mcs/class/corlib/System.Security.Cryptography/DSA.cs

   1 //
   2 // System.Security.Cryptography.DSA.cs class implementation
   3 //
   4 // Authors:
   5 //   Thomas Neidhart (tome@sbox.tugraz.at)
   6 //   Sebastien Pouliot (spouliot@motus.com)
   7 //
   8 // Portions (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
   9 //
  10
  11 using System;
  12 using System.Text;
  13
  14 using Mono.Xml;
  15
  16 // References:
  17 // a.   FIPS PUB 186-2: Digital Signature Standard (DSS)
  18 //      http://csrc.nist.gov/publications/fips/fips186-2/fips186-2-change1.pdf
  19
  20 namespace System.Security.Cryptography {
  21
  22         /// <summary>
  23         /// Abstract base class for all implementations of the DSA algorithm
  24         /// </summary>
  25         public abstract class DSA : AsymmetricAlgorithm {
  26
  27                 // LAMESPEC: It says to derive new DSA implemenation from DSA class.
  28                 // Well it's aint gonna be easy this way.
  29                 // RSA constructor is public
  30                 internal DSA () {}
  31
  32                 public static new DSA Create ()
  33                 {
  34                         return Create ("System.Security.Cryptography.DSA");
  35                 }
  36
  37                 public static new DSA Create (string algName)
  38                 {
  39                         return (DSA) CryptoConfig.CreateFromName (algName);
  40                 }
  41
  42                 public abstract byte[] CreateSignature (byte[] rgbHash);
  43
  44                 public abstract DSAParameters ExportParameters (bool includePrivateParameters);
  45
  46                 internal void ZeroizePrivateKey (DSAParameters parameters)
  47                 {
  48                         if (parameters.X != null)
  49                                 Array.Clear (parameters.X, 0, parameters.X.Length);
  50                 }
  51
  52                 private byte[] GetNamedParam (SecurityElement se, string param)
  53                 {
  54                         SecurityElement sep = se.SearchForChildByTag (param);
  55                         if (sep == null)
  56                                 return null;
  57                         return Convert.FromBase64String (sep.Text);
  58                 }
  59
  60                 public override void FromXmlString (string xmlString)
  61                 {
  62                         if (xmlString == null)
  63                                 throw new ArgumentNullException ("xmlString");
  64
  65                         DSAParameters dsaParams = new DSAParameters ();
  66                         try {
  67                                 SecurityParser sp = new SecurityParser ();
  68                                 sp.LoadXml (xmlString);
  69                                 SecurityElement se = sp.ToXml ();
  70                                 if (se.Tag != "DSAKeyValue")
  71                                         throw new Exception ();
  72                                 dsaParams.P = GetNamedParam (se, "P");
  73                                 dsaParams.Q = GetNamedParam (se, "Q");
  74                                 dsaParams.G = GetNamedParam (se, "G");
  75                                 dsaParams.J = GetNamedParam (se, "J");
  76                                 dsaParams.Y = GetNamedParam (se, "Y");
  77                                 dsaParams.X = GetNamedParam (se, "X");
  78                                 dsaParams.Seed = GetNamedParam (se, "Seed");
  79                                 byte[] counter = GetNamedParam (se, "PgenCounter");
  80                                 if (counter != null) {
  81                                         byte[] counter4b = new byte [4]; // always 4 bytes
  82                                         Array.Copy (counter, 0, counter4b, 0, counter.Length);
  83                                         dsaParams.Counter = BitConverter.ToInt32 (counter4b, 0);
  84                                 }
  85                                 ImportParameters (dsaParams);
  86                         }
  87                         catch {
  88                                 ZeroizePrivateKey (dsaParams);
  89                                 throw;
  90                         }
  91                         finally {
  92                                 ZeroizePrivateKey (dsaParams);
  93                         }
  94                 }
  95
  96                 public abstract void ImportParameters (DSAParameters parameters);
  97
  98                 // note: using SecurityElement.ToXml wouldn't generate the same string as the MS implementation
  99                 public override string ToXmlString (bool includePrivateParameters)
 100                 {
 101                         StringBuilder sb = new StringBuilder ();
 102                         DSAParameters dsaParams = ExportParameters (includePrivateParameters);
 103                         try {
 104                                 sb.Append ("<DSAKeyValue>");
 105
 106                                 sb.Append ("<P>");
 107                                 sb.Append (Convert.ToBase64String (dsaParams.P));
 108                                 sb.Append ("</P>");
 109
 110                                 sb.Append ("<Q>");
 111                                 sb.Append (Convert.ToBase64String (dsaParams.Q));
 112                                 sb.Append ("</Q>");
 113
 114                                 sb.Append ("<G>");
 115                                 sb.Append (Convert.ToBase64String (dsaParams.G));
 116                                 sb.Append ("</G>");
 117
 118                                 sb.Append ("<Y>");
 119                                 sb.Append (Convert.ToBase64String (dsaParams.Y));
 120                                 sb.Append( "</Y>");
 121
 122                                 sb.Append ("<J>");
 123                                 sb.Append (Convert.ToBase64String (dsaParams.J));
 124                                 sb.Append ("</J>");
 125
 126                                 if (dsaParams.Seed != null) {
 127                                         sb.Append ("<Seed>");
 128                                         sb.Append (Convert.ToBase64String (dsaParams.Seed));
 129                                         sb.Append ("</Seed>");
 130
 131                                         sb.Append ("<PgenCounter>");
 132                                         // the number of bytes is important (no matter == 0x00)
 133                                         byte[] inArr = BitConverter.GetBytes (dsaParams.Counter);
 134                                         int l = inArr.Length;
 135                                         while (inArr[l-1] == 0x00)
 136                                                 l--;
 137                                         byte[] c = new byte[l];
 138                                         Array.Copy (inArr, 0, c, 0, l);
 139                                         sb.Append (Convert.ToBase64String (c));
 140                                         sb.Append ("</PgenCounter>");
 141                                 }
 142
 143                                 if (dsaParams.X != null) {
 144                                         sb.Append ("<X>");
 145                                         sb.Append (Convert.ToBase64String (dsaParams.X));
 146                                         sb.Append ("</X>");
 147                                 }
 148                                 else if (includePrivateParameters)
 149                                         throw new CryptographicException();
 150
 151                                 sb.Append ("</DSAKeyValue>");
 152                         }
 153                         catch (NotImplementedException ex) {
 154                                 ZeroizePrivateKey (dsaParams);
 155                                 throw;
 156                         }
 157
 158                         return sb.ToString ();
 159                 }
 160
 161                 public abstract bool VerifySignature (byte[] rgbHash, byte[] rgbSignature);
 162
 163         } // DSA
 164
 165 } // System.Security.Cryptography