admin/Azaion.Services/Security.cs

using System.Security.Cryptography;
using System.Text;

namespace Azaion.Services;

public static class Security
{
    private const int BUFFER_SIZE = 81920; // 80 KB buffer size

    public static string ToHash(this string str) =>
        Convert.ToBase64String(SHA384.HashData(Encoding.UTF8.GetBytes(str)));

    public static string MakeEncryptionKey(string username, string password) =>
        $"{username}-{password}---#%@AzaionKey@%#---";

    public static async Task Encrypt(this Stream stream, Stream outputStream, string key, CancellationToken cancellationToken = default)
    {
        if (stream is { CanSeek: false }) throw new ArgumentNullException(nameof(stream));
        if (key is not { Length: > 0 }) throw new ArgumentNullException(nameof(key));

        using var aes = Aes.Create();
        aes.Key = SHA256.HashData(Encoding.UTF8.GetBytes(key));
        aes.GenerateIV();

        using var encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
        await using var cs = new CryptoStream(outputStream, encryptor, CryptoStreamMode.Write);

        // Prepend IV to the encrypted data
        await outputStream.WriteAsync(aes.IV.AsMemory(0, aes.IV.Length), cancellationToken);

        var buffer = new byte[BUFFER_SIZE];
        int bytesRead;
        while ((bytesRead = await stream.ReadAsync(buffer, cancellationToken)) > 0)
            await cs.WriteAsync(buffer.AsMemory(0, bytesRead), cancellationToken);
    }

    public static async Task Decrypt(this Stream encryptedStream,  Stream outputStream, string key, CancellationToken cancellationToken = default)
    {
        using var aes = Aes.Create();
        aes.Key = SHA256.HashData(Encoding.UTF8.GetBytes(key));

        // Read the IV from the start of the input stream
        var iv = new byte[aes.BlockSize / 8];
        _ = await encryptedStream.ReadAsync(iv, cancellationToken);
        aes.IV = iv;

        using var decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
        await using var cryptoStream = new CryptoStream(encryptedStream, decryptor, CryptoStreamMode.Read);

        // Read and write in chunks
        var buffer = new byte[BUFFER_SIZE];
        int bytesRead;
        while ((bytesRead = await cryptoStream.ReadAsync(buffer, cancellationToken)) > 0)
            await outputStream.WriteAsync(buffer.AsMemory(0, bytesRead), cancellationToken);
    }
}