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// MmapWriteExecChecker.cpp - Check for the prot argument -----------------===//
//
// 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 checker tests the 3rd argument of mmap's calls to check if
// it is writable and executable in the same time. It's somehow
// an optional checker since for example in JIT libraries it is pretty common.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
namespace {
class MmapWriteExecChecker : public Checker<check::PreCall> {
CallDescription MmapFn{CDM::CLibrary, {"mmap"}, 6};
CallDescription MprotectFn{CDM::CLibrary, {"mprotect"}, 3};
static int ProtWrite;
static int ProtExec;
static int ProtRead;
const BugType BT{this, "W^X check fails, Write Exec prot flags set",
"Security"};
public:
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
int ProtExecOv;
int ProtReadOv;
};
}
int MmapWriteExecChecker::ProtWrite = 0x02;
int MmapWriteExecChecker::ProtExec = 0x04;
int MmapWriteExecChecker::ProtRead = 0x01;
void MmapWriteExecChecker::checkPreCall(const CallEvent &Call,
CheckerContext &C) const {
if (matchesAny(Call, MmapFn, MprotectFn)) {
SVal ProtVal = Call.getArgSVal(2);
auto ProtLoc = ProtVal.getAs<nonloc::ConcreteInt>();
if (!ProtLoc)
return;
int64_t Prot = ProtLoc->getValue().getSExtValue();
if (ProtExecOv != ProtExec)
ProtExec = ProtExecOv;
if (ProtReadOv != ProtRead)
ProtRead = ProtReadOv;
// Wrong settings
if (ProtRead == ProtExec)
return;
if ((Prot & (ProtWrite | ProtExec)) == (ProtWrite | ProtExec)) {
ExplodedNode *N = C.generateNonFatalErrorNode();
if (!N)
return;
auto Report = std::make_unique<PathSensitiveBugReport>(
BT,
"Both PROT_WRITE and PROT_EXEC flags are set. This can "
"lead to exploitable memory regions, which could be overwritten "
"with malicious code",
N);
Report->addRange(Call.getArgSourceRange(2));
C.emitReport(std::move(Report));
}
}
}
void ento::registerMmapWriteExecChecker(CheckerManager &mgr) {
MmapWriteExecChecker *Mwec =
mgr.registerChecker<MmapWriteExecChecker>();
Mwec->ProtExecOv =
mgr.getAnalyzerOptions()
.getCheckerIntegerOption(Mwec, "MmapProtExec");
Mwec->ProtReadOv =
mgr.getAnalyzerOptions()
.getCheckerIntegerOption(Mwec, "MmapProtRead");
}
bool ento::shouldRegisterMmapWriteExecChecker(const CheckerManager &mgr) {
return true;
}
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