1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
// MmapWriteExecChecker.cpp - Check for the prot argument -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 "ClangSACheckers.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
using llvm::APSInt;
namespace {
class MmapWriteExecChecker : public Checker<check::PreCall> {
CallDescription MmapFn;
CallDescription MprotectFn;
static int ProtWrite;
static int ProtExec;
static int ProtRead;
mutable std::unique_ptr<BugType> BT;
public:
MmapWriteExecChecker() : MmapFn("mmap", 6), MprotectFn("mprotect", 3) {}
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 (Call.isCalled(MmapFn) || Call.isCalled(MprotectFn)) {
SVal ProtVal = Call.getArgSVal(2);
Optional<nonloc::ConcreteInt> ProtLoc = ProtVal.getAs<nonloc::ConcreteInt>();
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)) {
if (!BT)
BT.reset(new BugType(this, "W^X check fails, Write Exec prot flags set", "Security"));
ExplodedNode *N = C.generateNonFatalErrorNode();
if (!N)
return;
auto Report = llvm::make_unique<BugReport>(
*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("MmapProtExec", 0x04, Mwec);
Mwec->ProtReadOv =
mgr.getAnalyzerOptions()
.getCheckerIntegerOption("MmapProtRead", 0x01, Mwec);
}
|
