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//===--- UnsafeFunctionsCheck.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 "UnsafeFunctionsCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/PPCallbacks.h"
#include "clang/Lex/Preprocessor.h"
#include <cassert>
using namespace clang::ast_matchers;
using namespace llvm;
namespace clang {
namespace tidy {
namespace bugprone {
static constexpr llvm::StringLiteral OptionNameReportMoreUnsafeFunctions =
"ReportMoreUnsafeFunctions";
static constexpr llvm::StringLiteral FunctionNamesWithAnnexKReplacementId =
"FunctionNamesWithAnnexKReplacement";
static constexpr llvm::StringLiteral FunctionNamesId = "FunctionsNames";
static constexpr llvm::StringLiteral AdditionalFunctionNamesId =
"AdditionalFunctionsNames";
static constexpr llvm::StringLiteral DeclRefId = "DRE";
static std::optional<std::string>
getAnnexKReplacementFor(StringRef FunctionName) {
return StringSwitch<std::string>(FunctionName)
.Case("strlen", "strnlen_s")
.Case("wcslen", "wcsnlen_s")
.Default((Twine{FunctionName} + "_s").str());
}
static StringRef getReplacementFor(StringRef FunctionName,
bool IsAnnexKAvailable) {
if (IsAnnexKAvailable) {
// Try to find a better replacement from Annex K first.
StringRef AnnexKReplacementFunction =
StringSwitch<StringRef>(FunctionName)
.Cases("asctime", "asctime_r", "asctime_s")
.Case("gets", "gets_s")
.Default({});
if (!AnnexKReplacementFunction.empty())
return AnnexKReplacementFunction;
}
// FIXME: Some of these functions are available in C++ under "std::", and
// should be matched and suggested.
return StringSwitch<StringRef>(FunctionName)
.Cases("asctime", "asctime_r", "strftime")
.Case("gets", "fgets")
.Case("rewind", "fseek")
.Case("setbuf", "setvbuf");
}
static StringRef getReplacementForAdditional(StringRef FunctionName,
bool IsAnnexKAvailable) {
if (IsAnnexKAvailable) {
// Try to find a better replacement from Annex K first.
StringRef AnnexKReplacementFunction = StringSwitch<StringRef>(FunctionName)
.Case("bcopy", "memcpy_s")
.Case("bzero", "memset_s")
.Default({});
if (!AnnexKReplacementFunction.empty())
return AnnexKReplacementFunction;
}
return StringSwitch<StringRef>(FunctionName)
.Case("bcmp", "memcmp")
.Case("bcopy", "memcpy")
.Case("bzero", "memset")
.Case("getpw", "getpwuid")
.Case("vfork", "posix_spawn");
}
/// \returns The rationale for replacing the function \p FunctionName with the
/// safer alternative.
static StringRef getRationaleFor(StringRef FunctionName) {
return StringSwitch<StringRef>(FunctionName)
.Cases("asctime", "asctime_r", "ctime",
"is not bounds-checking and non-reentrant")
.Cases("bcmp", "bcopy", "bzero", "is deprecated")
.Cases("fopen", "freopen", "has no exclusive access to the opened file")
.Case("gets", "is insecure, was deprecated and removed in C11 and C++14")
.Case("getpw", "is dangerous as it may overflow the provided buffer")
.Cases("rewind", "setbuf", "has no error detection")
.Case("vfork", "is insecure as it can lead to denial of service "
"situations in the parent process")
.Default("is not bounds-checking");
}
/// Calculates whether Annex K is available for the current translation unit
/// based on the macro definitions and the language options.
///
/// The result is cached and saved in \p CacheVar.
static bool isAnnexKAvailable(std::optional<bool> &CacheVar, Preprocessor *PP,
const LangOptions &LO) {
if (CacheVar.has_value())
return *CacheVar;
if (!LO.C11)
// TODO: How is "Annex K" available in C++ mode?
return (CacheVar = false).value();
assert(PP && "No Preprocessor registered.");
if (!PP->isMacroDefined("__STDC_LIB_EXT1__") ||
!PP->isMacroDefined("__STDC_WANT_LIB_EXT1__"))
return (CacheVar = false).value();
const auto *MI =
PP->getMacroInfo(PP->getIdentifierInfo("__STDC_WANT_LIB_EXT1__"));
if (!MI || MI->tokens_empty())
return (CacheVar = false).value();
const Token &T = MI->tokens().back();
if (!T.isLiteral() || !T.getLiteralData())
return (CacheVar = false).value();
CacheVar = StringRef(T.getLiteralData(), T.getLength()) == "1";
return CacheVar.value();
}
UnsafeFunctionsCheck::UnsafeFunctionsCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
ReportMoreUnsafeFunctions(
Options.get(OptionNameReportMoreUnsafeFunctions, true)) {}
void UnsafeFunctionsCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, OptionNameReportMoreUnsafeFunctions,
ReportMoreUnsafeFunctions);
}
void UnsafeFunctionsCheck::registerMatchers(MatchFinder *Finder) {
if (getLangOpts().C11) {
// Matching functions with safe replacements only in Annex K.
auto FunctionNamesWithAnnexKReplacementMatcher = hasAnyName(
"::bsearch", "::ctime", "::fopen", "::fprintf", "::freopen", "::fscanf",
"::fwprintf", "::fwscanf", "::getenv", "::gmtime", "::localtime",
"::mbsrtowcs", "::mbstowcs", "::memcpy", "::memmove", "::memset",
"::printf", "::qsort", "::scanf", "::snprintf", "::sprintf", "::sscanf",
"::strcat", "::strcpy", "::strerror", "::strlen", "::strncat",
"::strncpy", "::strtok", "::swprintf", "::swscanf", "::vfprintf",
"::vfscanf", "::vfwprintf", "::vfwscanf", "::vprintf", "::vscanf",
"::vsnprintf", "::vsprintf", "::vsscanf", "::vswprintf", "::vswscanf",
"::vwprintf", "::vwscanf", "::wcrtomb", "::wcscat", "::wcscpy",
"::wcslen", "::wcsncat", "::wcsncpy", "::wcsrtombs", "::wcstok",
"::wcstombs", "::wctomb", "::wmemcpy", "::wmemmove", "::wprintf",
"::wscanf");
Finder->addMatcher(
declRefExpr(to(functionDecl(FunctionNamesWithAnnexKReplacementMatcher)
.bind(FunctionNamesWithAnnexKReplacementId)))
.bind(DeclRefId),
this);
}
// Matching functions with replacements without Annex K.
auto FunctionNamesMatcher =
hasAnyName("::asctime", "asctime_r", "::gets", "::rewind", "::setbuf");
Finder->addMatcher(
declRefExpr(to(functionDecl(FunctionNamesMatcher).bind(FunctionNamesId)))
.bind(DeclRefId),
this);
if (ReportMoreUnsafeFunctions) {
// Matching functions with replacements without Annex K, at user request.
auto AdditionalFunctionNamesMatcher =
hasAnyName("::bcmp", "::bcopy", "::bzero", "::getpw", "::vfork");
Finder->addMatcher(
declRefExpr(to(functionDecl(AdditionalFunctionNamesMatcher)
.bind(AdditionalFunctionNamesId)))
.bind(DeclRefId),
this);
}
}
void UnsafeFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
const auto *DeclRef = Result.Nodes.getNodeAs<DeclRefExpr>(DeclRefId);
const auto *FuncDecl = cast<FunctionDecl>(DeclRef->getDecl());
assert(DeclRef && FuncDecl && "No valid matched node in check()");
const auto *AnnexK = Result.Nodes.getNodeAs<FunctionDecl>(
FunctionNamesWithAnnexKReplacementId);
const auto *Normal = Result.Nodes.getNodeAs<FunctionDecl>(FunctionNamesId);
const auto *Additional =
Result.Nodes.getNodeAs<FunctionDecl>(AdditionalFunctionNamesId);
assert((AnnexK || Normal || Additional) && "No valid match category.");
bool AnnexKIsAvailable =
isAnnexKAvailable(IsAnnexKAvailable, PP, getLangOpts());
StringRef FunctionName = FuncDecl->getName();
const std::optional<std::string> ReplacementFunctionName =
[&]() -> std::optional<std::string> {
if (AnnexK) {
if (AnnexKIsAvailable)
return getAnnexKReplacementFor(FunctionName);
return std::nullopt;
}
if (Normal)
return getReplacementFor(FunctionName, AnnexKIsAvailable).str();
if (Additional)
return getReplacementForAdditional(FunctionName, AnnexKIsAvailable).str();
llvm_unreachable("Unhandled match category");
}();
if (!ReplacementFunctionName)
return;
diag(DeclRef->getExprLoc(), "function %0 %1; '%2' should be used instead")
<< FuncDecl << getRationaleFor(FunctionName)
<< ReplacementFunctionName.value() << DeclRef->getSourceRange();
}
void UnsafeFunctionsCheck::registerPPCallbacks(
const SourceManager &SM, Preprocessor *PP,
Preprocessor * /*ModuleExpanderPP*/) {
this->PP = PP;
}
void UnsafeFunctionsCheck::onEndOfTranslationUnit() {
this->PP = nullptr;
IsAnnexKAvailable.reset();
}
} // namespace bugprone
} // namespace tidy
} // namespace clang
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