mcs/class/referencesource/mscorlib/system/security/cryptography/rsapkcs1keyexchangeformatter.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // <OWNER>[....]</OWNER>
   7 //
   8
   9 namespace System.Security.Cryptography {
  10     using System.Globalization;
  11     using System.Diagnostics.Contracts;
  12
  13     [System.Runtime.InteropServices.ComVisible(true)]
  14     public class RSAPKCS1KeyExchangeFormatter : AsymmetricKeyExchangeFormatter {
  15         RandomNumberGenerator RngValue;
  16         RSA _rsaKey;
  17         bool?  _rsaOverridesEncrypt;
  18
  19         //
  20         // public constructors
  21         //
  22
  23         public RSAPKCS1KeyExchangeFormatter() {}
  24
  25         public RSAPKCS1KeyExchangeFormatter(AsymmetricAlgorithm key) {
  26             if (key == null)
  27                 throw new ArgumentNullException("key");
  28             Contract.EndContractBlock();
  29             _rsaKey = (RSA) key;
  30         }
  31
  32         //
  33         // public properties
  34         //
  35
  36         public override String Parameters {
  37             get { return "<enc:KeyEncryptionMethod enc:Algorithm=\"http://www.microsoft.com/xml/security/algorithm/PKCS1-v1.5-KeyEx\" xmlns:enc=\"http://www.microsoft.com/xml/security/encryption/v1.0\" />"; }
  38         }
  39
  40         public RandomNumberGenerator Rng {
  41             get { return RngValue; }
  42             set { RngValue = value; }
  43         }
  44
  45         //
  46         // public methods
  47         //
  48
  49         public override void SetKey(AsymmetricAlgorithm key) {
  50             if (key == null)
  51                 throw new ArgumentNullException("key");
  52             Contract.EndContractBlock();
  53             _rsaKey = (RSA) key;
  54             _rsaOverridesEncrypt = default(bool?);
  55         }
  56
  57         public override byte[] CreateKeyExchange(byte[] rgbData) {
  58 #if MONO
  59                         if (rgbData == null)
  60                                 throw new ArgumentNullException ("rgbData");
  61 #endif
  62
  63             if (_rsaKey == null)
  64                 throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
  65
  66             byte[] rgbKeyEx;
  67             if (OverridesEncrypt) {
  68                 rgbKeyEx = _rsaKey.Encrypt(rgbData, RSAEncryptionPadding.Pkcs1);
  69             }
  70             else {
  71                 int cb = _rsaKey.KeySize/8;
  72                 if ((rgbData.Length + 11) > cb)
  73                     throw new CryptographicException(Environment.GetResourceString("Cryptography_Padding_EncDataTooBig", cb-11));
  74                 byte[]  rgbInput = new byte[cb];
  75
  76                 //
  77                 //  We want to pad to the following format:
  78                 //      00 || 02 || PS || 00 || D
  79                 //
  80                 //      PS - pseudorandom non zero bytes
  81                 //      D - data
  82                 //
  83
  84                 if (RngValue == null) {
  85                     RngValue = RandomNumberGenerator.Create();
  86                 }
  87
  88                 Rng.GetNonZeroBytes(rgbInput);
  89                 rgbInput[0] = 0;
  90                 rgbInput[1] = 2;
  91                 rgbInput[cb-rgbData.Length-1] = 0;
  92                 Buffer.InternalBlockCopy(rgbData, 0, rgbInput, cb-rgbData.Length, rgbData.Length);
  93
  94                 //
  95                 //  Now encrypt the value and return it. (apply public key)
  96                 //
  97
  98                 rgbKeyEx = _rsaKey.EncryptValue(rgbInput);
  99             }
 100             return rgbKeyEx;
 101         }
 102
 103         public override byte[] CreateKeyExchange(byte[] rgbData, Type symAlgType) {
 104             return CreateKeyExchange(rgbData);
 105         }
 106
 107         private bool OverridesEncrypt {
 108             get {
 109                 if (!_rsaOverridesEncrypt.HasValue) {
 110                     _rsaOverridesEncrypt = Utils.DoesRsaKeyOverride(_rsaKey, "Encrypt", new Type[] { typeof(byte[]), typeof(RSAEncryptionPadding) });
 111                 }
 112                 return _rsaOverridesEncrypt.Value;
 113             }
 114         }
 115     }
 116 }