Repository: llvm/llvm-project
File: clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp (C++)

Code before:
      Mgr->getAnalyzerOptions().getCheckerStringOption(this, Option);
  std::optional<TaintConfiguration> Config =
      getConfiguration<TaintConfiguration>(*Mgr, this, Option, ConfigFile);
  if (!Config) {
    // We don't have external taint config, no parsing required.
    DynamicTaintRules = RuleLookupTy{};
    return;
  }

  GenericTaintRuleParser::RulesContTy Rules{
      ConfigParser.parseConfiguration(Option, std::move(*Config))};

  DynamicTaintRules.emplace(std::make_move_iterator(Rules.begin()),
                            std::make_move_iterator(Rules.end()));
}

// The incoming parameters of the main function get tainted
// if the program called in an untrusted environment.
void GenericTaintChecker::checkBeginFunction(CheckerContext &C) const {
  if (!C.inTopFrame() || C.getAnalysisManager()
                             .getAnalyzerOptions()
                             .ShouldAssumeControlledEnvironment)
    return;

  const auto *FD = dyn_cast<FunctionDecl>(C.getLocationContext()->getDecl());
  if (!FD || !FD->isMain() || FD->param_size() < 2)
    return;

  ProgramStateRef State = C.getState();
  const MemRegion *ArgvReg =
      State->getRegion(FD->parameters()[1], C.getLocationContext());
  SVal ArgvSval = State->getSVal(ArgvReg);
  // Add taintedness to argv**
  State = addTaint(State, ArgvSval);

  const NoteTag *OriginatingTag =
      C.getNoteTag([ArgvSval](PathSensitiveBugReport &BR) -> std::string {
        // We give diagnostics only for taint related reports
        if (!BR.isInteresting(ArgvSval) ||
            BR.getBugType().getCategory() != categories::TaintedData)
          return "";

        return MsgTaintOrigin;
      });
  C.addTransition(State, OriginatingTag);
}

void GenericTaintChecker::checkPreCall(const CallEvent &Call,
                                       CheckerContext &C) const {

  initTaintRules(C);

Review comment (suggestion):
As we discussed in person, you decided to only apply taint to `argv`, because putting taint on `argc` wouldn't be useful in practice. I support this decision, but please update the comments accordingly.

Code after:
      Mgr->getAnalyzerOptions().getCheckerStringOption(this, Option);
  std::optional<TaintConfiguration> Config =
      getConfiguration<TaintConfiguration>(*Mgr, this, Option, ConfigFile);
  if (!Config) {
    // We don't have external taint config, no parsing required.
    DynamicTaintRules = RuleLookupTy{};
    return;
  }

  GenericTaintRuleParser::RulesContTy Rules{
      ConfigParser.parseConfiguration(Option, std::move(*Config))};

  DynamicTaintRules.emplace(std::make_move_iterator(Rules.begin()),
                            std::make_move_iterator(Rules.end()));
}

bool isPointerToCharArray(const QualType &QT) {
  if (!QT->isPointerType())
    return false;
  QualType PointeeType = QT->getPointeeType();
  return PointeeType->isPointerType() &&
         PointeeType->getPointeeType()->isCharType();
}

// The incoming parameters of the main function get tainted
// if the program called in an untrusted environment.
void GenericTaintChecker::checkBeginFunction(CheckerContext &C) const {
  if (!C.inTopFrame() || C.getAnalysisManager()
                             .getAnalyzerOptions()
                             .ShouldAssumeControlledEnvironment)
    return;

  const auto *FD = dyn_cast<FunctionDecl>(C.getLocationContext()->getDecl());
  if (!FD || !FD->isMain() || FD->param_size() < 2)
    return;

  if (!FD->parameters()[0]->getType()->isIntegerType())
    return;

  if (!isPointerToCharArray(FD->parameters()[1]->getType()))
    return;
  ProgramStateRef State = C.getState();

  const MemRegion *ArgcReg =
      State->getRegion(FD->parameters()[0], C.getLocationContext());
  SVal ArgcSVal = State->getSVal(ArgcReg);
  State = addTaint(State, ArgcSVal);
  StringRef ArgcName = FD->parameters()[0]->getName();
  if (auto N = ArgcSVal.getAs<NonLoc>()) {
    ConstraintManager &CM = C.getConstraintManager();
    // The upper bound is the ARG_MAX on an arbitrary Linux