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原文链接：https://mp.weixin.qq.com/s/rbSGnq83mmUT5sV_vuyrcg
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