckerContext &C) { ProgramStateRef State = C.getState(); SVal ArgV = State->getSVal(Expr, C.getLocationContext()); if (const loc::MemRegionVal *X = dyn_cast<loc::MemRegionVal>(&ArgV)) { StoreManager& SM = C.getStoreManager(); SymbolRef sym = SM.getBinding(State->getStore(), *X).getAsLocSymbol(); if (sym) return sym; } return 0; } // When checking for error code, we need to consider the following cases: // 1) noErr / [0] // 2) someErr / [1, inf] // 3) unknown // If noError, returns true iff (1). // If !noError, returns true iff (2). bool MacOSKeychainAPIChecker::definitelyReturnedError(SymbolRef RetSym, ProgramStateRef State, SValBuilder &Builder, bool noError) const { DefinedOrUnknownSVal NoErrVal = Builder.makeIntVal(NoErr, Builder.getSymbolManager().getType(RetSym)); DefinedOrUnknownSVal NoErr = Builder.evalEQ(State, NoErrVal, nonloc::SymbolVal(RetSym)); ProgramStateRef ErrState = State->assume(NoErr, noError); if (ErrState == State) { return true; } return false; } // Report deallocator mismatch. Remove the region from tracking - reporting a // missing free error after this one is redundant. void MacOSKeychainAPIChecker:: generateDeallocatorMismatchReport(const AllocationPair &AP, const Expr *ArgExpr, CheckerContext &C) const { ProgramStateRef State = C.getState(); State = State->remove<AllocatedData>(AP.first); ExplodedNode *N = C.addTransition(State); if (!N) return; initBugType(); SmallString<80> sbuf; llvm::raw_svector_ostream os(sbuf); unsigned int PDeallocIdx = FunctionsToTrack[AP.second->AllocatorIdx].DeallocatorIdx; os << "Deallocator doesn't match the allocator: '" << FunctionsToTrack[PDeallocIdx].Name << "' should be used."; BugReport *Report = new BugReport(*BT, os.str(), N); Report->addVisitor(new SecKeychainBugVisitor(AP.first)); Report->addRange(ArgExpr->getSourceRange()); markInteresting(Report, AP); C.EmitReport(Report); } void MacOSKeychainAPIChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const { unsigned idx = InvalidIdx; ProgramStateRef State = C.getState(); StringRef funName = C.getCalleeName(CE); if (funName.empty()) return; // If it is a call to an allocator function, it could be a double allocation. idx = getTrackedFunctionIndex(funName, true); if (idx != InvalidIdx) { const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param); if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C)) if (const AllocationState *AS = State->get<AllocatedData>(V)) { if (!definitelyReturnedError(AS->Region, State, C.getSValBuilder())) { // Remove the value from the state. The new symbol will be added for // tracking when the second allocator is processed in checkPostStmt(). State = State->remove<AllocatedData>(V); ExplodedNode *N = C.addTransition(State); if (!N) return; initBugType(); SmallString<128> sbuf; llvm::raw_svector_ostream os(sbuf); unsigned int DIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx; os << "Allocated data should be released before another call to " << "the allocator: missing a call to '" << FunctionsToTrack[DIdx].Name << "'."; BugReport *Report = new BugReport(*BT, os.str(), N); Report->addVisitor(new SecKeychainBugVisitor(V)); Report->addRange(ArgExpr->getSourceRange()); Report->markInteresting(AS->Region); C.EmitReport(Report); } } return; } // Is it a call to one of deallocator functions? idx = getTrackedFunctionIndex(funName, false); if (idx == InvalidIdx) return; // Check the argument to the deallocator. const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param); SVal ArgSVal = State->getSVal(ArgExpr, C.getLocationContext()); // Undef is reported by another checker. if (ArgSVal.isUndef()) return; SymbolRef ArgSM = ArgSVal.getAsLocSymbol(); // If the argument is coming from the heap, globals, or unknown, do not // report it. bool RegionArgIsBad = false; if (!ArgSM) { if (!isBadDeallocationArgument(ArgSVal.getAsRegion())) return; RegionArgIsBad = true; } // Is the argument to the call being tracked? const AllocationState *AS = State->get<AllocatedData>(ArgSM); if (!AS && FunctionsToTrack[idx].Kind != ValidAPI) { return; } // If trying to free data which has not been allocated yet, report as a bug. // TODO: We might want a more precise diagnostic for double free // (that would involve tracking all the freed symbols in the checker state). if (!AS || RegionArgIsBad) { // It is possible that this is a false positive - the argument might // have entered as an enclosing function parameter. if (isEnclosingFunctionParam(ArgExpr)) return; ExplodedNode *N = C.addTransition(State); if (!N) return; initBugType(); BugReport *Report = new BugReport(*BT, "Trying to free data which has not been allocated.", N); Report->addRange(ArgExpr->getSourceRange()); if (AS) Report->markInteresting(AS->Region); C.EmitReport(Report); return; } // Process functions which might deallocate. if (FunctionsToTrack[idx].Kind == PossibleAPI) { if (funName == "CFStringCreateWithBytesNoCopy") { const Expr *DeallocatorExpr = CE->getArg(5)->IgnoreParenCasts(); // NULL ~ default deallocator, so warn. if (DeallocatorExpr->isNullPointerConstant(C.getASTContext(), Expr::NPC_ValueDependentIsNotNull)) { const AllocationPair AP = std::make_pair(ArgSM, AS); generateDeallocatorMismatchReport(AP, ArgExpr, C); return; } // One of the default allocators, so warn. if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(DeallocatorExpr)) { StringRef DeallocatorName = DE->getFoundDecl()->getName(); if (DeallocatorName == "kCFAllocatorDefault" || DeallocatorName == "kCFAllocatorSystemDefault" || DeallocatorName == "kCFAllocatorMalloc") { const AllocationPair AP = std::make_pair(ArgSM, AS); generateDeallocatorMismatchReport(AP, ArgExpr, C); return; } // If kCFAllocatorNull, which does not deallocate, we still have to // find the deallocator. Otherwise, assume that the user had written a // custom deallocator which does the right thing. if (DE->getFoundDecl()->getName() != "kCFAllocatorNull") { State = State->remove<AllocatedData>(ArgSM); C.addTransition(State); return; } } } return; } // The call is deallocating a value we previously allocated, so remove it // from the next state. State = State->remove<AllocatedData>(ArgSM); // Check if the proper deallocator is used. unsigned int PDeallocIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx; if (PDeallocIdx != idx || (FunctionsToTrack[idx].Kind == ErrorAPI)) { const AllocationPair AP = std::make_pair(ArgSM, AS); generateDeallocatorMismatchReport(AP, ArgExpr, C); return; } // If the buffer can be null and the return status can be an error, // report a bad call to free. if (State->assume(cast<DefinedSVal>(ArgSVal), false) && !definitelyDidnotReturnError(AS->Region, State, C.getSValBuilder())) { ExplodedNode *N = C.addTransition(State); if (!N) return; initBugType(); BugReport *Report = new BugReport(*BT, "Only call free if a valid (non-NULL) buffer was returned.", N); Report->addVisitor(new SecKeychainBugVisitor(ArgSM)); Report->addRange(ArgExpr->getSourceRange()); Report->markInteresting(AS->Region); C.EmitReport(Report); return; } C.addTransition(State); } void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const { ProgramStateRef State = C.getState(); StringRef funName = C.getCalleeName(CE); // If a value has been allocated, add it to the set for tracking. unsigned idx = getTrackedFunctionIndex(funName, true); if (idx == InvalidIdx) return; const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param); // If the argument entered as an enclosing function parameter, skip it to // avoid false positives. if (isEnclosingFunctionParam(ArgExpr) && C.getLocationContext()->getParent() == 0) return; if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C)) { // If the argument points to something that's not a symbolic region, it // can be: // - unknown (cannot reason about it) // - undefined (already reported by other checker) // - constant (null - should not be tracked, // other constant will generate a compiler warning) // - goto (should be reported by other checker) // The call return value symbol should stay alive for as long as the // allocated value symbol, since our diagnostics depend on the value // returned by the call. Ex: Data should only be freed if noErr was // returned during allocation.) SymbolRef RetStatusSymbol = State->getSVal(CE, C.getLocationContext()).getAsSymbol(); C.getSymbolManager().addSymbolDependency(V, RetStatusSymbol); // Track the allocated value in the checker state. State = State->set<AllocatedData>(V, AllocationState(ArgExpr, idx, RetStatusSymbol)); assert(State); C.addTransition(State); } } void MacOSKeychainAPIChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const { const Expr *retExpr = S->getRetValue(); if (!retExpr) return; // If inside inlined call, skip it. const LocationContext *LC = C.getLocationContext(); if (LC->getParent() != 0) return; // Check if the value is escaping through the return. ProgramStateRef state = C.getState(); SymbolRef sym = state->getSVal(retExpr, LC).getAsLocSymbol(); if (!sym) return; state = state->remove<AllocatedData>(sym); // Proceed from the new state. C.addTransition(state); } // TODO: This logic is the same as in Malloc checker. const Stmt * MacOSKeychainAPIChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym, CheckerContext &C) const { const LocationContext *LeakContext = N->getLocationContext(); // Walk the ExplodedGraph backwards and find the first node that referred to // the tracked symbol. const ExplodedNode *AllocNode = N; while (N) { if (!N->getState()->get<AllocatedData>(Sym)) break; // Allocation node, is the last node in the current context in which the // symbol was tracked. if (N->getLocationContext() == LeakContext) AllocNode = N; N = N->pred_empty() ? NULL : *(N->pred_begin()); } ProgramPoint P = AllocNode->getLocation(); if (!isa<StmtPoint>(P)) return 0; return cast<clang::PostStmt>(P).getStmt(); } BugReport *MacOSKeychainAPIChecker:: generateAllocatedDataNotReleasedReport(const AllocationPair &AP, ExplodedNode *N, CheckerContext &C) const { const ADFunctionInfo &FI = FunctionsToTrack[AP.second->AllocatorIdx]; initBugType(); SmallString<70> sbuf; llvm::raw_svector_ostream os(sbuf); os << "Allocated data is not released: missing a call to '" << FunctionsToTrack[FI.DeallocatorIdx].Name << "'."; // Most bug reports are cached at the location where they occurred. // With leaks, we want to unique them by the location where they were // allocated, and only report a single path. PathDiagnosticLocation LocUsedForUniqueing; if (const Stmt *AllocStmt = getAllocationSite(N, AP.first, C)) LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt, C.getSourceManager(), N->getLocationContext()); BugReport *Report = new BugReport(*BT, os.str(), N, LocUsedForUniqueing); Report->addVisitor(new SecKeychainBugVisitor(AP.first)); markInteresting(Report, AP); return Report; } void MacOSKeychainAPIChecker::checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const { ProgramStateRef State = C.getState(); AllocatedSetTy ASet = State->get<AllocatedData>(); if (ASet.isEmpty()) return; bool Changed = false; AllocationPairVec Errors; for (AllocatedSetTy::iterator I = ASet.begin(), E = ASet.end(); I != E; ++I) { if (SR.isLive(I->first)) continue; Changed = true; State = State->remove<AllocatedData>(I->first); // If the allocated symbol is null or if the allocation call might have // returned an error, do not report. if (State->getSymVal(I->first) || definitelyReturnedError(I->second.Region, State, C.getSValBuilder())) continue; Errors.push_back(std::make_pair(I->first, &I->second)); } if (!Changed) { // Generate the new, cleaned up state. C.addTransition(State); return; } static SimpleProgramPointTag Tag("MacOSKeychainAPIChecker : DeadSymbolsLeak"); ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag); // Generate the error reports. for (AllocationPairVec::iterator I = Errors.begin(), E = Errors.end(); I != E; ++I) { C.EmitReport(generateAllocatedDataNotReleasedReport(*I, N, C)); } // Generate the new, cleaned up state. C.addTransition(State, N); } // TODO: Remove this after we ensure that checkDeadSymbols are always called. void MacOSKeychainAPIChecker::checkEndPath(CheckerContext &C) const { ProgramStateRef state = C.getState(); // If inside inlined call, skip it. if (C.getLocationContext()->getParent() != 0) return; AllocatedSetTy AS = state->get<AllocatedData>(); if (AS.isEmpty()) return; // Anything which has been allocated but not freed (nor escaped) will be // found here, so report it. bool Changed = false; AllocationPairVec Errors; for (AllocatedSetTy::iterator I = AS.begin(), E = AS.end(); I != E; ++I ) { Changed = true; state = state->remove<AllocatedData>(I->first); // If the allocated symbol is null or if error code was returned at // allocation, do not report. if (state->getSymVal(I.getKey()) || definitelyReturnedError(I->second.Region, state, C.getSValBuilder())) { continue; } Errors.push_back(std::make_pair(I->first, &I->second)); } // If no change, do not generate a new state. if (!Changed) { C.addTransition(state); return; } static SimpleProgramPointTag Tag("MacOSKeychainAPIChecker : EndPathLeak"); ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag); // Generate the error reports. for (AllocationPairVec::iterator I = Errors.begin(), E = Errors.end(); I != E; ++I) { C.EmitReport(generateAllocatedDataNotReleasedReport(*I, N, C)); } C.addTransition(state, N); } PathDiagnosticPiece *MacOSKeychainAPIChecker::SecKeychainBugVisitor::VisitNode( const ExplodedNode *N, const ExplodedNode *PrevN, BugReporterContext &BRC, BugReport &BR) { const AllocationState *AS = N->getState()->get<AllocatedData>(Sym); if (!AS) return 0; const AllocationState *ASPrev = PrevN->getState()->get<AllocatedData>(Sym); if (ASPrev) return 0; // (!ASPrev && AS) ~ We started tracking symbol in node N, it must be the // allocation site. const CallExpr *CE = cast<CallExpr>(cast<StmtPoint>(N->getLocation()) .getStmt()); const FunctionDecl *funDecl = CE->getDirectCallee(); assert(funDecl && "We do not support indirect function calls as of now."); StringRef funName = funDecl->getName(); // Get the expression of the corresponding argument. unsigned Idx = getTrackedFunctionIndex(funName, true); assert(Idx != InvalidIdx && "This should be a call to an allocator."); const Expr *ArgExpr = CE->getArg(FunctionsToTrack[Idx].Param); PathDiagnosticLocation Pos(ArgExpr, BRC.getSourceManager(), N->getLocationContext()); return new PathDiagnosticEventPiece(Pos, "Data is allocated here."); } void ento::registerMacOSKeychainAPIChecker(CheckerManager &mgr) { mgr.registerChecker<MacOSKeychainAPIChecker>(); }