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GoodBoyAlex
Asked:2023-09-02 04:05:31 +0000 UTC2023-09-02 04:05:31 +0000 UTC

FormatException：加密文本时输入不是有效的 Base-64 字符串错误

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有一个关键类：

public class EncryptKey
{
    public EncryptKey (byte[] key) => Key = key;

    public EncryptKey (string key) => FromString(key);

    public byte[] Key { get; set; }

    public void FromString (string s)
    {
        using SymmetricAlgorithm sa = Aes.Create();

        using Rfc2898DeriveBytes hasher = new(s, sa.IV, 5000, HashAlgorithmName.SHA512);

        Key = hasher.GetBytes(32);
    }

    public override string ToString() => Convert.ToBase64String(Key);
}

加密实现如下所示：

public static string Encrypt (string text, IEncryptKey key)
{
    string textToEncode = text.Replace("/", "%SL%").Replace("+", "%PL%");

    using Aes aes = Aes.Create();

    aes.Key = key.Key;

    using MemoryStream ms = new();

    ms.Write(aes.IV);

    using (CryptoStream cs = new(ms, aes.CreateEncryptor(), CryptoStreamMode.Write, true))

        cs.Write(Encoding.UTF8.GetBytes(textToEncode));

    return Convert.ToBase64String(ms.ToArray());
}

public static string Decrypt (string text, IEncryptKey key)
{
    string textToDecode = text.Replace("%SL%", "/").Replace("%PL%", "+");

    using MemoryStream ms = new(Convert.FromBase64String(textToDecode));

    byte[] iv = new byte[16];

    _ = ms.Read(iv);

    using Aes aes = Aes.Create();

    aes.Key = key.Key;

    aes.IV = iv;

    using CryptoStream cs = new(ms, aes.CreateDecryptor(), CryptoStreamMode.Read, true);

    using MemoryStream output = new();

    cs.CopyTo(output);

    return Encoding.UTF8.GetString(output.ToArray());
}

我这样称呼：

var encText = Encrypt(Guid.NewGuid().ToString, new("123"));
var decText = Decrypt(encText, new("123"));

结果，出现错误：

FormatException: The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters
c#

1 个回答

  1. Best Answer

    对密码进行哈希处理时，IV 不应随意使用，而应使用相同的值。也就是说，加密时使用哪个IV，解密时也应该使用相同的IV。

    嗯，他们在课程上很聪明，此外，将密钥永久存储在内存中对于安全来说是一个坏兆头。5000 次迭代 - 剥夺不会增加可靠性的工作。对 256 位密钥使用 512 位哈希值也不好。

    凡事适度就好。即使知道盐的人也无法对密码进行哈希处理，即使经过哈希处理、重新哈希 1000 次甚至更多次。阅读RFC 2898。

    private static byte[] KeyFromString(string s, byte[] salt)
{
    using Rfc2898DeriveBytes hasher = new(s, salt, 1000, HashAlgorithmName.SHA256);
    return hasher.GetBytes(32);
}

public static string Encrypt(string text, string password)
{
    using Aes aes = Aes.Create();
    aes.Key = KeyFromString(password, aes.IV);
    using MemoryStream ms = new();
    ms.Write(aes.IV);
    using (CryptoStream cs = new(ms, aes.CreateEncryptor(), CryptoStreamMode.Write, true))
        cs.Write(Encoding.UTF8.GetBytes(text));
    return Convert.ToBase64String(ms.ToArray());
}

public static string Decrypt(string base64, string password)
{
    using MemoryStream ms = new(Convert.FromBase64String(base64));
    byte[] iv = new byte[16];
    ms.Read(iv);
    using Aes aes = Aes.Create();
    aes.Key = KeyFromString(password, iv);
    aes.IV = iv;
    using CryptoStream cs = new(ms, aes.CreateDecryptor(), CryptoStreamMode.Read, true);
    using MemoryStream output = new();
    cs.CopyTo(output);
    return Encoding.UTF8.GetString(output.ToArray());
}

    如果需要Base64 URL格式，那么可以按照标准进行转换

    public static string Base64UrlEncode(string base64)
{
    return base64.TrimEnd('=').Replace('+', '-').Replace('/', '_');
}

public static string Base64UrlDecode(string base64)
{
    string result = base64.Replace('_', '/').Replace('-', '+');
    if (result.Length % 4 == 2)
        result += "==";
    else
    if (result.Length % 4 == 3)
        result += "=";
    return result;
}

    尽量不要在一种方法中混合多种不同类型的问题。该方法必须做一件事。

    string text = "Hello World!";
string password = "qwe123";
string base64 = Encrypt(text, password);
Console.WriteLine(base64);
string urlSafeBase64 = Base64UrlEncode(base64);
Console.WriteLine(urlSafeBase64);

string base64decoded = Base64UrlDecode(urlSafeBase64);
string textDecrypted = Decrypt(base64decoded, password);
Console.WriteLine(textDecrypted);

    输出到控制台（每次输出不同的base64，但应该是这样）

    +SslYF2B/sNcZzYZ2f6dGrNMPv0EHgld5+buiAVWyCM=
-SslYF2B_sNcZzYZ2f6dGrNMPv0EHgld5-buiAVWyCM
Hello World!

    现在，当它工作时，您已经可以在其上包装抽象、类和其他 OOP。祝你好运！

    • 2

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