/*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project licenses this file to you 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 io.netty.handler.ssl;
  
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentMap;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Converts a Java cipher suite string to an OpenSSL cipher suite string and vice versa.
   *
   * @see <a href="http://en.wikipedia.org/wiki/Cipher_suite">Wikipedia page about cipher suite</a>
   */
  final class CipherSuiteConverter {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(CipherSuiteConverter.class);
  
      /**
       * A_B_WITH_C_D, where:
       *
       * A - TLS or SSL (protocol)
       * B - handshake algorithm (key exchange and authentication algorithms to be precise)
       * C - bulk cipher
       * D - HMAC algorithm
       *
       * This regular expression assumes that:
       *
       * 1) A is always TLS or SSL, and
       * 2) D is always a single word.
       */
      private static final Pattern JAVA_CIPHERSUITE_PATTERN =
              Pattern.compile("^(?:TLS|SSL)_((?:(?!_WITH_).)+)_WITH_(.*)_(.*)$");
  
      /**
       * A-B-C, where:
       *
       * A - handshake algorithm (key exchange and authentication algorithms to be precise)
       * B - bulk cipher
       * C - HMAC algorithm
       *
       * This regular expression assumes that:
       *
       * 1) A has some deterministic pattern as shown below, and
       * 2) C is always a single word
       */
      private static final Pattern OPENSSL_CIPHERSUITE_PATTERN =
              // Be very careful not to break the indentation while editing.
              Pattern.compile(
                      "^(?:(" + // BEGIN handshake algorithm
                          "(?:(?:EXP-)?" +
                              "(?:" +
                                  "(?:DHE|EDH|ECDH|ECDHE|SRP|RSA)-(?:DSS|RSA|ECDSA|PSK)|" +
                                  "(?:ADH|AECDH|KRB5|PSK|SRP)" +
                              ')' +
                          ")|" +
                          "EXP" +
                      ")-)?" +  // END handshake algorithm
                      "(.*)-(.*)$");
  
      private static final Pattern JAVA_AES_CBC_PATTERN = Pattern.compile("^(AES)_([0-9]+)_CBC$");
      private static final Pattern JAVA_AES_PATTERN = Pattern.compile("^(AES)_([0-9]+)_(.*)$");
      private static final Pattern OPENSSL_AES_CBC_PATTERN = Pattern.compile("^(AES)([0-9]+)$");
      private static final Pattern OPENSSL_AES_PATTERN = Pattern.compile("^(AES)([0-9]+)-(.*)$");
  
      /**
       * Java-to-OpenSSL cipher suite conversion map
       * Note that the Java cipher suite has the protocol prefix (TLS_, SSL_)
       */
      private static final ConcurrentMap<String, String> j2o = PlatformDependent.newConcurrentHashMap();
  
      /**
       * OpenSSL-to-Java cipher suite conversion map.
       * Note that one OpenSSL cipher suite can be converted to more than one Java cipher suites because
       * a Java cipher suite has the protocol name prefix (TLS_, SSL_)
       */
      private static final ConcurrentMap<String, Map<String, String>> o2j = PlatformDependent.newConcurrentHashMap();
  
      /**
       * Clears the cache for testing purpose.
      */
     static void clearCache() {
         j2o.clear();
         o2j.clear();
     }
 
     /**
      * Tests if the specified key-value pair has been cached in Java-to-OpenSSL cache.
      */
     static boolean isJ2OCached(String key, String value) {
         return value.equals(j2o.get(key));
     }
 
     /**
      * Tests if the specified key-value pair has been cached in OpenSSL-to-Java cache.
      */
     static boolean isO2JCached(String key, String protocol, String value) {
         Map<String, String> p2j = o2j.get(key);
         if (p2j == null) {
             return false;
         } else {
             return value.equals(p2j.get(protocol));
         }
     }
 
     /**
      * Converts the specified Java cipher suites to the colon-separated OpenSSL cipher suite specification.
      */
     static String toOpenSsl(Iterable<String> javaCipherSuites) {
         final StringBuilder buf = new StringBuilder();
         for (String c: javaCipherSuites) {
             if (c == null) {
                 break;
             }
 
             String converted = toOpenSsl(c);
             if (converted != null) {
                 c = converted;
             }
 
             buf.append(c);
             buf.append(':');
         }
 
         if (buf.length() > 0) {
             buf.setLength(buf.length() - 1);
             return buf.toString();
         } else {
             return "";
         }
     }
 
     /**
      * Converts the specified Java cipher suite to its corresponding OpenSSL cipher suite name.
      *
      * @return {@code null} if the conversion has failed
      */
     static String toOpenSsl(String javaCipherSuite) {
         String converted = j2o.get(javaCipherSuite);
         if (converted != null) {
             return converted;
         } else {
             return cacheFromJava(javaCipherSuite);
         }
     }
 
     private static String cacheFromJava(String javaCipherSuite) {
         String openSslCipherSuite = toOpenSslUncached(javaCipherSuite);
         if (openSslCipherSuite == null) {
             return null;
         }
 
         // Cache the mapping.
         j2o.putIfAbsent(javaCipherSuite, openSslCipherSuite);
 
         // Cache the reverse mapping after stripping the protocol prefix (TLS_ or SSL_)
         final String javaCipherSuiteSuffix = javaCipherSuite.substring(4);
         Map<String, String> p2j = new HashMap<String, String>(4);
         p2j.put("", javaCipherSuiteSuffix);
         p2j.put("SSL", "SSL_" + javaCipherSuiteSuffix);
         p2j.put("TLS", "TLS_" + javaCipherSuiteSuffix);
         o2j.put(openSslCipherSuite, p2j);
 
         logger.debug("Cipher suite mapping: {} => {}", javaCipherSuite, openSslCipherSuite);
 
         return openSslCipherSuite;
     }
 
     static String toOpenSslUncached(String javaCipherSuite) {
         Matcher m = JAVA_CIPHERSUITE_PATTERN.matcher(javaCipherSuite);
         if (!m.matches()) {
             return null;
         }
 
         String handshakeAlgo = toOpenSslHandshakeAlgo(m.group(1));
         String bulkCipher = toOpenSslBulkCipher(m.group(2));
         String hmacAlgo = toOpenSslHmacAlgo(m.group(3));
         if (handshakeAlgo.isEmpty()) {
             return bulkCipher + '-' + hmacAlgo;
         } else if (bulkCipher.contains("CHACHA20")) {
             return handshakeAlgo + '-' + bulkCipher;
         } else {
             return handshakeAlgo + '-' + bulkCipher + '-' + hmacAlgo;
         }
     }
 
     private static String toOpenSslHandshakeAlgo(String handshakeAlgo) {
         final boolean export = handshakeAlgo.endsWith("_EXPORT");
         if (export) {
             handshakeAlgo = handshakeAlgo.substring(0, handshakeAlgo.length() - 7);
         }
 
         if ("RSA".equals(handshakeAlgo)) {
             handshakeAlgo = "";
         } else if (handshakeAlgo.endsWith("_anon")) {
             handshakeAlgo = 'A' + handshakeAlgo.substring(0, handshakeAlgo.length() - 5);
         }
 
         if (export) {
             if (handshakeAlgo.isEmpty()) {
                 handshakeAlgo = "EXP";
             } else {
                 handshakeAlgo = "EXP-" + handshakeAlgo;
             }
         }
 
         return handshakeAlgo.replace('_', '-');
     }
 
     private static String toOpenSslBulkCipher(String bulkCipher) {
         if (bulkCipher.startsWith("AES_")) {
             Matcher m = JAVA_AES_CBC_PATTERN.matcher(bulkCipher);
             if (m.matches()) {
                 return m.replaceFirst("$1$2");
             }
 
             m = JAVA_AES_PATTERN.matcher(bulkCipher);
             if (m.matches()) {
                 return m.replaceFirst("$1$2-$3");
             }
         }
 
         if ("3DES_EDE_CBC".equals(bulkCipher)) {
             return "DES-CBC3";
         }
 
         if ("RC4_128".equals(bulkCipher) || "RC4_40".equals(bulkCipher)) {
             return "RC4";
         }
 
         if ("DES40_CBC".equals(bulkCipher) || "DES_CBC_40".equals(bulkCipher)) {
             return "DES-CBC";
         }
 
         if ("RC2_CBC_40".equals(bulkCipher)) {
             return "RC2-CBC";
         }
 
         return bulkCipher.replace('_', '-');
     }
 
     private static String toOpenSslHmacAlgo(String hmacAlgo) {
         // Java and OpenSSL use the same algorithm names for:
         //
         //   * SHA
         //   * SHA256
         //   * MD5
         //
         return hmacAlgo;
     }
 
     /**
      * Convert from OpenSSL cipher suite name convention to java cipher suite name convention.
      * @param openSslCipherSuite An OpenSSL cipher suite name.
      * @param protocol The cryptographic protocol (i.e. SSL, TLS, ...).
      * @return The translated cipher suite name according to java conventions. This will not be {@code null}.
      */
     static String toJava(String openSslCipherSuite, String protocol) {
         Map<String, String> p2j = o2j.get(openSslCipherSuite);
         if (p2j == null) {
             p2j = cacheFromOpenSsl(openSslCipherSuite);
             // This may happen if this method is queried when OpenSSL doesn't yet have a cipher setup. It will return
             // "(NONE)" in this case.
             if (p2j == null) {
                 return null;
             }
         }
 
         String javaCipherSuite = p2j.get(protocol);
         if (javaCipherSuite == null) {
             javaCipherSuite = protocol + '_' + p2j.get("");
         }
 
         return javaCipherSuite;
     }
 
     private static Map<String, String> cacheFromOpenSsl(String openSslCipherSuite) {
         String javaCipherSuiteSuffix = toJavaUncached(openSslCipherSuite);
         if (javaCipherSuiteSuffix == null) {
             return null;
         }
 
         final String javaCipherSuiteSsl = "SSL_" + javaCipherSuiteSuffix;
         final String javaCipherSuiteTls = "TLS_" + javaCipherSuiteSuffix;
 
         // Cache the mapping.
         final Map<String, String> p2j = new HashMap<String, String>(4);
         p2j.put("", javaCipherSuiteSuffix);
         p2j.put("SSL", javaCipherSuiteSsl);
         p2j.put("TLS", javaCipherSuiteTls);
         o2j.putIfAbsent(openSslCipherSuite, p2j);
 
         // Cache the reverse mapping after adding the protocol prefix (TLS_ or SSL_)
         j2o.putIfAbsent(javaCipherSuiteTls, openSslCipherSuite);
         j2o.putIfAbsent(javaCipherSuiteSsl, openSslCipherSuite);
 
         logger.debug("Cipher suite mapping: {} => {}", javaCipherSuiteTls, openSslCipherSuite);
         logger.debug("Cipher suite mapping: {} => {}", javaCipherSuiteSsl, openSslCipherSuite);
 
         return p2j;
     }
 
     static String toJavaUncached(String openSslCipherSuite) {
         Matcher m = OPENSSL_CIPHERSUITE_PATTERN.matcher(openSslCipherSuite);
         if (!m.matches()) {
             return null;
         }
 
         String handshakeAlgo = m.group(1);
         final boolean export;
         if (handshakeAlgo == null) {
             handshakeAlgo = "";
             export = false;
         } else if (handshakeAlgo.startsWith("EXP-")) {
             handshakeAlgo = handshakeAlgo.substring(4);
             export = true;
         } else if ("EXP".equals(handshakeAlgo)) {
             handshakeAlgo = "";
             export = true;
         } else {
             export = false;
         }
 
         handshakeAlgo = toJavaHandshakeAlgo(handshakeAlgo, export);
         String bulkCipher = toJavaBulkCipher(m.group(2), export);
         String hmacAlgo = toJavaHmacAlgo(m.group(3));
 
         String javaCipherSuite = handshakeAlgo + "_WITH_" + bulkCipher + '_' + hmacAlgo;
         // For historical reasons the CHACHA20 ciphers do not follow OpenSSL's custom naming convention and omits the
         // HMAC algorithm portion of the name. There is currently no way to derive this information because it is
         // omitted from the OpenSSL cipher name, but they currently all use SHA256 for HMAC [1].
         // [1] https://www.openssl.org/docs/man1.1.0/apps/ciphers.html
         return bulkCipher.contains("CHACHA20") ? javaCipherSuite + "_SHA256" : javaCipherSuite;
     }
 
     private static String toJavaHandshakeAlgo(String handshakeAlgo, boolean export) {
         if (handshakeAlgo.isEmpty()) {
             handshakeAlgo = "RSA";
         } else if ("ADH".equals(handshakeAlgo)) {
             handshakeAlgo = "DH_anon";
         } else if ("AECDH".equals(handshakeAlgo)) {
             handshakeAlgo = "ECDH_anon";
         }
 
         handshakeAlgo = handshakeAlgo.replace('-', '_');
         if (export) {
             return handshakeAlgo + "_EXPORT";
         } else {
             return handshakeAlgo;
         }
     }
 
     private static String toJavaBulkCipher(String bulkCipher, boolean export) {
         if (bulkCipher.startsWith("AES")) {
             Matcher m = OPENSSL_AES_CBC_PATTERN.matcher(bulkCipher);
             if (m.matches()) {
                 return m.replaceFirst("$1_$2_CBC");
             }
 
             m = OPENSSL_AES_PATTERN.matcher(bulkCipher);
             if (m.matches()) {
                 return m.replaceFirst("$1_$2_$3");
             }
         }
 
         if ("DES-CBC3".equals(bulkCipher)) {
             return "3DES_EDE_CBC";
         }
 
         if ("RC4".equals(bulkCipher)) {
             if (export) {
                 return "RC4_40";
             } else {
                 return "RC4_128";
             }
         }
 
         if ("DES-CBC".equals(bulkCipher)) {
             if (export) {
                 return "DES_CBC_40";
             } else {
                 return "DES_CBC";
             }
         }
 
         if ("RC2-CBC".equals(bulkCipher)) {
             if (export) {
                 return "RC2_CBC_40";
             } else {
                 return "RC2_CBC";
             }
         }
 
         return bulkCipher.replace('-', '_');
     }
 
     private static String toJavaHmacAlgo(String hmacAlgo) {
         // Java and OpenSSL use the same algorithm names for:
         //
         //   * SHA
         //   * SHA256
         //   * MD5
         //
         return hmacAlgo;
     }
 
     private CipherSuiteConverter() { }
 }