1 //== ReturnPointerRangeChecker.cpp ------------------------------*- 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 ReturnPointerRangeChecker, which is a path-sensitive check
11 // which looks for an out-of-bound pointer being returned to callers.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
21
22 using namespace clang;
23 using namespace ento;
24
25 namespace {
26 class ReturnPointerRangeChecker :
27 public Checker< check::PreStmt<ReturnStmt> > {
28 mutable llvm::OwningPtr<BuiltinBug> BT;
29 public:
30 void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
31 };
32 }
33
checkPreStmt(const ReturnStmt * RS,CheckerContext & C) const34 void ReturnPointerRangeChecker::checkPreStmt(const ReturnStmt *RS,
35 CheckerContext &C) const {
36 const GRState *state = C.getState();
37
38 const Expr *RetE = RS->getRetValue();
39 if (!RetE)
40 return;
41
42 SVal V = state->getSVal(RetE);
43 const MemRegion *R = V.getAsRegion();
44
45 const ElementRegion *ER = dyn_cast_or_null<ElementRegion>(R);
46 if (!ER)
47 return;
48
49 DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex());
50 // Zero index is always in bound, this also passes ElementRegions created for
51 // pointer casts.
52 if (Idx.isZeroConstant())
53 return;
54 // FIXME: All of this out-of-bounds checking should eventually be refactored
55 // into a common place.
56
57 DefinedOrUnknownSVal NumElements
58 = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(),
59 ER->getValueType());
60
61 const GRState *StInBound = state->assumeInBound(Idx, NumElements, true);
62 const GRState *StOutBound = state->assumeInBound(Idx, NumElements, false);
63 if (StOutBound && !StInBound) {
64 ExplodedNode *N = C.generateSink(StOutBound);
65
66 if (!N)
67 return;
68
69 // FIXME: This bug correspond to CWE-466. Eventually we should have bug
70 // types explicitly reference such exploit categories (when applicable).
71 if (!BT)
72 BT.reset(new BuiltinBug("Return of pointer value outside of expected range",
73 "Returned pointer value points outside the original object "
74 "(potential buffer overflow)"));
75
76 // FIXME: It would be nice to eventually make this diagnostic more clear,
77 // e.g., by referencing the original declaration or by saying *why* this
78 // reference is outside the range.
79
80 // Generate a report for this bug.
81 RangedBugReport *report =
82 new RangedBugReport(*BT, BT->getDescription(), N);
83
84 report->addRange(RetE->getSourceRange());
85 C.EmitReport(report);
86 }
87 }
88
registerReturnPointerRangeChecker(CheckerManager & mgr)89 void ento::registerReturnPointerRangeChecker(CheckerManager &mgr) {
90 mgr.registerChecker<ReturnPointerRangeChecker>();
91 }
92