ECDsaCng.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Security / Cryptography / ECDsaCng.cs / 1305376 / ECDsaCng.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 

using System; 
using System.Diagnostics; 
using System.IO;
using System.Security; 
using System.Security.Permissions;
using System.Diagnostics.Contracts;
using Microsoft.Win32.SafeHandles;
 
namespace System.Security.Cryptography {
    ///  
    ///     Wrapper for NCrypt's implementation of elliptic curve DSA 
    /// 
    [System.Security.Permissions.HostProtection(MayLeakOnAbort = true)] 
    public sealed class ECDsaCng : ECDsa {
        private static KeySizes[] s_legalKeySizes = new KeySizes[] { new KeySizes(256, 384, 128), new KeySizes(521, 521, 0) };

        private CngKey m_key; 
        private CngAlgorithm m_hashAlgorithm = CngAlgorithm.Sha256;
 
        // 
        // Constructors
        // 

        public ECDsaCng() : this(521) {
            Contract.Ensures(LegalKeySizesValue != null);
        } 

        //  
        //  
        // 
        [System.Security.SecurityCritical] 
        public ECDsaCng(int keySize) {
            Contract.Ensures(LegalKeySizesValue != null);

            if (!NCryptNative.NCryptSupported) { 
                throw new PlatformNotSupportedException(SR.GetString(SR.Cryptography_PlatformNotSupported));
            } 
 
            LegalKeySizesValue = s_legalKeySizes;
            KeySize = keySize; 
        }

        // 
        //  
        // 
        //  
        [System.Security.SecurityCritical] 
        public ECDsaCng(CngKey key) {
            Contract.Ensures(LegalKeySizesValue != null); 
            Contract.Ensures(m_key != null && m_key.AlgorithmGroup == CngAlgorithmGroup.ECDsa);

            if (key == null) {
                throw new ArgumentNullException("key"); 
            }
            if (key.AlgorithmGroup != CngAlgorithmGroup.ECDsa) { 
                throw new ArgumentException(SR.GetString(SR.Cryptography_ArgECDsaRequiresECDsaKey), "key"); 
            }
 
            if (!NCryptNative.NCryptSupported) {
                throw new PlatformNotSupportedException(SR.GetString(SR.Cryptography_PlatformNotSupported));
            }
 
            LegalKeySizesValue = s_legalKeySizes;
 
            // Make a copy of the key so that we continue to work if it gets disposed before this algorithm 
            //
            // This requires an assert for UnmanagedCode since we'll need to access the raw handles of the key 
            // and the handle constructor of CngKey.  The assert is safe since ECDsaCng will never expose the
            // key handles to calling code (without first demanding UnmanagedCode via the Handle property of
            // CngKey).
            new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert(); 
            Key = CngKey.Open(key.Handle, key.IsEphemeral ? CngKeyHandleOpenOptions.EphemeralKey : CngKeyHandleOpenOptions.None);
            CodeAccessPermission.RevertAssert(); 
 
            KeySize = m_key.KeySize;
        } 

        /// 
        ///     Hash algorithm to use when generating a signature over arbitrary data
        ///  
        public CngAlgorithm HashAlgorithm {
            get { 
                Contract.Ensures(Contract.Result() != null); 
                return m_hashAlgorithm;
            } 

            set {
                Contract.Ensures(m_hashAlgorithm != null);
 
                if (value == null) {
                    throw new ArgumentNullException("value"); 
                } 

                m_hashAlgorithm = value; 
            }
        }

        ///  
        ///     Key to use for signing
        ///  
        public CngKey Key { 
            get {
                Contract.Ensures(Contract.Result() != null); 
                Contract.Ensures(Contract.Result().AlgorithmGroup == CngAlgorithmGroup.ECDsa);
                Contract.Ensures(m_key != null && m_key.AlgorithmGroup == CngAlgorithmGroup.ECDsa);

                // If the size of the key no longer matches our stored value, then we need to replace it with 
                // a new key of the correct size.
                if (m_key != null && m_key.KeySize != KeySize) { 
                    m_key.Dispose(); 
                    m_key = null;
                } 

                if (m_key == null) {
                    // Map the current key size to a CNG algorithm name
                    CngAlgorithm algorithm = null; 
                    switch (KeySize) {
                        case 256: 
                            algorithm = CngAlgorithm.ECDsaP256; 
                            break;
 
                        case 384:
                            algorithm = CngAlgorithm.ECDsaP384;
                            break;
 
                        case 521:
                            algorithm = CngAlgorithm.ECDsaP521; 
                            break; 

                        default: 
                            Debug.Assert(false, "Illegal key size set");
                            break;
                    }
 
                    m_key = CngKey.Create(algorithm);
                } 
 
                return m_key;
            } 

            private set {
                Contract.Requires(value != null);
                Contract.Ensures(m_key != null && m_key.AlgorithmGroup == CngAlgorithmGroup.ECDsa); 

                if (value.AlgorithmGroup != CngAlgorithmGroup.ECDsa) { 
                    throw new ArgumentException(SR.GetString(SR.Cryptography_ArgECDsaRequiresECDsaKey)); 
                }
 
                if (m_key != null) {
                    m_key.Dispose();
                }
 
                //
                // We do not duplicate the handle because the only time the user has access to the key itself 
                // to dispose underneath us is when they construct via the CngKey constructor, which does a 
                // copy. Otherwise all key lifetimes are controlled directly by the ECDsaCng class.
                // 

                m_key = value;
                KeySize = m_key.KeySize;
            } 
        }
 
        ///  
        ///     Clean up the algorithm
        ///  
        protected override void Dispose(bool disposing) {
            try {
                if (m_key != null) {
                    m_key.Dispose(); 
                }
            } 
            finally { 
                base.Dispose(disposing);
            } 
        }

        //
        // XML Import 
        //
        // #ECCXMLFormat 
        // 
        // There is currently not a standard XML format for ECC keys, so we will not implement the default
        // To/FromXmlString so that we're not tied to one format when a standard one does exist. Instead we'll 
        // use an overload which allows the user to specify the format they'd like to serialize into.
        //
        // See code:System.Security.Cryptography.Rfc4050KeyFormatter#RFC4050ECKeyFormat for information about
        // the currently supported format. 
        //
 
        public override void FromXmlString(string xmlString) { 
            throw new NotImplementedException(SR.GetString(SR.Cryptography_ECXmlSerializationFormatRequired));
        } 

        public void FromXmlString(string xml, ECKeyXmlFormat format) {
            if (xml == null) {
                throw new ArgumentNullException("xml"); 
            }
            if (format != ECKeyXmlFormat.Rfc4050) { 
                throw new ArgumentOutOfRangeException("format"); 
            }
 
            Key = Rfc4050KeyFormatter.FromXml(xml);
        }

        // 
        // Signature generation
        // 
 
        public byte[] SignData(byte[] data) {
            Contract.Ensures(Contract.Result() != null); 

            if (data == null) {
                throw new ArgumentNullException("data");
            } 

            return SignData(data, 0, data.Length); 
        } 

        //  
        // 
        // 
        // 
        //  
        [System.Security.SecurityCritical]
        public byte[] SignData(byte[] data, int offset, int count) { 
            Contract.Ensures(Contract.Result() != null); 

            if (data == null) { 
                throw new ArgumentNullException("data");
            }
            if (offset < 0 || offset > data.Length) {
                throw new ArgumentOutOfRangeException("offset"); 
            }
            if (count < 0 || count > data.Length - offset) { 
                throw new ArgumentOutOfRangeException("count"); 
            }
 
            using (BCryptHashAlgorithm hashAlgorithm = new BCryptHashAlgorithm(HashAlgorithm, BCryptNative.ProviderName.MicrosoftPrimitiveProvider)) {
                hashAlgorithm.HashCore(data, offset, count);
                byte[] hashValue = hashAlgorithm.HashFinal();
 
                return SignHash(hashValue);
            } 
        } 

        //  
        // 
        // 
        // 
        //  
        [System.Security.SecurityCritical]
        public byte[] SignData(Stream data) { 
            Contract.Ensures(Contract.Result() != null); 

            if (data == null) { 
                throw new ArgumentNullException("data");
            }

            using (BCryptHashAlgorithm hashAlgorithm = new BCryptHashAlgorithm(HashAlgorithm, BCryptNative.ProviderName.MicrosoftPrimitiveProvider)) { 
                hashAlgorithm.HashStream(data);
                byte[] hashValue = hashAlgorithm.HashFinal(); 
 
                return SignHash(hashValue);
            } 
        }

        // 
        //  
        // 
        //  
        //  
        [System.Security.SecurityCritical]
        public override byte[] SignHash(byte[] hash) { 
            if (hash == null) {
                throw new ArgumentNullException("hash");
            }
 
            // Make sure we're allowed to sign using this key
            KeyContainerPermission permission = Key.BuildKeyContainerPermission(KeyContainerPermissionFlags.Sign); 
            if (permission != null) { 
                permission.Demand();
            } 

            // Now that know we have permission to use this key for signing, pull the key value out, which
            // will require unmanaged code permission
            new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert(); 
            SafeNCryptKeyHandle keyHandle = Key.Handle;
            CodeAccessPermission.RevertAssert(); 
 
            return NCryptNative.SignHash(keyHandle, hash);
        } 

        //
        // XML Export
        // 
        // See  code:System.Security.Cryptography.ECDsaCng#ECCXMLFormat and
        // code:System.Security.Cryptography.Rfc4050KeyFormatter#RFC4050ECKeyFormat for information about 
        // XML serialization of elliptic curve keys 
        //
 
        public override string ToXmlString(bool includePrivateParameters) {
            throw new NotImplementedException(SR.GetString(SR.Cryptography_ECXmlSerializationFormatRequired));
        }
 
        public string ToXmlString(ECKeyXmlFormat format) {
            Contract.Ensures(Contract.Result() != null); 
 
            if (format != ECKeyXmlFormat.Rfc4050) {
                throw new ArgumentOutOfRangeException("format"); 
            }

            return Rfc4050KeyFormatter.ToXml(Key);
        } 

        // 
        // Signature verification 
        //
 
        public bool VerifyData(byte[] data, byte[] signature) {
            if (data == null) {
                throw new ArgumentNullException("data");
            } 

            return VerifyData(data, 0, data.Length, signature); 
        } 

        //  
        // 
        // 
        // 
        //  
        [System.Security.SecurityCritical]
        public bool VerifyData(byte[] data, int offset, int count, byte[] signature) { 
            if (data == null) { 
                throw new ArgumentNullException("data");
            } 
            if (offset < 0 || offset > data.Length) {
                throw new ArgumentOutOfRangeException("offset");
            }
            if (count < 0 || count > data.Length - offset) { 
                throw new ArgumentOutOfRangeException("count");
            } 
            if (signature == null) { 
                throw new ArgumentNullException("signature");
            } 

            using (BCryptHashAlgorithm hashAlgorithm = new BCryptHashAlgorithm(HashAlgorithm, BCryptNative.ProviderName.MicrosoftPrimitiveProvider)) {
                hashAlgorithm.HashCore(data, offset, count);
                byte[] hashValue = hashAlgorithm.HashFinal(); 

                return VerifyHash(hashValue, signature); 
            } 
        }
 
        // 
        // 
        // 
        //  
        // 
        [System.Security.SecurityCritical] 
        public bool VerifyData(Stream data, byte[] signature) { 
            if (data == null) {
                throw new ArgumentNullException("data"); 
            }
            if (signature == null) {
                throw new ArgumentNullException("signature");
            } 

            using (BCryptHashAlgorithm hashAlgorithm = new BCryptHashAlgorithm(HashAlgorithm, BCryptNative.ProviderName.MicrosoftPrimitiveProvider)) { 
                hashAlgorithm.HashStream(data); 
                byte[] hashValue = hashAlgorithm.HashFinal();
 
                return VerifyHash(hashValue, signature);
            }
        }
 
        // 
        //  
        //  
        // 
        [System.Security.SecurityCritical] 
        public override bool VerifyHash(byte[] hash, byte[] signature) {
            if (hash == null) {
                throw new ArgumentNullException("hash");
            } 
            if (signature == null) {
                throw new ArgumentNullException("signature"); 
            } 

            // We need to get the raw key handle to verify the signature. Asserting here is safe since verifiation 
            // is not a protected operation, and we do not expose the handle to the user code.
            new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert();
            SafeNCryptKeyHandle keyHandle = Key.Handle;
            CodeAccessPermission.RevertAssert(); 

            return NCryptNative.VerifySignature(keyHandle, hash, signature); 
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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