RSAPKCS1SignatureDeformatter.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Security / Cryptography / RSAPKCS1SignatureDeformatter.cs / 1 / RSAPKCS1SignatureDeformatter.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 

// 
// RSAPKCS1SignatureDeformatter.cs 
//
 
namespace System.Security.Cryptography {
    [System.Runtime.InteropServices.ComVisible(true)]
    public class RSAPKCS1SignatureDeformatter : AsymmetricSignatureDeformatter {
        // 
        //  This class provides the PKCS#1 v1.5 signature format processing during
        //  the verification process (i.e. decrypting the object).  The class has 
        //  some special code for dealing with the CSP based RSA keys as the 
        //  formatting and verification is done within the CSP rather than in
        //  managed code. 
        //

        private RSA    _rsaKey; // RSA Key value to do decrypt operation
        private String _strOID; // OID value for the HASH algorithm 

        // 
        // public constructors 
        //
 
        public RSAPKCS1SignatureDeformatter() {}
        public RSAPKCS1SignatureDeformatter(AsymmetricAlgorithm key) {
            if (key == null)
                throw new ArgumentNullException("key"); 
            _rsaKey = (RSA) key;
        } 
 
        //
        // public methods 
        //

        public override void SetKey(AsymmetricAlgorithm key) {
            if (key == null) 
                throw new ArgumentNullException("key");
            _rsaKey = (RSA) key; 
        } 

        public override void SetHashAlgorithm(String strName) { 
            _strOID = CryptoConfig.MapNameToOID(strName);
        }

        public override bool VerifySignature(byte[] rgbHash, byte[] rgbSignature) { 
            if (_strOID == null)
                throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingOID")); 
            if (_rsaKey == null) 
                throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
            if (rgbHash == null) 
                throw new ArgumentNullException("rgbHash");
            if (rgbSignature == null)
                throw new ArgumentNullException("rgbSignature");
 
            // Two cases here -- if we are talking to the CSP version or if we are talking to some other RSA provider.
            if (_rsaKey is RSACryptoServiceProvider) { 
                return ((RSACryptoServiceProvider) _rsaKey).VerifyHash(rgbHash, _strOID, rgbSignature); 
            }
            else { 
                byte[] pad = Utils.RsaPkcs1Padding(_rsaKey, CryptoConfig.EncodeOID(_strOID), rgbHash);
                // Apply the public key to the signature data to get back the padded buffer actually signed.
                // Compare the two buffers to see if they match; ignoring any leading zeros
                return Utils.CompareBigIntArrays(_rsaKey.EncryptValue(rgbSignature), pad); 
            }
        } 
    } 
}

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