mcs/class/referencesource/mscorlib/system/security/cryptography/rsapkcs1signaturedeformatter.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // <OWNER>Microsoft</OWNER>
   7 //
   8
   9 //
  10 // RSAPKCS1SignatureDeformatter.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 RSAPKCS1SignatureDeformatter : AsymmetricSignatureDeformatter {
  20         //
  21         //  This class provides the PKCS#1 v1.5 signature format processing during
  22         //  the verification process (i.e. decrypting the object).  The class has
  23         //  some special code for dealing with the CSP based RSA keys as the
  24         //  formatting and verification is done within the CSP rather than in
  25         //  managed code.
  26         //
  27
  28         private RSA    _rsaKey; // RSA Key value to do decrypt operation
  29         private String _strOID; // OID value for the HASH algorithm
  30
  31         //
  32         // public constructors
  33         //
  34
  35         public RSAPKCS1SignatureDeformatter() {}
  36         public RSAPKCS1SignatureDeformatter(AsymmetricAlgorithm key) {
  37             if (key == null)
  38                 throw new ArgumentNullException("key");
  39             Contract.EndContractBlock();
  40             _rsaKey = (RSA) key;
  41         }
  42
  43         //
  44         // public methods
  45         //
  46
  47         public override void SetKey(AsymmetricAlgorithm key) {
  48             if (key == null)
  49                 throw new ArgumentNullException("key");
  50             Contract.EndContractBlock();
  51             _rsaKey = (RSA) key;
  52         }
  53
  54         public override void SetHashAlgorithm(String strName) {
  55             _strOID = CryptoConfig.MapNameToOID(strName, OidGroup.HashAlgorithm);
  56         }
  57
  58         [System.Security.SecuritySafeCritical]  // auto-generated
  59         public override bool VerifySignature(byte[] rgbHash, byte[] rgbSignature) {
  60             if (rgbHash == null)
  61                 throw new ArgumentNullException("rgbHash");
  62             if (rgbSignature == null)
  63                 throw new ArgumentNullException("rgbSignature");
  64             Contract.EndContractBlock();
  65
  66             if (_strOID == null)
  67                 throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingOID"));
  68             if (_rsaKey == null)
  69                 throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
  70
  71             // Two cases here -- if we are talking to the CSP version or if we are talking to some other RSA provider.
  72             if (_rsaKey is RSACryptoServiceProvider) {
  73                 int calgHash = X509Utils.GetAlgIdFromOid(_strOID, OidGroup.HashAlgorithm);
  74                 return ((RSACryptoServiceProvider)_rsaKey).VerifyHash(rgbHash, calgHash, rgbSignature);
  75             }
  76             else {
  77                 byte[] pad = Utils.RsaPkcs1Padding(_rsaKey, CryptoConfig.EncodeOID(_strOID), rgbHash);
  78                 // Apply the public key to the signature data to get back the padded buffer actually signed.
  79                 // Compare the two buffers to see if they match; ignoring any leading zeros
  80                 return Utils.CompareBigIntArrays(_rsaKey.EncryptValue(rgbSignature), pad);
  81             }
  82         }
  83     }
  84 }