// Copyright 2022 Code Intelligence GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.example;

import com.code_intelligence.jazzer.api.FuzzedDataProvider;
import java.util.regex.Pattern;

/**
 * Compiling a regex pattern can lead to stack overflows and thus is caught
 * in the constructor of {@link java.util.regex.Pattern} and rethrown as a
 * {@link java.util.regex.PatternSyntaxException}.
 * The {@link com.code_intelligence.jazzer.sanitizers.RegexInjection} sanitizer
 * uses this exception to detect injections and would incorrectly report a
 * finding. Exceptions caused by stack overflows should not be handled in the
 * hook as it's very unlikely that the fuzzer generates a pattern causing a
 * stack overflow before it generates an invalid one.
 */
@SuppressWarnings({"ReplaceOnLiteralHasNoEffect", "ResultOfMethodCallIgnored"})
public class StackOverflowRegexInjection {
  public static void fuzzerTestOneInput(FuzzedDataProvider ignored) {
    // load regex classes by using them beforehand,
    // otherwise initialization would cause other issues.
    Pattern.compile("\n").matcher("some string").replaceAll("\\\\n");

    generatePatternSyntaxException();
  }

  @SuppressWarnings("InfiniteRecursion")
  private static void generatePatternSyntaxException() {
    // try-catch on every level to not unwind the stack
    try {
      // generate stack overflow
      generatePatternSyntaxException();
    } catch (StackOverflowError e) {
      // invoke regex injection hook
      "some sting".replaceAll("\n", "\\\\n");
    }
  }
}