mcs/class/referencesource/mscorlib/system/security/cryptography/rsapkcs1keyexchangedeformatter.cs

   1 using System.Diagnostics.Contracts;
   2 // ==++==
   3 //
   4 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   5 //
   6 // ==--==
   7 // <OWNER>[....]</OWNER>
   8 //
   9
  10 namespace System.Security.Cryptography {
  11     [System.Runtime.InteropServices.ComVisible(true)]
  12     public class RSAPKCS1KeyExchangeDeformatter : AsymmetricKeyExchangeDeformatter {
  13         RSA _rsaKey;
  14         bool?  _rsaOverridesDecrypt;
  15         RandomNumberGenerator RngValue;
  16
  17         // Constructors
  18
  19         public RSAPKCS1KeyExchangeDeformatter() {}
  20
  21         public RSAPKCS1KeyExchangeDeformatter(AsymmetricAlgorithm key) {
  22             if (key == null)
  23                 throw new ArgumentNullException("key");
  24             Contract.EndContractBlock();
  25             _rsaKey = (RSA) key;
  26         }
  27
  28         //
  29         // public properties
  30         //
  31
  32         public RandomNumberGenerator RNG {
  33             get { return RngValue; }
  34             set { RngValue = value; }
  35         }
  36
  37         public override String Parameters {
  38             get { return null; }
  39             set { ;}
  40         }
  41
  42         //
  43         // public methods
  44         //
  45
  46         public override byte[] DecryptKeyExchange(byte[] rgbIn) {
  47             if (_rsaKey == null)
  48                 throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
  49
  50             byte[] rgbOut;
  51             if (OverridesDecrypt) {
  52                 rgbOut = _rsaKey.Decrypt(rgbIn, RSAEncryptionPadding.Pkcs1);
  53             }
  54             else {
  55                 int i;
  56                 byte[] rgb;
  57                 rgb = _rsaKey.DecryptValue(rgbIn);
  58
  59                 //
  60                 //  Expected format is:
  61                 //      00 || 02 || PS || 00 || D
  62                 //      where PS does not contain any zeros.
  63                 //
  64
  65                 for (i = 2; i<rgb.Length; i++) {
  66                     if (rgb[i] == 0) {
  67                         break;
  68                     }
  69                 }
  70
  71                 if (i >= rgb.Length)
  72                     throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_PKCS1Decoding"));
  73
  74                 i++;            // Skip over the zero
  75
  76                 rgbOut = new byte[rgb.Length - i];
  77                 Buffer.InternalBlockCopy(rgb, i, rgbOut, 0, rgbOut.Length);
  78             }
  79             return rgbOut;
  80         }
  81
  82         public override void SetKey(AsymmetricAlgorithm key) {
  83             if (key == null)
  84                 throw new ArgumentNullException("key");
  85             Contract.EndContractBlock();
  86             _rsaKey = (RSA) key;
  87             _rsaOverridesDecrypt = default(bool?);
  88         }
  89
  90         private bool OverridesDecrypt {
  91             get {
  92                 if (!_rsaOverridesDecrypt.HasValue) {
  93                     _rsaOverridesDecrypt = Utils.DoesRsaKeyOverride(_rsaKey, "Decrypt", new Type[] { typeof(byte[]), typeof(RSAEncryptionPadding) });
  94                 }
  95                 return _rsaOverridesDecrypt.Value;
  96             }
  97         }
  98     }
  99 }