mcs/class/Mono.Security/Mono.Security.Cryptography/DiffieHellman.cs

   1 //
   2 // DiffieHellman.cs: Defines a base class from which all Diffie-Hellman implementations inherit
   3 //
   4 // Author:
   5 //      Pieter Philippaerts (Pieter@mentalis.org)
   6 //
   7 // (C) 2003 The Mentalis.org Team (http://www.mentalis.org/)
   8 //
   9
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30
  31 using System;
  32 using System.Text;
  33 using System.Security;
  34 using System.Security.Cryptography;
  35 using Mono.Xml;
  36 using Mono.Math;
  37
  38 namespace Mono.Security.Cryptography {
  39         /// <summary>
  40         /// Defines a base class from which all Diffie-Hellman implementations inherit.
  41         /// </summary>
  42         public abstract class DiffieHellman : AsymmetricAlgorithm {
  43                 /// <summary>
  44                 /// Creates an instance of the default implementation of the <see cref="DiffieHellman"/> algorithm.
  45                 /// </summary>
  46                 /// <returns>A new instance of the default implementation of DiffieHellman.</returns>
  47                 public static new DiffieHellman Create () {
  48                         return Create ("Mono.Security.Cryptography.DiffieHellman");
  49                 }
  50                 /// <summary>
  51                 /// Creates an instance of the specified implementation of <see cref="DiffieHellman"/>.
  52                 /// </summary>
  53                 /// <param name="algName">The name of the implementation of DiffieHellman to use.</param>
  54                 /// <returns>A new instance of the specified implementation of DiffieHellman.</returns>
  55                 public static new DiffieHellman Create (string algName) {
  56                         return (DiffieHellman) CryptoConfig.CreateFromName (algName);
  57                 }
  58
  59                 /// <summary>
  60                 /// When overridden in a derived class, creates the key exchange data.
  61                 /// </summary>
  62                 /// <returns>The key exchange data to be sent to the intended recipient.</returns>
  63                 public abstract byte[] CreateKeyExchange();
  64                 /// <summary>
  65                 /// When overridden in a derived class, extracts secret information from the key exchange data.
  66                 /// </summary>
  67                 /// <param name="keyex">The key exchange data within which the secret information is hidden.</param>
  68                 /// <returns>The secret information derived from the key exchange data.</returns>
  69                 public abstract byte[] DecryptKeyExchange (byte[] keyex);
  70
  71                 /// <summary>
  72                 /// When overridden in a derived class, exports the <see cref="DHParameters"/>.
  73                 /// </summary>
  74                 /// <param name="includePrivate"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
  75                 /// <returns>The parameters for Diffie-Hellman.</returns>
  76                 public abstract DHParameters ExportParameters (bool includePrivate);
  77                 /// <summary>
  78                 /// When overridden in a derived class, imports the specified <see cref="DHParameters"/>.
  79                 /// </summary>
  80                 /// <param name="parameters">The parameters for Diffie-Hellman.</param>
  81                 public abstract void ImportParameters (DHParameters parameters);
  82
  83                 private byte[] GetNamedParam(SecurityElement se, string param) {
  84                         SecurityElement sep = se.SearchForChildByTag(param);
  85                         if (sep == null)
  86                                 return null;
  87                         return Convert.FromBase64String(sep.Text);
  88                 }
  89                 /// <summary>
  90                 /// Reconstructs a <see cref="DiffieHellman"/> object from an XML string.
  91                 /// </summary>
  92                 /// <param name="xmlString">The XML string to use to reconstruct the DiffieHellman object.</param>
  93                 /// <exception cref="CryptographicException">One of the values in the XML string is invalid.</exception>
  94                 public override void FromXmlString (string xmlString) {
  95                         if (xmlString == null)
  96                                 throw new ArgumentNullException ("xmlString");
  97
  98                         DHParameters dhParams = new DHParameters();
  99                         try {
 100                                 SecurityParser sp = new SecurityParser();
 101                                 sp.LoadXml(xmlString);
 102                                 SecurityElement se = sp.ToXml();
 103                                 if (se.Tag != "DHKeyValue")
 104                                         throw new CryptographicException();
 105                                 dhParams.P = GetNamedParam(se, "P");
 106                                 dhParams.G = GetNamedParam(se, "G");
 107                                 dhParams.X = GetNamedParam(se, "X");
 108                                 ImportParameters(dhParams);
 109                         } finally {
 110                                 if (dhParams.P != null)
 111                                         Array.Clear(dhParams.P, 0, dhParams.P.Length);
 112                                 if (dhParams.G != null)
 113                                         Array.Clear(dhParams.G, 0, dhParams.G.Length);
 114                                 if (dhParams.X != null)
 115                                         Array.Clear(dhParams.X, 0, dhParams.X.Length);
 116                         }
 117                 }
 118                 /// <summary>
 119                 /// Creates and returns an XML string representation of the current <see cref="DiffieHellman"/> object.
 120                 /// </summary>
 121                 /// <param name="includePrivateParameters"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
 122                 /// <returns>An XML string encoding of the current DiffieHellman object.</returns>
 123                 public override string ToXmlString (bool includePrivateParameters) {
 124                         StringBuilder sb = new StringBuilder ();
 125                         DHParameters dhParams = ExportParameters(includePrivateParameters);
 126                         try {
 127                                 sb.Append ("<DHKeyValue>");
 128
 129                                 sb.Append ("<P>");
 130                                 sb.Append (Convert.ToBase64String (dhParams.P));
 131                                 sb.Append ("</P>");
 132
 133                                 sb.Append ("<G>");
 134                                 sb.Append (Convert.ToBase64String (dhParams.G));
 135                                 sb.Append ("</G>");
 136
 137                                 if (includePrivateParameters) {
 138                                         sb.Append ("<X>");
 139                                         sb.Append (Convert.ToBase64String (dhParams.X));
 140                                         sb.Append ("</X>");
 141                                 }
 142
 143                                 sb.Append ("</DHKeyValue>");
 144                         } finally {
 145                                 Array.Clear(dhParams.P, 0, dhParams.P.Length);
 146                                 Array.Clear(dhParams.G, 0, dhParams.G.Length);
 147                                 if (dhParams.X != null)
 148                                         Array.Clear(dhParams.X, 0, dhParams.X.Length);
 149                         }
 150                         return sb.ToString ();
 151                 }
 152         }
 153 }