MmapWriteExecChecker.cpp source code [clang_source_code/lib/StaticAnalyzer/Checkers/MmapWriteExecChecker.cpp]

1	// MmapWriteExecChecker.cpp - Check for the prot argument -----------------===//
2	//
3	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4	// See https://llvm.org/LICENSE.txt for license information.
5	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6	//
7	//===----------------------------------------------------------------------===//
8	//
9	// This checker tests the 3rd argument of mmap's calls to check if
10	// it is writable and executable in the same time. It's somehow
11	// an optional checker since for example in JIT libraries it is pretty common.
12	//
13	//===----------------------------------------------------------------------===//
14
15	#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
16
17	#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
18	#include "clang/StaticAnalyzer/Core/Checker.h"
19	#include "clang/StaticAnalyzer/Core/CheckerManager.h"
20	#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
21	#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
22
23	using namespace clang;
24	using namespace ento;
25	using llvm::APSInt;
26
27	namespace {
28	class MmapWriteExecChecker : public Checker<check::PreCall> {
29	CallDescription MmapFn;
30	CallDescription MprotectFn;
31	static int ProtWrite;
32	static int ProtExec;
33	static int ProtRead;
34	mutable std::unique_ptr<BugType> BT;
35	public:
36	MmapWriteExecChecker() : MmapFn("mmap", 6), MprotectFn("mprotect", 3) {}
37	void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
38	int ProtExecOv;
39	int ProtReadOv;
40	};
41	}
42
43	int MmapWriteExecChecker::ProtWrite = 0x02;
44	int MmapWriteExecChecker::ProtExec = 0x04;
45	int MmapWriteExecChecker::ProtRead = 0x01;
46
47	void MmapWriteExecChecker::checkPreCall(const CallEvent &Call,
48	CheckerContext &C) const {
49	if (Call.isCalled(MmapFn) \|\| Call.isCalled(MprotectFn)) {
50	SVal ProtVal = Call.getArgSVal(2);
51	Optional<nonloc::ConcreteInt> ProtLoc = ProtVal.getAs<nonloc::ConcreteInt>();
52	int64_t Prot = ProtLoc->getValue().getSExtValue();
53	if (ProtExecOv != ProtExec)
54	ProtExec = ProtExecOv;
55	if (ProtReadOv != ProtRead)
56	ProtRead = ProtReadOv;
57
58	// Wrong settings
59	if (ProtRead == ProtExec)
60	return;
61
62	if ((Prot & (ProtWrite \| ProtExec)) == (ProtWrite \| ProtExec)) {
63	if (!BT)
64	BT.reset(new BugType(this, "W^X check fails, Write Exec prot flags set", "Security"));
65
66	ExplodedNode *N = C.generateNonFatalErrorNode();
67	if (!N)
68	return;
69
70	auto Report = llvm::make_unique<BugReport>(
71	*BT, "Both PROT_WRITE and PROT_EXEC flags are set. This can "
72	"lead to exploitable memory regions, which could be overwritten "
73	"with malicious code", N);
74	Report->addRange(Call.getArgSourceRange(2));
75	C.emitReport(std::move(Report));
76	}
77	}
78	}
79
80	void ento::registerMmapWriteExecChecker(CheckerManager &mgr) {
81	MmapWriteExecChecker *Mwec =
82	mgr.registerChecker<MmapWriteExecChecker>();
83	Mwec->ProtExecOv =
84	mgr.getAnalyzerOptions()
85	.getCheckerIntegerOption(Mwec, "MmapProtExec", 0x04);
86	Mwec->ProtReadOv =
87	mgr.getAnalyzerOptions()
88	.getCheckerIntegerOption(Mwec, "MmapProtRead", 0x01);
89	}
90
91	bool ento::shouldRegisterMmapWriteExecChecker(const LangOptions &LO) {
92	return true;
93	}
94

Clang Project