clang 10.0.0git

ChrootChecker.cpp
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1 //===-- ChrootChecker.cpp - chroot usage checks ---------------------------===//
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 file defines chroot checker, which checks improper use of chroot.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
14 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
15 #include "clang/StaticAnalyzer/Core/Checker.h"
16 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
22
23 using namespace clang;
24 using namespace ento;
25
26 namespace {
27
28 // enum value that represent the jail state
29 enum Kind { NO_CHROOT, ROOT_CHANGED, JAIL_ENTERED };
30
31 bool isRootChanged(intptr_t k) { return k == ROOT_CHANGED; }
32 //bool isJailEntered(intptr_t k) { return k == JAIL_ENTERED; }
33
34 // This checker checks improper use of chroot.
35 // The state transition:
36 // NO_CHROOT ---chroot(path)--> ROOT_CHANGED ---chdir(/) --> JAIL_ENTERED
37 // | |
38 // ROOT_CHANGED<--chdir(..)-- JAIL_ENTERED<--chdir(..)--
39 // | |
40 // bug<--foo()-- JAIL_ENTERED<--foo()--
41 class ChrootChecker : public Checker<eval::Call, check::PreCall> {
42 // This bug refers to possibly break out of a chroot() jail.
43 mutable std::unique_ptr<BuiltinBug> BT_BreakJail;
44
45 const CallDescription Chroot{"chroot", 1}, Chdir{"chdir", 1};
46
47 public:
48 ChrootChecker() {}
49
50 static void *getTag() {
51 static int x;
52 return &x;
53 }
54
55 bool evalCall(const CallEvent &Call, CheckerContext &C) const;
56 void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
57
58 private:
59 void evalChroot(const CallEvent &Call, CheckerContext &C) const;
60 void evalChdir(const CallEvent &Call, CheckerContext &C) const;
61 };
62
63 } // end anonymous namespace
64
65 bool ChrootChecker::evalCall(const CallEvent &Call, CheckerContext &C) const {
66 if (Call.isCalled(Chroot)) {
67 evalChroot(Call, C);
68 return true;
69 }
70 if (Call.isCalled(Chdir)) {
71 evalChdir(Call, C);
72 return true;
73 }
74
75 return false;
76 }
77
78 void ChrootChecker::evalChroot(const CallEvent &Call, CheckerContext &C) const {
79 ProgramStateRef state = C.getState();
80 ProgramStateManager &Mgr = state->getStateManager();
81
82 // Once encouter a chroot(), set the enum value ROOT_CHANGED directly in
83 // the GDM.
84 state = Mgr.addGDM(state, ChrootChecker::getTag(), (void*) ROOT_CHANGED);
85 C.addTransition(state);
86 }
87
88 void ChrootChecker::evalChdir(const CallEvent &Call, CheckerContext &C) const {
89 ProgramStateRef state = C.getState();
90 ProgramStateManager &Mgr = state->getStateManager();
91
92 // If there are no jail state in the GDM, just return.
93 const void *k = state->FindGDM(ChrootChecker::getTag());
94 if (!k)
95 return;
96
97 // After chdir("/"), enter the jail, set the enum value JAIL_ENTERED.
98 const Expr *ArgExpr = Call.getArgExpr(0);
99 SVal ArgVal = C.getSVal(ArgExpr);
100
101 if (const MemRegion *R = ArgVal.getAsRegion()) {
102 R = R->StripCasts();
103 if (const StringRegion* StrRegion= dyn_cast<StringRegion>(R)) {
104 const StringLiteral* Str = StrRegion->getStringLiteral();
105 if (Str->getString() == "/")
106 state = Mgr.addGDM(state, ChrootChecker::getTag(),
107 (void*) JAIL_ENTERED);
108 }
109 }
110
111 C.addTransition(state);
112 }
113
114 // Check the jail state before any function call except chroot and chdir().
115 void ChrootChecker::checkPreCall(const CallEvent &Call,
116 CheckerContext &C) const {
117 // Ignore chroot and chdir.
118 if (Call.isCalled(Chroot) || Call.isCalled(Chdir))
119 return;
120
121 // If jail state is ROOT_CHANGED, generate BugReport.
122 void *const* k = C.getState()->FindGDM(ChrootChecker::getTag());
123 if (k)
124 if (isRootChanged((intptr_t) *k))
125 if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
126 if (!BT_BreakJail)
127 BT_BreakJail.reset(new BuiltinBug(
128 this, "Break out of jail", "No call of chdir(\"/\") immediately "
129 "after chroot"));
130 C.emitReport(std::make_unique<PathSensitiveBugReport>(
131 *BT_BreakJail, BT_BreakJail->getDescription(), N));
132 }
133 }
134
135 void ento::registerChrootChecker(CheckerManager &mgr) {
136 mgr.registerChecker<ChrootChecker>();
137 }
138
139 bool ento::shouldRegisterChrootChecker(const LangOptions &LO) {
140 return true;
141 }
ento
clang::ento::ProgramStateRef
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
Definition: ProgramState_Fwd.h:37
BugType.h
Checker.h
CheckerManager.h
clang::LangOptions
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:53
clang::CodeGen::state
i32 captured_struct **param SharedsTy A type which contains references the shared variables *param Shareds Context with the list of shared variables from the p *TaskFunction *param Data Additional data for task generation like final * state
Definition: CGOpenMPRuntime.h:802
clang::CallDescription
This class represents a description of a function call using the number of arguments and the name of ...
Definition: CallEvent.h:1058
clang::StringLiteral::getString
StringRef getString() const
Definition: Expr.h:1794
clang::Expr
This represents one expression.
Definition: Expr.h:108
ProgramState.h
BuiltinCheckerRegistration.h
intptr_t
__INTPTR_TYPE__ intptr_t
A signed integer type with the property that any valid pointer to void can be converted to this type...
Definition: opencl-c-base.h:55
Kind
Kind
Definition: ChrootChecker.cpp:29
SymbolManager.h
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:21
clang::StringLiteral
StringLiteral - This represents a string literal expression, e.g.
Definition: Expr.h:1711
ProgramStateTrait.h
CallEvent.h
CallEvent
CheckerContext.h