1 //==--- MacOSKeychainAPIChecker.cpp ------------------------------*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
9 // This checker flags misuses of KeyChainAPI. In particular, the password data
10 // allocated/returned by SecKeychainItemCopyContent,
11 // SecKeychainFindGenericPassword, SecKeychainFindInternetPassword functions has
12 // to be freed using a call to SecKeychainItemFreeContent.
13 //===----------------------------------------------------------------------===//
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
22 #include "llvm/ADT/SmallString.h"
23 #include "llvm/Support/raw_ostream.h"
25 using namespace clang;
29 class MacOSKeychainAPIChecker : public Checker<check::PreStmt<CallExpr>,
30 check::PostStmt<CallExpr>,
32 mutable std::unique_ptr<BugType> BT;
35 /// AllocationState is a part of the checker specific state together with the
36 /// MemRegion corresponding to the allocated data.
37 struct AllocationState {
38 /// The index of the allocator function.
39 unsigned int AllocatorIdx;
42 AllocationState(const Expr *E, unsigned int Idx, SymbolRef R) :
46 bool operator==(const AllocationState &X) const {
47 return (AllocatorIdx == X.AllocatorIdx &&
51 void Profile(llvm::FoldingSetNodeID &ID) const {
52 ID.AddInteger(AllocatorIdx);
53 ID.AddPointer(Region);
57 void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
58 void checkPostStmt(const CallExpr *S, CheckerContext &C) const;
59 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
62 typedef std::pair<SymbolRef, const AllocationState*> AllocationPair;
63 typedef SmallVector<AllocationPair, 2> AllocationPairVec;
66 /// Denotes functions tracked by this checker.
68 /// The functions commonly/mistakenly used in place of the given API.
70 /// The functions which may allocate the data. These are tracked to reduce
71 /// the false alarm rate.
74 /// Stores the information about the allocator and deallocator functions -
75 /// these are the functions the checker is tracking.
76 struct ADFunctionInfo {
79 unsigned int DeallocatorIdx;
82 static const unsigned InvalidIdx = 100000;
83 static const unsigned FunctionsToTrackSize = 8;
84 static const ADFunctionInfo FunctionsToTrack[FunctionsToTrackSize];
85 /// The value, which represents no error return value for allocator functions.
86 static const unsigned NoErr = 0;
88 /// Given the function name, returns the index of the allocator/deallocator
90 static unsigned getTrackedFunctionIndex(StringRef Name, bool IsAllocator);
92 inline void initBugType() const {
94 BT.reset(new BugType(this, "Improper use of SecKeychain API",
95 "API Misuse (Apple)"));
98 void generateDeallocatorMismatchReport(const AllocationPair &AP,
100 CheckerContext &C) const;
102 /// Find the allocation site for Sym on the path leading to the node N.
103 const ExplodedNode *getAllocationNode(const ExplodedNode *N, SymbolRef Sym,
104 CheckerContext &C) const;
106 std::unique_ptr<BugReport> generateAllocatedDataNotReleasedReport(
107 const AllocationPair &AP, ExplodedNode *N, CheckerContext &C) const;
109 /// Check if RetSym evaluates to an error value in the current state.
110 bool definitelyReturnedError(SymbolRef RetSym,
111 ProgramStateRef State,
112 SValBuilder &Builder,
113 bool noError = false) const;
115 /// Check if RetSym evaluates to a NoErr value in the current state.
116 bool definitelyDidnotReturnError(SymbolRef RetSym,
117 ProgramStateRef State,
118 SValBuilder &Builder) const {
119 return definitelyReturnedError(RetSym, State, Builder, true);
122 /// Mark an AllocationPair interesting for diagnostic reporting.
123 void markInteresting(BugReport *R, const AllocationPair &AP) const {
124 R->markInteresting(AP.first);
125 R->markInteresting(AP.second->Region);
128 /// The bug visitor which allows us to print extra diagnostics along the
129 /// BugReport path. For example, showing the allocation site of the leaked
131 class SecKeychainBugVisitor
132 : public BugReporterVisitorImpl<SecKeychainBugVisitor> {
134 // The allocated region symbol tracked by the main analysis.
138 SecKeychainBugVisitor(SymbolRef S) : Sym(S) {}
140 void Profile(llvm::FoldingSetNodeID &ID) const override {
146 PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
147 const ExplodedNode *PrevN,
148 BugReporterContext &BRC,
149 BugReport &BR) override;
154 /// ProgramState traits to store the currently allocated (and not yet freed)
155 /// symbols. This is a map from the allocated content symbol to the
156 /// corresponding AllocationState.
157 REGISTER_MAP_WITH_PROGRAMSTATE(AllocatedData,
159 MacOSKeychainAPIChecker::AllocationState)
161 static bool isEnclosingFunctionParam(const Expr *E) {
162 E = E->IgnoreParenCasts();
163 if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
164 const ValueDecl *VD = DRE->getDecl();
165 if (isa<ImplicitParamDecl>(VD) || isa<ParmVarDecl>(VD))
171 const MacOSKeychainAPIChecker::ADFunctionInfo
172 MacOSKeychainAPIChecker::FunctionsToTrack[FunctionsToTrackSize] = {
173 {"SecKeychainItemCopyContent", 4, 3, ValidAPI}, // 0
174 {"SecKeychainFindGenericPassword", 6, 3, ValidAPI}, // 1
175 {"SecKeychainFindInternetPassword", 13, 3, ValidAPI}, // 2
176 {"SecKeychainItemFreeContent", 1, InvalidIdx, ValidAPI}, // 3
177 {"SecKeychainItemCopyAttributesAndData", 5, 5, ValidAPI}, // 4
178 {"SecKeychainItemFreeAttributesAndData", 1, InvalidIdx, ValidAPI}, // 5
179 {"free", 0, InvalidIdx, ErrorAPI}, // 6
180 {"CFStringCreateWithBytesNoCopy", 1, InvalidIdx, PossibleAPI}, // 7
183 unsigned MacOSKeychainAPIChecker::getTrackedFunctionIndex(StringRef Name,
185 for (unsigned I = 0; I < FunctionsToTrackSize; ++I) {
186 ADFunctionInfo FI = FunctionsToTrack[I];
189 // Make sure the function is of the right type (allocator vs deallocator).
190 if (IsAllocator && (FI.DeallocatorIdx == InvalidIdx))
192 if (!IsAllocator && (FI.DeallocatorIdx != InvalidIdx))
197 // The function is not tracked.
201 static bool isBadDeallocationArgument(const MemRegion *Arg) {
204 return isa<AllocaRegion>(Arg) || isa<BlockDataRegion>(Arg) ||
205 isa<TypedRegion>(Arg);
208 /// Given the address expression, retrieve the value it's pointing to. Assume
209 /// that value is itself an address, and return the corresponding symbol.
210 static SymbolRef getAsPointeeSymbol(const Expr *Expr,
212 ProgramStateRef State = C.getState();
213 SVal ArgV = State->getSVal(Expr, C.getLocationContext());
215 if (Optional<loc::MemRegionVal> X = ArgV.getAs<loc::MemRegionVal>()) {
216 StoreManager& SM = C.getStoreManager();
217 SymbolRef sym = SM.getBinding(State->getStore(), *X).getAsLocSymbol();
224 // When checking for error code, we need to consider the following cases:
226 // 2) someErr / [1, inf]
228 // If noError, returns true iff (1).
229 // If !noError, returns true iff (2).
230 bool MacOSKeychainAPIChecker::definitelyReturnedError(SymbolRef RetSym,
231 ProgramStateRef State,
232 SValBuilder &Builder,
233 bool noError) const {
234 DefinedOrUnknownSVal NoErrVal = Builder.makeIntVal(NoErr,
235 Builder.getSymbolManager().getType(RetSym));
236 DefinedOrUnknownSVal NoErr = Builder.evalEQ(State, NoErrVal,
237 nonloc::SymbolVal(RetSym));
238 ProgramStateRef ErrState = State->assume(NoErr, noError);
239 return ErrState == State;
242 // Report deallocator mismatch. Remove the region from tracking - reporting a
243 // missing free error after this one is redundant.
244 void MacOSKeychainAPIChecker::
245 generateDeallocatorMismatchReport(const AllocationPair &AP,
247 CheckerContext &C) const {
248 ProgramStateRef State = C.getState();
249 State = State->remove<AllocatedData>(AP.first);
250 ExplodedNode *N = C.generateNonFatalErrorNode(State);
255 SmallString<80> sbuf;
256 llvm::raw_svector_ostream os(sbuf);
257 unsigned int PDeallocIdx =
258 FunctionsToTrack[AP.second->AllocatorIdx].DeallocatorIdx;
260 os << "Deallocator doesn't match the allocator: '"
261 << FunctionsToTrack[PDeallocIdx].Name << "' should be used.";
262 auto Report = llvm::make_unique<BugReport>(*BT, os.str(), N);
263 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(AP.first));
264 Report->addRange(ArgExpr->getSourceRange());
265 markInteresting(Report.get(), AP);
266 C.emitReport(std::move(Report));
269 void MacOSKeychainAPIChecker::checkPreStmt(const CallExpr *CE,
270 CheckerContext &C) const {
271 unsigned idx = InvalidIdx;
272 ProgramStateRef State = C.getState();
274 const FunctionDecl *FD = C.getCalleeDecl(CE);
275 if (!FD || FD->getKind() != Decl::Function)
278 StringRef funName = C.getCalleeName(FD);
282 // If it is a call to an allocator function, it could be a double allocation.
283 idx = getTrackedFunctionIndex(funName, true);
284 if (idx != InvalidIdx) {
285 unsigned paramIdx = FunctionsToTrack[idx].Param;
286 if (CE->getNumArgs() <= paramIdx)
289 const Expr *ArgExpr = CE->getArg(paramIdx);
290 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C))
291 if (const AllocationState *AS = State->get<AllocatedData>(V)) {
292 if (!definitelyReturnedError(AS->Region, State, C.getSValBuilder())) {
293 // Remove the value from the state. The new symbol will be added for
294 // tracking when the second allocator is processed in checkPostStmt().
295 State = State->remove<AllocatedData>(V);
296 ExplodedNode *N = C.generateNonFatalErrorNode(State);
300 SmallString<128> sbuf;
301 llvm::raw_svector_ostream os(sbuf);
302 unsigned int DIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
303 os << "Allocated data should be released before another call to "
304 << "the allocator: missing a call to '"
305 << FunctionsToTrack[DIdx].Name
307 auto Report = llvm::make_unique<BugReport>(*BT, os.str(), N);
308 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(V));
309 Report->addRange(ArgExpr->getSourceRange());
310 Report->markInteresting(AS->Region);
311 C.emitReport(std::move(Report));
317 // Is it a call to one of deallocator functions?
318 idx = getTrackedFunctionIndex(funName, false);
319 if (idx == InvalidIdx)
322 unsigned paramIdx = FunctionsToTrack[idx].Param;
323 if (CE->getNumArgs() <= paramIdx)
326 // Check the argument to the deallocator.
327 const Expr *ArgExpr = CE->getArg(paramIdx);
328 SVal ArgSVal = State->getSVal(ArgExpr, C.getLocationContext());
330 // Undef is reported by another checker.
331 if (ArgSVal.isUndef())
334 SymbolRef ArgSM = ArgSVal.getAsLocSymbol();
336 // If the argument is coming from the heap, globals, or unknown, do not
338 bool RegionArgIsBad = false;
340 if (!isBadDeallocationArgument(ArgSVal.getAsRegion()))
342 RegionArgIsBad = true;
345 // Is the argument to the call being tracked?
346 const AllocationState *AS = State->get<AllocatedData>(ArgSM);
347 if (!AS && FunctionsToTrack[idx].Kind != ValidAPI) {
350 // If trying to free data which has not been allocated yet, report as a bug.
351 // TODO: We might want a more precise diagnostic for double free
352 // (that would involve tracking all the freed symbols in the checker state).
353 if (!AS || RegionArgIsBad) {
354 // It is possible that this is a false positive - the argument might
355 // have entered as an enclosing function parameter.
356 if (isEnclosingFunctionParam(ArgExpr))
359 ExplodedNode *N = C.generateNonFatalErrorNode(State);
363 auto Report = llvm::make_unique<BugReport>(
364 *BT, "Trying to free data which has not been allocated.", N);
365 Report->addRange(ArgExpr->getSourceRange());
367 Report->markInteresting(AS->Region);
368 C.emitReport(std::move(Report));
372 // Process functions which might deallocate.
373 if (FunctionsToTrack[idx].Kind == PossibleAPI) {
375 if (funName == "CFStringCreateWithBytesNoCopy") {
376 const Expr *DeallocatorExpr = CE->getArg(5)->IgnoreParenCasts();
377 // NULL ~ default deallocator, so warn.
378 if (DeallocatorExpr->isNullPointerConstant(C.getASTContext(),
379 Expr::NPC_ValueDependentIsNotNull)) {
380 const AllocationPair AP = std::make_pair(ArgSM, AS);
381 generateDeallocatorMismatchReport(AP, ArgExpr, C);
384 // One of the default allocators, so warn.
385 if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(DeallocatorExpr)) {
386 StringRef DeallocatorName = DE->getFoundDecl()->getName();
387 if (DeallocatorName == "kCFAllocatorDefault" ||
388 DeallocatorName == "kCFAllocatorSystemDefault" ||
389 DeallocatorName == "kCFAllocatorMalloc") {
390 const AllocationPair AP = std::make_pair(ArgSM, AS);
391 generateDeallocatorMismatchReport(AP, ArgExpr, C);
394 // If kCFAllocatorNull, which does not deallocate, we still have to
395 // find the deallocator.
396 if (DE->getFoundDecl()->getName() == "kCFAllocatorNull")
399 // In all other cases, assume the user supplied a correct deallocator
400 // that will free memory so stop tracking.
401 State = State->remove<AllocatedData>(ArgSM);
402 C.addTransition(State);
406 llvm_unreachable("We know of no other possible APIs.");
409 // The call is deallocating a value we previously allocated, so remove it
410 // from the next state.
411 State = State->remove<AllocatedData>(ArgSM);
413 // Check if the proper deallocator is used.
414 unsigned int PDeallocIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
415 if (PDeallocIdx != idx || (FunctionsToTrack[idx].Kind == ErrorAPI)) {
416 const AllocationPair AP = std::make_pair(ArgSM, AS);
417 generateDeallocatorMismatchReport(AP, ArgExpr, C);
421 // If the buffer can be null and the return status can be an error,
422 // report a bad call to free.
423 if (State->assume(ArgSVal.castAs<DefinedSVal>(), false) &&
424 !definitelyDidnotReturnError(AS->Region, State, C.getSValBuilder())) {
425 ExplodedNode *N = C.generateNonFatalErrorNode(State);
429 auto Report = llvm::make_unique<BugReport>(
430 *BT, "Only call free if a valid (non-NULL) buffer was returned.", N);
431 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(ArgSM));
432 Report->addRange(ArgExpr->getSourceRange());
433 Report->markInteresting(AS->Region);
434 C.emitReport(std::move(Report));
438 C.addTransition(State);
441 void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE,
442 CheckerContext &C) const {
443 ProgramStateRef State = C.getState();
444 const FunctionDecl *FD = C.getCalleeDecl(CE);
445 if (!FD || FD->getKind() != Decl::Function)
448 StringRef funName = C.getCalleeName(FD);
450 // If a value has been allocated, add it to the set for tracking.
451 unsigned idx = getTrackedFunctionIndex(funName, true);
452 if (idx == InvalidIdx)
455 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
456 // If the argument entered as an enclosing function parameter, skip it to
457 // avoid false positives.
458 if (isEnclosingFunctionParam(ArgExpr) &&
459 C.getLocationContext()->getParent() == nullptr)
462 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C)) {
463 // If the argument points to something that's not a symbolic region, it
465 // - unknown (cannot reason about it)
466 // - undefined (already reported by other checker)
467 // - constant (null - should not be tracked,
468 // other constant will generate a compiler warning)
469 // - goto (should be reported by other checker)
471 // The call return value symbol should stay alive for as long as the
472 // allocated value symbol, since our diagnostics depend on the value
473 // returned by the call. Ex: Data should only be freed if noErr was
474 // returned during allocation.)
475 SymbolRef RetStatusSymbol =
476 State->getSVal(CE, C.getLocationContext()).getAsSymbol();
477 C.getSymbolManager().addSymbolDependency(V, RetStatusSymbol);
479 // Track the allocated value in the checker state.
480 State = State->set<AllocatedData>(V, AllocationState(ArgExpr, idx,
483 C.addTransition(State);
487 // TODO: This logic is the same as in Malloc checker.
489 MacOSKeychainAPIChecker::getAllocationNode(const ExplodedNode *N,
491 CheckerContext &C) const {
492 const LocationContext *LeakContext = N->getLocationContext();
493 // Walk the ExplodedGraph backwards and find the first node that referred to
494 // the tracked symbol.
495 const ExplodedNode *AllocNode = N;
498 if (!N->getState()->get<AllocatedData>(Sym))
500 // Allocation node, is the last node in the current or parent context in
501 // which the symbol was tracked.
502 const LocationContext *NContext = N->getLocationContext();
503 if (NContext == LeakContext ||
504 NContext->isParentOf(LeakContext))
506 N = N->pred_empty() ? nullptr : *(N->pred_begin());
512 std::unique_ptr<BugReport>
513 MacOSKeychainAPIChecker::generateAllocatedDataNotReleasedReport(
514 const AllocationPair &AP, ExplodedNode *N, CheckerContext &C) const {
515 const ADFunctionInfo &FI = FunctionsToTrack[AP.second->AllocatorIdx];
517 SmallString<70> sbuf;
518 llvm::raw_svector_ostream os(sbuf);
519 os << "Allocated data is not released: missing a call to '"
520 << FunctionsToTrack[FI.DeallocatorIdx].Name << "'.";
522 // Most bug reports are cached at the location where they occurred.
523 // With leaks, we want to unique them by the location where they were
524 // allocated, and only report a single path.
525 PathDiagnosticLocation LocUsedForUniqueing;
526 const ExplodedNode *AllocNode = getAllocationNode(N, AP.first, C);
527 const Stmt *AllocStmt = nullptr;
528 ProgramPoint P = AllocNode->getLocation();
529 if (Optional<CallExitEnd> Exit = P.getAs<CallExitEnd>())
530 AllocStmt = Exit->getCalleeContext()->getCallSite();
531 else if (Optional<clang::PostStmt> PS = P.getAs<clang::PostStmt>())
532 AllocStmt = PS->getStmt();
535 LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
536 C.getSourceManager(),
537 AllocNode->getLocationContext());
540 llvm::make_unique<BugReport>(*BT, os.str(), N, LocUsedForUniqueing,
541 AllocNode->getLocationContext()->getDecl());
543 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(AP.first));
544 markInteresting(Report.get(), AP);
548 void MacOSKeychainAPIChecker::checkDeadSymbols(SymbolReaper &SR,
549 CheckerContext &C) const {
550 ProgramStateRef State = C.getState();
551 AllocatedDataTy ASet = State->get<AllocatedData>();
555 bool Changed = false;
556 AllocationPairVec Errors;
557 for (AllocatedDataTy::iterator I = ASet.begin(), E = ASet.end(); I != E; ++I) {
558 if (SR.isLive(I->first))
562 State = State->remove<AllocatedData>(I->first);
563 // If the allocated symbol is null or if the allocation call might have
564 // returned an error, do not report.
565 ConstraintManager &CMgr = State->getConstraintManager();
566 ConditionTruthVal AllocFailed = CMgr.isNull(State, I.getKey());
567 if (AllocFailed.isConstrainedTrue() ||
568 definitelyReturnedError(I->second.Region, State, C.getSValBuilder()))
570 Errors.push_back(std::make_pair(I->first, &I->second));
573 // Generate the new, cleaned up state.
574 C.addTransition(State);
578 static CheckerProgramPointTag Tag(this, "DeadSymbolsLeak");
579 ExplodedNode *N = C.generateNonFatalErrorNode(C.getState(), &Tag);
583 // Generate the error reports.
584 for (const auto &P : Errors)
585 C.emitReport(generateAllocatedDataNotReleasedReport(P, N, C));
587 // Generate the new, cleaned up state.
588 C.addTransition(State, N);
592 PathDiagnosticPiece *MacOSKeychainAPIChecker::SecKeychainBugVisitor::VisitNode(
593 const ExplodedNode *N,
594 const ExplodedNode *PrevN,
595 BugReporterContext &BRC,
597 const AllocationState *AS = N->getState()->get<AllocatedData>(Sym);
600 const AllocationState *ASPrev = PrevN->getState()->get<AllocatedData>(Sym);
604 // (!ASPrev && AS) ~ We started tracking symbol in node N, it must be the
607 cast<CallExpr>(N->getLocation().castAs<StmtPoint>().getStmt());
608 const FunctionDecl *funDecl = CE->getDirectCallee();
609 assert(funDecl && "We do not support indirect function calls as of now.");
610 StringRef funName = funDecl->getName();
612 // Get the expression of the corresponding argument.
613 unsigned Idx = getTrackedFunctionIndex(funName, true);
614 assert(Idx != InvalidIdx && "This should be a call to an allocator.");
615 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[Idx].Param);
616 PathDiagnosticLocation Pos(ArgExpr, BRC.getSourceManager(),
617 N->getLocationContext());
618 return new PathDiagnosticEventPiece(Pos, "Data is allocated here.");
621 void ento::registerMacOSKeychainAPIChecker(CheckerManager &mgr) {
622 mgr.registerChecker<MacOSKeychainAPIChecker>();