forked from OSchip/llvm-project
143 lines
4.9 KiB
C++
143 lines
4.9 KiB
C++
//===-- ChrootChecker.cpp - chroot usage checks ---------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines chroot checker, which checks improper use of chroot.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
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using namespace clang;
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using namespace ento;
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namespace {
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// enum value that represent the jail state
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enum Kind { NO_CHROOT, ROOT_CHANGED, JAIL_ENTERED };
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bool isRootChanged(intptr_t k) { return k == ROOT_CHANGED; }
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//bool isJailEntered(intptr_t k) { return k == JAIL_ENTERED; }
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// This checker checks improper use of chroot.
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// The state transition:
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// NO_CHROOT ---chroot(path)--> ROOT_CHANGED ---chdir(/) --> JAIL_ENTERED
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// | |
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// ROOT_CHANGED<--chdir(..)-- JAIL_ENTERED<--chdir(..)--
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// | |
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// bug<--foo()-- JAIL_ENTERED<--foo()--
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class ChrootChecker : public Checker<eval::Call, check::PreCall> {
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// This bug refers to possibly break out of a chroot() jail.
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mutable std::unique_ptr<BuiltinBug> BT_BreakJail;
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const CallDescription Chroot{"chroot", 1}, Chdir{"chdir", 1};
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public:
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ChrootChecker() {}
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static void *getTag() {
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static int x;
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return &x;
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}
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bool evalCall(const CallEvent &Call, CheckerContext &C) const;
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void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
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private:
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void evalChroot(const CallEvent &Call, CheckerContext &C) const;
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void evalChdir(const CallEvent &Call, CheckerContext &C) const;
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};
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} // end anonymous namespace
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bool ChrootChecker::evalCall(const CallEvent &Call, CheckerContext &C) const {
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if (Chroot.matches(Call)) {
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evalChroot(Call, C);
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return true;
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}
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if (Chdir.matches(Call)) {
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evalChdir(Call, C);
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return true;
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}
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return false;
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}
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void ChrootChecker::evalChroot(const CallEvent &Call, CheckerContext &C) const {
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ProgramStateRef state = C.getState();
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ProgramStateManager &Mgr = state->getStateManager();
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// Once encouter a chroot(), set the enum value ROOT_CHANGED directly in
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// the GDM.
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state = Mgr.addGDM(state, ChrootChecker::getTag(), (void*) ROOT_CHANGED);
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C.addTransition(state);
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}
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void ChrootChecker::evalChdir(const CallEvent &Call, CheckerContext &C) const {
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ProgramStateRef state = C.getState();
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ProgramStateManager &Mgr = state->getStateManager();
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// If there are no jail state in the GDM, just return.
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const void *k = state->FindGDM(ChrootChecker::getTag());
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if (!k)
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return;
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// After chdir("/"), enter the jail, set the enum value JAIL_ENTERED.
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const Expr *ArgExpr = Call.getArgExpr(0);
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SVal ArgVal = C.getSVal(ArgExpr);
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if (const MemRegion *R = ArgVal.getAsRegion()) {
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R = R->StripCasts();
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if (const StringRegion* StrRegion= dyn_cast<StringRegion>(R)) {
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const StringLiteral* Str = StrRegion->getStringLiteral();
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if (Str->getString() == "/")
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state = Mgr.addGDM(state, ChrootChecker::getTag(),
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(void*) JAIL_ENTERED);
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}
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}
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C.addTransition(state);
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}
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// Check the jail state before any function call except chroot and chdir().
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void ChrootChecker::checkPreCall(const CallEvent &Call,
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CheckerContext &C) const {
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// Ignore chroot and chdir.
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if (matchesAny(Call, Chroot, Chdir))
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return;
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// If jail state is ROOT_CHANGED, generate BugReport.
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void *const* k = C.getState()->FindGDM(ChrootChecker::getTag());
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if (k)
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if (isRootChanged((intptr_t) *k))
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if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
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if (!BT_BreakJail)
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BT_BreakJail.reset(new BuiltinBug(
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this, "Break out of jail", "No call of chdir(\"/\") immediately "
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"after chroot"));
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C.emitReport(std::make_unique<PathSensitiveBugReport>(
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*BT_BreakJail, BT_BreakJail->getDescription(), N));
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}
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}
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void ento::registerChrootChecker(CheckerManager &mgr) {
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mgr.registerChecker<ChrootChecker>();
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}
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bool ento::shouldRegisterChrootChecker(const CheckerManager &mgr) {
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return true;
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}
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