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 * OPC Foundation MIT License 1.00
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using System;
using System.Threading.Tasks;
using NUnit.Framework;
using Opc.Ua.Server.TestFramework;
using Quickstarts.ReferenceServer;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Tests for client lockout functionality after failed authentication attempts.
    /// </summary>
    [TestFixture]
    [Category("Session")]
    [Category("Security")]
    public class ClientLockoutTests
    {
        private ServerFixture<StandardServer> m_fixture;
        private StandardServer m_server;

        [OneTimeSetUp]
        public async Task OneTimeSetUpAsync()
        {
            m_fixture = new ServerFixture<StandardServer>(t => new ReferenceServer(t));
            m_server = await m_fixture.StartAsync().ConfigureAwait(false);
        }

        [OneTimeTearDown]
        public async Task OneTimeTearDownAsync()
        {
            await m_fixture.StopAsync().ConfigureAwait(false);
        }

        [Test]
        public async Task FailedAuthenticationAttemptsAreTrackedAsync()
        {
            const string sessionName = nameof(FailedAuthenticationAttemptsAreTrackedAsync);
            ArrayOf<EndpointDescription> endpoints = m_server.GetEndpoints();
            EndpointDescription endpoint = FindTcpEndpoint(endpoints);

            SecureChannelContext secureChannelContext = CreateSecureChannelContext(sessionName, endpoint);
            var requestHeader = new RequestHeader();

            CreateSessionResponse createResponse = await m_server.CreateSessionAsync(
                secureChannelContext,
                requestHeader,
                null,
                null,
                null,
                sessionName,
                default,
                default,
                ServerFixtureUtils.DefaultSessionTimeout,
                ServerFixtureUtils.DefaultMaxResponseMessageSize,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(createResponse.ResponseHeader);
            requestHeader.AuthenticationToken = createResponse.AuthenticationToken;

            var invalidToken = new UserNameIdentityToken
            {
                UserName = "invaliduser",
                Password = System.Text.Encoding.UTF8.GetBytes("wrongpassword").ToByteString(),
                PolicyId = "0"
            };

            for (int i = 0; i < 4; i++)
            {
                ServiceResultException exception = Assert.ThrowsAsync<ServiceResultException>(async () => await m_server.ActivateSessionAsync(
                        secureChannelContext,
                        requestHeader,
                        createResponse.ServerSignature,
                        [],
                        [],
                        new ExtensionObject(invalidToken),
                        null,
                        RequestLifetime.None).ConfigureAwait(false));

                Assert.That(exception, Is.Not.Null);
                Assert.That(
                    exception.StatusCode == StatusCodes.BadIdentityTokenInvalid ||
                    exception.StatusCode == StatusCodes.BadIdentityTokenRejected ||
                    exception.StatusCode == StatusCodes.BadUserAccessDenied,
                    Is.True,
                    $"Expected authentication failure status code, got {exception.StatusCode}");
            }

            await m_server.CloseSessionAsync(
                secureChannelContext,
                requestHeader,
                true,
                RequestLifetime.None).ConfigureAwait(false);
        }

        [Test]
        public async Task ClientIsLockedOutAfterFiveFailedAttemptsAsync()
        {
            const string sessionName = nameof(ClientIsLockedOutAfterFiveFailedAttemptsAsync);
            ArrayOf<EndpointDescription> endpoints = m_server.GetEndpoints();
            EndpointDescription endpoint = FindTcpEndpoint(endpoints);

            SecureChannelContext secureChannelContext = CreateSecureChannelContext(sessionName, endpoint);
            var requestHeader = new RequestHeader();

            CreateSessionResponse createResponse = await m_server.CreateSessionAsync(
                secureChannelContext,
                requestHeader,
                null,
                null,
                null,
                sessionName,
                default,
                default,
                ServerFixtureUtils.DefaultSessionTimeout,
                ServerFixtureUtils.DefaultMaxResponseMessageSize,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(createResponse.ResponseHeader);
            requestHeader.AuthenticationToken = createResponse.AuthenticationToken;

            var invalidToken = new UserNameIdentityToken
            {
                UserName = "lockoutuser",
                Password = System.Text.Encoding.UTF8.GetBytes("wrongpassword").ToByteString(),
                PolicyId = "0"
            };

            var validToken = new UserNameIdentityToken
            {
                UserName = "user1",
                Password = System.Text.Encoding.UTF8.GetBytes("password").ToByteString(),
                PolicyId = "0"
            };

            for (int i = 0; i < 5; i++)
            {
                try
                {
                    await m_server.ActivateSessionAsync(
                        secureChannelContext,
                        requestHeader,
                        createResponse.ServerSignature,
                        [],
                        [],
                        new ExtensionObject(invalidToken),
                        null,
                        RequestLifetime.None).ConfigureAwait(false);
                }
                catch (ServiceResultException)
                {
                }
            }

            CreateSessionResponse newCreateResponse = await m_server.CreateSessionAsync(
                secureChannelContext,
                requestHeader,
                null,
                null,
                null,
                sessionName + "_2",
                default,
                default,
                ServerFixtureUtils.DefaultSessionTimeout,
                ServerFixtureUtils.DefaultMaxResponseMessageSize,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(newCreateResponse.ResponseHeader);
            requestHeader.AuthenticationToken = newCreateResponse.AuthenticationToken;

            ServiceResultException lockoutException = Assert.ThrowsAsync<ServiceResultException>(async () => await m_server.ActivateSessionAsync(
                    secureChannelContext,
                    requestHeader,
                    newCreateResponse.ServerSignature,
                    [],
                    [],
                    new ExtensionObject(validToken),
                    null,
                    RequestLifetime.None).ConfigureAwait(false));

            Assert.That(lockoutException, Is.Not.Null);
            Assert.That(lockoutException.StatusCode, Is.EqualTo(StatusCodes.BadUserAccessDenied));

            await m_server.CloseSessionAsync(
                secureChannelContext,
                requestHeader,
                true,
                RequestLifetime.None).ConfigureAwait(false);
        }

        [Test]
        public async Task SuccessfulAuthenticationClearsFailedAttemptsAsync()
        {
            const string sessionName = nameof(SuccessfulAuthenticationClearsFailedAttemptsAsync);
            ArrayOf<EndpointDescription> endpoints = m_server.GetEndpoints();
            EndpointDescription endpoint = FindTcpEndpoint(endpoints);

            SecureChannelContext secureChannelContext = CreateSecureChannelContext(sessionName, endpoint);
            var requestHeader = new RequestHeader();

            CreateSessionResponse createResponse = await m_server.CreateSessionAsync(
                secureChannelContext,
                requestHeader,
                null,
                null,
                null,
                sessionName,
                default,
                default,
                ServerFixtureUtils.DefaultSessionTimeout,
                ServerFixtureUtils.DefaultMaxResponseMessageSize,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(createResponse.ResponseHeader);
            requestHeader.AuthenticationToken = createResponse.AuthenticationToken;

            var invalidToken = new UserNameIdentityToken
            {
                UserName = "clearuser",
                Password = System.Text.Encoding.UTF8.GetBytes("wrongpassword").ToByteString(),
                PolicyId = "0"
            };

            // Only successful authentication with a real (non-anonymous) identity
            // clears the failed authentication counter. Anonymous activations
            // intentionally do not reset the counter to prevent attackers from
            // interleaving anonymous logins to bypass the lockout.
            var validToken = new UserNameIdentityToken
            {
                UserName = "user1",
                Password = System.Text.Encoding.UTF8.GetBytes("password").ToByteString(),
                PolicyId = "1"
            };

            for (int i = 0; i < 3; i++)
            {
                try
                {
                    await m_server.ActivateSessionAsync(
                        secureChannelContext,
                        requestHeader,
                        createResponse.ServerSignature,
                        [],
                        [],
                        new ExtensionObject(invalidToken),
                        null,
                        RequestLifetime.None).ConfigureAwait(false);
                }
                catch (ServiceResultException)
                {
                }
            }

            ActivateSessionResponse activateResponse = await m_server.ActivateSessionAsync(
                secureChannelContext,
                requestHeader,
                createResponse.ServerSignature,
                [],
                [],
                new ExtensionObject(validToken),
                null,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(activateResponse.ResponseHeader);

            for (int i = 0; i < 4; i++)
            {
                try
                {
                    await m_server.ActivateSessionAsync(
                        secureChannelContext,
                        requestHeader,
                        createResponse.ServerSignature,
                        [],
                        [],
                        new ExtensionObject(invalidToken),
                        null,
                        RequestLifetime.None).ConfigureAwait(false);
                }
                catch (ServiceResultException)
                {
                }
            }

            activateResponse = await m_server.ActivateSessionAsync(
                secureChannelContext,
                requestHeader,
                createResponse.ServerSignature,
                [],
                [],
                new ExtensionObject(validToken),
                null,
                RequestLifetime.None).ConfigureAwait(false);

            ServerFixtureUtils.ValidateResponse(activateResponse.ResponseHeader);

            await m_server.CloseSessionAsync(
                secureChannelContext,
                requestHeader,
                true,
                RequestLifetime.None).ConfigureAwait(false);
        }

        private static EndpointDescription FindTcpEndpoint(ArrayOf<EndpointDescription> endpoints)
        {
            EndpointDescription endpoint = endpoints.Find(e =>
                e.TransportProfileUri.Equals(Profiles.UaTcpTransport, StringComparison.Ordinal) ||
                e.TransportProfileUri.Equals(Profiles.HttpsBinaryTransport, StringComparison.Ordinal))
                ?? throw new NotSupportedException("No supported transport profile found.");

            endpoint.SecurityMode = MessageSecurityMode.None;
            endpoint.SecurityPolicyUri = SecurityPolicies.None;
            return endpoint;
        }

        private static SecureChannelContext CreateSecureChannelContext(string sessionName, EndpointDescription endpoint)
        {
            return new SecureChannelContext(
                sessionName,
                endpoint,
                RequestEncoding.Binary,
                clientChannelCertificate: null,
                serverChannelCertificate: null,
                channelThumbprint: null);
        }
    }
}