1 //=- NSErrorChecker.cpp - Coding conventions for uses of NSError -*- C++ -*-==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines a CheckNSError, a flow-insensitive check
10 // that determines if an Objective-C class interface correctly returns
11 // a non-void return type.
12 //
13 // File under feature request PR 2600.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
18 #include "clang/AST/Decl.h"
19 #include "clang/AST/DeclObjC.h"
20 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
21 #include "clang/StaticAnalyzer/Core/Checker.h"
22 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
23 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
24 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
25 #include "llvm/ADT/SmallString.h"
26 #include "llvm/Support/raw_ostream.h"
27 #include <optional>
28
29 using namespace clang;
30 using namespace ento;
31
32 static bool IsNSError(QualType T, IdentifierInfo *II);
33 static bool IsCFError(QualType T, IdentifierInfo *II);
34
35 //===----------------------------------------------------------------------===//
36 // NSErrorMethodChecker
37 //===----------------------------------------------------------------------===//
38
39 namespace {
40 class NSErrorMethodChecker
41 : public Checker< check::ASTDecl<ObjCMethodDecl> > {
42 mutable IdentifierInfo *II = nullptr;
43
44 public:
45 NSErrorMethodChecker() = default;
46
47 void checkASTDecl(const ObjCMethodDecl *D,
48 AnalysisManager &mgr, BugReporter &BR) const;
49 };
50 }
51
checkASTDecl(const ObjCMethodDecl * D,AnalysisManager & mgr,BugReporter & BR) const52 void NSErrorMethodChecker::checkASTDecl(const ObjCMethodDecl *D,
53 AnalysisManager &mgr,
54 BugReporter &BR) const {
55 if (!D->isThisDeclarationADefinition())
56 return;
57 if (!D->getReturnType()->isVoidType())
58 return;
59
60 if (!II)
61 II = &D->getASTContext().Idents.get("NSError");
62
63 bool hasNSError = false;
64 for (const auto *I : D->parameters()) {
65 if (IsNSError(I->getType(), II)) {
66 hasNSError = true;
67 break;
68 }
69 }
70
71 if (hasNSError) {
72 const char *err = "Method accepting NSError** "
73 "should have a non-void return value to indicate whether or not an "
74 "error occurred";
75 PathDiagnosticLocation L =
76 PathDiagnosticLocation::create(D, BR.getSourceManager());
77 BR.EmitBasicReport(D, this, "Bad return type when passing NSError**",
78 "Coding conventions (Apple)", err, L);
79 }
80 }
81
82 //===----------------------------------------------------------------------===//
83 // CFErrorFunctionChecker
84 //===----------------------------------------------------------------------===//
85
86 namespace {
87 class CFErrorFunctionChecker
88 : public Checker< check::ASTDecl<FunctionDecl> > {
89 mutable IdentifierInfo *II;
90
91 public:
CFErrorFunctionChecker()92 CFErrorFunctionChecker() : II(nullptr) {}
93
94 void checkASTDecl(const FunctionDecl *D,
95 AnalysisManager &mgr, BugReporter &BR) const;
96 };
97 }
98
hasReservedReturnType(const FunctionDecl * D)99 static bool hasReservedReturnType(const FunctionDecl *D) {
100 if (isa<CXXConstructorDecl>(D))
101 return true;
102
103 // operators delete and delete[] are required to have 'void' return type
104 auto OperatorKind = D->getOverloadedOperator();
105 return OperatorKind == OO_Delete || OperatorKind == OO_Array_Delete;
106 }
107
checkASTDecl(const FunctionDecl * D,AnalysisManager & mgr,BugReporter & BR) const108 void CFErrorFunctionChecker::checkASTDecl(const FunctionDecl *D,
109 AnalysisManager &mgr,
110 BugReporter &BR) const {
111 if (!D->doesThisDeclarationHaveABody())
112 return;
113 if (!D->getReturnType()->isVoidType())
114 return;
115 if (hasReservedReturnType(D))
116 return;
117
118 if (!II)
119 II = &D->getASTContext().Idents.get("CFErrorRef");
120
121 bool hasCFError = false;
122 for (auto *I : D->parameters()) {
123 if (IsCFError(I->getType(), II)) {
124 hasCFError = true;
125 break;
126 }
127 }
128
129 if (hasCFError) {
130 const char *err = "Function accepting CFErrorRef* "
131 "should have a non-void return value to indicate whether or not an "
132 "error occurred";
133 PathDiagnosticLocation L =
134 PathDiagnosticLocation::create(D, BR.getSourceManager());
135 BR.EmitBasicReport(D, this, "Bad return type when passing CFErrorRef*",
136 "Coding conventions (Apple)", err, L);
137 }
138 }
139
140 //===----------------------------------------------------------------------===//
141 // NSOrCFErrorDerefChecker
142 //===----------------------------------------------------------------------===//
143
144 namespace {
145
146 class NSErrorDerefBug : public BugType {
147 public:
NSErrorDerefBug(const CheckerNameRef Checker)148 NSErrorDerefBug(const CheckerNameRef Checker)
149 : BugType(Checker, "NSError** null dereference",
150 "Coding conventions (Apple)") {}
151 };
152
153 class CFErrorDerefBug : public BugType {
154 public:
CFErrorDerefBug(const CheckerNameRef Checker)155 CFErrorDerefBug(const CheckerNameRef Checker)
156 : BugType(Checker, "CFErrorRef* null dereference",
157 "Coding conventions (Apple)") {}
158 };
159
160 }
161
162 namespace {
163 class NSOrCFErrorDerefChecker
164 : public Checker< check::Location,
165 check::Event<ImplicitNullDerefEvent> > {
166 mutable IdentifierInfo *NSErrorII, *CFErrorII;
167 mutable std::unique_ptr<NSErrorDerefBug> NSBT;
168 mutable std::unique_ptr<CFErrorDerefBug> CFBT;
169 public:
170 bool ShouldCheckNSError = false, ShouldCheckCFError = false;
171 CheckerNameRef NSErrorName, CFErrorName;
NSOrCFErrorDerefChecker()172 NSOrCFErrorDerefChecker() : NSErrorII(nullptr), CFErrorII(nullptr) {}
173
174 void checkLocation(SVal loc, bool isLoad, const Stmt *S,
175 CheckerContext &C) const;
176 void checkEvent(ImplicitNullDerefEvent event) const;
177 };
178 }
179
180 typedef llvm::ImmutableMap<SymbolRef, unsigned> ErrorOutFlag;
REGISTER_TRAIT_WITH_PROGRAMSTATE(NSErrorOut,ErrorOutFlag)181 REGISTER_TRAIT_WITH_PROGRAMSTATE(NSErrorOut, ErrorOutFlag)
182 REGISTER_TRAIT_WITH_PROGRAMSTATE(CFErrorOut, ErrorOutFlag)
183
184 template <typename T>
185 static bool hasFlag(SVal val, ProgramStateRef state) {
186 if (SymbolRef sym = val.getAsSymbol())
187 if (const unsigned *attachedFlags = state->get<T>(sym))
188 return *attachedFlags;
189 return false;
190 }
191
192 template <typename T>
setFlag(ProgramStateRef state,SVal val,CheckerContext & C)193 static void setFlag(ProgramStateRef state, SVal val, CheckerContext &C) {
194 // We tag the symbol that the SVal wraps.
195 if (SymbolRef sym = val.getAsSymbol())
196 C.addTransition(state->set<T>(sym, true));
197 }
198
parameterTypeFromSVal(SVal val,CheckerContext & C)199 static QualType parameterTypeFromSVal(SVal val, CheckerContext &C) {
200 const StackFrameContext * SFC = C.getStackFrame();
201 if (std::optional<loc::MemRegionVal> X = val.getAs<loc::MemRegionVal>()) {
202 const MemRegion* R = X->getRegion();
203 if (const VarRegion *VR = R->getAs<VarRegion>())
204 if (const StackArgumentsSpaceRegion *
205 stackReg = dyn_cast<StackArgumentsSpaceRegion>(VR->getMemorySpace()))
206 if (stackReg->getStackFrame() == SFC)
207 return VR->getValueType();
208 }
209
210 return QualType();
211 }
212
checkLocation(SVal loc,bool isLoad,const Stmt * S,CheckerContext & C) const213 void NSOrCFErrorDerefChecker::checkLocation(SVal loc, bool isLoad,
214 const Stmt *S,
215 CheckerContext &C) const {
216 if (!isLoad)
217 return;
218 if (loc.isUndef() || !isa<Loc>(loc))
219 return;
220
221 ASTContext &Ctx = C.getASTContext();
222 ProgramStateRef state = C.getState();
223
224 // If we are loading from NSError**/CFErrorRef* parameter, mark the resulting
225 // SVal so that we can later check it when handling the
226 // ImplicitNullDerefEvent event.
227 // FIXME: Cumbersome! Maybe add hook at construction of SVals at start of
228 // function ?
229
230 QualType parmT = parameterTypeFromSVal(loc, C);
231 if (parmT.isNull())
232 return;
233
234 if (!NSErrorII)
235 NSErrorII = &Ctx.Idents.get("NSError");
236 if (!CFErrorII)
237 CFErrorII = &Ctx.Idents.get("CFErrorRef");
238
239 if (ShouldCheckNSError && IsNSError(parmT, NSErrorII)) {
240 setFlag<NSErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C);
241 return;
242 }
243
244 if (ShouldCheckCFError && IsCFError(parmT, CFErrorII)) {
245 setFlag<CFErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C);
246 return;
247 }
248 }
249
checkEvent(ImplicitNullDerefEvent event) const250 void NSOrCFErrorDerefChecker::checkEvent(ImplicitNullDerefEvent event) const {
251 if (event.IsLoad)
252 return;
253
254 SVal loc = event.Location;
255 ProgramStateRef state = event.SinkNode->getState();
256 BugReporter &BR = *event.BR;
257
258 bool isNSError = hasFlag<NSErrorOut>(loc, state);
259 bool isCFError = false;
260 if (!isNSError)
261 isCFError = hasFlag<CFErrorOut>(loc, state);
262
263 if (!(isNSError || isCFError))
264 return;
265
266 // Storing to possible null NSError/CFErrorRef out parameter.
267 SmallString<128> Buf;
268 llvm::raw_svector_ostream os(Buf);
269
270 os << "Potential null dereference. According to coding standards ";
271 os << (isNSError
272 ? "in 'Creating and Returning NSError Objects' the parameter"
273 : "documented in CoreFoundation/CFError.h the parameter");
274
275 os << " may be null";
276
277 BugType *bug = nullptr;
278 if (isNSError) {
279 if (!NSBT)
280 NSBT.reset(new NSErrorDerefBug(NSErrorName));
281 bug = NSBT.get();
282 }
283 else {
284 if (!CFBT)
285 CFBT.reset(new CFErrorDerefBug(CFErrorName));
286 bug = CFBT.get();
287 }
288 BR.emitReport(
289 std::make_unique<PathSensitiveBugReport>(*bug, os.str(), event.SinkNode));
290 }
291
IsNSError(QualType T,IdentifierInfo * II)292 static bool IsNSError(QualType T, IdentifierInfo *II) {
293
294 const PointerType* PPT = T->getAs<PointerType>();
295 if (!PPT)
296 return false;
297
298 const ObjCObjectPointerType* PT =
299 PPT->getPointeeType()->getAs<ObjCObjectPointerType>();
300
301 if (!PT)
302 return false;
303
304 const ObjCInterfaceDecl *ID = PT->getInterfaceDecl();
305
306 // FIXME: Can ID ever be NULL?
307 if (ID)
308 return II == ID->getIdentifier();
309
310 return false;
311 }
312
IsCFError(QualType T,IdentifierInfo * II)313 static bool IsCFError(QualType T, IdentifierInfo *II) {
314 const PointerType* PPT = T->getAs<PointerType>();
315 if (!PPT) return false;
316
317 const TypedefType* TT = PPT->getPointeeType()->getAs<TypedefType>();
318 if (!TT) return false;
319
320 return TT->getDecl()->getIdentifier() == II;
321 }
322
registerNSOrCFErrorDerefChecker(CheckerManager & mgr)323 void ento::registerNSOrCFErrorDerefChecker(CheckerManager &mgr) {
324 mgr.registerChecker<NSOrCFErrorDerefChecker>();
325 }
326
shouldRegisterNSOrCFErrorDerefChecker(const CheckerManager & mgr)327 bool ento::shouldRegisterNSOrCFErrorDerefChecker(const CheckerManager &mgr) {
328 return true;
329 }
330
registerNSErrorChecker(CheckerManager & mgr)331 void ento::registerNSErrorChecker(CheckerManager &mgr) {
332 mgr.registerChecker<NSErrorMethodChecker>();
333 NSOrCFErrorDerefChecker *checker = mgr.getChecker<NSOrCFErrorDerefChecker>();
334 checker->ShouldCheckNSError = true;
335 checker->NSErrorName = mgr.getCurrentCheckerName();
336 }
337
shouldRegisterNSErrorChecker(const CheckerManager & mgr)338 bool ento::shouldRegisterNSErrorChecker(const CheckerManager &mgr) {
339 return true;
340 }
341
registerCFErrorChecker(CheckerManager & mgr)342 void ento::registerCFErrorChecker(CheckerManager &mgr) {
343 mgr.registerChecker<CFErrorFunctionChecker>();
344 NSOrCFErrorDerefChecker *checker = mgr.getChecker<NSOrCFErrorDerefChecker>();
345 checker->ShouldCheckCFError = true;
346 checker->CFErrorName = mgr.getCurrentCheckerName();
347 }
348
shouldRegisterCFErrorChecker(const CheckerManager & mgr)349 bool ento::shouldRegisterCFErrorChecker(const CheckerManager &mgr) {
350 return true;
351 }
352