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