ObjCContainersChecker.cpp source code [clang_source_code/lib/StaticAnalyzer/Checkers/ObjCContainersChecker.cpp]

1	//== ObjCContainersChecker.cpp - Path sensitive checker for CFArray - 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	// Performs path sensitive checks of Core Foundation static containers like
10	// CFArray.
11	// 1) Check for buffer overflows:
12	// In CFArrayGetArrayAtIndex( myArray, index), if the index is outside the
13	// index space of theArray (0 to N-1 inclusive (where N is the count of
14	// theArray), the behavior is undefined.
15	//
16	//===----------------------------------------------------------------------===//
17
18	#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
19	#include "clang/AST/ParentMap.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
26	using namespace clang;
27	using namespace ento;
28
29	namespace {
30	class ObjCContainersChecker : public Checker< check::PreStmt<CallExpr>,
31	check::PostStmt<CallExpr>,
32	check::PointerEscape> {
33	mutable std::unique_ptr<BugType> BT;
34	inline void initBugType() const {
35	if (!BT)
36	BT.reset(new BugType(this, "CFArray API",
37	categories::CoreFoundationObjectiveC));
38	}
39
40	inline SymbolRef getArraySym(const Expr *E, CheckerContext &C) const {
41	SVal ArrayRef = C.getSVal(E);
42	SymbolRef ArraySym = ArrayRef.getAsSymbol();
43	return ArraySym;
44	}
45
46	void addSizeInfo(const Expr Array, const Expr Size,
47	CheckerContext &C) const;
48
49	public:
50	/// A tag to id this checker.
51	static void *getTag() { static int Tag; return &Tag; }
52
53	void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
54	void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
55	ProgramStateRef checkPointerEscape(ProgramStateRef State,
56	const InvalidatedSymbols &Escaped,
57	const CallEvent *Call,
58	PointerEscapeKind Kind) const;
59
60	void printState(raw_ostream &OS, ProgramStateRef State,
61	const char NL, const char Sep) const;
62	};
63	} // end anonymous namespace
64
65	// ProgramState trait - a map from array symbol to its state.
66	REGISTER_MAP_WITH_PROGRAMSTATE(ArraySizeMap, SymbolRef, DefinedSVal)
67
68	void ObjCContainersChecker::addSizeInfo(const Expr Array, const Expr Size,
69	CheckerContext &C) const {
70	ProgramStateRef State = C.getState();
71	SVal SizeV = C.getSVal(Size);
72	// Undefined is reported by another checker.
73	if (SizeV.isUnknownOrUndef())
74	return;
75
76	// Get the ArrayRef symbol.
77	SVal ArrayRef = C.getSVal(Array);
78	SymbolRef ArraySym = ArrayRef.getAsSymbol();
79	if (!ArraySym)
80	return;
81
82	C.addTransition(
83	State->set<ArraySizeMap>(ArraySym, SizeV.castAs<DefinedSVal>()));
84	}
85
86	void ObjCContainersChecker::checkPostStmt(const CallExpr *CE,
87	CheckerContext &C) const {
88	StringRef Name = C.getCalleeName(CE);
89	if (Name.empty() \|\| CE->getNumArgs() < 1)
90	return;
91
92	// Add array size information to the state.
93	if (Name.equals("CFArrayCreate")) {
94	if (CE->getNumArgs() < 3)
95	return;
96	// Note, we can visit the Create method in the post-visit because
97	// the CFIndex parameter is passed in by value and will not be invalidated
98	// by the call.
99	addSizeInfo(CE, CE->getArg(2), C);
100	return;
101	}
102
103	if (Name.equals("CFArrayGetCount")) {
104	addSizeInfo(CE->getArg(0), CE, C);
105	return;
106	}
107	}
108
109	void ObjCContainersChecker::checkPreStmt(const CallExpr *CE,
110	CheckerContext &C) const {
111	StringRef Name = C.getCalleeName(CE);
112	if (Name.empty() \|\| CE->getNumArgs() < 2)
113	return;
114
115	// Check the array access.
116	if (Name.equals("CFArrayGetValueAtIndex")) {
117	ProgramStateRef State = C.getState();
118	// Retrieve the size.
119	// Find out if we saw this array symbol before and have information about
120	// it.
121	const Expr *ArrayExpr = CE->getArg(0);
122	SymbolRef ArraySym = getArraySym(ArrayExpr, C);
123	if (!ArraySym)
124	return;
125
126	const DefinedSVal *Size = State->get<ArraySizeMap>(ArraySym);
127
128	if (!Size)
129	return;
130
131	// Get the index.
132	const Expr *IdxExpr = CE->getArg(1);
133	SVal IdxVal = C.getSVal(IdxExpr);
134	if (IdxVal.isUnknownOrUndef())
135	return;
136	DefinedSVal Idx = IdxVal.castAs<DefinedSVal>();
137
138	// Now, check if 'Idx in [0, Size-1]'.
139	const QualType T = IdxExpr->getType();
140	ProgramStateRef StInBound = State->assumeInBound(Idx, *Size, true, T);
141	ProgramStateRef StOutBound = State->assumeInBound(Idx, *Size, false, T);
142	if (StOutBound && !StInBound) {
143	ExplodedNode *N = C.generateErrorNode(StOutBound);
144	if (!N)
145	return;
146	initBugType();
147	auto R = llvm::make_unique<BugReport>(*BT, "Index is out of bounds", N);
148	R->addRange(IdxExpr->getSourceRange());
149	bugreporter::trackExpressionValue(N, IdxExpr, *R,
150	/EnableNullFPSuppression=/false);
151	C.emitReport(std::move(R));
152	return;
153	}
154	}
155	}
156
157	ProgramStateRef
158	ObjCContainersChecker::checkPointerEscape(ProgramStateRef State,
159	const InvalidatedSymbols &Escaped,
160	const CallEvent *Call,
161	PointerEscapeKind Kind) const {
162	for (const auto &Sym : Escaped) {
163	// When a symbol for a mutable array escapes, we can't reason precisely
164	// about its size any more -- so remove it from the map.
165	// Note that we aren't notified here when a CFMutableArrayRef escapes as a
166	// CFArrayRef. This is because CFArrayRef is typedef'd as a pointer to a
167	// const-qualified type.
168	State = State->remove<ArraySizeMap>(Sym);
169	}
170	return State;
171	}
172
173	void ObjCContainersChecker::printState(raw_ostream &OS, ProgramStateRef State,
174	const char NL, const char Sep) const {
175	ArraySizeMapTy Map = State->get<ArraySizeMap>();
176	if (Map.isEmpty())
177	return;
178
179	OS << Sep << "ObjC container sizes :" << NL;
180	for (auto I : Map) {
181	OS << I.first << " : " << I.second << NL;
182	}
183	}
184
185	/// Register checker.
186	void ento::registerObjCContainersChecker(CheckerManager &mgr) {
187	mgr.registerChecker<ObjCContainersChecker>();
188	}
189
190	bool ento::shouldRegisterObjCContainersChecker(const LangOptions &LO) {
191	return true;
192	}
193

Clang Project