Code:
/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Security / Cryptography / HMAC.cs / 2 / HMAC.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // // HMAC.cs // // // For test vectors, see RFC2104, e.g. http://www.faqs.org/rfcs/rfc2104.html // namespace System.Security.Cryptography { [System.Runtime.InteropServices.ComVisible(true)] public abstract class HMAC : KeyedHashAlgorithm { // // protected members // // an HMAC uses a hash function where data is hashed by iterating a basic compression // function on blocks of data. BlockSizeValue is the byte size of such a block private int blockSizeValue = 64; protected int BlockSizeValue { get { return blockSizeValue; } set { blockSizeValue = value; } } internal string m_hashName; internal HashAlgorithm m_hash1; internal HashAlgorithm m_hash2; // // private members // // m_inner = PaddedKey ^ {0x36,...,0x36} // m_outer = PaddedKey ^ {0x5C,...,0x5C} private byte[] m_inner; private byte[] m_outer; private bool m_hashing = false; private void UpdateIOPadBuffers () { if (m_inner == null) m_inner = new byte[BlockSizeValue]; if (m_outer == null) m_outer = new byte[BlockSizeValue]; int i; for (i=0; i < BlockSizeValue; i++) { m_inner[i] = 0x36; m_outer[i] = 0x5C; } for (i=0; i < KeyValue.Length; i++) { m_inner[i] ^= KeyValue[i]; m_outer[i] ^= KeyValue[i]; } } internal void InitializeKey (byte[] key) { // When we change the key value, we'll need to update the initial values of the inner and outter // computation buffers. In the case of correct HMAC vs Whidbey HMAC, these buffers could get // generated to a different size than when we started. m_inner = null; m_outer = null; if (key.Length > BlockSizeValue) { KeyValue = m_hash1.ComputeHash(key); // No need to call Initialize, ComputeHash will do it for us } else { KeyValue = (byte[]) key.Clone(); } UpdateIOPadBuffers(); } // // public properties // public override byte[] Key { get { return (byte[]) KeyValue.Clone(); } set { if (m_hashing) throw new CryptographicException(Environment.GetResourceString("Cryptography_HashKeySet")); InitializeKey(value); } } public string HashName { get { return m_hashName; } set { if (m_hashing) throw new CryptographicException(Environment.GetResourceString("Cryptography_HashNameSet")); m_hashName = value; // create the hash algorithms m_hash1 = HashAlgorithm.Create(m_hashName); m_hash2 = HashAlgorithm.Create(m_hashName); } } // // public methods // new static public HMAC Create () { return Create("System.Security.Cryptography.HMAC"); } new static public HMAC Create (string algorithmName) { return (HMAC) CryptoConfig.CreateFromName(algorithmName); } public override void Initialize () { m_hash1.Initialize(); m_hash2.Initialize(); m_hashing = false; } protected override void HashCore (byte[] rgb, int ib, int cb) { if (m_hashing == false) { m_hash1.TransformBlock(m_inner, 0, m_inner.Length, m_inner, 0); m_hashing = true; } m_hash1.TransformBlock(rgb, ib, cb, rgb, ib); } protected override byte[] HashFinal () { if (m_hashing == false) { m_hash1.TransformBlock(m_inner, 0, m_inner.Length, m_inner, 0); m_hashing = true; } // finalize the original hash m_hash1.TransformFinalBlock(new byte[0], 0, 0); byte[] hashValue1 = m_hash1.HashValue; // write the outer array m_hash2.TransformBlock(m_outer, 0, m_outer.Length, m_outer, 0); // write the inner hash and finalize the hash m_hash2.TransformBlock(hashValue1, 0, hashValue1.Length, hashValue1, 0); m_hashing = false; m_hash2.TransformFinalBlock(new byte[0], 0, 0); return m_hash2.HashValue; } // // IDisposable methods // protected override void Dispose (bool disposing) { if (disposing) { if (m_hash1 != null) m_hash1.Clear(); if (m_hash2 != null) m_hash2.Clear(); if (m_inner != null) Array.Clear(m_inner, 0, m_inner.Length); if (m_outer != null) Array.Clear(m_outer, 0, m_outer.Length); } // call the base class's Dispose base.Dispose(disposing); } } }
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