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
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
|
//===-- StrToNumCheck.cpp - clang-tidy ------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "StrToNumCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/AST/FormatString.h"
#include "llvm/ADT/StringSwitch.h"
#include <cassert>
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace cert {
void StrToNumCheck::registerMatchers(MatchFinder *Finder) {
// Match any function call to the C standard library string conversion
// functions that do no error checking.
Finder->addMatcher(
callExpr(
callee(functionDecl(anyOf(
functionDecl(hasAnyName("::atoi", "::atof", "::atol", "::atoll"))
.bind("converter"),
functionDecl(hasAnyName("::scanf", "::sscanf", "::fscanf",
"::vfscanf", "::vscanf", "::vsscanf"))
.bind("formatted")))))
.bind("expr"),
this);
}
namespace {
enum class ConversionKind {
None,
ToInt,
ToUInt,
ToLongInt,
ToLongUInt,
ToIntMax,
ToUIntMax,
ToFloat,
ToDouble,
ToLongDouble
};
ConversionKind ClassifyConversionFunc(const FunctionDecl *FD) {
return llvm::StringSwitch<ConversionKind>(FD->getName())
.Cases("atoi", "atol", ConversionKind::ToInt)
.Case("atoll", ConversionKind::ToLongInt)
.Case("atof", ConversionKind::ToDouble)
.Default(ConversionKind::None);
}
ConversionKind ClassifyFormatString(StringRef Fmt, const LangOptions &LO,
const TargetInfo &TI) {
// Scan the format string for the first problematic format specifier, then
// report that as the conversion type. This will miss additional conversion
// specifiers, but that is acceptable behavior.
class Handler : public analyze_format_string::FormatStringHandler {
ConversionKind CK;
bool HandleScanfSpecifier(const analyze_scanf::ScanfSpecifier &FS,
const char *startSpecifier,
unsigned specifierLen) override {
// If we just consume the argument without assignment, we don't care
// about it having conversion errors.
if (!FS.consumesDataArgument())
return true;
// Get the conversion specifier and use it to determine the conversion
// kind.
analyze_scanf::ScanfConversionSpecifier SCS = FS.getConversionSpecifier();
if (SCS.isIntArg()) {
switch (FS.getLengthModifier().getKind()) {
case analyze_scanf::LengthModifier::AsLongLong:
CK = ConversionKind::ToLongInt;
break;
case analyze_scanf::LengthModifier::AsIntMax:
CK = ConversionKind::ToIntMax;
break;
default:
CK = ConversionKind::ToInt;
break;
}
} else if (SCS.isUIntArg()) {
switch (FS.getLengthModifier().getKind()) {
case analyze_scanf::LengthModifier::AsLongLong:
CK = ConversionKind::ToLongUInt;
break;
case analyze_scanf::LengthModifier::AsIntMax:
CK = ConversionKind::ToUIntMax;
break;
default:
CK = ConversionKind::ToUInt;
break;
}
} else if (SCS.isDoubleArg()) {
switch (FS.getLengthModifier().getKind()) {
case analyze_scanf::LengthModifier::AsLongDouble:
CK = ConversionKind::ToLongDouble;
break;
case analyze_scanf::LengthModifier::AsLong:
CK = ConversionKind::ToDouble;
break;
default:
CK = ConversionKind::ToFloat;
break;
}
}
// Continue if we have yet to find a conversion kind that we care about.
return CK == ConversionKind::None;
}
public:
Handler() : CK(ConversionKind::None) {}
ConversionKind get() const { return CK; }
};
Handler H;
analyze_format_string::ParseScanfString(H, Fmt.begin(), Fmt.end(), LO, TI);
return H.get();
}
StringRef ClassifyConversionType(ConversionKind K) {
switch (K) {
case ConversionKind::None:
llvm_unreachable("Unexpected conversion kind");
case ConversionKind::ToInt:
case ConversionKind::ToLongInt:
case ConversionKind::ToIntMax:
return "an integer value";
case ConversionKind::ToUInt:
case ConversionKind::ToLongUInt:
case ConversionKind::ToUIntMax:
return "an unsigned integer value";
case ConversionKind::ToFloat:
case ConversionKind::ToDouble:
case ConversionKind::ToLongDouble:
return "a floating-point value";
}
llvm_unreachable("Unknown conversion kind");
}
StringRef ClassifyReplacement(ConversionKind K) {
switch (K) {
case ConversionKind::None:
llvm_unreachable("Unexpected conversion kind");
case ConversionKind::ToInt:
return "strtol";
case ConversionKind::ToUInt:
return "strtoul";
case ConversionKind::ToIntMax:
return "strtoimax";
case ConversionKind::ToLongInt:
return "strtoll";
case ConversionKind::ToLongUInt:
return "strtoull";
case ConversionKind::ToUIntMax:
return "strtoumax";
case ConversionKind::ToFloat:
return "strtof";
case ConversionKind::ToDouble:
return "strtod";
case ConversionKind::ToLongDouble:
return "strtold";
}
llvm_unreachable("Unknown conversion kind");
}
} // unnamed namespace
void StrToNumCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Call = Result.Nodes.getNodeAs<CallExpr>("expr");
const FunctionDecl *FuncDecl = nullptr;
ConversionKind Conversion;
if (const auto *ConverterFunc =
Result.Nodes.getNodeAs<FunctionDecl>("converter")) {
// Converter functions are always incorrect to use.
FuncDecl = ConverterFunc;
Conversion = ClassifyConversionFunc(ConverterFunc);
} else if (const auto *FFD =
Result.Nodes.getNodeAs<FunctionDecl>("formatted")) {
StringRef FmtStr;
// The format string comes from the call expression and depends on which
// flavor of scanf is called.
// Index 0: scanf, vscanf, Index 1: fscanf, sscanf, vfscanf, vsscanf.
unsigned Idx =
(FFD->getName() == "scanf" || FFD->getName() == "vscanf") ? 0 : 1;
// Given the index, see if the call expression argument at that index is
// a string literal.
if (Call->getNumArgs() < Idx)
return;
if (const Expr *Arg = Call->getArg(Idx)->IgnoreParenImpCasts()) {
if (const auto *SL = dyn_cast<StringLiteral>(Arg)) {
FmtStr = SL->getString();
}
}
// If we could not get the format string, bail out.
if (FmtStr.empty())
return;
// Formatted input functions need further checking of the format string to
// determine whether a problematic conversion may be happening.
Conversion = ClassifyFormatString(FmtStr, getLangOpts(),
Result.Context->getTargetInfo());
if (Conversion != ConversionKind::None)
FuncDecl = FFD;
}
if (!FuncDecl)
return;
diag(Call->getExprLoc(),
"%0 used to convert a string to %1, but function will not report "
"conversion errors; consider using '%2' instead")
<< FuncDecl << ClassifyConversionType(Conversion)
<< ClassifyReplacement(Conversion);
}
} // namespace cert
} // namespace tidy
} // namespace clang
|
