| //==--- 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" |
| |
| 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 llvm::OwningPtr<BugType> BT; |
| |
| public: |
| /// AllocationState is a part of the checker specific state together with the |
| /// MemRegion corresponding to the allocated data. |
| struct AllocationState { |
| const Expr *Address; |
| /// The index of the allocator function. |
| unsigned int AllocatorIdx; |
| SymbolRef RetValue; |
| |
| AllocationState(const Expr *E, unsigned int Idx, SymbolRef R) : |
| Address(E), |
| AllocatorIdx(Idx), |
| RetValue(R) {} |
| |
| bool operator==(const AllocationState &X) const { |
| return Address == X.Address; |
| } |
| void Profile(llvm::FoldingSetNodeID &ID) const { |
| ID.AddPointer(Address); |
| ID.AddInteger(AllocatorIdx); |
| } |
| }; |
| |
| 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(EndOfFunctionNodeBuilder &B, ExprEngine &Eng) const; |
| |
| private: |
| /// 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; |
| }; |
| static const unsigned InvalidIdx = 100000; |
| static const unsigned FunctionsToTrackSize = 6; |
| 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. |
| unsigned getTrackedFunctionIndex(StringRef Name, bool IsAllocator) const; |
| |
| inline void initBugType() const { |
| if (!BT) |
| BT.reset(new BugType("Improper use of SecKeychain API", "Mac OS API")); |
| } |
| |
| RangedBugReport *generateAllocatedDataNotReleasedReport( |
| const AllocationState &AS, |
| ExplodedNode *N) const; |
| |
| /// Check if RetSym evaluates to an error value in the current state. |
| bool definitelyReturnedError(SymbolRef RetSym, |
| const ProgramState *State, |
| SValBuilder &Builder, |
| bool noError = false) const; |
| |
| /// Check if RetSym evaluates to a NoErr value in the current state. |
| bool definitelyDidnotReturnError(SymbolRef RetSym, |
| const ProgramState *State, |
| SValBuilder &Builder) const { |
| return definitelyReturnedError(RetSym, State, Builder, true); |
| } |
| |
| }; |
| } |
| |
| /// 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}, // 0 |
| {"SecKeychainFindGenericPassword", 6, 3}, // 1 |
| {"SecKeychainFindInternetPassword", 13, 3}, // 2 |
| {"SecKeychainItemFreeContent", 1, InvalidIdx}, // 3 |
| {"SecKeychainItemCopyAttributesAndData", 5, 5}, // 4 |
| {"SecKeychainItemFreeAttributesAndData", 1, InvalidIdx}, // 5 |
| }; |
| |
| unsigned MacOSKeychainAPIChecker::getTrackedFunctionIndex(StringRef Name, |
| bool IsAllocator) const { |
| 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 SymbolRef getSymbolForRegion(CheckerContext &C, |
| const MemRegion *R) { |
| if (!isa<SymbolicRegion>(R)) |
| return 0; |
| return cast<SymbolicRegion>(R)->getSymbol(); |
| } |
| |
| static bool isBadDeallocationArgument(const MemRegion *Arg) { |
| 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) { |
| const ProgramState *State = C.getState(); |
| SVal ArgV = State->getSVal(Expr); |
| |
| if (const loc::MemRegionVal *X = dyn_cast<loc::MemRegionVal>(&ArgV)) { |
| StoreManager& SM = C.getStoreManager(); |
| const MemRegion *V = SM.Retrieve(State->getStore(), *X).getAsRegion(); |
| if (V) |
| return getSymbolForRegion(C, V); |
| } |
| 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, |
| const ProgramState *State, |
| SValBuilder &Builder, |
| bool noError) const { |
| DefinedOrUnknownSVal NoErrVal = Builder.makeIntVal(NoErr, |
| Builder.getSymbolManager().getType(RetSym)); |
| DefinedOrUnknownSVal NoErr = Builder.evalEQ(State, NoErrVal, |
| nonloc::SymbolVal(RetSym)); |
| const ProgramState *ErrState = State->assume(NoErr, noError); |
| if (ErrState == State) { |
| return true; |
| } |
| |
| return false; |
| } |
| |
| void MacOSKeychainAPIChecker::checkPreStmt(const CallExpr *CE, |
| CheckerContext &C) const { |
| const ProgramState *State = C.getState(); |
| const Expr *Callee = CE->getCallee(); |
| SVal L = State->getSVal(Callee); |
| unsigned idx = InvalidIdx; |
| |
| const FunctionDecl *funDecl = L.getAsFunctionDecl(); |
| if (!funDecl) |
| return; |
| IdentifierInfo *funI = funDecl->getIdentifier(); |
| if (!funI) |
| return; |
| StringRef funName = funI->getName(); |
| |
| // 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)) { |
| ExplodedNode *N = C.generateSink(State); |
| if (!N) |
| return; |
| initBugType(); |
| llvm::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 |
| << "'."; |
| RangedBugReport *Report = new RangedBugReport(*BT, os.str(), N); |
| Report->addRange(ArgExpr->getSourceRange()); |
| 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); |
| |
| // Undef is reported by another checker. |
| if (ArgSVal.isUndef()) |
| return; |
| |
| const MemRegion *Arg = ArgSVal.getAsRegion(); |
| if (!Arg) |
| return; |
| |
| SymbolRef ArgSM = getSymbolForRegion(C, Arg); |
| bool RegionArgIsBad = ArgSM ? false : isBadDeallocationArgument(Arg); |
| // If the argument is coming from the heap, globals, or unknown, do not |
| // report it. |
| if (!ArgSM && !RegionArgIsBad) |
| return; |
| |
| // If trying to free data which has not been allocated yet, report as a bug. |
| const AllocationState *AS = State->get<AllocatedData>(ArgSM); |
| 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.generateNode(State); |
| if (!N) |
| return; |
| initBugType(); |
| RangedBugReport *Report = new RangedBugReport(*BT, |
| "Trying to free data which has not been allocated.", N); |
| Report->addRange(ArgExpr->getSourceRange()); |
| C.EmitReport(Report); |
| return; |
| } |
| |
| // Check if the proper deallocator is used. |
| unsigned int PDeallocIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx; |
| if (PDeallocIdx != idx) { |
| ExplodedNode *N = C.generateSink(State); |
| if (!N) |
| return; |
| initBugType(); |
| |
| llvm::SmallString<80> sbuf; |
| llvm::raw_svector_ostream os(sbuf); |
| os << "Allocator doesn't match the deallocator: '" |
| << FunctionsToTrack[PDeallocIdx].Name << "' should be used."; |
| RangedBugReport *Report = new RangedBugReport(*BT, os.str(), N); |
| Report->addRange(ArgExpr->getSourceRange()); |
| C.EmitReport(Report); |
| return; |
| } |
| |
| // The call is deallocating a value we previously allocated, so remove it |
| // from the next state. |
| State = State->remove<AllocatedData>(ArgSM); |
| |
| // If the return status is undefined or is error, report a bad call to free. |
| if (!definitelyDidnotReturnError(AS->RetValue, State, C.getSValBuilder())) { |
| ExplodedNode *N = C.generateNode(State); |
| if (!N) |
| return; |
| initBugType(); |
| RangedBugReport *Report = new RangedBugReport(*BT, |
| "Call to free data when error was returned during allocation.", N); |
| Report->addRange(ArgExpr->getSourceRange()); |
| C.EmitReport(Report); |
| return; |
| } |
| |
| C.addTransition(State); |
| } |
| |
| void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE, |
| CheckerContext &C) const { |
| const ProgramState *State = C.getState(); |
| const Expr *Callee = CE->getCallee(); |
| SVal L = State->getSVal(Callee); |
| |
| const FunctionDecl *funDecl = L.getAsFunctionDecl(); |
| if (!funDecl) |
| return; |
| IdentifierInfo *funI = funDecl->getIdentifier(); |
| if (!funI) |
| return; |
| StringRef funName = funI->getName(); |
| |
| // 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)) |
| 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).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; |
| |
| // Check if the value is escaping through the return. |
| const ProgramState *state = C.getState(); |
| const MemRegion *V = state->getSVal(retExpr).getAsRegion(); |
| if (!V) |
| return; |
| state = state->remove<AllocatedData>(getSymbolForRegion(C, V)); |
| |
| // Proceed from the new state. |
| C.addTransition(state); |
| } |
| |
| // TODO: The report has to mention the expression which contains the |
| // allocated content as well as the point at which it has been allocated. |
| RangedBugReport *MacOSKeychainAPIChecker:: |
| generateAllocatedDataNotReleasedReport(const AllocationState &AS, |
| ExplodedNode *N) const { |
| const ADFunctionInfo &FI = FunctionsToTrack[AS.AllocatorIdx]; |
| initBugType(); |
| llvm::SmallString<70> sbuf; |
| llvm::raw_svector_ostream os(sbuf); |
| os << "Allocated data is not released: missing a call to '" |
| << FunctionsToTrack[FI.DeallocatorIdx].Name << "'."; |
| RangedBugReport *Report = new RangedBugReport(*BT, os.str(), N); |
| Report->addRange(AS.Address->getSourceRange()); |
| return Report; |
| } |
| |
| void MacOSKeychainAPIChecker::checkDeadSymbols(SymbolReaper &SR, |
| CheckerContext &C) const { |
| const ProgramState *State = C.getState(); |
| AllocatedSetTy ASet = State->get<AllocatedData>(); |
| if (ASet.isEmpty()) |
| return; |
| |
| bool Changed = false; |
| llvm::SmallVector<const AllocationState*, 1> 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.RetValue, State, C.getSValBuilder())) |
| continue; |
| Errors.push_back(&I->second); |
| } |
| if (!Changed) |
| return; |
| |
| // Generate the new, cleaned up state. |
| ExplodedNode *N = C.generateNode(State); |
| if (!N) |
| return; |
| |
| // Generate the error reports. |
| for (llvm::SmallVector<const AllocationState*, 3>::iterator |
| I = Errors.begin(), E = Errors.end(); I != E; ++I) { |
| C.EmitReport(generateAllocatedDataNotReleasedReport(**I, N)); |
| } |
| } |
| |
| // TODO: Remove this after we ensure that checkDeadSymbols are always called. |
| void MacOSKeychainAPIChecker::checkEndPath(EndOfFunctionNodeBuilder &B, |
| ExprEngine &Eng) const { |
| const ProgramState *state = B.getState(); |
| 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; |
| llvm::SmallVector<const AllocationState*, 1> 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.RetValue, state, |
| Eng.getSValBuilder())) { |
| continue; |
| } |
| Errors.push_back(&I->second); |
| } |
| |
| // If no change, do not generate a new state. |
| if (!Changed) |
| return; |
| |
| ExplodedNode *N = B.generateNode(state); |
| if (!N) |
| return; |
| |
| // Generate the error reports. |
| for (llvm::SmallVector<const AllocationState*, 3>::iterator |
| I = Errors.begin(), E = Errors.end(); I != E; ++I) { |
| Eng.getBugReporter().EmitReport( |
| generateAllocatedDataNotReleasedReport(**I, N)); |
| } |
| |
| } |
| |
| void ento::registerMacOSKeychainAPIChecker(CheckerManager &mgr) { |
| mgr.registerChecker<MacOSKeychainAPIChecker>(); |
| } |