d8b6fbc0d0
This is a security check which is disabled by default but will be enabled whenever the user consciously enables the security package. If mmap()ed memory is both writable and executable, it makes it easier for the attacker to execute arbitrary code when contents of this memory are compromised. Some applications require such mmap()s though, such as different sorts of JIT. Patch by David Carlier! Differential Revision: https://reviews.llvm.org/D42645 llvm-svn: 324166
76 lines
2.5 KiB
C++
76 lines
2.5 KiB
C++
// MmapWriteExecChecker.cpp - Check for the prot argument -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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 "ClangSACheckers.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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static int ProtWrite;
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static int ProtExec;
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mutable std::unique_ptr<BugType> BT;
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public:
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MmapWriteExecChecker() : MmapFn("mmap", 6) {}
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void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
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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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void MmapWriteExecChecker::checkPreCall(const CallEvent &Call,
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CheckerContext &C) const {
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if (Call.isCalled(MmapFn)) {
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llvm::Triple Triple = C.getASTContext().getTargetInfo().getTriple();
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if (Triple.isOSGlibc())
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ProtExec = 0x01;
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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 ((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 = llvm::make_unique<BugReport>(
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*BT, "Both PROT_WRITE and PROT_EXEC flags had been set. It can "
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"lead to exploitable memory regions, overwritten with malicious code"
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, 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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mgr.registerChecker<MmapWriteExecChecker>();
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}
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