[cfe-commits] r116163 - in /cfe/trunk: lib/Checker/ChrootChecker.cpp lib/Checker/GRExprEngineExperimentalChecks.cpp lib/Checker/GRExprEngineExperimentalChecks.h test/Analysis/chroot.c
Zhongxing Xu
xuzhongxing at gmail.com
Sat Oct 9 22:45:31 PDT 2010
Author: zhongxingxu
Date: Sun Oct 10 00:45:30 2010
New Revision: 116163
URL: http://llvm.org/viewvc/llvm-project?rev=116163&view=rev
Log:
Add experimental chroot check which checks improper use of chroot(). Patch by
Lei Zhang.
Added:
cfe/trunk/lib/Checker/ChrootChecker.cpp
cfe/trunk/test/Analysis/chroot.c
Modified:
cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.cpp
cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.h
Added: cfe/trunk/lib/Checker/ChrootChecker.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Checker/ChrootChecker.cpp?rev=116163&view=auto
==============================================================================
--- cfe/trunk/lib/Checker/ChrootChecker.cpp (added)
+++ cfe/trunk/lib/Checker/ChrootChecker.cpp Sun Oct 10 00:45:30 2010
@@ -0,0 +1,161 @@
+//===- 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 "GRExprEngineExperimentalChecks.h"
+#include "clang/Checker/BugReporter/BugType.h"
+#include "clang/Checker/PathSensitive/CheckerVisitor.h"
+#include "clang/Checker/PathSensitive/GRState.h"
+#include "clang/Checker/PathSensitive/GRStateTrait.h"
+#include "clang/Checker/PathSensitive/SymbolManager.h"
+#include "llvm/ADT/ImmutableMap.h"
+using namespace clang;
+
+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 CheckerVisitor<ChrootChecker> {
+ IdentifierInfo *II_chroot, *II_chdir;
+ // This bug refers to possibly break out of a chroot() jail.
+ BuiltinBug *BT_BreakJail;
+
+public:
+ ChrootChecker() : II_chroot(0), II_chdir(0), BT_BreakJail(0) {}
+
+ static void *getTag() {
+ static int x;
+ return &x;
+ }
+
+ virtual bool EvalCallExpr(CheckerContext &C, const CallExpr *CE);
+ virtual void PreVisitCallExpr(CheckerContext &C, const CallExpr *CE);
+
+private:
+ void Chroot(CheckerContext &C, const CallExpr *CE);
+ void Chdir(CheckerContext &C, const CallExpr *CE);
+};
+
+} // end anonymous namespace
+
+void clang::RegisterChrootChecker(GRExprEngine &Eng) {
+ Eng.registerCheck(new ChrootChecker());
+}
+
+bool ChrootChecker::EvalCallExpr(CheckerContext &C, const CallExpr *CE) {
+ const GRState *state = C.getState();
+ const Expr *Callee = CE->getCallee();
+ SVal L = state->getSVal(Callee);
+ const FunctionDecl *FD = L.getAsFunctionDecl();
+ 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 GRState *state = C.getState();
+ GRStateManager &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 GRState *state = C.getState();
+ GRStateManager &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);
+
+ 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::PreVisitCallExpr(CheckerContext &C, const CallExpr *CE) {
+ const GRState *state = C.getState();
+ const Expr *Callee = CE->getCallee();
+ SVal L = state->getSVal(Callee);
+ const FunctionDecl *FD = L.getAsFunctionDecl();
+ 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 = state->FindGDM(ChrootChecker::getTag());
+ if (k)
+ if (isRootChanged((intptr_t) *k))
+ if (ExplodedNode *N = C.GenerateNode()) {
+ if (!BT_BreakJail)
+ BT_BreakJail = new BuiltinBug("Break out of jail",
+ "No call of chdir(\"/\") immediately "
+ "after chroot");
+ BugReport *R = new BugReport(*BT_BreakJail,
+ BT_BreakJail->getDescription(), N);
+ C.EmitReport(R);
+ }
+
+ return;
+}
Modified: cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.cpp?rev=116163&r1=116162&r2=116163&view=diff
==============================================================================
--- cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.cpp (original)
+++ cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.cpp Sun Oct 10 00:45:30 2010
@@ -22,6 +22,7 @@
// These are checks that never belong as internal checks
// within GRExprEngine.
RegisterCStringChecker(Eng);
+ RegisterChrootChecker(Eng);
RegisterMallocChecker(Eng);
RegisterPthreadLockChecker(Eng);
RegisterStreamChecker(Eng);
Modified: cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.h?rev=116163&r1=116162&r2=116163&view=diff
==============================================================================
--- cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.h (original)
+++ cfe/trunk/lib/Checker/GRExprEngineExperimentalChecks.h Sun Oct 10 00:45:30 2010
@@ -20,6 +20,7 @@
class GRExprEngine;
void RegisterAnalyzerStatsChecker(GRExprEngine &Eng);
+void RegisterChrootChecker(GRExprEngine &Eng);
void RegisterCStringChecker(GRExprEngine &Eng);
void RegisterIdempotentOperationChecker(GRExprEngine &Eng);
void RegisterMallocChecker(GRExprEngine &Eng);
Added: cfe/trunk/test/Analysis/chroot.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/chroot.c?rev=116163&view=auto
==============================================================================
--- cfe/trunk/test/Analysis/chroot.c (added)
+++ cfe/trunk/test/Analysis/chroot.c Sun Oct 10 00:45:30 2010
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -analyze -analyzer-check-objc-mem -analyzer-experimental-checks -analyzer-store region -verify %s
+
+extern int chroot(const char* path);
+extern int chdir(const char* path);
+
+void foo(void) {
+}
+
+void f1(void) {
+ chroot("/usr/local"); // root changed.
+ foo(); // expected-warning {{No call of chdir("/") immediately after chroot}}
+}
+
+void f2(void) {
+ chroot("/usr/local"); // root changed.
+ chdir("/"); // enter the jail.
+ foo(); // no-warning
+}
+
+void f3(void) {
+ chroot("/usr/local"); // root changed.
+ chdir("../"); // change working directory, still out of jail.
+ foo(); // expected-warning {{No call of chdir("/") immediately after chroot}}
+}
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