/*
    * This file is part of dependency-check-core.
    *
    * 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.
   *
   * Copyright (c) 2015 Institute for Defense Analyses. All Rights Reserved.
   */
  package org.owasp.dependencycheck.analyzer;
  
  import org.apache.commons.io.FileUtils;
  import org.owasp.dependencycheck.Engine;
  import org.owasp.dependencycheck.analyzer.exception.AnalysisException;
  import org.owasp.dependencycheck.dependency.Confidence;
  import org.owasp.dependencycheck.dependency.Dependency;
  import org.owasp.dependencycheck.utils.FileFilterBuilder;
  import org.owasp.dependencycheck.utils.Settings;
  
  import java.io.File;
  import java.io.FileFilter;
  import java.io.IOException;
  import java.nio.charset.Charset;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Used to analyze OpenSSL source code present in the file system.
   *
   * @author Dale Visser
   */
  public class OpenSSLAnalyzer extends AbstractFileTypeAnalyzer {
  
      /**
       * Hexadecimal.
       */
      private static final int HEXADECIMAL = 16;
      /**
       * Filename to analyze. All other .h files get removed from consideration.
       */
      private static final String OPENSSLV_H = "opensslv.h";
  
      /**
       * Filter that detects files named "__init__.py".
       */
      private static final FileFilter OPENSSLV_FILTER = FileFilterBuilder.newInstance().addFilenames(OPENSSLV_H).build();
      /**
       * Open SSL Version number pattern.
       */
      private static final Pattern VERSION_PATTERN = Pattern.compile(
              "define\\s+OPENSSL_VERSION_NUMBER\\s+0x([0-9a-zA-Z]{8})L", Pattern.DOTALL
              | Pattern.CASE_INSENSITIVE);
      /**
       * The offset of the major version number.
       */
      private static final int MAJOR_OFFSET = 28;
      /**
       * The mask for the minor version number.
       */
      private static final long MINOR_MASK = 0x0ff00000L;
      /**
       * The offset of the minor version number.
       */
      private static final int MINOR_OFFSET = 20;
      /**
       * The max for the fix version.
       */
      private static final long FIX_MASK = 0x000ff000L;
      /**
       * The offset for the fix version.
       */
      private static final int FIX_OFFSET = 12;
      /**
       * The mask for the patch version.
       */
      private static final long PATCH_MASK = 0x00000ff0L;
      /**
       * The offset for the patch version.
       */
      private static final int PATCH_OFFSET = 4;
      /**
       * Number of letters.
       */
      private static final int NUM_LETTERS = 26;
      /**
       * The status mask.
       */
      private static final int STATUS_MASK = 0x0000000f;
  
      /**
       * Returns the open SSL version as a string.
      *
      * @param openSSLVersionConstant The open SSL version
      * @return the version of openssl
      */
     static String getOpenSSLVersion(long openSSLVersionConstant) {
         final long major = openSSLVersionConstant >>> MAJOR_OFFSET;
         final long minor = (openSSLVersionConstant & MINOR_MASK) >>> MINOR_OFFSET;
         final long fix = (openSSLVersionConstant & FIX_MASK) >>> FIX_OFFSET;
         final long patchLevel = (openSSLVersionConstant & PATCH_MASK) >>> PATCH_OFFSET;
         final String patch = 0 == patchLevel || patchLevel > NUM_LETTERS ? "" : String.valueOf((char) (patchLevel + 'a' - 1));
         final int statusCode = (int) (openSSLVersionConstant & STATUS_MASK);
         final String status = 0xf == statusCode ? "" : (0 == statusCode ? "-dev" : "-beta" + statusCode);
         return String.format("%d.%d.%d%s%s", major, minor, fix, patch, status);
     }
 
     /**
      * Returns the name of the Python Package Analyzer.
      *
      * @return the name of the analyzer
      */
     @Override
     public String getName() {
         return "OpenSSL Source Analyzer";
     }
 
     /**
      * Tell that we are used for information collection.
      *
      * @return INFORMATION_COLLECTION
      */
     @Override
     public AnalysisPhase getAnalysisPhase() {
         return AnalysisPhase.INFORMATION_COLLECTION;
     }
 
     /**
      * Returns the set of supported file extensions.
      *
      * @return the set of supported file extensions
      */
     @Override
     protected FileFilter getFileFilter() {
         return OPENSSLV_FILTER;
     }
 
     /**
      * No-op initializer implementation.
      *
      * @throws Exception never thrown
      */
     @Override
     protected void initializeFileTypeAnalyzer() throws Exception {
         // Nothing to do here.
     }
 
     /**
      * Analyzes python packages and adds evidence to the dependency.
      *
      * @param dependency the dependency being analyzed
      * @param engine the engine being used to perform the scan
      * @throws AnalysisException thrown if there is an unrecoverable error
      * analyzing the dependency
      */
     @Override
     protected void analyzeFileType(Dependency dependency, Engine engine)
             throws AnalysisException {
         final File file = dependency.getActualFile();
         final String parentName = file.getParentFile().getName();
         boolean found = false;
         final String contents = getFileContents(file);
         if (!contents.isEmpty()) {
             final Matcher matcher = VERSION_PATTERN.matcher(contents);
             if (matcher.find()) {
                 dependency.getVersionEvidence().addEvidence(OPENSSLV_H, "Version Constant",
                         getOpenSSLVersion(Long.parseLong(matcher.group(1), HEXADECIMAL)), Confidence.HIGH);
                 found = true;
             }
         }
         if (found) {
             dependency.setDisplayFileName(parentName + File.separatorChar + OPENSSLV_H);
             dependency.getVendorEvidence().addEvidence(OPENSSLV_H, "Vendor", "OpenSSL", Confidence.HIGHEST);
             dependency.getProductEvidence().addEvidence(OPENSSLV_H, "Product", "OpenSSL", Confidence.HIGHEST);
         } else {
             engine.getDependencies().remove(dependency);
         }
     }
 
     /**
      * Retrieves the contents of a given file.
      *
      * @param actualFile the file to read
      * @return the contents of the file
      * @throws AnalysisException thrown if there is an IO Exception
      */
     private String getFileContents(final File actualFile)
             throws AnalysisException {
         try {
             return FileUtils.readFileToString(actualFile, Charset.defaultCharset()).trim();
         } catch (IOException e) {
             throw new AnalysisException(
                     "Problem occurred while reading dependency file.", e);
         }
     }
 
     /**
      * Returns the setting for the analyzer enabled setting key.
      *
      * @return the setting for the analyzer enabled setting key
      */
     @Override
     protected String getAnalyzerEnabledSettingKey() {
         return Settings.KEYS.ANALYZER_OPENSSL_ENABLED;
     }
 }