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using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using MediaBrowser.Common.Extensions;
using MediaBrowser.Model.Cryptography;
using static MediaBrowser.Common.Cryptography.Constants;
namespace Emby.Server.Implementations.Cryptography
{
/// <summary>
/// Class providing abstractions over cryptographic functions.
/// </summary>
public class CryptographyProvider : ICryptoProvider
{
// FIXME: When we get DotNet Standard 2.1 we need to revisit how we do the crypto
// Currently supported hash methods from https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.cryptoconfig?view=netcore-2.1
// there might be a better way to autogenerate this list as dotnet updates, but I couldn't find one
// Please note the default method of PBKDF2 is not included, it cannot be used to generate hashes cleanly as it is actually a pbkdf with sha1
private static readonly HashSet<string> _supportedHashMethods = new HashSet<string>()
{
"MD5",
"System.Security.Cryptography.MD5",
"SHA",
"SHA1",
"System.Security.Cryptography.SHA1",
"SHA256",
"SHA-256",
"System.Security.Cryptography.SHA256",
"SHA384",
"SHA-384",
"System.Security.Cryptography.SHA384",
"SHA512",
"SHA-512",
"System.Security.Cryptography.SHA512"
};
/// <inheritdoc />
public string DefaultHashMethod => "PBKDF2";
/// <inheritdoc />
public IEnumerable<string> GetSupportedHashMethods()
=> _supportedHashMethods;
private byte[] PBKDF2(string method, byte[] bytes, byte[] salt, int iterations)
{
// downgrading for now as we need this library to be dotnetstandard compliant
// with this downgrade we'll add a check to make sure we're on the downgrade method at the moment
if (method != DefaultHashMethod)
{
throw new CryptographicException($"Cannot currently use PBKDF2 with requested hash method: {method}");
}
using var r = new Rfc2898DeriveBytes(bytes, salt, iterations);
return r.GetBytes(32);
}
/// <inheritdoc />
public byte[] ComputeHash(string hashMethod, byte[] bytes, byte[] salt)
{
if (hashMethod == DefaultHashMethod)
{
return PBKDF2(hashMethod, bytes, salt, DefaultIterations);
}
if (!_supportedHashMethods.Contains(hashMethod))
{
throw new CryptographicException($"Requested hash method is not supported: {hashMethod}");
}
using var h = HashAlgorithm.Create(hashMethod) ?? throw new ResourceNotFoundException($"Unknown hash method: {hashMethod}.");
if (salt.Length == 0)
{
return h.ComputeHash(bytes);
}
byte[] salted = new byte[bytes.Length + salt.Length];
Array.Copy(bytes, salted, bytes.Length);
Array.Copy(salt, 0, salted, bytes.Length, salt.Length);
return h.ComputeHash(salted);
}
/// <inheritdoc />
public byte[] ComputeHashWithDefaultMethod(byte[] bytes, byte[] salt)
=> PBKDF2(DefaultHashMethod, bytes, salt, DefaultIterations);
/// <inheritdoc />
public byte[] GenerateSalt()
=> GenerateSalt(DefaultSaltLength);
/// <inheritdoc />
public byte[] GenerateSalt(int length)
=> RandomNumberGenerator.GetBytes(length);
}
}
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