.NET6中哈希算法的简化用法的实现

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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