/// <summary>
/// Returns the <see cref="SymmetricAlgorithm"/>.
/// </summary>
/// <returns></returns>
/// <exception cref="ArgumentException">The <see cref="SecurityKey"/> cannot be converted to byte array</exception>
/// <exception cref="ArgumentOutOfRangeException">The keysize doesn't match the algorithm.</exception>
/// <exception cref="InvalidOperationException">Failed to create symmetric algorithm with provided key and algorithm.</exception>
protected virtual SymmetricAlgorithm GetSymmetricAlgorithm(SecurityKey key, string algorithm)
{
if (key == null)
{
throw LogHelper.LogArgumentNullException(nameof(key));
}
if (!IsSupportedAlgorithm(key, algorithm))
{
throw LogHelper.LogExceptionMessage(new NotSupportedException(LogHelper.FormatInvariant(LogMessages.IDX10661, algorithm, key)));
}
byte[] keyBytes = null;
if (key is SymmetricSecurityKey symmetricSecurityKey)
{
keyBytes = symmetricSecurityKey.Key;
}
else if (key is JsonWebKey jsonWebKey)
{
if (JsonWebKeyConverter.TryConvertToSymmetricSecurityKey(jsonWebKey, out SecurityKey securityKey))
{
keyBytes = (securityKey as SymmetricSecurityKey).Key;
}
}
if (keyBytes == null)
{
throw LogHelper.LogExceptionMessage(new ArgumentException(LogHelper.FormatInvariant(LogMessages.IDX10657, key.GetType())));
}
ValidateKeySize(keyBytes, algorithm);
try
{
// Create the AES provider
SymmetricAlgorithm symmetricAlgorithm = Aes.Create();
symmetricAlgorithm.Mode = CipherMode.ECB;
symmetricAlgorithm.Padding = PaddingMode.None;
symmetricAlgorithm.KeySize = keyBytes.Length * 8;
symmetricAlgorithm.Key = keyBytes;
// Set the AES IV to Zeroes
var aesIv = new byte[symmetricAlgorithm.BlockSize >> 3];
Utility.Zero(aesIv);
symmetricAlgorithm.IV = aesIv;
return(symmetricAlgorithm);
}
catch (Exception ex)
{
throw LogHelper.LogExceptionMessage(new InvalidOperationException(LogHelper.FormatInvariant(LogMessages.IDX10663, key, algorithm), ex));
}
}
/// <summary>
/// Called to obtain the byte[] needed to create a <see cref="KeyedHashAlgorithm"/>
/// </summary>
/// <param name="key"><see cref="SecurityKey"/>that will be used to obtain the byte[].</param>
/// <returns><see cref="byte"/>[] that is used to populated the KeyedHashAlgorithm.</returns>
/// <exception cref="ArgumentNullException">if <paramref name="key"/> is null.</exception>
/// <exception cref="ArgumentException">if a byte[] can not be obtained from SecurityKey.</exception>
/// <remarks><see cref="SymmetricSecurityKey"/> and <see cref="JsonWebKey"/> are supported.
/// <para>For a <see cref="SymmetricSecurityKey"/> .Key is returned</para>
/// <para>For a <see cref="JsonWebKey"/>Base64UrlEncoder.DecodeBytes is called with <see cref="JsonWebKey.K"/> if <see cref="JsonWebKey.Kty"/> == JsonWebAlgorithmsKeyTypes.Octet</para>
/// </remarks>
protected virtual byte[] GetKeyBytes(SecurityKey key)
{
if (key == null)
{
throw LogHelper.LogArgumentNullException(nameof(key));
}
if (key is SymmetricSecurityKey symmetricSecurityKey)
{
return(symmetricSecurityKey.Key);
}
if (key is JsonWebKey jsonWebKey && JsonWebKeyConverter.TryConvertToSymmetricSecurityKey(jsonWebKey, out SecurityKey securityKey))
{
return(GetKeyBytes(securityKey));
}
throw LogHelper.LogExceptionMessage(new ArgumentException(LogHelper.FormatInvariant(LogMessages.IDX10667, key)));
}
