clang-tools 10.0.0

StringLiteralWithEmbeddedNulCheck.cpp
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1 //===--- StringLiteralWithEmbeddedNulCheck.cpp - clang-tidy----------------===//
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 #include "StringLiteralWithEmbeddedNulCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12
13 using namespace clang::ast_matchers;
14
15 namespace clang {
16 namespace tidy {
17 namespace bugprone {
18
19 namespace {
20 AST_MATCHER(StringLiteral, containsNul) {
21 for (size_t i = 0; i < Node.getLength(); ++i)
22 if (Node.getCodeUnit(i) == '\0')
23 return true;
24 return false;
25 }
26 } // namespace
27
28 void StringLiteralWithEmbeddedNulCheck::registerMatchers(MatchFinder *Finder) {
29 // Match a string that contains embedded NUL character. Extra-checks are
30 // applied in |check| to find incorrectly escaped characters.
31 Finder->addMatcher(stringLiteral(containsNul()).bind("strlit"), this);
32
33 // The remaining checks only apply to C++.
34 if (!getLangOpts().CPlusPlus)
35 return;
36
37 const auto StrLitWithNul =
38 ignoringParenImpCasts(stringLiteral(containsNul()).bind("truncated"));
39
40 // Match string constructor.
41 const auto StringConstructorExpr = expr(anyOf(
42 cxxConstructExpr(argumentCountIs(1),
43 hasDeclaration(cxxMethodDecl(hasName("basic_string")))),
44 // If present, the second argument is the alloc object which must not
45 // be present explicitly.
46 cxxConstructExpr(argumentCountIs(2),
47 hasDeclaration(cxxMethodDecl(hasName("basic_string"))),
48 hasArgument(1, cxxDefaultArgExpr()))));
49
50 // Detect passing a suspicious string literal to a string constructor.
51 // example: std::string str = "abc\0def";
52 Finder->addMatcher(
53 cxxConstructExpr(StringConstructorExpr, hasArgument(0, StrLitWithNul)),
54 this);
55
56 // Detect passing a suspicious string literal through an overloaded operator.
57 Finder->addMatcher(cxxOperatorCallExpr(hasAnyArgument(StrLitWithNul)), this);
58 }
59
60 void StringLiteralWithEmbeddedNulCheck::check(
61 const MatchFinder::MatchResult &Result) {
62 if (const auto *SL = Result.Nodes.getNodeAs<StringLiteral>("strlit")) {
63 for (size_t Offset = 0, Length = SL->getLength(); Offset < Length;
64 ++Offset) {
65 // Find a sequence of character like "\0x12".
66 if (Offset + 3 < Length && SL->getCodeUnit(Offset) == '\0' &&
67 SL->getCodeUnit(Offset + 1) == 'x' &&
68 isDigit(SL->getCodeUnit(Offset + 2)) &&
69 isDigit(SL->getCodeUnit(Offset + 3))) {
70 diag(SL->getBeginLoc(), "suspicious embedded NUL character");
71 return;
72 }
73 }
74 }
75
76 if (const auto *SL = Result.Nodes.getNodeAs<StringLiteral>("truncated")) {
77 diag(SL->getBeginLoc(),
78 "truncated string literal with embedded NUL character");
79 }
80 }
81
82 } // namespace bugprone
83 } // namespace tidy
84 } // namespace clang
clang::ast_matchers
Definition: AbseilMatcher.h:14
clang::ast_matchers::AST_MATCHER
AST_MATCHER(Expr, isMacroID)
Definition: PreferIsaOrDynCastInConditionalsCheck.cpp:18
Offset
size_t Offset
Definition: CodeComplete.cpp:1022
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
Length
unsigned Length
Definition: SourceCodeTests.cpp:87
StringLiteralWithEmbeddedNulCheck.h