MireaBackend/Security/Services/PreAuthService.cs

using Mirea.Api.Security.Common.Domain;
using Mirea.Api.Security.Common.Dto.Requests;
using Mirea.Api.Security.Common.Dto.Responses;
using Mirea.Api.Security.Common.Interfaces;
using System;
using System.Security;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;

namespace Mirea.Api.Security.Services;

public class PreAuthService(ICacheService cache)
{
    public TimeSpan Lifetime { private get; init; }

    private static string GeneratePreAuthToken() => Guid.NewGuid().ToString().Replace("-", "") +
                                                      GeneratorKey.GenerateString(16);

    private static string GetPreAuthCacheKey(string fingerprint) => $"{fingerprint}_pre_auth_token";

    public async Task<PreAuthTokenResponse> GeneratePreAuthTokenAsync(TokenRequest request, string userId, CancellationToken cancellation = default)
    {
        var preAuthToken = GeneratePreAuthToken();

        var preAuthTokenStruct = new PreAuthToken
        {
            Fingerprint = request.Fingerprint,
            UserId = userId,
            UserAgent = request.UserAgent,
            Token = preAuthToken,
            Ip = request.Ip
        };

        await cache.SetAsync(
            GetPreAuthCacheKey(request.Fingerprint),
            JsonSerializer.SerializeToUtf8Bytes(preAuthTokenStruct),
            absoluteExpirationRelativeToNow: Lifetime,
            cancellationToken: cancellation);

        return new PreAuthTokenResponse
        {
            Token = preAuthToken,
            ExpiresIn = DateTime.UtcNow.Add(Lifetime)
        };
    }
    public async Task<string> MatchToken(TokenRequest request, string preAuthToken, CancellationToken cancellation = default)
    {
        var preAuthTokenStruct = await cache.GetAsync<PreAuthToken>(GetPreAuthCacheKey(request.Fingerprint), cancellation)
            ?? throw new SecurityException($"The token was not found using fingerprint \"{request.Fingerprint}\"");

        if (preAuthTokenStruct == null ||
            preAuthTokenStruct.Token != preAuthToken ||
            (preAuthTokenStruct.UserAgent != request.UserAgent &&
             preAuthTokenStruct.Ip != request.Ip))
        {
            throw new SecurityException("It was not possible to verify the authenticity of the token");
        }

        await cache.RemoveAsync(GetPreAuthCacheKey(request.Fingerprint), cancellation);

        return preAuthTokenStruct.UserId;
    }
}