mcs/class/referencesource/mscorlib/system/security/cryptography/rsapkcs1signatureformatter.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // <OWNER>Microsoft</OWNER>
   7 //
   8
   9 //
  10 // RSAPKCS1SignatureFormatter.cs
  11 //
  12
  13 using System;
  14 using System.Diagnostics.Contracts;
  15 using System.Security.Cryptography.X509Certificates;
  16
  17 namespace System.Security.Cryptography {
  18     [System.Runtime.InteropServices.ComVisible(true)]
  19     public class RSAPKCS1SignatureFormatter : AsymmetricSignatureFormatter {
  20         private RSA    _rsaKey;
  21         private String _strOID;
  22         private bool?  _rsaOverridesSignHash;
  23
  24         //
  25         // public constructors
  26         //
  27
  28         public RSAPKCS1SignatureFormatter() {}
  29
  30         public RSAPKCS1SignatureFormatter(AsymmetricAlgorithm key) {
  31             if (key == null)
  32                 throw new ArgumentNullException("key");
  33             Contract.EndContractBlock();
  34             _rsaKey = (RSA) key;
  35         }
  36
  37         //
  38         // public methods
  39         //
  40
  41         public override void SetKey(AsymmetricAlgorithm key) {
  42             if (key == null)
  43                 throw new ArgumentNullException("key");
  44             Contract.EndContractBlock();
  45             _rsaKey = (RSA) key;
  46             _rsaOverridesSignHash = default(bool?);
  47         }
  48
  49         public override void SetHashAlgorithm(String strName) {
  50             _strOID = CryptoConfig.MapNameToOID(strName, OidGroup.HashAlgorithm);
  51         }
  52
  53         [System.Security.SecuritySafeCritical]  // auto-generated
  54         public override byte[] CreateSignature(byte[] rgbHash) {
  55             if (rgbHash == null)
  56                 throw new ArgumentNullException("rgbHash");
  57             Contract.EndContractBlock();
  58
  59             if (_strOID == null)
  60                 throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingOID"));
  61             if (_rsaKey == null)
  62                 throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
  63
  64             // Two cases here -- if we are talking to the CSP version or if we are talking to some other RSA provider.
  65             if (_rsaKey is RSACryptoServiceProvider) {
  66                 // This path is kept around for desktop compat: in case someone is using this with a hash algorithm that's known to GetAlgIdFromOid but
  67                 // not from OidToHashAlgorithmName.
  68                 int calgHash = X509Utils.GetAlgIdFromOid(_strOID, OidGroup.HashAlgorithm);
  69                 return ((RSACryptoServiceProvider)_rsaKey).SignHash(rgbHash, calgHash);
  70             }
  71             else if (OverridesSignHash) {
  72                 HashAlgorithmName hashAlgorithmName = Utils.OidToHashAlgorithmName(_strOID);
  73                 return _rsaKey.SignHash(rgbHash, hashAlgorithmName, RSASignaturePadding.Pkcs1);
  74             }
  75             else {
  76                 // Fallback compat path for 3rd-party RSA classes that don't override SignHash()
  77
  78                 byte[] pad = Utils.RsaPkcs1Padding(_rsaKey, CryptoConfig.EncodeOID(_strOID), rgbHash);
  79                 // Create the signature by applying the private key to the padded buffer we just created.
  80                 return _rsaKey.DecryptValue(pad);
  81             }
  82         }
  83
  84         private bool OverridesSignHash {
  85             get {
  86                 if (!_rsaOverridesSignHash.HasValue) {
  87                     _rsaOverridesSignHash = Utils.DoesRsaKeyOverride(_rsaKey, "SignHash", new Type[] { typeof(byte[]), typeof(HashAlgorithmName), typeof(RSASignaturePadding) });
  88                 }
  89                 return _rsaOverridesSignHash.Value;
  90             }
  91         }
  92     }
  93 }