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
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
//===- Chrootchecker.cpp -------- Basic security checks ---------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines chroot checker, which checks improper use of chroot.
//
//===----------------------------------------------------------------------===//
#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/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
using namespace clang;
using namespace ento;
namespace {
// enum value that represent the jail state
enum Kind { NO_CHROOT, ROOT_CHANGED, JAIL_ENTERED };
bool isRootChanged(intptr_t k) { return k == ROOT_CHANGED; }
//bool isJailEntered(intptr_t k) { return k == JAIL_ENTERED; }
// This checker checks improper use of chroot.
// The state transition:
// NO_CHROOT ---chroot(path)--> ROOT_CHANGED ---chdir(/) --> JAIL_ENTERED
// | |
// ROOT_CHANGED<--chdir(..)-- JAIL_ENTERED<--chdir(..)--
// | |
// bug<--foo()-- JAIL_ENTERED<--foo()--
class ChrootChecker : public Checker<eval::Call, check::PreStmt<CallExpr> > {
mutable IdentifierInfo *II_chroot, *II_chdir;
// This bug refers to possibly break out of a chroot() jail.
mutable std::unique_ptr<BuiltinBug> BT_BreakJail;
public:
ChrootChecker() : II_chroot(nullptr), II_chdir(nullptr) {}
static void *getTag() {
static int x;
return &x;
}
bool evalCall(const CallExpr *CE, CheckerContext &C) const;
void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
private:
void Chroot(CheckerContext &C, const CallExpr *CE) const;
void Chdir(CheckerContext &C, const CallExpr *CE) const;
};
} // end anonymous namespace
bool ChrootChecker::evalCall(const CallExpr *CE, CheckerContext &C) const {
const FunctionDecl *FD = C.getCalleeDecl(CE);
if (!FD)
return false;
ASTContext &Ctx = C.getASTContext();
if (!II_chroot)
II_chroot = &Ctx.Idents.get("chroot");
if (!II_chdir)
II_chdir = &Ctx.Idents.get("chdir");
if (FD->getIdentifier() == II_chroot) {
Chroot(C, CE);
return true;
}
if (FD->getIdentifier() == II_chdir) {
Chdir(C, CE);
return true;
}
return false;
}
void ChrootChecker::Chroot(CheckerContext &C, const CallExpr *CE) const {
ProgramStateRef state = C.getState();
ProgramStateManager &Mgr = state->getStateManager();
// Once encouter a chroot(), set the enum value ROOT_CHANGED directly in
// the GDM.
state = Mgr.addGDM(state, ChrootChecker::getTag(), (void*) ROOT_CHANGED);
C.addTransition(state);
}
void ChrootChecker::Chdir(CheckerContext &C, const CallExpr *CE) const {
ProgramStateRef state = C.getState();
ProgramStateManager &Mgr = state->getStateManager();
// If there are no jail state in the GDM, just return.
const void *k = state->FindGDM(ChrootChecker::getTag());
if (!k)
return;
// After chdir("/"), enter the jail, set the enum value JAIL_ENTERED.
const Expr *ArgExpr = CE->getArg(0);
SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
if (const MemRegion *R = ArgVal.getAsRegion()) {
R = R->StripCasts();
if (const StringRegion* StrRegion= dyn_cast<StringRegion>(R)) {
const StringLiteral* Str = StrRegion->getStringLiteral();
if (Str->getString() == "/")
state = Mgr.addGDM(state, ChrootChecker::getTag(),
(void*) JAIL_ENTERED);
}
}
C.addTransition(state);
}
// Check the jail state before any function call except chroot and chdir().
void ChrootChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
const FunctionDecl *FD = C.getCalleeDecl(CE);
if (!FD)
return;
ASTContext &Ctx = C.getASTContext();
if (!II_chroot)
II_chroot = &Ctx.Idents.get("chroot");
if (!II_chdir)
II_chdir = &Ctx.Idents.get("chdir");
// Ingnore chroot and chdir.
if (FD->getIdentifier() == II_chroot || FD->getIdentifier() == II_chdir)
return;
// If jail state is ROOT_CHANGED, generate BugReport.
void *const* k = C.getState()->FindGDM(ChrootChecker::getTag());
if (k)
if (isRootChanged((intptr_t) *k))
if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
if (!BT_BreakJail)
BT_BreakJail.reset(new BuiltinBug(
this, "Break out of jail", "No call of chdir(\"/\") immediately "
"after chroot"));
C.emitReport(llvm::make_unique<BugReport>(
*BT_BreakJail, BT_BreakJail->getDescription(), N));
}
}
void ento::registerChrootChecker(CheckerManager &mgr) {
mgr.registerChecker<ChrootChecker>();
}
|
