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//=- NSErrorChecker.cpp - Coding conventions for uses of NSError -*- 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
//
//===----------------------------------------------------------------------===//
//
// This file defines a CheckNSError, a flow-insenstive check
// that determines if an Objective-C class interface correctly returns
// a non-void return type.
//
// File under feature request PR 2600.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclObjC.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"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
static bool IsNSError(QualType T, IdentifierInfo *II);
static bool IsCFError(QualType T, IdentifierInfo *II);
//===----------------------------------------------------------------------===//
// NSErrorMethodChecker
//===----------------------------------------------------------------------===//
namespace {
class NSErrorMethodChecker
: public Checker< check::ASTDecl<ObjCMethodDecl> > {
mutable IdentifierInfo *II;
public:
NSErrorMethodChecker() : II(nullptr) {}
void checkASTDecl(const ObjCMethodDecl *D,
AnalysisManager &mgr, BugReporter &BR) const;
};
}
void NSErrorMethodChecker::checkASTDecl(const ObjCMethodDecl *D,
AnalysisManager &mgr,
BugReporter &BR) const {
if (!D->isThisDeclarationADefinition())
return;
if (!D->getReturnType()->isVoidType())
return;
if (!II)
II = &D->getASTContext().Idents.get("NSError");
bool hasNSError = false;
for (const auto *I : D->parameters()) {
if (IsNSError(I->getType(), II)) {
hasNSError = true;
break;
}
}
if (hasNSError) {
const char *err = "Method accepting NSError** "
"should have a non-void return value to indicate whether or not an "
"error occurred";
PathDiagnosticLocation L =
PathDiagnosticLocation::create(D, BR.getSourceManager());
BR.EmitBasicReport(D, this, "Bad return type when passing NSError**",
"Coding conventions (Apple)", err, L);
}
}
//===----------------------------------------------------------------------===//
// CFErrorFunctionChecker
//===----------------------------------------------------------------------===//
namespace {
class CFErrorFunctionChecker
: public Checker< check::ASTDecl<FunctionDecl> > {
mutable IdentifierInfo *II;
public:
CFErrorFunctionChecker() : II(nullptr) {}
void checkASTDecl(const FunctionDecl *D,
AnalysisManager &mgr, BugReporter &BR) const;
};
}
void CFErrorFunctionChecker::checkASTDecl(const FunctionDecl *D,
AnalysisManager &mgr,
BugReporter &BR) const {
if (!D->doesThisDeclarationHaveABody())
return;
if (!D->getReturnType()->isVoidType())
return;
if (!II)
II = &D->getASTContext().Idents.get("CFErrorRef");
bool hasCFError = false;
for (auto I : D->parameters()) {
if (IsCFError(I->getType(), II)) {
hasCFError = true;
break;
}
}
if (hasCFError) {
const char *err = "Function accepting CFErrorRef* "
"should have a non-void return value to indicate whether or not an "
"error occurred";
PathDiagnosticLocation L =
PathDiagnosticLocation::create(D, BR.getSourceManager());
BR.EmitBasicReport(D, this, "Bad return type when passing CFErrorRef*",
"Coding conventions (Apple)", err, L);
}
}
//===----------------------------------------------------------------------===//
// NSOrCFErrorDerefChecker
//===----------------------------------------------------------------------===//
namespace {
class NSErrorDerefBug : public BugType {
public:
NSErrorDerefBug(const CheckerBase *Checker)
: BugType(Checker, "NSError** null dereference",
"Coding conventions (Apple)") {}
};
class CFErrorDerefBug : public BugType {
public:
CFErrorDerefBug(const CheckerBase *Checker)
: BugType(Checker, "CFErrorRef* null dereference",
"Coding conventions (Apple)") {}
};
}
namespace {
class NSOrCFErrorDerefChecker
: public Checker< check::Location,
check::Event<ImplicitNullDerefEvent> > {
mutable IdentifierInfo *NSErrorII, *CFErrorII;
mutable std::unique_ptr<NSErrorDerefBug> NSBT;
mutable std::unique_ptr<CFErrorDerefBug> CFBT;
public:
bool ShouldCheckNSError, ShouldCheckCFError;
NSOrCFErrorDerefChecker() : NSErrorII(nullptr), CFErrorII(nullptr),
ShouldCheckNSError(0), ShouldCheckCFError(0) { }
void checkLocation(SVal loc, bool isLoad, const Stmt *S,
CheckerContext &C) const;
void checkEvent(ImplicitNullDerefEvent event) const;
};
}
typedef llvm::ImmutableMap<SymbolRef, unsigned> ErrorOutFlag;
REGISTER_TRAIT_WITH_PROGRAMSTATE(NSErrorOut, ErrorOutFlag)
REGISTER_TRAIT_WITH_PROGRAMSTATE(CFErrorOut, ErrorOutFlag)
template <typename T>
static bool hasFlag(SVal val, ProgramStateRef state) {
if (SymbolRef sym = val.getAsSymbol())
if (const unsigned *attachedFlags = state->get<T>(sym))
return *attachedFlags;
return false;
}
template <typename T>
static void setFlag(ProgramStateRef state, SVal val, CheckerContext &C) {
// We tag the symbol that the SVal wraps.
if (SymbolRef sym = val.getAsSymbol())
C.addTransition(state->set<T>(sym, true));
}
static QualType parameterTypeFromSVal(SVal val, CheckerContext &C) {
const StackFrameContext * SFC = C.getStackFrame();
if (Optional<loc::MemRegionVal> X = val.getAs<loc::MemRegionVal>()) {
const MemRegion* R = X->getRegion();
if (const VarRegion *VR = R->getAs<VarRegion>())
if (const StackArgumentsSpaceRegion *
stackReg = dyn_cast<StackArgumentsSpaceRegion>(VR->getMemorySpace()))
if (stackReg->getStackFrame() == SFC)
return VR->getValueType();
}
return QualType();
}
void NSOrCFErrorDerefChecker::checkLocation(SVal loc, bool isLoad,
const Stmt *S,
CheckerContext &C) const {
if (!isLoad)
return;
if (loc.isUndef() || !loc.getAs<Loc>())
return;
ASTContext &Ctx = C.getASTContext();
ProgramStateRef state = C.getState();
// If we are loading from NSError**/CFErrorRef* parameter, mark the resulting
// SVal so that we can later check it when handling the
// ImplicitNullDerefEvent event.
// FIXME: Cumbersome! Maybe add hook at construction of SVals at start of
// function ?
QualType parmT = parameterTypeFromSVal(loc, C);
if (parmT.isNull())
return;
if (!NSErrorII)
NSErrorII = &Ctx.Idents.get("NSError");
if (!CFErrorII)
CFErrorII = &Ctx.Idents.get("CFErrorRef");
if (ShouldCheckNSError && IsNSError(parmT, NSErrorII)) {
setFlag<NSErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C);
return;
}
if (ShouldCheckCFError && IsCFError(parmT, CFErrorII)) {
setFlag<CFErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C);
return;
}
}
void NSOrCFErrorDerefChecker::checkEvent(ImplicitNullDerefEvent event) const {
if (event.IsLoad)
return;
SVal loc = event.Location;
ProgramStateRef state = event.SinkNode->getState();
BugReporter &BR = *event.BR;
bool isNSError = hasFlag<NSErrorOut>(loc, state);
bool isCFError = false;
if (!isNSError)
isCFError = hasFlag<CFErrorOut>(loc, state);
if (!(isNSError || isCFError))
return;
// Storing to possible null NSError/CFErrorRef out parameter.
SmallString<128> Buf;
llvm::raw_svector_ostream os(Buf);
os << "Potential null dereference. According to coding standards ";
os << (isNSError
? "in 'Creating and Returning NSError Objects' the parameter"
: "documented in CoreFoundation/CFError.h the parameter");
os << " may be null";
BugType *bug = nullptr;
if (isNSError) {
if (!NSBT)
NSBT.reset(new NSErrorDerefBug(this));
bug = NSBT.get();
}
else {
if (!CFBT)
CFBT.reset(new CFErrorDerefBug(this));
bug = CFBT.get();
}
BR.emitReport(
std::make_unique<PathSensitiveBugReport>(*bug, os.str(), event.SinkNode));
}
static bool IsNSError(QualType T, IdentifierInfo *II) {
const PointerType* PPT = T->getAs<PointerType>();
if (!PPT)
return false;
const ObjCObjectPointerType* PT =
PPT->getPointeeType()->getAs<ObjCObjectPointerType>();
if (!PT)
return false;
const ObjCInterfaceDecl *ID = PT->getInterfaceDecl();
// FIXME: Can ID ever be NULL?
if (ID)
return II == ID->getIdentifier();
return false;
}
static bool IsCFError(QualType T, IdentifierInfo *II) {
const PointerType* PPT = T->getAs<PointerType>();
if (!PPT) return false;
const TypedefType* TT = PPT->getPointeeType()->getAs<TypedefType>();
if (!TT) return false;
return TT->getDecl()->getIdentifier() == II;
}
void ento::registerNSOrCFErrorDerefChecker(CheckerManager &mgr) {
mgr.registerChecker<NSOrCFErrorDerefChecker>();
}
bool ento::shouldRegisterNSOrCFErrorDerefChecker(const LangOptions &LO) {
return true;
}
void ento::registerNSErrorChecker(CheckerManager &mgr) {
mgr.registerChecker<NSErrorMethodChecker>();
NSOrCFErrorDerefChecker *checker = mgr.getChecker<NSOrCFErrorDerefChecker>();
checker->ShouldCheckNSError = true;
}
bool ento::shouldRegisterNSErrorChecker(const LangOptions &LO) {
return true;
}
void ento::registerCFErrorChecker(CheckerManager &mgr) {
mgr.registerChecker<CFErrorFunctionChecker>();
NSOrCFErrorDerefChecker *checker = mgr.getChecker<NSOrCFErrorDerefChecker>();
checker->ShouldCheckCFError = true;
}
bool ento::shouldRegisterCFErrorChecker(const LangOptions &LO) {
return true;
}