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 OwningPtr<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("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 virtual ~SecKeychainBugVisitor() {}
142 void Profile(llvm::FoldingSetNodeID &ID) const {
148 PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
149 const ExplodedNode *PrevN,
150 BugReporterContext &BRC,
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(new 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 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
296 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C))
297 if (const AllocationState *AS = State->get<AllocatedData>(V)) {
298 if (!definitelyReturnedError(AS->Region, State, C.getSValBuilder())) {
299 // Remove the value from the state. The new symbol will be added for
300 // tracking when the second allocator is processed in checkPostStmt().
301 State = State->remove<AllocatedData>(V);
302 ExplodedNode *N = C.addTransition(State);
306 SmallString<128> sbuf;
307 llvm::raw_svector_ostream os(sbuf);
308 unsigned int DIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
309 os << "Allocated data should be released before another call to "
310 << "the allocator: missing a call to '"
311 << FunctionsToTrack[DIdx].Name
313 BugReport *Report = new BugReport(*BT, os.str(), N);
314 Report->addVisitor(new SecKeychainBugVisitor(V));
315 Report->addRange(ArgExpr->getSourceRange());
316 Report->markInteresting(AS->Region);
317 C.emitReport(Report);
323 // Is it a call to one of deallocator functions?
324 idx = getTrackedFunctionIndex(funName, false);
325 if (idx == InvalidIdx)
328 // Check the argument to the deallocator.
329 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
330 SVal ArgSVal = State->getSVal(ArgExpr, C.getLocationContext());
332 // Undef is reported by another checker.
333 if (ArgSVal.isUndef())
336 SymbolRef ArgSM = ArgSVal.getAsLocSymbol();
338 // If the argument is coming from the heap, globals, or unknown, do not
340 bool RegionArgIsBad = false;
342 if (!isBadDeallocationArgument(ArgSVal.getAsRegion()))
344 RegionArgIsBad = true;
347 // Is the argument to the call being tracked?
348 const AllocationState *AS = State->get<AllocatedData>(ArgSM);
349 if (!AS && FunctionsToTrack[idx].Kind != ValidAPI) {
352 // If trying to free data which has not been allocated yet, report as a bug.
353 // TODO: We might want a more precise diagnostic for double free
354 // (that would involve tracking all the freed symbols in the checker state).
355 if (!AS || RegionArgIsBad) {
356 // It is possible that this is a false positive - the argument might
357 // have entered as an enclosing function parameter.
358 if (isEnclosingFunctionParam(ArgExpr))
361 ExplodedNode *N = C.addTransition(State);
365 BugReport *Report = new BugReport(*BT,
366 "Trying to free data which has not been allocated.", N);
367 Report->addRange(ArgExpr->getSourceRange());
369 Report->markInteresting(AS->Region);
370 C.emitReport(Report);
374 // Process functions which might deallocate.
375 if (FunctionsToTrack[idx].Kind == PossibleAPI) {
377 if (funName == "CFStringCreateWithBytesNoCopy") {
378 const Expr *DeallocatorExpr = CE->getArg(5)->IgnoreParenCasts();
379 // NULL ~ default deallocator, so warn.
380 if (DeallocatorExpr->isNullPointerConstant(C.getASTContext(),
381 Expr::NPC_ValueDependentIsNotNull)) {
382 const AllocationPair AP = std::make_pair(ArgSM, AS);
383 generateDeallocatorMismatchReport(AP, ArgExpr, C);
386 // One of the default allocators, so warn.
387 if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(DeallocatorExpr)) {
388 StringRef DeallocatorName = DE->getFoundDecl()->getName();
389 if (DeallocatorName == "kCFAllocatorDefault" ||
390 DeallocatorName == "kCFAllocatorSystemDefault" ||
391 DeallocatorName == "kCFAllocatorMalloc") {
392 const AllocationPair AP = std::make_pair(ArgSM, AS);
393 generateDeallocatorMismatchReport(AP, ArgExpr, C);
396 // If kCFAllocatorNull, which does not deallocate, we still have to
397 // find the deallocator.
398 if (DE->getFoundDecl()->getName() == "kCFAllocatorNull")
401 // In all other cases, assume the user supplied a correct deallocator
402 // that will free memory so stop tracking.
403 State = State->remove<AllocatedData>(ArgSM);
404 C.addTransition(State);
408 llvm_unreachable("We know of no other possible APIs.");
411 // The call is deallocating a value we previously allocated, so remove it
412 // from the next state.
413 State = State->remove<AllocatedData>(ArgSM);
415 // Check if the proper deallocator is used.
416 unsigned int PDeallocIdx = FunctionsToTrack[AS->AllocatorIdx].DeallocatorIdx;
417 if (PDeallocIdx != idx || (FunctionsToTrack[idx].Kind == ErrorAPI)) {
418 const AllocationPair AP = std::make_pair(ArgSM, AS);
419 generateDeallocatorMismatchReport(AP, ArgExpr, C);
423 // If the buffer can be null and the return status can be an error,
424 // report a bad call to free.
425 if (State->assume(ArgSVal.castAs<DefinedSVal>(), false) &&
426 !definitelyDidnotReturnError(AS->Region, State, C.getSValBuilder())) {
427 ExplodedNode *N = C.addTransition(State);
431 BugReport *Report = new BugReport(*BT,
432 "Only call free if a valid (non-NULL) buffer was returned.", N);
433 Report->addVisitor(new SecKeychainBugVisitor(ArgSM));
434 Report->addRange(ArgExpr->getSourceRange());
435 Report->markInteresting(AS->Region);
436 C.emitReport(Report);
440 C.addTransition(State);
443 void MacOSKeychainAPIChecker::checkPostStmt(const CallExpr *CE,
444 CheckerContext &C) const {
445 ProgramStateRef State = C.getState();
446 const FunctionDecl *FD = C.getCalleeDecl(CE);
447 if (!FD || FD->getKind() != Decl::Function)
450 StringRef funName = C.getCalleeName(FD);
452 // If a value has been allocated, add it to the set for tracking.
453 unsigned idx = getTrackedFunctionIndex(funName, true);
454 if (idx == InvalidIdx)
457 const Expr *ArgExpr = CE->getArg(FunctionsToTrack[idx].Param);
458 // If the argument entered as an enclosing function parameter, skip it to
459 // avoid false positives.
460 if (isEnclosingFunctionParam(ArgExpr) &&
461 C.getLocationContext()->getParent() == 0)
464 if (SymbolRef V = getAsPointeeSymbol(ArgExpr, C)) {
465 // If the argument points to something that's not a symbolic region, it
467 // - unknown (cannot reason about it)
468 // - undefined (already reported by other checker)
469 // - constant (null - should not be tracked,
470 // other constant will generate a compiler warning)
471 // - goto (should be reported by other checker)
473 // The call return value symbol should stay alive for as long as the
474 // allocated value symbol, since our diagnostics depend on the value
475 // returned by the call. Ex: Data should only be freed if noErr was
476 // returned during allocation.)
477 SymbolRef RetStatusSymbol =
478 State->getSVal(CE, C.getLocationContext()).getAsSymbol();
479 C.getSymbolManager().addSymbolDependency(V, RetStatusSymbol);
481 // Track the allocated value in the checker state.
482 State = State->set<AllocatedData>(V, AllocationState(ArgExpr, idx,
485 C.addTransition(State);
489 // TODO: This logic is the same as in Malloc checker.
491 MacOSKeychainAPIChecker::getAllocationNode(const ExplodedNode *N,
493 CheckerContext &C) const {
494 const LocationContext *LeakContext = N->getLocationContext();
495 // Walk the ExplodedGraph backwards and find the first node that referred to
496 // the tracked symbol.
497 const ExplodedNode *AllocNode = N;
500 if (!N->getState()->get<AllocatedData>(Sym))
502 // Allocation node, is the last node in the current context in which the
503 // symbol was tracked.
504 if (N->getLocationContext() == LeakContext)
506 N = N->pred_empty() ? NULL : *(N->pred_begin());
512 BugReport *MacOSKeychainAPIChecker::
513 generateAllocatedDataNotReleasedReport(const AllocationPair &AP,
515 CheckerContext &C) const {
516 const ADFunctionInfo &FI = FunctionsToTrack[AP.second->AllocatorIdx];
518 SmallString<70> sbuf;
519 llvm::raw_svector_ostream os(sbuf);
520 os << "Allocated data is not released: missing a call to '"
521 << FunctionsToTrack[FI.DeallocatorIdx].Name << "'.";
523 // Most bug reports are cached at the location where they occurred.
524 // With leaks, we want to unique them by the location where they were
525 // allocated, and only report a single path.
526 PathDiagnosticLocation LocUsedForUniqueing;
527 const ExplodedNode *AllocNode = getAllocationNode(N, AP.first, C);
528 const Stmt *AllocStmt = 0;
529 ProgramPoint P = AllocNode->getLocation();
530 if (Optional<CallExitEnd> Exit = P.getAs<CallExitEnd>())
531 AllocStmt = Exit->getCalleeContext()->getCallSite();
532 else if (Optional<clang::PostStmt> PS = P.getAs<clang::PostStmt>())
533 AllocStmt = PS->getStmt();
536 LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
537 C.getSourceManager(),
538 AllocNode->getLocationContext());
540 BugReport *Report = new BugReport(*BT, os.str(), N, LocUsedForUniqueing,
541 AllocNode->getLocationContext()->getDecl());
543 Report->addVisitor(new SecKeychainBugVisitor(AP.first));
544 markInteresting(Report, 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 SimpleProgramPointTag Tag("MacOSKeychainAPIChecker : DeadSymbolsLeak");
579 ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
581 // Generate the error reports.
582 for (AllocationPairVec::iterator I = Errors.begin(), E = Errors.end();
584 C.emitReport(generateAllocatedDataNotReleasedReport(*I, 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>();