1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
//== ObjCContainersChecker.cpp - Path sensitive checker for CFArray *- C++ -*=//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Performs path sensitive checks of Core Foundation static containers like
// CFArray.
// 1) Check for buffer overflows:
// In CFArrayGetArrayAtIndex( myArray, index), if the index is outside the
// index space of theArray (0 to N-1 inclusive (where N is the count of
// theArray), the behavior is undefined.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/AST/ParentMap.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
using namespace clang;
using namespace ento;
namespace {
class ObjCContainersChecker : public Checker< check::PreStmt<CallExpr>,
check::PostStmt<CallExpr>,
check::PointerEscape> {
mutable std::unique_ptr<BugType> BT;
inline void initBugType() const {
if (!BT)
BT.reset(new BugType(this, "CFArray API",
categories::CoreFoundationObjectiveC));
}
inline SymbolRef getArraySym(const Expr *E, CheckerContext &C) const {
SVal ArrayRef = C.getSVal(E);
SymbolRef ArraySym = ArrayRef.getAsSymbol();
return ArraySym;
}
void addSizeInfo(const Expr *Array, const Expr *Size,
CheckerContext &C) const;
public:
void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
ProgramStateRef checkPointerEscape(ProgramStateRef State,
const InvalidatedSymbols &Escaped,
const CallEvent *Call,
PointerEscapeKind Kind) const;
void printState(raw_ostream &OS, ProgramStateRef State,
const char *NL, const char *Sep) const override;
};
} // end anonymous namespace
// ProgramState trait - a map from array symbol to its state.
REGISTER_MAP_WITH_PROGRAMSTATE(ArraySizeMap, SymbolRef, DefinedSVal)
void ObjCContainersChecker::addSizeInfo(const Expr *Array, const Expr *Size,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
SVal SizeV = C.getSVal(Size);
// Undefined is reported by another checker.
if (SizeV.isUnknownOrUndef())
return;
// Get the ArrayRef symbol.
SVal ArrayRef = C.getSVal(Array);
SymbolRef ArraySym = ArrayRef.getAsSymbol();
if (!ArraySym)
return;
C.addTransition(
State->set<ArraySizeMap>(ArraySym, SizeV.castAs<DefinedSVal>()));
}
void ObjCContainersChecker::checkPostStmt(const CallExpr *CE,
CheckerContext &C) const {
StringRef Name = C.getCalleeName(CE);
if (Name.empty() || CE->getNumArgs() < 1)
return;
// Add array size information to the state.
if (Name.equals("CFArrayCreate")) {
if (CE->getNumArgs() < 3)
return;
// Note, we can visit the Create method in the post-visit because
// the CFIndex parameter is passed in by value and will not be invalidated
// by the call.
addSizeInfo(CE, CE->getArg(2), C);
return;
}
if (Name.equals("CFArrayGetCount")) {
addSizeInfo(CE->getArg(0), CE, C);
return;
}
}
void ObjCContainersChecker::checkPreStmt(const CallExpr *CE,
CheckerContext &C) const {
StringRef Name = C.getCalleeName(CE);
if (Name.empty() || CE->getNumArgs() < 2)
return;
// Check the array access.
if (Name.equals("CFArrayGetValueAtIndex")) {
ProgramStateRef State = C.getState();
// Retrieve the size.
// Find out if we saw this array symbol before and have information about
// it.
const Expr *ArrayExpr = CE->getArg(0);
SymbolRef ArraySym = getArraySym(ArrayExpr, C);
if (!ArraySym)
return;
const DefinedSVal *Size = State->get<ArraySizeMap>(ArraySym);
if (!Size)
return;
// Get the index.
const Expr *IdxExpr = CE->getArg(1);
SVal IdxVal = C.getSVal(IdxExpr);
if (IdxVal.isUnknownOrUndef())
return;
DefinedSVal Idx = IdxVal.castAs<DefinedSVal>();
// Now, check if 'Idx in [0, Size-1]'.
const QualType T = IdxExpr->getType();
ProgramStateRef StInBound, StOutBound;
std::tie(StInBound, StOutBound) = State->assumeInBoundDual(Idx, *Size, T);
if (StOutBound && !StInBound) {
ExplodedNode *N = C.generateErrorNode(StOutBound);
if (!N)
return;
initBugType();
auto R = std::make_unique<PathSensitiveBugReport>(
*BT, "Index is out of bounds", N);
R->addRange(IdxExpr->getSourceRange());
bugreporter::trackExpressionValue(N, IdxExpr, *R,
{bugreporter::TrackingKind::Thorough,
/*EnableNullFPSuppression=*/false});
C.emitReport(std::move(R));
return;
}
}
}
ProgramStateRef
ObjCContainersChecker::checkPointerEscape(ProgramStateRef State,
const InvalidatedSymbols &Escaped,
const CallEvent *Call,
PointerEscapeKind Kind) const {
for (const auto &Sym : Escaped) {
// When a symbol for a mutable array escapes, we can't reason precisely
// about its size any more -- so remove it from the map.
// Note that we aren't notified here when a CFMutableArrayRef escapes as a
// CFArrayRef. This is because CFArrayRef is typedef'd as a pointer to a
// const-qualified type.
State = State->remove<ArraySizeMap>(Sym);
}
return State;
}
void ObjCContainersChecker::printState(raw_ostream &OS, ProgramStateRef State,
const char *NL, const char *Sep) const {
ArraySizeMapTy Map = State->get<ArraySizeMap>();
if (Map.isEmpty())
return;
OS << Sep << "ObjC container sizes :" << NL;
for (auto I : Map) {
OS << I.first << " : " << I.second << NL;
}
}
/// Register checker.
void ento::registerObjCContainersChecker(CheckerManager &mgr) {
mgr.registerChecker<ObjCContainersChecker>();
}
bool ento::shouldRegisterObjCContainersChecker(const CheckerManager &mgr) {
return true;
}
|
