Intro
微软在 .NET 6 中引入一些更简单的 API 来使用 HMAC 哈希算法(MD5/SHA1/SHA256/SHA384/SHA512)
微软的叫法叫做 HMAC One-Shoot method, HMAC 算法在普通的哈希算法基础上增加了一个 key，通过 key 提升了安全性，能够有效避免密码泄露被彩虹表反推出真实密码， JWT(Json Web Token) 除了可以使用 RSA 方式外也支持使用 HMAC 。
New API
新增的 API 定义如下：
namespace System.Security.Cryptography {
public partial class HMACMD5 {
public static byte[] HashData(byte[] key, byte[] source);
public static byte[] HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source);
public static int HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination);
public static bool TryHashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten);
}
public partial class HMACSHA1 {
public static byte[] HashData(byte[] key, byte[] source);
public static byte[] HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source);
public static int HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination);
public static bool TryHashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten);
}
public partial class HMACSHA256 {
public static byte[] HashData(byte[] key, byte[] source);
public static byte[] HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source);
public static int HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination);
public static bool TryHashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten);
}
public partial class HMACSHA384 {
public static byte[] HashData(byte[] key, byte[] source);
public static byte[] HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source);
public static int HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination);
public static bool TryHashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten);
}
public partial class HMACSHA512 {
public static byte[] HashData(byte[] key, byte[] source);
public static byte[] HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source);
public static int HashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination);
public static bool TryHashData(ReadOnlySpan<byte> key, ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten);
}
} Sample Before
在之前的版本中想要实现计算 HMAC 算法会比较复杂，之前实现了一个 HashHelper 来封装了常用的 Hash 算法和 HMAC 算法，HashHelper 部分代码如下，完整代码可以从 Github 获取：https://github.com/WeihanLi/WeihanLi.Common/blob/dev/src/WeihanLi.Common/Helpers/HashHelper.cs
/// <summary>
/// 获取哈希之后的字符串
/// </summary>
/// <param name="type">哈希类型</param>
/// <param name="source">源</param>
/// <param name="key">key</param>
/// <param name="isLower">是否是小写</param>
/// <returns>哈希算法处理之后的字符串</returns>
public static string GetHashedString(HashType type, byte[] source, byte[]? key, bool isLower = false)
{
Guard.NotNull(source, nameof(source));
if (source.Length == 0)
{
return string.Empty;
}
var hashedBytes = GetHashedBytes(type, source, key);
var sbText = new StringBuilder();
if (isLower)
{
foreach (var b in hashedBytes)
{
sbText.Append(b.ToString("x2"));
}
}
else
{
foreach (var b in hashedBytes)
{
sbText.Append(b.ToString("X2"));
}
}
return sbText.ToString();
}
/// <summary>
/// 计算字符串Hash值
/// </summary>
/// <param name="type">hash类型</param>
/// <param name="str">要hash的字符串</param>
/// <returns>hash过的字节数组</returns>
public static byte[] GetHashedBytes(HashType type, string str) => GetHashedBytes(type, str, Encoding.UTF8);
/// <summary>
/// 计算字符串Hash值
/// </summary>
/// <param name="type">hash类型</param>
/// <param name="str">要hash的字符串</param>
/// <param name="encoding">编码类型</param>
/// <returns>hash过的字节数组</returns>
public static byte[] GetHashedBytes(HashType type, string str, Encoding encoding)
{
Guard.NotNull(str, nameof(str));
if (str == string.Empty)
{
return Array.Empty<byte>();
}
var bytes = encoding.GetBytes(str);
return GetHashedBytes(type, bytes);
}
/// <summary>
/// 获取Hash后的字节数组
/// </summary>
/// <param name="type">哈希类型</param>
/// <param name="bytes">原字节数组</param>
/// <returns></returns>
public static byte[] GetHashedBytes(HashType type, byte[] bytes) => GetHashedBytes(type, bytes, null);
/// <summary>
/// 获取Hash后的字节数组
/// </summary>
/// <param name="type">哈希类型</param>
/// <param name="key">key</param>
/// <param name="bytes">原字节数组</param>
/// <returns></returns>
public static byte[] GetHashedBytes(HashType type, byte[] bytes, byte[]? key)
{
Guard.NotNull(bytes, nameof(bytes));
if (bytes.Length == 0)
{
return bytes;
}
HashAlgorithm algorithm = null!;
try
{
if (key == null)
{
algorithm = type switch
{
HashType.SHA1 => new SHA1Managed(),
HashType.SHA256 => new SHA256Managed(),
HashType.SHA384 => new SHA384Managed(),
HashType.SHA512 => new SHA512Managed(),
_ => MD5.Create()
};
}
else
{
algorithm = type switch
{
HashType.SHA1 => new HMACSHA1(key),
HashType.SHA256 => new HMACSHA256(key),
HashType.SHA384 => new HMACSHA384(key),
HashType.SHA512 => new HMACSHA512(key),
_ => new HMACMD5(key)
};
}
return algorithm.ComputeHash(bytes);
}
finally
{
algorithm.Dispose();
}
} 使用示例如下：
HashHelper.GetHashedBytes(HashType.MD5, "test");
HashHelper.GetHashedBytes(HashType.MD5, "test".GetBytes());
HashHelper.GetHashedBytes(HashType.MD5, "test", "testKey");
HashHelper.GetHashedBytes(HashType.MD5, "test".GetBytes(), "testKey".GetBytes());
HashHelper.GetHashedString(HashType.MD5, "test");
HashHelper.GetHashedString(HashType.SHA1, "test".GetBytes());
HashHelper.GetHashedString(HashType.SHA256, "test", "testKey");
HashHelper.GetHashedString(HashType.MD5, "test".GetBytes(), "testKey".GetBytes());
New API Sample
有了新的 API 以后可以怎么简化呢，来看下面的示例：
var bytes = "test".GetBytes();
var keyBytes = "test-key".GetBytes();
// HMACMD5
var hmd5V1 = HMACMD5.HashData(keyBytes, bytes);
var hmd5V2 = HashHelper.GetHashedBytes(HashType.MD5, bytes, keyBytes);
Console.WriteLine(hmd5V2.SequenceEqual(hmd5V1));
// HMACSHA1
var hsha1V1 = HMACSHA1.HashData(keyBytes, bytes);
var hsha1V2 = HashHelper.GetHashedBytes(HashType.SHA1, bytes, keyBytes);
Console.WriteLine(hsha1V2.SequenceEqual(hsha1V1));
// HMACSHA256
var hsha256V1 = HMACSHA256.HashData(keyBytes, bytes);
var hsha256V2 = HashHelper.GetHashedBytes(HashType.SHA256, bytes, keyBytes);
Console.WriteLine(hsha256V2.SequenceEqual(hsha256V1));
// HMACSHA384
var hsha384V1 = HMACSHA384.HashData(keyBytes ,bytes);
var hsha384V2 = HashHelper.GetHashedBytes(HashType.SHA384, bytes, keyBytes);
Console.WriteLine(hsha384V2.SequenceEqual(hsha384V1));
// HMACSHA512
var hsha512V1 = HMACSHA512.HashData(keyBytes ,bytes);
var hsha512V2 = HashHelper.GetHashedBytes(HashType.SHA512, bytes, keyBytes);
Console.WriteLine(hsha512V2.SequenceEqual(hsha512V1)); 直接使用对应的 HMAC 哈希算法的 HashData 方法即可，传入对应的 key 和 原始内容就可以了，上面是和我们 HashHelper 封装的方法进行对比，看结果是否一致，都是一致的，输出结果如下：
More
对于普通的哈希算法，微软其实在 .NET 5 就已经支持了上面的用法，可以尝试一下下面的代码：
var bytes = "test".GetBytes();
// MD5
var md5V1 = MD5.HashData(bytes);
var md5V2 = HashHelper.GetHashedBytes(HashType.MD5, bytes);
Console.WriteLine(md5V2.SequenceEqual(md5V1));
// SHA1
var sha1V1 = SHA1.HashData(bytes);
var sha1V2 = HashHelper.GetHashedBytes(HashType.SHA1, bytes);
Console.WriteLine(sha1V2.SequenceEqual(sha1V1));
// SHA256
var sha256V1 = SHA256.HashData(bytes);
var sha256V2 = HashHelper.GetHashedBytes(HashType.SHA256, bytes);
Console.WriteLine(sha256V2.SequenceEqual(sha256V1));
// SHA384
var sha384V1 = SHA384.HashData(bytes);
var sha384V2 = HashHelper.GetHashedBytes(HashType.SHA384, bytes);
Console.WriteLine(sha384V2.SequenceEqual(sha384V1));
// SHA512
var sha512V1 = SHA512.HashData(bytes);
var sha512V2 = HashHelper.GetHashedBytes(HashType.SHA512, bytes);
Console.WriteLine(sha512V2.SequenceEqual(sha512V1));
很多时候我们可能都会要使用 MD5 或者 SHA1 之后的字符串，不知道为什么微软没有直接获取一个字符串的方法，如果有这样一个方法，就会更方便了，相比之后，感觉还是自己封装的 HashHelper 使用起来更舒服一些，哈哈，这样的静态方法不够抽象如果要动态替换哈希算法代码可能就有点...
References
https://github.com/dotnet/runtime/pull/53487
https://github.com/dotnet/runtime/issues/40012
https://github.com/dotnet/core/issues/6569#issuecomment-913876347
https://baike.baidu.com/item/hmac/7307543?fr=aladdin
https://github.com/WeihanLi/SamplesInPractice/blob/master/net6sample/HashSample/Program.cs
https://github.com/WeihanLi/WeihanLi.Common/blob/dev/src/WeihanLi.Common/Helpers/HashHelper.cs
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