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/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.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"
24 using namespace clang;
28 class MacOSKeychainAPIChecker : public Checker<check::PreStmt<CallExpr>,
29 check::PreStmt<ReturnStmt>,
30 check::PostStmt<CallExpr>,
33 mutable OwningPtr<BugType> BT;
36 /// AllocationState is a part of the checker specific state together with the
37 /// MemRegion corresponding to the allocated data.
38 struct AllocationState {
39 /// The index of the allocator function.
40 unsigned int AllocatorIdx;
43 AllocationState(const Expr *E, unsigned int Idx, SymbolRef R) :
47 bool operator==(const AllocationState &X) const {
48 return (AllocatorIdx == X.AllocatorIdx &&
52 void Profile(llvm::FoldingSetNodeID &ID) const {
53 ID.AddInteger(AllocatorIdx);
54 ID.AddPointer(Region);
58 void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
59 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
60 void checkPostStmt(const CallExpr *S, CheckerContext &C) const;
61 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
62 void checkEndPath(CheckerContext &C) const;
65 typedef std::pair<SymbolRef, const AllocationState*> AllocationPair;
66 typedef llvm::SmallVector<AllocationPair, 2> AllocationPairVec;
69 /// Denotes functions tracked by this checker.
71 /// The functions commonly/mistakenly used in place of the given API.
73 /// The functions which may allocate the data. These are tracked to reduce
74 /// the false alarm rate.
77 /// Stores the information about the allocator and deallocator functions -
78 /// these are the functions the checker is tracking.
79 struct ADFunctionInfo {
82 unsigned int DeallocatorIdx;
85 static const unsigned InvalidIdx = 100000;
86 static const unsigned FunctionsToTrackSize = 8;
87 static const ADFunctionInfo FunctionsToTrack[FunctionsToTrackSize];
88 /// The value, which represents no error return value for allocator functions.
89 static const unsigned NoErr = 0;
91 /// Given the function name, returns the index of the allocator/deallocator
93 static unsigned getTrackedFunctionIndex(StringRef Name, bool IsAllocator);
95 inline void initBugType() const {
97 BT.reset(new BugType("Improper use of SecKeychain API", "Mac OS API"));
100 void generateDeallocatorMismatchReport(const AllocationPair &AP,
102 CheckerContext &C) const;
104 /// Find the allocation site for Sym on the path leading to the node N.
105 const Stmt *getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
106 CheckerContext &C) const;
108 BugReport *generateAllocatedDataNotReleasedReport(const AllocationPair &AP,
110 CheckerContext &C) const;
112 /// Check if RetSym evaluates to an error value in the current state.
113 bool definitelyReturnedError(SymbolRef RetSym,
114 ProgramStateRef State,
115 SValBuilder &Builder,
116 bool noError = false) const;
118 /// Check if RetSym evaluates to a NoErr value in the current state.
119 bool definitelyDidnotReturnError(SymbolRef RetSym,
120 ProgramStateRef State,
121 SValBuilder &Builder) const {
122 return definitelyReturnedError(RetSym, State, Builder, true);
125 /// Mark an AllocationPair interesting for diagnostic reporting.
126 void markInteresting(BugReport *R, const AllocationPair &AP) const {
127 R->markInteresting(AP.first);
128 R->markInteresting(AP.second->Region);
131 /// The bug visitor which allows us to print extra diagnostics along the
132 /// BugReport path. For example, showing the allocation site of the leaked
134 class SecKeychainBugVisitor
135 : public BugReporterVisitorImpl<SecKeychainBugVisitor> {
137 // The allocated region symbol tracked by the main analysis.
141 SecKeychainBugVisitor(SymbolRef S) : Sym(S) {}
142 virtual ~SecKeychainBugVisitor() {}
144 void Profile(llvm::FoldingSetNodeID &ID) const {
150 PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
151 const ExplodedNode *PrevN,
152 BugReporterContext &BRC,
158 /// ProgramState traits to store the currently allocated (and not yet freed)
159 /// symbols. This is a map from the allocated content symbol to the
160 /// corresponding AllocationState.
161 typedef llvm::ImmutableMap<SymbolRef,
162 MacOSKeychainAPIChecker::AllocationState> AllocatedSetTy;
164 namespace { struct AllocatedData {}; }
165 namespace clang { namespace ento {
166 template<> struct ProgramStateTrait<AllocatedData>
167 : public ProgramStatePartialTrait<AllocatedSetTy > {
168 static void *GDMIndex() { static int index = 0; return &index; }
172 static bool isEnclosingFunctionParam(const Expr *E) {
173 E = E->IgnoreParenCasts();
174 if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
175 const ValueDecl *VD = DRE->getDecl();
176 if (isa<ImplicitParamDecl>(VD) || isa<ParmVarDecl>(VD))
182 const MacOSKeychainAPIChecker::ADFunctionInfo
183 MacOSKeychainAPIChecker::FunctionsToTrack[FunctionsToTrackSize] = {
184 {"SecKeychainItemCopyContent", 4, 3, ValidAPI}, // 0
185 {"SecKeychainFindGenericPassword", 6, 3, ValidAPI}, // 1
186 {"SecKeychainFindInternetPassword", 13, 3, ValidAPI}, // 2
187 {"SecKeychainItemFreeContent", 1, InvalidIdx, ValidAPI}, // 3
188 {"SecKeychainItemCopyAttributesAndData", 5, 5, ValidAPI}, // 4
189 {"SecKeychainItemFreeAttributesAndData", 1, InvalidIdx, ValidAPI}, // 5
190 {"free", 0, InvalidIdx, ErrorAPI}, // 6
191 {"CFStringCreateWithBytesNoCopy", 1, InvalidIdx, PossibleAPI}, // 7
194 unsigned MacOSKeychainAPIChecker::getTrackedFunctionIndex(StringRef Name,
196 for (unsigned I = 0; I < FunctionsToTrackSize; ++I) {
197 ADFunctionInfo FI = FunctionsToTrack[I];
200 // Make sure the function is of the right type (allocator vs deallocator).
201 if (IsAllocator && (FI.DeallocatorIdx == InvalidIdx))
203 if (!IsAllocator && (FI.DeallocatorIdx != InvalidIdx))
208 // The function is not tracked.
212 static bool isBadDeallocationArgument(const MemRegion *Arg) {
215 if (isa<AllocaRegion>(Arg) ||
216 isa<BlockDataRegion>(Arg) ||
217 isa<TypedRegion>(Arg)) {
223 /// Given the address expression, retrieve the value it's pointing to. Assume
224 /// that value is itself an address, and return the corresponding symbol.
225 static SymbolRef getAsPointeeSymbol(const Expr *Expr,
227 ProgramStateRef State = C.getState();
228 SVal ArgV = State->getSVal(Expr, C.getLocationContext());
230 if (const loc::MemRegionVal *X = dyn_cast<loc::MemRegionVal>(&ArgV)) {
231 StoreManager& SM = C.getStoreManager();
232 SymbolRef sym = SM.getBinding(State->getStore(), *X).getAsLocSymbol();
239 // When checking for error code, we need to consider the following cases:
241 // 2) someErr / [1, inf]
243 // If noError, returns true iff (1).
244 // If !noError, returns true iff (2).
245 bool MacOSKeychainAPIChecker::definitelyReturnedError(SymbolRef RetSym,
246 ProgramStateRef State,
247 SValBuilder &Builder,
248 bool noError) const {
249 DefinedOrUnknownSVal NoErrVal = Builder.makeIntVal(NoErr,
250 Builder.getSymbolManager().getType(RetSym));
251 DefinedOrUnknownSVal NoErr = Builder.evalEQ(State, NoErrVal,
252 nonloc::SymbolVal(RetSym));
253 ProgramStateRef ErrState = State->assume(NoErr, noError);
254 if (ErrState == State) {
261 // Report deallocator mismatch. Remove the region from tracking - reporting a
262 // missing free error after this one is redundant.
263 void MacOSKeychainAPIChecker::
264 generateDeallocatorMismatchReport(const AllocationPair &AP,
266 CheckerContext &C) const {
267 ProgramStateRef State = C.getState();
268 State = State->remove<AllocatedData>(AP.first);
269 ExplodedNode *N = C.addTransition(State);
274 SmallString<80> sbuf;
275 llvm::raw_svector_ostream os(sbuf);
276 unsigned int PDeallocIdx =
277 FunctionsToTrack[AP.second->AllocatorIdx].DeallocatorIdx;
279 os << "Deallocator doesn't match the allocator: '"
280 << FunctionsToTrack[PDeallocIdx].Name << "' should be used.";
281 BugReport *Report = new BugReport(*BT, os.str(), N);
282 Report->addVisitor(new SecKeychainBugVisitor(AP.first));
283 Report->addRange(ArgExpr->getSourceRange());
284 markInteresting(Report, AP);
285 C.EmitReport(Report);
288 void MacOSKeychainAPIChecker::checkPreStmt(const CallExpr *CE,
289 CheckerContext &C) const {
290 unsigned idx = InvalidIdx;
291 ProgramStateRef State = C.getState();
293 StringRef funName = C.getCalleeName(CE);
297 // If it is a call to an allocator function, it could be a double allocation.
298 idx = getTrackedFunctionIndex(funName, true);
299 if (idx != InvalidIdx) {
300 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
301 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C))
302 if (const AllocationState *AS = State->get<AllocatedData>(V)) {
303 if (!definitelyReturnedError(AS->Region, State, C.getSValBuilder())) {
304 // Remove the value from the state. The new symbol will be added for
305 // tracking when the second allocator is processed in checkPostStmt().
306 State = State->remove<AllocatedData>(V);
307 ExplodedNode *N = C.addTransition(State);
311 SmallString<128> sbuf;
312 llvm::raw_svector_ostream os(sbuf);
313 unsigned int DIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
314 os << "Allocated data should be released before another call to "
315 << "the allocator: missing a call to '"
316 << FunctionsToTrack[DIdx].Name
318 BugReport *Report = new BugReport(*BT, os.str(), N);
319 Report->addVisitor(new SecKeychainBugVisitor(V));
320 Report->addRange(ArgExpr->getSourceRange());
321 Report->markInteresting(AS->Region);
322 C.EmitReport(Report);
328 // Is it a call to one of deallocator functions?
329 idx = getTrackedFunctionIndex(funName, false);
330 if (idx == InvalidIdx)
333 // Check the argument to the deallocator.
334 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
335 SVal ArgSVal = State->getSVal(ArgExpr, C.getLocationContext());
337 // Undef is reported by another checker.
338 if (ArgSVal.isUndef())
341 SymbolRef ArgSM = ArgSVal.getAsLocSymbol();
343 // If the argument is coming from the heap, globals, or unknown, do not
345 bool RegionArgIsBad = false;
347 if (!isBadDeallocationArgument(ArgSVal.getAsRegion()))
349 RegionArgIsBad = true;
352 // Is the argument to the call being tracked?
353 const AllocationState *AS = State->get<AllocatedData>(ArgSM);
354 if (!AS && FunctionsToTrack[idx].Kind != ValidAPI) {
357 // If trying to free data which has not been allocated yet, report as a bug.
358 // TODO: We might want a more precise diagnostic for double free
359 // (that would involve tracking all the freed symbols in the checker state).
360 if (!AS || RegionArgIsBad) {
361 // It is possible that this is a false positive - the argument might
362 // have entered as an enclosing function parameter.
363 if (isEnclosingFunctionParam(ArgExpr))
366 ExplodedNode *N = C.addTransition(State);
370 BugReport *Report = new BugReport(*BT,
371 "Trying to free data which has not been allocated.", N);
372 Report->addRange(ArgExpr->getSourceRange());
374 Report->markInteresting(AS->Region);
375 C.EmitReport(Report);
379 // Process functions which might deallocate.
380 if (FunctionsToTrack[idx].Kind == PossibleAPI) {
382 if (funName == "CFStringCreateWithBytesNoCopy") {
383 const Expr *DeallocatorExpr = CE->getArg(5)->IgnoreParenCasts();
384 // NULL ~ default deallocator, so warn.
385 if (DeallocatorExpr->isNullPointerConstant(C.getASTContext(),
386 Expr::NPC_ValueDependentIsNotNull)) {
387 const AllocationPair AP = std::make_pair(ArgSM, AS);
388 generateDeallocatorMismatchReport(AP, ArgExpr, C);
391 // One of the default allocators, so warn.
392 if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(DeallocatorExpr)) {
393 StringRef DeallocatorName = DE->getFoundDecl()->getName();
394 if (DeallocatorName == "kCFAllocatorDefault" ||
395 DeallocatorName == "kCFAllocatorSystemDefault" ||
396 DeallocatorName == "kCFAllocatorMalloc") {
397 const AllocationPair AP = std::make_pair(ArgSM, AS);
398 generateDeallocatorMismatchReport(AP, ArgExpr, C);
401 // If kCFAllocatorNull, which does not deallocate, we still have to
402 // find the deallocator. Otherwise, assume that the user had written a
403 // custom deallocator which does the right thing.
404 if (DE->getFoundDecl()->getName() != "kCFAllocatorNull") {
405 State = State->remove<AllocatedData>(ArgSM);
406 C.addTransition(State);
414 // The call is deallocating a value we previously allocated, so remove it
415 // from the next state.
416 State = State->remove<AllocatedData>(ArgSM);
418 // Check if the proper deallocator is used.
419 unsigned int PDeallocIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
420 if (PDeallocIdx != idx || (FunctionsToTrack[idx].Kind == ErrorAPI)) {
421 const AllocationPair AP = std::make_pair(ArgSM, AS);
422 generateDeallocatorMismatchReport(AP, ArgExpr, C);
426 // If the buffer can be null and the return status can be an error,
427 // report a bad call to free.
428 if (State->assume(cast<DefinedSVal>(ArgSVal), false) &&
429 !definitelyDidnotReturnError(AS->Region, State, C.getSValBuilder())) {
430 ExplodedNode *N = C.addTransition(State);
434 BugReport *Report = new BugReport(*BT,
435 "Only call free if a valid (non-NULL) buffer was returned.", N);
436 Report->addVisitor(new SecKeychainBugVisitor(ArgSM));
437 Report->addRange(ArgExpr->getSourceRange());
438 Report->markInteresting(AS->Region);
439 C.EmitReport(Report);
443 C.addTransition(State);
446 void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE,
447 CheckerContext &C) const {
448 ProgramStateRef State = C.getState();
449 StringRef funName = C.getCalleeName(CE);
451 // If a value has been allocated, add it to the set for tracking.
452 unsigned idx = getTrackedFunctionIndex(funName, true);
453 if (idx == InvalidIdx)
456 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
457 // If the argument entered as an enclosing function parameter, skip it to
458 // avoid false positives.
459 if (isEnclosingFunctionParam(ArgExpr) &&
460 C.getLocationContext()->getParent() == 0)
463 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C)) {
464 // If the argument points to something that's not a symbolic region, it
466 // - unknown (cannot reason about it)
467 // - undefined (already reported by other checker)
468 // - constant (null - should not be tracked,
469 // other constant will generate a compiler warning)
470 // - goto (should be reported by other checker)
472 // The call return value symbol should stay alive for as long as the
473 // allocated value symbol, since our diagnostics depend on the value
474 // returned by the call. Ex: Data should only be freed if noErr was
475 // returned during allocation.)
476 SymbolRef RetStatusSymbol =
477 State->getSVal(CE, C.getLocationContext()).getAsSymbol();
478 C.getSymbolManager().addSymbolDependency(V, RetStatusSymbol);
480 // Track the allocated value in the checker state.
481 State = State->set<AllocatedData>(V, AllocationState(ArgExpr, idx,
484 C.addTransition(State);
488 void MacOSKeychainAPIChecker::checkPreStmt(const ReturnStmt *S,
489 CheckerContext &C) const {
490 const Expr *retExpr = S->getRetValue();
494 // If inside inlined call, skip it.
495 const LocationContext *LC = C.getLocationContext();
496 if (LC->getParent() != 0)
499 // Check if the value is escaping through the return.
500 ProgramStateRef state = C.getState();
501 SymbolRef sym = state->getSVal(retExpr, LC).getAsLocSymbol();
504 state = state->remove<AllocatedData>(sym);
506 // Proceed from the new state.
507 C.addTransition(state);
510 // TODO: This logic is the same as in Malloc checker.
512 MacOSKeychainAPIChecker::getAllocationSite(const ExplodedNode *N,
514 CheckerContext &C) const {
515 const LocationContext *LeakContext = N->getLocationContext();
516 // Walk the ExplodedGraph backwards and find the first node that referred to
517 // the tracked symbol.
518 const ExplodedNode *AllocNode = N;
521 if (!N->getState()->get<AllocatedData>(Sym))
523 // Allocation node, is the last node in the current context in which the
524 // symbol was tracked.
525 if (N->getLocationContext() == LeakContext)
527 N = N->pred_empty() ? NULL : *(N->pred_begin());
530 ProgramPoint P = AllocNode->getLocation();
531 if (!isa<StmtPoint>(P))
533 return cast<clang::PostStmt>(P).getStmt();
536 BugReport *MacOSKeychainAPIChecker::
537 generateAllocatedDataNotReleasedReport(const AllocationPair &AP,
539 CheckerContext &C) const {
540 const ADFunctionInfo &FI = FunctionsToTrack[AP.second->AllocatorIdx];
542 SmallString<70> sbuf;
543 llvm::raw_svector_ostream os(sbuf);
544 os << "Allocated data is not released: missing a call to '"
545 << FunctionsToTrack[FI.DeallocatorIdx].Name << "'.";
547 // Most bug reports are cached at the location where they occurred.
548 // With leaks, we want to unique them by the location where they were
549 // allocated, and only report a single path.
550 PathDiagnosticLocation LocUsedForUniqueing;
551 if (const Stmt *AllocStmt = getAllocationSite(N, AP.first, C))
552 LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
553 C.getSourceManager(), N->getLocationContext());
555 BugReport *Report = new BugReport(*BT, os.str(), N, LocUsedForUniqueing);
556 Report->addVisitor(new SecKeychainBugVisitor(AP.first));
557 markInteresting(Report, AP);
561 void MacOSKeychainAPIChecker::checkDeadSymbols(SymbolReaper &SR,
562 CheckerContext &C) const {
563 ProgramStateRef State = C.getState();
564 AllocatedSetTy ASet = State->get<AllocatedData>();
568 bool Changed = false;
569 AllocationPairVec Errors;
570 for (AllocatedSetTy::iterator I = ASet.begin(), E = ASet.end(); I != E; ++I) {
571 if (SR.isLive(I->first))
575 State = State->remove<AllocatedData>(I->first);
576 // If the allocated symbol is null or if the allocation call might have
577 // returned an error, do not report.
578 if (State->getSymVal(I->first) ||
579 definitelyReturnedError(I->second.Region, State, C.getSValBuilder()))
581 Errors.push_back(std::make_pair(I->first, &I->second));
584 // Generate the new, cleaned up state.
585 C.addTransition(State);
589 static SimpleProgramPointTag Tag("MacOSKeychainAPIChecker : DeadSymbolsLeak");
590 ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
592 // Generate the error reports.
593 for (AllocationPairVec::iterator I = Errors.begin(), E = Errors.end();
595 C.EmitReport(generateAllocatedDataNotReleasedReport(*I, N, C));
598 // Generate the new, cleaned up state.
599 C.addTransition(State, N);
602 // TODO: Remove this after we ensure that checkDeadSymbols are always called.
603 void MacOSKeychainAPIChecker::checkEndPath(CheckerContext &C) const {
604 ProgramStateRef state = C.getState();
606 // If inside inlined call, skip it.
607 if (C.getLocationContext()->getParent() != 0)
610 AllocatedSetTy AS = state->get<AllocatedData>();
614 // Anything which has been allocated but not freed (nor escaped) will be
615 // found here, so report it.
616 bool Changed = false;
617 AllocationPairVec Errors;
618 for (AllocatedSetTy::iterator I = AS.begin(), E = AS.end(); I != E; ++I ) {
620 state = state->remove<AllocatedData>(I->first);
621 // If the allocated symbol is null or if error code was returned at
622 // allocation, do not report.
623 if (state->getSymVal(I.getKey()) ||
624 definitelyReturnedError(I->second.Region, state,
625 C.getSValBuilder())) {
628 Errors.push_back(std::make_pair(I->first, &I->second));
631 // If no change, do not generate a new state.
633 C.addTransition(state);
637 static SimpleProgramPointTag Tag("MacOSKeychainAPIChecker : EndPathLeak");
638 ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
640 // Generate the error reports.
641 for (AllocationPairVec::iterator I = Errors.begin(), E = Errors.end();
643 C.EmitReport(generateAllocatedDataNotReleasedReport(*I, N, C));
646 C.addTransition(state, N);
650 PathDiagnosticPiece *MacOSKeychainAPIChecker::SecKeychainBugVisitor::VisitNode(
651 const ExplodedNode *N,
652 const ExplodedNode *PrevN,
653 BugReporterContext &BRC,
655 const AllocationState *AS = N->getState()->get<AllocatedData>(Sym);
658 const AllocationState *ASPrev = PrevN->getState()->get<AllocatedData>(Sym);
662 // (!ASPrev && AS) ~ We started tracking symbol in node N, it must be the
664 const CallExpr *CE = cast<CallExpr>(cast<StmtPoint>(N->getLocation())
666 const FunctionDecl *funDecl = CE->getDirectCallee();
667 assert(funDecl && "We do not support indirect function calls as of now.");
668 StringRef funName = funDecl->getName();
670 // Get the expression of the corresponding argument.
671 unsigned Idx = getTrackedFunctionIndex(funName, true);
672 assert(Idx != InvalidIdx && "This should be a call to an allocator.");
673 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[Idx].Param);
674 PathDiagnosticLocation Pos(ArgExpr, BRC.getSourceManager(),
675 N->getLocationContext());
676 return new PathDiagnosticEventPiece(Pos, "Data is allocated here.");
679 void ento::registerMacOSKeychainAPIChecker(CheckerManager &mgr) {
680 mgr.registerChecker<MacOSKeychainAPIChecker>();