513 lines
18 KiB
C++
513 lines
18 KiB
C++
//= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This defines UnixAPIChecker, which is an assortment of checks on calls
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// to various, widely used UNIX/Posix functions.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/Basic/TargetInfo.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace clang;
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using namespace ento;
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enum class OpenVariant {
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/// The standard open() call:
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/// int open(const char *path, int oflag, ...);
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Open,
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/// The variant taking a directory file descriptor and a relative path:
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/// int openat(int fd, const char *path, int oflag, ...);
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OpenAt
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};
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namespace {
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class UnixAPIMisuseChecker : public Checker< check::PreStmt<CallExpr> > {
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mutable std::unique_ptr<BugType> BT_open, BT_pthreadOnce;
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mutable Optional<uint64_t> Val_O_CREAT;
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public:
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DefaultBool CheckMisuse, CheckPortability;
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void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
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void CheckOpen(CheckerContext &C, const CallExpr *CE) const;
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void CheckOpenAt(CheckerContext &C, const CallExpr *CE) const;
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void CheckPthreadOnce(CheckerContext &C, const CallExpr *CE) const;
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void CheckOpenVariant(CheckerContext &C,
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const CallExpr *CE, OpenVariant Variant) const;
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void ReportOpenBug(CheckerContext &C,
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ProgramStateRef State,
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const char *Msg,
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SourceRange SR) const;
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};
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class UnixAPIPortabilityChecker : public Checker< check::PreStmt<CallExpr> > {
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public:
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void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
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private:
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mutable std::unique_ptr<BugType> BT_mallocZero;
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void CheckCallocZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckMallocZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckReallocZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckReallocfZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckAllocaWithAlignZero(CheckerContext &C, const CallExpr *CE) const;
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void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;
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bool ReportZeroByteAllocation(CheckerContext &C,
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ProgramStateRef falseState,
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const Expr *arg,
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const char *fn_name) const;
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void BasicAllocationCheck(CheckerContext &C,
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const CallExpr *CE,
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const unsigned numArgs,
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const unsigned sizeArg,
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const char *fn) const;
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};
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} //end anonymous namespace
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static void LazyInitialize(const CheckerBase *Checker,
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std::unique_ptr<BugType> &BT,
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const char *name) {
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if (BT)
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return;
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BT.reset(new BugType(Checker, name, categories::UnixAPI));
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}
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//===----------------------------------------------------------------------===//
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// "open" (man 2 open)
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//===----------------------------------------------------------------------===/
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void UnixAPIMisuseChecker::checkPreStmt(const CallExpr *CE,
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CheckerContext &C) const {
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const FunctionDecl *FD = C.getCalleeDecl(CE);
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if (!FD || FD->getKind() != Decl::Function)
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return;
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// Don't treat functions in namespaces with the same name a Unix function
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// as a call to the Unix function.
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const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext();
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if (NamespaceCtx && isa<NamespaceDecl>(NamespaceCtx))
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return;
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StringRef FName = C.getCalleeName(FD);
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if (FName.empty())
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return;
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if (FName == "open")
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CheckOpen(C, CE);
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else if (FName == "openat")
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CheckOpenAt(C, CE);
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else if (FName == "pthread_once")
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CheckPthreadOnce(C, CE);
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}
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void UnixAPIMisuseChecker::ReportOpenBug(CheckerContext &C,
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ProgramStateRef State,
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const char *Msg,
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SourceRange SR) const {
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ExplodedNode *N = C.generateErrorNode(State);
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if (!N)
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return;
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LazyInitialize(this, BT_open, "Improper use of 'open'");
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auto Report = std::make_unique<PathSensitiveBugReport>(*BT_open, Msg, N);
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Report->addRange(SR);
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C.emitReport(std::move(Report));
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}
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void UnixAPIMisuseChecker::CheckOpen(CheckerContext &C,
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const CallExpr *CE) const {
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CheckOpenVariant(C, CE, OpenVariant::Open);
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}
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void UnixAPIMisuseChecker::CheckOpenAt(CheckerContext &C,
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const CallExpr *CE) const {
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CheckOpenVariant(C, CE, OpenVariant::OpenAt);
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}
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void UnixAPIMisuseChecker::CheckOpenVariant(CheckerContext &C,
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const CallExpr *CE,
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OpenVariant Variant) const {
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// The index of the argument taking the flags open flags (O_RDONLY,
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// O_WRONLY, O_CREAT, etc.),
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unsigned int FlagsArgIndex;
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const char *VariantName;
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switch (Variant) {
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case OpenVariant::Open:
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FlagsArgIndex = 1;
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VariantName = "open";
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break;
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case OpenVariant::OpenAt:
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FlagsArgIndex = 2;
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VariantName = "openat";
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break;
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};
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// All calls should at least provide arguments up to the 'flags' parameter.
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unsigned int MinArgCount = FlagsArgIndex + 1;
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// If the flags has O_CREAT set then open/openat() require an additional
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// argument specifying the file mode (permission bits) for the created file.
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unsigned int CreateModeArgIndex = FlagsArgIndex + 1;
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// The create mode argument should be the last argument.
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unsigned int MaxArgCount = CreateModeArgIndex + 1;
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ProgramStateRef state = C.getState();
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if (CE->getNumArgs() < MinArgCount) {
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// The frontend should issue a warning for this case, so this is a sanity
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// check.
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return;
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} else if (CE->getNumArgs() == MaxArgCount) {
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const Expr *Arg = CE->getArg(CreateModeArgIndex);
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QualType QT = Arg->getType();
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if (!QT->isIntegerType()) {
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SmallString<256> SBuf;
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llvm::raw_svector_ostream OS(SBuf);
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OS << "The " << CreateModeArgIndex + 1
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<< llvm::getOrdinalSuffix(CreateModeArgIndex + 1)
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<< " argument to '" << VariantName << "' is not an integer";
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ReportOpenBug(C, state,
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SBuf.c_str(),
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Arg->getSourceRange());
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return;
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}
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} else if (CE->getNumArgs() > MaxArgCount) {
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SmallString<256> SBuf;
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llvm::raw_svector_ostream OS(SBuf);
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OS << "Call to '" << VariantName << "' with more than " << MaxArgCount
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<< " arguments";
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ReportOpenBug(C, state,
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SBuf.c_str(),
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CE->getArg(MaxArgCount)->getSourceRange());
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return;
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}
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// The definition of O_CREAT is platform specific. We need a better way
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// of querying this information from the checking environment.
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if (!Val_O_CREAT.hasValue()) {
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if (C.getASTContext().getTargetInfo().getTriple().getVendor()
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== llvm::Triple::Apple)
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Val_O_CREAT = 0x0200;
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else {
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// FIXME: We need a more general way of getting the O_CREAT value.
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// We could possibly grovel through the preprocessor state, but
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// that would require passing the Preprocessor object to the ExprEngine.
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// See also: MallocChecker.cpp / M_ZERO.
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return;
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}
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}
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// Now check if oflags has O_CREAT set.
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const Expr *oflagsEx = CE->getArg(FlagsArgIndex);
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const SVal V = C.getSVal(oflagsEx);
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if (!V.getAs<NonLoc>()) {
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// The case where 'V' can be a location can only be due to a bad header,
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// so in this case bail out.
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return;
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}
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NonLoc oflags = V.castAs<NonLoc>();
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NonLoc ocreateFlag = C.getSValBuilder()
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.makeIntVal(Val_O_CREAT.getValue(), oflagsEx->getType()).castAs<NonLoc>();
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SVal maskedFlagsUC = C.getSValBuilder().evalBinOpNN(state, BO_And,
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oflags, ocreateFlag,
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oflagsEx->getType());
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if (maskedFlagsUC.isUnknownOrUndef())
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return;
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DefinedSVal maskedFlags = maskedFlagsUC.castAs<DefinedSVal>();
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// Check if maskedFlags is non-zero.
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ProgramStateRef trueState, falseState;
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std::tie(trueState, falseState) = state->assume(maskedFlags);
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// Only emit an error if the value of 'maskedFlags' is properly
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// constrained;
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if (!(trueState && !falseState))
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return;
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if (CE->getNumArgs() < MaxArgCount) {
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SmallString<256> SBuf;
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llvm::raw_svector_ostream OS(SBuf);
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OS << "Call to '" << VariantName << "' requires a "
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<< CreateModeArgIndex + 1
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<< llvm::getOrdinalSuffix(CreateModeArgIndex + 1)
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<< " argument when the 'O_CREAT' flag is set";
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ReportOpenBug(C, trueState,
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SBuf.c_str(),
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oflagsEx->getSourceRange());
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}
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}
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//===----------------------------------------------------------------------===//
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// pthread_once
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//===----------------------------------------------------------------------===//
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void UnixAPIMisuseChecker::CheckPthreadOnce(CheckerContext &C,
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const CallExpr *CE) const {
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// This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.
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// They can possibly be refactored.
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if (CE->getNumArgs() < 1)
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return;
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// Check if the first argument is stack allocated. If so, issue a warning
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// because that's likely to be bad news.
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ProgramStateRef state = C.getState();
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const MemRegion *R = C.getSVal(CE->getArg(0)).getAsRegion();
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if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
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return;
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ExplodedNode *N = C.generateErrorNode(state);
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if (!N)
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return;
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SmallString<256> S;
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llvm::raw_svector_ostream os(S);
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os << "Call to 'pthread_once' uses";
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if (const VarRegion *VR = dyn_cast<VarRegion>(R))
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os << " the local variable '" << VR->getDecl()->getName() << '\'';
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else
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os << " stack allocated memory";
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os << " for the \"control\" value. Using such transient memory for "
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"the control value is potentially dangerous.";
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if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
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os << " Perhaps you intended to declare the variable as 'static'?";
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LazyInitialize(this, BT_pthreadOnce, "Improper use of 'pthread_once'");
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auto report =
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std::make_unique<PathSensitiveBugReport>(*BT_pthreadOnce, os.str(), N);
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report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(report));
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}
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//===----------------------------------------------------------------------===//
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// "calloc", "malloc", "realloc", "reallocf", "alloca" and "valloc"
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// with allocation size 0
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//===----------------------------------------------------------------------===//
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// FIXME: Eventually these should be rolled into the MallocChecker, but right now
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// they're more basic and valuable for widespread use.
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// Returns true if we try to do a zero byte allocation, false otherwise.
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// Fills in trueState and falseState.
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static bool IsZeroByteAllocation(ProgramStateRef state,
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const SVal argVal,
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ProgramStateRef *trueState,
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ProgramStateRef *falseState) {
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std::tie(*trueState, *falseState) =
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state->assume(argVal.castAs<DefinedSVal>());
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return (*falseState && !*trueState);
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}
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// Generates an error report, indicating that the function whose name is given
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// will perform a zero byte allocation.
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// Returns false if an error occurred, true otherwise.
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bool UnixAPIPortabilityChecker::ReportZeroByteAllocation(
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CheckerContext &C,
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ProgramStateRef falseState,
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const Expr *arg,
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const char *fn_name) const {
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ExplodedNode *N = C.generateErrorNode(falseState);
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if (!N)
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return false;
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LazyInitialize(this, BT_mallocZero,
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"Undefined allocation of 0 bytes (CERT MEM04-C; CWE-131)");
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SmallString<256> S;
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llvm::raw_svector_ostream os(S);
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os << "Call to '" << fn_name << "' has an allocation size of 0 bytes";
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auto report =
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std::make_unique<PathSensitiveBugReport>(*BT_mallocZero, os.str(), N);
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report->addRange(arg->getSourceRange());
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bugreporter::trackExpressionValue(N, arg, *report);
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C.emitReport(std::move(report));
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return true;
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}
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// Does a basic check for 0-sized allocations suitable for most of the below
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// functions (modulo "calloc")
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void UnixAPIPortabilityChecker::BasicAllocationCheck(CheckerContext &C,
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const CallExpr *CE,
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const unsigned numArgs,
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const unsigned sizeArg,
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const char *fn) const {
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// Sanity check for the correct number of arguments
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if (CE->getNumArgs() != numArgs)
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return;
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// Check if the allocation size is 0.
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ProgramStateRef state = C.getState();
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ProgramStateRef trueState = nullptr, falseState = nullptr;
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const Expr *arg = CE->getArg(sizeArg);
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SVal argVal = C.getSVal(arg);
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if (argVal.isUnknownOrUndef())
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return;
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// Is the value perfectly constrained to zero?
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if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
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(void) ReportZeroByteAllocation(C, falseState, arg, fn);
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return;
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}
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// Assume the value is non-zero going forward.
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assert(trueState);
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if (trueState != state)
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C.addTransition(trueState);
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}
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void UnixAPIPortabilityChecker::CheckCallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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unsigned int nArgs = CE->getNumArgs();
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if (nArgs != 2)
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return;
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ProgramStateRef state = C.getState();
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ProgramStateRef trueState = nullptr, falseState = nullptr;
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unsigned int i;
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for (i = 0; i < nArgs; i++) {
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const Expr *arg = CE->getArg(i);
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SVal argVal = C.getSVal(arg);
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if (argVal.isUnknownOrUndef()) {
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if (i == 0)
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continue;
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else
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return;
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}
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if (IsZeroByteAllocation(state, argVal, &trueState, &falseState)) {
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if (ReportZeroByteAllocation(C, falseState, arg, "calloc"))
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return;
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else if (i == 0)
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continue;
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else
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return;
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}
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}
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// Assume the value is non-zero going forward.
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assert(trueState);
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if (trueState != state)
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C.addTransition(trueState);
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}
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void UnixAPIPortabilityChecker::CheckMallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 1, 0, "malloc");
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}
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void UnixAPIPortabilityChecker::CheckReallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 2, 1, "realloc");
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}
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void UnixAPIPortabilityChecker::CheckReallocfZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 2, 1, "reallocf");
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}
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void UnixAPIPortabilityChecker::CheckAllocaZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 1, 0, "alloca");
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}
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void UnixAPIPortabilityChecker::CheckAllocaWithAlignZero(
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CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 2, 0, "__builtin_alloca_with_align");
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}
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void UnixAPIPortabilityChecker::CheckVallocZero(CheckerContext &C,
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const CallExpr *CE) const {
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BasicAllocationCheck(C, CE, 1, 0, "valloc");
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}
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void UnixAPIPortabilityChecker::checkPreStmt(const CallExpr *CE,
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CheckerContext &C) const {
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const FunctionDecl *FD = C.getCalleeDecl(CE);
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if (!FD || FD->getKind() != Decl::Function)
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return;
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// Don't treat functions in namespaces with the same name a Unix function
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// as a call to the Unix function.
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const DeclContext *NamespaceCtx = FD->getEnclosingNamespaceContext();
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if (NamespaceCtx && isa<NamespaceDecl>(NamespaceCtx))
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return;
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StringRef FName = C.getCalleeName(FD);
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if (FName.empty())
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return;
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if (FName == "calloc")
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CheckCallocZero(C, CE);
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else if (FName == "malloc")
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CheckMallocZero(C, CE);
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else if (FName == "realloc")
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CheckReallocZero(C, CE);
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else if (FName == "reallocf")
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CheckReallocfZero(C, CE);
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else if (FName == "alloca" || FName == "__builtin_alloca")
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CheckAllocaZero(C, CE);
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else if (FName == "__builtin_alloca_with_align")
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CheckAllocaWithAlignZero(C, CE);
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else if (FName == "valloc")
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CheckVallocZero(C, CE);
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}
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//===----------------------------------------------------------------------===//
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// Registration.
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//===----------------------------------------------------------------------===//
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#define REGISTER_CHECKER(CHECKERNAME) \
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void ento::register##CHECKERNAME(CheckerManager &mgr) { \
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mgr.registerChecker<CHECKERNAME>(); \
|
|
} \
|
|
\
|
|
bool ento::shouldRegister##CHECKERNAME(const CheckerManager &mgr) { \
|
|
return true; \
|
|
}
|
|
|
|
REGISTER_CHECKER(UnixAPIMisuseChecker)
|
|
REGISTER_CHECKER(UnixAPIPortabilityChecker)
|