Exemplo n.º 1
0
void ArrayBoundChecker::checkLocation(SVal l, bool isLoad,
                                      CheckerContext &C) const {
  // Check for out of bound array element access.
  const MemRegion *R = l.getAsRegion();
  if (!R)
    return;

  const ElementRegion *ER = dyn_cast<ElementRegion>(R);
  if (!ER)
    return;

  // Get the index of the accessed element.
  DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex());

  // Zero index is always in bound, this also passes ElementRegions created for
  // pointer casts.
  if (Idx.isZeroConstant())
    return;

  const GRState *state = C.getState();

  // Get the size of the array.
  DefinedOrUnknownSVal NumElements 
    = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(), 
                                            ER->getValueType());

  const GRState *StInBound = state->assumeInBound(Idx, NumElements, true);
  const GRState *StOutBound = state->assumeInBound(Idx, NumElements, false);
  if (StOutBound && !StInBound) {
    ExplodedNode *N = C.generateSink(StOutBound);
    if (!N)
      return;
  
    if (!BT)
      BT.reset(new BuiltinBug("Out-of-bound array access",
                       "Access out-of-bound array element (buffer overflow)"));

    // FIXME: It would be nice to eventually make this diagnostic more clear,
    // e.g., by referencing the original declaration or by saying *why* this
    // reference is outside the range.

    // Generate a report for this bug.
    RangedBugReport *report = 
      new RangedBugReport(*BT, BT->getDescription(), N);

    report->addRange(C.getStmt()->getSourceRange());
    C.EmitReport(report);
    return;
  }
  
  // Array bound check succeeded.  From this point forward the array bound
  // should always succeed.
  assert(StInBound);
  C.addTransition(StInBound);
}
Exemplo n.º 2
0
void ReturnPointerRangeChecker::checkPreStmt(const ReturnStmt *RS,
                                             CheckerContext &C) const {
  ProgramStateRef state = C.getState();

  const Expr *RetE = RS->getRetValue();
  if (!RetE)
    return;

  SVal V = state->getSVal(RetE, C.getLocationContext());
  const MemRegion *R = V.getAsRegion();

  const ElementRegion *ER = dyn_cast_or_null<ElementRegion>(R);
  if (!ER)
    return;

  DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
  // Zero index is always in bound, this also passes ElementRegions created for
  // pointer casts.
  if (Idx.isZeroConstant())
    return;
  // FIXME: All of this out-of-bounds checking should eventually be refactored
  // into a common place.

  DefinedOrUnknownSVal NumElements
    = C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(),
                                           ER->getValueType());

  ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true);
  ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false);
  if (StOutBound && !StInBound) {
    ExplodedNode *N = C.generateSink(StOutBound);

    if (!N)
      return;

    // FIXME: This bug correspond to CWE-466.  Eventually we should have bug
    // types explicitly reference such exploit categories (when applicable).
    if (!BT)
      BT.reset(new BuiltinBug(
          this, "Return of pointer value outside of expected range",
          "Returned pointer value points outside the original object "
          "(potential buffer overflow)"));

    // FIXME: It would be nice to eventually make this diagnostic more clear,
    // e.g., by referencing the original declaration or by saying *why* this
    // reference is outside the range.

    // Generate a report for this bug.
    auto report = llvm::make_unique<BugReport>(*BT, BT->getDescription(), N);

    report->addRange(RetE->getSourceRange());
    C.emitReport(std::move(report));
  }
}
Exemplo n.º 3
0
DefinedOrUnknownSVal FieldRegion::getExtent(SValBuilder &svalBuilder) const {
  DefinedOrUnknownSVal Extent = DeclRegion::getExtent(svalBuilder);

  // A zero-length array at the end of a struct often stands for dynamically-
  // allocated extra memory.
  if (Extent.isZeroConstant()) {
    QualType T = getDesugaredValueType(svalBuilder.getContext());

    if (isa<ConstantArrayType>(T))
      return UnknownVal();
  }

  return Extent;
}