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 BugReport *generateAllocatedDataNotReleasedReport(const AllocationPair &AP,
108 CheckerContext &C) const;
110 /// Check if RetSym evaluates to an error value in the current state.
111 bool definitelyReturnedError(SymbolRef RetSym,
112 ProgramStateRef State,
113 SValBuilder &Builder,
114 bool noError = false) const;
116 /// Check if RetSym evaluates to a NoErr value in the current state.
117 bool definitelyDidnotReturnError(SymbolRef RetSym,
118 ProgramStateRef State,
119 SValBuilder &Builder) const {
120 return definitelyReturnedError(RetSym, State, Builder, true);
123 /// Mark an AllocationPair interesting for diagnostic reporting.
124 void markInteresting(BugReport *R, const AllocationPair &AP) const {
125 R->markInteresting(AP.first);
126 R->markInteresting(AP.second->Region);
129 /// The bug visitor which allows us to print extra diagnostics along the
130 /// BugReport path. For example, showing the allocation site of the leaked
132 class SecKeychainBugVisitor
133 : public BugReporterVisitorImpl<SecKeychainBugVisitor> {
135 // The allocated region symbol tracked by the main analysis.
139 SecKeychainBugVisitor(SymbolRef S) : Sym(S) {}
140 ~SecKeychainBugVisitor() override {}
142 void Profile(llvm::FoldingSetNodeID &ID) const override {
148 PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
149 const ExplodedNode *PrevN,
150 BugReporterContext &BRC,
151 BugReport &BR) override;
156 /// ProgramState traits to store the currently allocated (and not yet freed)
157 /// symbols. This is a map from the allocated content symbol to the
158 /// corresponding AllocationState.
159 REGISTER_MAP_WITH_PROGRAMSTATE(AllocatedData,
161 MacOSKeychainAPIChecker::AllocationState)
163 static bool isEnclosingFunctionParam(const Expr *E) {
164 E = E->IgnoreParenCasts();
165 if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
166 const ValueDecl *VD = DRE->getDecl();
167 if (isa<ImplicitParamDecl>(VD) || isa<ParmVarDecl>(VD))
173 const MacOSKeychainAPIChecker::ADFunctionInfo
174 MacOSKeychainAPIChecker::FunctionsToTrack[FunctionsToTrackSize] = {
175 {"SecKeychainItemCopyContent", 4, 3, ValidAPI}, // 0
176 {"SecKeychainFindGenericPassword", 6, 3, ValidAPI}, // 1
177 {"SecKeychainFindInternetPassword", 13, 3, ValidAPI}, // 2
178 {"SecKeychainItemFreeContent", 1, InvalidIdx, ValidAPI}, // 3
179 {"SecKeychainItemCopyAttributesAndData", 5, 5, ValidAPI}, // 4
180 {"SecKeychainItemFreeAttributesAndData", 1, InvalidIdx, ValidAPI}, // 5
181 {"free", 0, InvalidIdx, ErrorAPI}, // 6
182 {"CFStringCreateWithBytesNoCopy", 1, InvalidIdx, PossibleAPI}, // 7
185 unsigned MacOSKeychainAPIChecker::getTrackedFunctionIndex(StringRef Name,
187 for (unsigned I = 0; I < FunctionsToTrackSize; ++I) {
188 ADFunctionInfo FI = FunctionsToTrack[I];
191 // Make sure the function is of the right type (allocator vs deallocator).
192 if (IsAllocator && (FI.DeallocatorIdx == InvalidIdx))
194 if (!IsAllocator && (FI.DeallocatorIdx != InvalidIdx))
199 // The function is not tracked.
203 static bool isBadDeallocationArgument(const MemRegion *Arg) {
206 if (isa<AllocaRegion>(Arg) ||
207 isa<BlockDataRegion>(Arg) ||
208 isa<TypedRegion>(Arg)) {
214 /// Given the address expression, retrieve the value it's pointing to. Assume
215 /// that value is itself an address, and return the corresponding symbol.
216 static SymbolRef getAsPointeeSymbol(const Expr *Expr,
218 ProgramStateRef State = C.getState();
219 SVal ArgV = State->getSVal(Expr, C.getLocationContext());
221 if (Optional<loc::MemRegionVal> X = ArgV.getAs<loc::MemRegionVal>()) {
222 StoreManager& SM = C.getStoreManager();
223 SymbolRef sym = SM.getBinding(State->getStore(), *X).getAsLocSymbol();
230 // When checking for error code, we need to consider the following cases:
232 // 2) someErr / [1, inf]
234 // If noError, returns true iff (1).
235 // If !noError, returns true iff (2).
236 bool MacOSKeychainAPIChecker::definitelyReturnedError(SymbolRef RetSym,
237 ProgramStateRef State,
238 SValBuilder &Builder,
239 bool noError) const {
240 DefinedOrUnknownSVal NoErrVal = Builder.makeIntVal(NoErr,
241 Builder.getSymbolManager().getType(RetSym));
242 DefinedOrUnknownSVal NoErr = Builder.evalEQ(State, NoErrVal,
243 nonloc::SymbolVal(RetSym));
244 ProgramStateRef ErrState = State->assume(NoErr, noError);
245 if (ErrState == State) {
252 // Report deallocator mismatch. Remove the region from tracking - reporting a
253 // missing free error after this one is redundant.
254 void MacOSKeychainAPIChecker::
255 generateDeallocatorMismatchReport(const AllocationPair &AP,
257 CheckerContext &C) const {
258 ProgramStateRef State = C.getState();
259 State = State->remove<AllocatedData>(AP.first);
260 ExplodedNode *N = C.addTransition(State);
265 SmallString<80> sbuf;
266 llvm::raw_svector_ostream os(sbuf);
267 unsigned int PDeallocIdx =
268 FunctionsToTrack[AP.second->AllocatorIdx].DeallocatorIdx;
270 os << "Deallocator doesn't match the allocator: '"
271 << FunctionsToTrack[PDeallocIdx].Name << "' should be used.";
272 BugReport *Report = new BugReport(*BT, os.str(), N);
273 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(AP.first));
274 Report->addRange(ArgExpr->getSourceRange());
275 markInteresting(Report, AP);
276 C.emitReport(Report);
279 void MacOSKeychainAPIChecker::checkPreStmt(const CallExpr *CE,
280 CheckerContext &C) const {
281 unsigned idx = InvalidIdx;
282 ProgramStateRef State = C.getState();
284 const FunctionDecl *FD = C.getCalleeDecl(CE);
285 if (!FD || FD->getKind() != Decl::Function)
288 StringRef funName = C.getCalleeName(FD);
292 // If it is a call to an allocator function, it could be a double allocation.
293 idx = getTrackedFunctionIndex(funName, true);
294 if (idx != InvalidIdx) {
295 unsigned paramIdx = FunctionsToTrack[idx].Param;
296 if (CE->getNumArgs() <= paramIdx)
299 const Expr *ArgExpr = CE->getArg(paramIdx);
300 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C))
301 if (const AllocationState *AS = State->get<AllocatedData>(V)) {
302 if (!definitelyReturnedError(AS->Region, State, C.getSValBuilder())) {
303 // Remove the value from the state. The new symbol will be added for
304 // tracking when the second allocator is processed in checkPostStmt().
305 State = State->remove<AllocatedData>(V);
306 ExplodedNode *N = C.addTransition(State);
310 SmallString<128> sbuf;
311 llvm::raw_svector_ostream os(sbuf);
312 unsigned int DIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
313 os << "Allocated data should be released before another call to "
314 << "the allocator: missing a call to '"
315 << FunctionsToTrack[DIdx].Name
317 BugReport *Report = new BugReport(*BT, os.str(), N);
318 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(V));
319 Report->addRange(ArgExpr->getSourceRange());
320 Report->markInteresting(AS->Region);
321 C.emitReport(Report);
327 // Is it a call to one of deallocator functions?
328 idx = getTrackedFunctionIndex(funName, false);
329 if (idx == InvalidIdx)
332 unsigned paramIdx = FunctionsToTrack[idx].Param;
333 if (CE->getNumArgs() <= paramIdx)
336 // Check the argument to the deallocator.
337 const Expr *ArgExpr = CE->getArg(paramIdx);
338 SVal ArgSVal = State->getSVal(ArgExpr, C.getLocationContext());
340 // Undef is reported by another checker.
341 if (ArgSVal.isUndef())
344 SymbolRef ArgSM = ArgSVal.getAsLocSymbol();
346 // If the argument is coming from the heap, globals, or unknown, do not
348 bool RegionArgIsBad = false;
350 if (!isBadDeallocationArgument(ArgSVal.getAsRegion()))
352 RegionArgIsBad = true;
355 // Is the argument to the call being tracked?
356 const AllocationState *AS = State->get<AllocatedData>(ArgSM);
357 if (!AS && FunctionsToTrack[idx].Kind != ValidAPI) {
360 // If trying to free data which has not been allocated yet, report as a bug.
361 // TODO: We might want a more precise diagnostic for double free
362 // (that would involve tracking all the freed symbols in the checker state).
363 if (!AS || RegionArgIsBad) {
364 // It is possible that this is a false positive - the argument might
365 // have entered as an enclosing function parameter.
366 if (isEnclosingFunctionParam(ArgExpr))
369 ExplodedNode *N = C.addTransition(State);
373 BugReport *Report = new BugReport(*BT,
374 "Trying to free data which has not been allocated.", N);
375 Report->addRange(ArgExpr->getSourceRange());
377 Report->markInteresting(AS->Region);
378 C.emitReport(Report);
382 // Process functions which might deallocate.
383 if (FunctionsToTrack[idx].Kind == PossibleAPI) {
385 if (funName == "CFStringCreateWithBytesNoCopy") {
386 const Expr *DeallocatorExpr = CE->getArg(5)->IgnoreParenCasts();
387 // NULL ~ default deallocator, so warn.
388 if (DeallocatorExpr->isNullPointerConstant(C.getASTContext(),
389 Expr::NPC_ValueDependentIsNotNull)) {
390 const AllocationPair AP = std::make_pair(ArgSM, AS);
391 generateDeallocatorMismatchReport(AP, ArgExpr, C);
394 // One of the default allocators, so warn.
395 if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(DeallocatorExpr)) {
396 StringRef DeallocatorName = DE->getFoundDecl()->getName();
397 if (DeallocatorName == "kCFAllocatorDefault" ||
398 DeallocatorName == "kCFAllocatorSystemDefault" ||
399 DeallocatorName == "kCFAllocatorMalloc") {
400 const AllocationPair AP = std::make_pair(ArgSM, AS);
401 generateDeallocatorMismatchReport(AP, ArgExpr, C);
404 // If kCFAllocatorNull, which does not deallocate, we still have to
405 // find the deallocator.
406 if (DE->getFoundDecl()->getName() == "kCFAllocatorNull")
409 // In all other cases, assume the user supplied a correct deallocator
410 // that will free memory so stop tracking.
411 State = State->remove<AllocatedData>(ArgSM);
412 C.addTransition(State);
416 llvm_unreachable("We know of no other possible APIs.");
419 // The call is deallocating a value we previously allocated, so remove it
420 // from the next state.
421 State = State->remove<AllocatedData>(ArgSM);
423 // Check if the proper deallocator is used.
424 unsigned int PDeallocIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
425 if (PDeallocIdx != idx || (FunctionsToTrack[idx].Kind == ErrorAPI)) {
426 const AllocationPair AP = std::make_pair(ArgSM, AS);
427 generateDeallocatorMismatchReport(AP, ArgExpr, C);
431 // If the buffer can be null and the return status can be an error,
432 // report a bad call to free.
433 if (State->assume(ArgSVal.castAs<DefinedSVal>(), false) &&
434 !definitelyDidnotReturnError(AS->Region, State, C.getSValBuilder())) {
435 ExplodedNode *N = C.addTransition(State);
439 BugReport *Report = new BugReport(*BT,
440 "Only call free if a valid (non-NULL) buffer was returned.", N);
441 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(ArgSM));
442 Report->addRange(ArgExpr->getSourceRange());
443 Report->markInteresting(AS->Region);
444 C.emitReport(Report);
448 C.addTransition(State);
451 void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE,
452 CheckerContext &C) const {
453 ProgramStateRef State = C.getState();
454 const FunctionDecl *FD = C.getCalleeDecl(CE);
455 if (!FD || FD->getKind() != Decl::Function)
458 StringRef funName = C.getCalleeName(FD);
460 // If a value has been allocated, add it to the set for tracking.
461 unsigned idx = getTrackedFunctionIndex(funName, true);
462 if (idx == InvalidIdx)
465 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
466 // If the argument entered as an enclosing function parameter, skip it to
467 // avoid false positives.
468 if (isEnclosingFunctionParam(ArgExpr) &&
469 C.getLocationContext()->getParent() == nullptr)
472 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C)) {
473 // If the argument points to something that's not a symbolic region, it
475 // - unknown (cannot reason about it)
476 // - undefined (already reported by other checker)
477 // - constant (null - should not be tracked,
478 // other constant will generate a compiler warning)
479 // - goto (should be reported by other checker)
481 // The call return value symbol should stay alive for as long as the
482 // allocated value symbol, since our diagnostics depend on the value
483 // returned by the call. Ex: Data should only be freed if noErr was
484 // returned during allocation.)
485 SymbolRef RetStatusSymbol =
486 State->getSVal(CE, C.getLocationContext()).getAsSymbol();
487 C.getSymbolManager().addSymbolDependency(V, RetStatusSymbol);
489 // Track the allocated value in the checker state.
490 State = State->set<AllocatedData>(V, AllocationState(ArgExpr, idx,
493 C.addTransition(State);
497 // TODO: This logic is the same as in Malloc checker.
499 MacOSKeychainAPIChecker::getAllocationNode(const ExplodedNode *N,
501 CheckerContext &C) const {
502 const LocationContext *LeakContext = N->getLocationContext();
503 // Walk the ExplodedGraph backwards and find the first node that referred to
504 // the tracked symbol.
505 const ExplodedNode *AllocNode = N;
508 if (!N->getState()->get<AllocatedData>(Sym))
510 // Allocation node, is the last node in the current or parent context in
511 // which the symbol was tracked.
512 const LocationContext *NContext = N->getLocationContext();
513 if (NContext == LeakContext ||
514 NContext->isParentOf(LeakContext))
516 N = N->pred_empty() ? nullptr : *(N->pred_begin());
522 BugReport *MacOSKeychainAPIChecker::
523 generateAllocatedDataNotReleasedReport(const AllocationPair &AP,
525 CheckerContext &C) const {
526 const ADFunctionInfo &FI = FunctionsToTrack[AP.second->AllocatorIdx];
528 SmallString<70> sbuf;
529 llvm::raw_svector_ostream os(sbuf);
530 os << "Allocated data is not released: missing a call to '"
531 << FunctionsToTrack[FI.DeallocatorIdx].Name << "'.";
533 // Most bug reports are cached at the location where they occurred.
534 // With leaks, we want to unique them by the location where they were
535 // allocated, and only report a single path.
536 PathDiagnosticLocation LocUsedForUniqueing;
537 const ExplodedNode *AllocNode = getAllocationNode(N, AP.first, C);
538 const Stmt *AllocStmt = nullptr;
539 ProgramPoint P = AllocNode->getLocation();
540 if (Optional<CallExitEnd> Exit = P.getAs<CallExitEnd>())
541 AllocStmt = Exit->getCalleeContext()->getCallSite();
542 else if (Optional<clang::PostStmt> PS = P.getAs<clang::PostStmt>())
543 AllocStmt = PS->getStmt();
546 LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
547 C.getSourceManager(),
548 AllocNode->getLocationContext());
550 BugReport *Report = new BugReport(*BT, os.str(), N, LocUsedForUniqueing,
551 AllocNode->getLocationContext()->getDecl());
553 Report->addVisitor(llvm::make_unique<SecKeychainBugVisitor>(AP.first));
554 markInteresting(Report, AP);
558 void MacOSKeychainAPIChecker::checkDeadSymbols(SymbolReaper &SR,
559 CheckerContext &C) const {
560 ProgramStateRef State = C.getState();
561 AllocatedDataTy ASet = State->get<AllocatedData>();
565 bool Changed = false;
566 AllocationPairVec Errors;
567 for (AllocatedDataTy::iterator I = ASet.begin(), E = ASet.end(); I != E; ++I) {
568 if (SR.isLive(I->first))
572 State = State->remove<AllocatedData>(I->first);
573 // If the allocated symbol is null or if the allocation call might have
574 // returned an error, do not report.
575 ConstraintManager &CMgr = State->getConstraintManager();
576 ConditionTruthVal AllocFailed = CMgr.isNull(State, I.getKey());
577 if (AllocFailed.isConstrainedTrue() ||
578 definitelyReturnedError(I->second.Region, State, C.getSValBuilder()))
580 Errors.push_back(std::make_pair(I->first, &I->second));
583 // Generate the new, cleaned up state.
584 C.addTransition(State);
588 static CheckerProgramPointTag Tag(this, "DeadSymbolsLeak");
589 ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
591 // Generate the error reports.
592 for (AllocationPairVec::iterator I = Errors.begin(), E = Errors.end();
594 C.emitReport(generateAllocatedDataNotReleasedReport(*I, N, C));
597 // Generate the new, cleaned up state.
598 C.addTransition(State, N);
602 PathDiagnosticPiece *MacOSKeychainAPIChecker::SecKeychainBugVisitor::VisitNode(
603 const ExplodedNode *N,
604 const ExplodedNode *PrevN,
605 BugReporterContext &BRC,
607 const AllocationState *AS = N->getState()->get<AllocatedData>(Sym);
610 const AllocationState *ASPrev = PrevN->getState()->get<AllocatedData>(Sym);
614 // (!ASPrev && AS) ~ We started tracking symbol in node N, it must be the
617 cast<CallExpr>(N->getLocation().castAs<StmtPoint>().getStmt());
618 const FunctionDecl *funDecl = CE->getDirectCallee();
619 assert(funDecl && "We do not support indirect function calls as of now.");
620 StringRef funName = funDecl->getName();
622 // Get the expression of the corresponding argument.
623 unsigned Idx = getTrackedFunctionIndex(funName, true);
624 assert(Idx != InvalidIdx && "This should be a call to an allocator.");
625 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[Idx].Param);
626 PathDiagnosticLocation Pos(ArgExpr, BRC.getSourceManager(),
627 N->getLocationContext());
628 return new PathDiagnosticEventPiece(Pos, "Data is allocated here.");
631 void ento::registerMacOSKeychainAPIChecker(CheckerManager &mgr) {
632 mgr.registerChecker<MacOSKeychainAPIChecker>();