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ScramSha256Authenticator.cs
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ScramSha256Authenticator.cs
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/* Copyright 2018–present MongoDB Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text;
using MongoDB.Bson.IO;
using MongoDB.Driver.Core.Misc;
// Use our vendored version of Rfc2898DeriveBytes for .NET Standard 2.0
// because this target does not support a version of Rfc2898DeriveBytes that allows to specify the hash algorithm
#if NETSTANDARD2_0
using Rfc2898DeriveBytes = MongoDB.Driver.Core.Authentication.Vendored.Rfc2898DeriveBytes;
#else
using Rfc2898DeriveBytes = System.Security.Cryptography.Rfc2898DeriveBytes;
#endif
namespace MongoDB.Driver.Core.Authentication
{
/// <summary>
/// A SCRAM-SHA256 SASL authenticator.
/// </summary>
public sealed class ScramSha256Authenticator : ScramShaAuthenticator
{
// static properties
/// <summary>
/// Gets the name of the mechanism.
/// </summary>
/// <value>
/// The name of the mechanism.
/// </value>
public static string MechanismName => "SCRAM-SHA-256";
// constructors
/// <summary>
/// Initializes a new instance of the <see cref="ScramSha256Authenticator"/> class.
/// </summary>
/// <param name="credential">The credential.</param>
[Obsolete("Use the newest overload instead.")]
public ScramSha256Authenticator(UsernamePasswordCredential credential)
: this(credential, serverApi: null)
{
}
/// <summary>
/// Initializes a new instance of the <see cref="ScramSha256Authenticator"/> class.
/// </summary>
/// <param name="credential">The credential.</param>
/// <param name="serverApi">The server API.</param>
public ScramSha256Authenticator(UsernamePasswordCredential credential, ServerApi serverApi)
: this(credential, new DefaultRandomStringGenerator(), serverApi)
{
}
internal ScramSha256Authenticator(
UsernamePasswordCredential credential,
IRandomStringGenerator randomStringGenerator,
ServerApi serverApi)
: base(credential, HashAlgorithmName.SHA256, randomStringGenerator, H256, Hi256, Hmac256, new ScramCache(), serverApi)
{
}
private static byte[] H256(byte[] data)
{
using (var sha256 = SHA256.Create())
{
return sha256.ComputeHash(data);
}
}
private static byte[] Hi256(UsernamePasswordCredential credential, byte[] salt, int iterations)
{
var passwordIntPtr = Marshal.SecureStringToGlobalAllocUnicode(credential.SaslPreppedPassword);
try
{
var passwordChars = new char[credential.SaslPreppedPassword.Length];
var passwordCharsHandle = GCHandle.Alloc(passwordChars, GCHandleType.Pinned);
try
{
Marshal.Copy(passwordIntPtr, passwordChars, 0, credential.SaslPreppedPassword.Length);
return Hi256(passwordChars, salt, iterations);
}
finally
{
Array.Clear(passwordChars, 0, passwordChars.Length);
passwordCharsHandle.Free();
}
}
finally
{
Marshal.ZeroFreeGlobalAllocUnicode(passwordIntPtr);
}
}
private static byte[] Hi256(char[] passwordChars, byte[] salt, int iterations)
{
var passwordBytes = new byte[Utf8Encodings.Strict.GetByteCount(passwordChars)];
var passwordBytesHandle = GCHandle.Alloc(passwordBytes, GCHandleType.Pinned);
try
{
Utf8Encodings.Strict.GetBytes(passwordChars, 0, passwordChars.Length, passwordBytes, 0);
using (var deriveBytes = new Rfc2898DeriveBytes(passwordBytes, salt, iterations, HashAlgorithmName.SHA256))
{
// 32 is the length of output of a sha-256 hmac
return deriveBytes.GetBytes(32);
}
}
finally
{
Array.Clear(passwordBytes, 0, passwordBytes.Length);
passwordBytesHandle.Free();
}
}
private static byte[] Hmac256(UTF8Encoding encoding, byte[] data, string key)
{
using (var hmac = new HMACSHA256(data))
{
return hmac.ComputeHash(encoding.GetBytes(key));
}
}
}
}