将字节数组转换为字符串，然后再返回，产生不同的结果 [英] Converting a byte array to string and then back again produced different results

问题描述

我正在使用 .net port of libsodium 一>。哈希生成函数有两种形式，一种接受字节数组和一种接受字符串：

  public static byte [] ArgonHashBinary字符串密码，字符串salt，long opsLimit，int memLimit，long outputLength = ARGON_SALTBYTES）
 
公共静态字节[] ArgonHashBinary（byte [] password，byte [] salt，long opsLimit，int memLimit，long outputLength = ARGON_SALTBYTES）
  

我遇到的问题是两种形式在输入时产生相同的散列值是相同的。

  var saltAsBytes = PasswordHash.ArgonGenerateSalt（）; 
 var saltAsString = Encoding.UTF8.GetString（saltAsBytes）; 
 var tmp = Encoding.UTF8.GetBytes（saltAsString）; 
 
 var hash1 = PasswordHash.ArgonHashBinary（password，saltAsString，6，134217728，16）; 
 var hash2 = PasswordHash.ArgonHashBinary（Encoding.UTF8.GetBytes（password），saltAsBytes，6，134217728，16）; 
  

任何包含PasswordHash的内容。是libsodium而不是我的代码。

从上面的代码中，我将它从字符串转换为字节数组，然后返回到字节数组。字节数组数组总是不同的长度。 ArgonGenerateSalt（）产生一个长度为16的字节数组。当我将它从一个大于30的字符串转换回来时（每次都因为生成不同的盐而不同）。

为什么我要转换为UTF8？因为那就是他们在内部做的事情：
https://github.com/adamcaudill/libsodium-net/blob/master/libsodium-net/PasswordHash.cs

  {
 return ArgonHashBinary（Encoding.UTF8.GetBytes（password），Encoding .UTF8.GetBytes（salt），limit，outputLength）; 
} 
  

当我将salt转换为UTF8字符串时，哈希函数将失败，因为它们正在检查字节数组的长度以确保其16个字节。如果我将它转换为ASCII字符串，但它会生成不同的哈希值（这是预期的）。

澄清此代码中的散列片段不是问题。找出为什么 tmp 不同，那么 saltAsBytes 是关键。

将字节数组转换为字符串，然后再返回，产生不同的结果

二进制数据不能转换为字符串，然后使用编码返回字节数组
[AnyEncoding] .GetBytes 和编码。[AnyEncoding] .GetString

改用 Convert.ToBase64String 和 Convert.FromBase64String

您可以轻松测试...

  var bytes = new byte [] {255，255，255}; 
 var buf = Encoding.UTF8.GetString（bytes）; 
 var newbytes = Encoding.UTF8.GetBytes（buf）; 
  

newbytes 的长度将为9。 ....

编辑：这是@Theo的测试用例

  var bytes = new byte [] {0，216}; //任何新的字节[] {X，216}; 
 var buf = Encoding.Unicode.GetString（bytes）; 
 var newbytes = Encoding.Unicode.GetBytes（buf）; // 253,255 
  

I'm using the .net port of libsodium. The hash generation function has two forms, one that accepts byte arrays and one that accepts strings:

public static byte[] ArgonHashBinary(string password, string salt, long opsLimit, int memLimit, long outputLength = ARGON_SALTBYTES)  

public static byte[] ArgonHashBinary(byte[] password, byte[] salt, long opsLimit, int memLimit, long outputLength = ARGON_SALTBYTES)

What i'm having an issue with is both forms producing the same hash when the input values are identical.

var saltAsBytes = PasswordHash.ArgonGenerateSalt();
var saltAsString = Encoding.UTF8.GetString(saltAsBytes);
var tmp = Encoding.UTF8.GetBytes(saltAsString);

var hash1 = PasswordHash.ArgonHashBinary(password, saltAsString, 6, 134217728, 16);
var hash2 = PasswordHash.ArgonHashBinary( Encoding.UTF8.GetBytes(password), saltAsBytes, 6, 134217728, 16);

Anything with "PasswordHash." is libsodium and not my code.

From the code above when i convert it from a string and then back to a byte array the byte array. The byte array array is always a different length. ArgonGenerateSalt() produces a byte array with a length of 16. When i convert it back from a string above its generally ~30 (different every time because of different salts produced).

Why am i converting to UTF8? Because thats what they are doing internally: https://github.com/adamcaudill/libsodium-net/blob/master/libsodium-net/PasswordHash.cs

public static byte[] ArgonHashBinary(string password, string salt, StrengthArgon limit = StrengthArgon.Interactive, long outputLength = ARGON_SALTBYTES)
    {
      return ArgonHashBinary(Encoding.UTF8.GetBytes(password), Encoding.UTF8.GetBytes(salt), limit, outputLength);
    }

When i convert the salt to a UTF8 string the hashing function will fail because they are checking the length of the byte array to make sure its 16 bytes. If i convert it to a ASCII string it works but produces a different hash (which is expected).

To clarify the hashing piece in this code is not the issue. Figuring out why tmp is different then saltAsBytes is the key.

解决方案

Converting a byte array to string and then back again produced different results

A binary data may not be converted to string and then back to byte array using Encoding.[AnyEncoding].GetBytes and Encoding.[AnyEncoding].GetString

Instead use Convert.ToBase64String and Convert.FromBase64String

You can easily test...

var bytes = new byte[] { 255, 255, 255 }; 
var buf = Encoding.UTF8.GetString(bytes);
var newbytes = Encoding.UTF8.GetBytes(buf);

newbytes's length will be 9.....

Edit: This is the test case for @Theo

var bytes = new byte[] { 0, 216 }; //any new byte[] { X, 216 };
var buf = Encoding.Unicode.GetString(bytes);
var newbytes = Encoding.Unicode.GetBytes(buf); //253,255

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