Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 1 | //===- Chrootchecker.cpp -------- Basic security checks ----------*- C++ -*-==// |
| 2 | // |
| 3 | // The LLVM Compiler Infrastructure |
| 4 | // |
| 5 | // This file is distributed under the University of Illinois Open Source |
| 6 | // License. See LICENSE.TXT for details. |
| 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | // |
| 10 | // This file defines chroot checker, which checks improper use of chroot. |
| 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
Argyrios Kyrtzidis | d2592a3 | 2010-12-22 18:53:44 +0000 | [diff] [blame^] | 14 | #include "ExprEngineExperimentalChecks.h" |
Argyrios Kyrtzidis | 98cabba | 2010-12-22 18:51:49 +0000 | [diff] [blame] | 15 | #include "clang/GR/BugReporter/BugType.h" |
| 16 | #include "clang/GR/PathSensitive/CheckerVisitor.h" |
| 17 | #include "clang/GR/PathSensitive/GRState.h" |
| 18 | #include "clang/GR/PathSensitive/GRStateTrait.h" |
| 19 | #include "clang/GR/PathSensitive/SymbolManager.h" |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 20 | #include "llvm/ADT/ImmutableMap.h" |
| 21 | using namespace clang; |
Argyrios Kyrtzidis | 5a4f98f | 2010-12-22 18:53:20 +0000 | [diff] [blame] | 22 | using namespace GR; |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 23 | |
| 24 | namespace { |
| 25 | |
| 26 | // enum value that represent the jail state |
| 27 | enum Kind { NO_CHROOT, ROOT_CHANGED, JAIL_ENTERED }; |
| 28 | |
| 29 | bool isRootChanged(intptr_t k) { return k == ROOT_CHANGED; } |
Chris Lattner | 4505d89 | 2010-10-11 05:38:10 +0000 | [diff] [blame] | 30 | //bool isJailEntered(intptr_t k) { return k == JAIL_ENTERED; } |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 31 | |
| 32 | // This checker checks improper use of chroot. |
| 33 | // The state transition: |
| 34 | // NO_CHROOT ---chroot(path)--> ROOT_CHANGED ---chdir(/) --> JAIL_ENTERED |
| 35 | // | | |
| 36 | // ROOT_CHANGED<--chdir(..)-- JAIL_ENTERED<--chdir(..)-- |
| 37 | // | | |
| 38 | // bug<--foo()-- JAIL_ENTERED<--foo()-- |
| 39 | class ChrootChecker : public CheckerVisitor<ChrootChecker> { |
| 40 | IdentifierInfo *II_chroot, *II_chdir; |
| 41 | // This bug refers to possibly break out of a chroot() jail. |
| 42 | BuiltinBug *BT_BreakJail; |
| 43 | |
| 44 | public: |
| 45 | ChrootChecker() : II_chroot(0), II_chdir(0), BT_BreakJail(0) {} |
| 46 | |
| 47 | static void *getTag() { |
| 48 | static int x; |
| 49 | return &x; |
| 50 | } |
| 51 | |
Ted Kremenek | 9c14953 | 2010-12-01 21:57:22 +0000 | [diff] [blame] | 52 | virtual bool evalCallExpr(CheckerContext &C, const CallExpr *CE); |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 53 | virtual void PreVisitCallExpr(CheckerContext &C, const CallExpr *CE); |
| 54 | |
| 55 | private: |
| 56 | void Chroot(CheckerContext &C, const CallExpr *CE); |
| 57 | void Chdir(CheckerContext &C, const CallExpr *CE); |
| 58 | }; |
| 59 | |
| 60 | } // end anonymous namespace |
| 61 | |
Argyrios Kyrtzidis | d2592a3 | 2010-12-22 18:53:44 +0000 | [diff] [blame^] | 62 | void GR::RegisterChrootChecker(ExprEngine &Eng) { |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 63 | Eng.registerCheck(new ChrootChecker()); |
| 64 | } |
| 65 | |
Ted Kremenek | 9c14953 | 2010-12-01 21:57:22 +0000 | [diff] [blame] | 66 | bool ChrootChecker::evalCallExpr(CheckerContext &C, const CallExpr *CE) { |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 67 | const GRState *state = C.getState(); |
| 68 | const Expr *Callee = CE->getCallee(); |
| 69 | SVal L = state->getSVal(Callee); |
| 70 | const FunctionDecl *FD = L.getAsFunctionDecl(); |
| 71 | if (!FD) |
| 72 | return false; |
| 73 | |
| 74 | ASTContext &Ctx = C.getASTContext(); |
| 75 | if (!II_chroot) |
| 76 | II_chroot = &Ctx.Idents.get("chroot"); |
| 77 | if (!II_chdir) |
| 78 | II_chdir = &Ctx.Idents.get("chdir"); |
| 79 | |
| 80 | if (FD->getIdentifier() == II_chroot) { |
| 81 | Chroot(C, CE); |
| 82 | return true; |
| 83 | } |
| 84 | if (FD->getIdentifier() == II_chdir) { |
| 85 | Chdir(C, CE); |
| 86 | return true; |
| 87 | } |
| 88 | |
| 89 | return false; |
| 90 | } |
| 91 | |
| 92 | void ChrootChecker::Chroot(CheckerContext &C, const CallExpr *CE) { |
| 93 | const GRState *state = C.getState(); |
| 94 | GRStateManager &Mgr = state->getStateManager(); |
| 95 | |
| 96 | // Once encouter a chroot(), set the enum value ROOT_CHANGED directly in |
| 97 | // the GDM. |
| 98 | state = Mgr.addGDM(state, ChrootChecker::getTag(), (void*) ROOT_CHANGED); |
| 99 | C.addTransition(state); |
| 100 | } |
| 101 | |
| 102 | void ChrootChecker::Chdir(CheckerContext &C, const CallExpr *CE) { |
| 103 | const GRState *state = C.getState(); |
| 104 | GRStateManager &Mgr = state->getStateManager(); |
| 105 | |
| 106 | // If there are no jail state in the GDM, just return. |
| 107 | const void* k = state->FindGDM(ChrootChecker::getTag()); |
| 108 | if (!k) |
| 109 | return; |
| 110 | |
| 111 | // After chdir("/"), enter the jail, set the enum value JAIL_ENTERED. |
| 112 | const Expr *ArgExpr = CE->getArg(0); |
| 113 | SVal ArgVal = state->getSVal(ArgExpr); |
| 114 | |
| 115 | if (const MemRegion *R = ArgVal.getAsRegion()) { |
| 116 | R = R->StripCasts(); |
| 117 | if (const StringRegion* StrRegion= dyn_cast<StringRegion>(R)) { |
| 118 | const StringLiteral* Str = StrRegion->getStringLiteral(); |
| 119 | if (Str->getString() == "/") |
| 120 | state = Mgr.addGDM(state, ChrootChecker::getTag(), |
| 121 | (void*) JAIL_ENTERED); |
| 122 | } |
| 123 | } |
| 124 | |
| 125 | C.addTransition(state); |
| 126 | } |
| 127 | |
| 128 | // Check the jail state before any function call except chroot and chdir(). |
| 129 | void ChrootChecker::PreVisitCallExpr(CheckerContext &C, const CallExpr *CE) { |
| 130 | const GRState *state = C.getState(); |
| 131 | const Expr *Callee = CE->getCallee(); |
| 132 | SVal L = state->getSVal(Callee); |
| 133 | const FunctionDecl *FD = L.getAsFunctionDecl(); |
| 134 | if (!FD) |
| 135 | return; |
| 136 | |
| 137 | ASTContext &Ctx = C.getASTContext(); |
| 138 | if (!II_chroot) |
| 139 | II_chroot = &Ctx.Idents.get("chroot"); |
| 140 | if (!II_chdir) |
| 141 | II_chdir = &Ctx.Idents.get("chdir"); |
| 142 | |
| 143 | // Ingnore chroot and chdir. |
| 144 | if (FD->getIdentifier() == II_chroot || FD->getIdentifier() == II_chdir) |
| 145 | return; |
| 146 | |
| 147 | // If jail state is ROOT_CHANGED, generate BugReport. |
| 148 | void* const* k = state->FindGDM(ChrootChecker::getTag()); |
| 149 | if (k) |
| 150 | if (isRootChanged((intptr_t) *k)) |
Ted Kremenek | d048c6e | 2010-12-20 21:19:09 +0000 | [diff] [blame] | 151 | if (ExplodedNode *N = C.generateNode()) { |
Zhongxing Xu | 1c9e6b1 | 2010-10-10 05:45:30 +0000 | [diff] [blame] | 152 | if (!BT_BreakJail) |
| 153 | BT_BreakJail = new BuiltinBug("Break out of jail", |
| 154 | "No call of chdir(\"/\") immediately " |
| 155 | "after chroot"); |
| 156 | BugReport *R = new BugReport(*BT_BreakJail, |
| 157 | BT_BreakJail->getDescription(), N); |
| 158 | C.EmitReport(R); |
| 159 | } |
| 160 | |
| 161 | return; |
| 162 | } |