Credential Stuffing in Aspnet with Cockroachdb

Credential stuffing is a brute-force technique where attackers use lists of previously compromised username and password pairs to gain unauthorized access. In an ASP.NET application backed by CockroachDB, the risk arises from a combination of application-level authentication logic and the distributed nature of the database. If the application does not enforce strict rate limiting and does not validate the origin of each authentication request, attackers can submit a high volume of credentials without triggering defenses.

ASP.NET identity systems often rely on patterns such as cookie authentication or JWT issuance after verifying a user record stored in a data store. When that store is CockroachDB, queries that fetch user credentials by username must be precise and safe. Without parameterized queries, an attacker may attempt injection to bypass authentication checks, but the primary concern in credential stuffing is the lack of per-user or per-IP rate limiting and the absence of multi-factor authentication (MFA). Because CockroachDB scales horizontally, connection pools and retry logic in the application must be configured to avoid inadvertently aiding rapid, automated attempts by not introducing delays that would normally slow down an attacker.

Additionally, if the ASP.NET application exposes an authentication endpoint without proper monitoring, credential stuffing campaigns can fly under the radar until validated accounts are compromised. The distributed SQL layer of CockroachDB can obscure the geographic origin of requests if the application does not log IP addresses consistently. Without correlating login attempts with user-agent and IP data, security teams cannot build effective heuristics to detect abnormal patterns. The use of weak or reused passwords amplifies the risk, and the presence of CockroachDB does not inherently mitigate this; it simply means that authentication checks must be robust and consistently applied across all nodes.

During a scan, middleBrick evaluates the authentication surface of an ASP.NET endpoint that uses CockroachDB by checking whether authentication relies on unauthenticated access, whether rate limiting is applied, and whether findings related to authentication map to the OWASP API Top 10 and compliance frameworks. The scanner tests whether an attacker can probe the system with multiple credentials and whether the application leaks information that could assist in automated attacks.

To secure an ASP.NET application using CockroachDB, implement strict input validation, parameterized queries, and robust authentication controls. The following examples demonstrate secure patterns for user authentication and account management.

Parameterized query for user lookup

Always use parameterized SQL to prevent injection and ensure predictable query plans. This example uses Npgsql with named parameters to fetch a user record securely.

using Npgsql;
using System;

public class UserRepository
{
    private readonly string _connectionString;

    public UserRepository(string connectionString)
    {
        _connectionString = connectionString;
    }

    public async Task<User> GetUserByUsernameAsync(string username)
    {
        await using var conn = new NpgsqlConnection(_connectionString);
        await conn.OpenAsync();
        await using var cmd = new NpgsqlCommand("SELECT id, username, password_hash, mfa_enabled FROM users WHERE username = @username", conn);
        cmd.Parameters.AddWithValue("username", username);
        await using var reader = await cmd.ExecuteReaderAsync();
        if (await reader.ReadAsync())
        {
            return new User
            {
                Id = reader.GetGuid(0),
                Username = reader.GetString(1),
                PasswordHash = reader.GetString(2),
                MfaEnabled = reader.GetBoolean(3)
            };
        }
        return null;
    }
}

Enforce rate limiting and secure password handling

Apply rate limiting at the middleware level to reduce the effectiveness of credential stuffing. Use a sliding window or token bucket algorithm to limit attempts per user or per IP. In parallel, ensure passwords are hashed with a strong algorithm such as bcrypt or Argon2.

using Microsoft.AspNetCore.Http;
using System;
using System.Collections.Concurrent;
using System.Threading.Tasks;

public class RateLimitMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ConcurrentDictionary<string, TokenBucket> _buckets = new();
    private readonly int _maxRequests;
    private readonly TimeSpan _replenishInterval;

    public RateLimitMiddleware(RequestDelegate next, int maxRequests = 10, int replenishSeconds = 60)
    {
        _next = next;
        _maxRequests = maxRequests;
        _replenishInterval = TimeSpan.FromSeconds(replenishSeconds);
    }

    public async Task InvokeAsync(HttpContext context)
    {
        var key = context.Connection.RemoteIpAddress?.ToString() ?? context.User.Identity?.Name ?? "unknown";
        var bucket = _buckets.GetOrAdd(key, _ => new TokenBucket(_maxRequests, _replenishInterval));
        if (bucket.Take())
        {
            await _next(context);
        }
        else
        {
            context.Response.StatusCode = 429;
            await context.Response.WriteAsync("Too many requests");
        }
    }

    private class TokenBucket
    {
        private int _tokens;
        private DateTime _lastRefill;
        private readonly int _capacity;
        private readonly TimeSpan _refillPeriod;

        public TokenBucket(int capacity, TimeSpan refillPeriod)
        {
            _capacity = capacity;
            _refillPeriod = refillPeriod;
            _tokens = capacity;
            _lastRefill = DateTime.UtcNow;
        }

        public bool Take()
        {
            Refill();
            if (_tokens > 0)
            {
                _tokens--;
                return true;
            }
            return false;
        }

        private void Refill()
        {
            var now = DateTime.UtcNow;
            var elapsed = now - _lastRefill;
            if (elapsed >= _refillPeriod)
            {
                var refillCount = (int)(elapsed.TotalSeconds / _refillPeriod.TotalSeconds);
                _tokens = Math.Min(_capacity, _tokens + refillCount);
                _lastRefill = now;
            }
        }
    }
}

Require MFA for sensitive operations

For accounts that support multi-factor authentication, enforce MFA when logging in from new devices or locations. Store MFA settings in CockroachDB and validate them during authentication flow.

using System.Threading.Tasks;

public class AuthenticationService
{
    private readonly UserRepository _userRepository;

    public AuthenticationService(UserRepository userRepository)
    {
        _userRepository = userRepository;
    }

    public async Task<bool>ValidateCredentialsAsync(string username, string password)
    {
        var user = await _userRepository.GetUserByUsernameAsync(username);
        if (user == null) return false;
        // Use a secure password verification library, e.g., BCrypt.Net-Next
        return BCrypt.Net.BCrypt.Verify(password, user.PasswordHash);
    }

    public async Task<bool>IsMfaRequiredAsync(Guid userId)
    {
        var user = await _userRepository.GetUserByIdAsync(userId);
        return user?.MfaEnabled == true;
    }
}