UA-.NETStandard/SampleApplications/Samples/Opc.Ua.Sample/SampleServer.UserAuthentication.cs

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 *
 * OPC Foundation MIT License 1.00
 * 
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 * obtaining a copy of this software and associated documentation
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using Opc.Ua.Server;
using System;
using System.IdentityModel.Selectors;
using System.Security.Cryptography.X509Certificates;
using System.Xml;

namespace Opc.Ua.Sample
{
    public partial class SampleServer
    {
        #region User Validation Functions
        /// <summary>
        /// Creates the objects used to validate the user identity tokens supported by the server.
        /// </summary>
        private void CreateUserIdentityValidators(ApplicationConfiguration configuration)
        { 
            for (int ii = 0; ii < configuration.ServerConfiguration.UserTokenPolicies.Count; ii++)
            {
                UserTokenPolicy policy = configuration.ServerConfiguration.UserTokenPolicies[ii];

                // create a validator for a certificate token policy.
                if (policy.TokenType == UserTokenType.Certificate)
                {
                    // check if user certificate trust lists are specified in configuration.
                    if (configuration.SecurityConfiguration.TrustedUserCertificates != null &&
                        configuration.SecurityConfiguration.UserIssuerCertificates != null)
                    {
                        CertificateValidator certificateValidator = new CertificateValidator();
                        certificateValidator.Update(configuration.SecurityConfiguration).Wait();
                        certificateValidator.Update(configuration.SecurityConfiguration.UserIssuerCertificates,
                            configuration.SecurityConfiguration.TrustedUserCertificates,
                            configuration.SecurityConfiguration.RejectedCertificateStore);

                        // set custom validator for user certificates.
                        m_certificateValidator = certificateValidator.GetChannelValidator();
                    }
                }
            }
        }

        /// <summary>
        /// Called when a client tries to change its user identity.
        /// </summary>
        private void SessionManager_ImpersonateUser(Session session, ImpersonateEventArgs args)
        {
            // check for a WSS token.
            IssuedIdentityToken wssToken = args.NewIdentity as IssuedIdentityToken;

            // check for a user name token.
            UserNameIdentityToken userNameToken = args.NewIdentity as UserNameIdentityToken;
            
            if (userNameToken != null)
            {
                VerifyPassword(userNameToken.UserName, userNameToken.DecryptedPassword);
                args.Identity = new UserIdentity(userNameToken);
                Utils.Trace("UserName Token Accepted: {0}", args.Identity.DisplayName);
                return;
            }

            // check for x509 user token.
            X509IdentityToken x509Token = args.NewIdentity as X509IdentityToken;
            
            if (x509Token != null)
            {
                VerifyCertificate(x509Token.Certificate);
                args.Identity = new UserIdentity(x509Token);
                Utils.Trace("X509 Token Accepted: {0}", args.Identity.DisplayName);
                return;
            }
        }

        /// <summary>
        /// Validates the password for a username token.
        /// </summary>
        private void VerifyPassword(string userName, string password)
        {
            if (String.IsNullOrEmpty(password))
            {
                // construct translation object with default text.
                TranslationInfo info = new TranslationInfo(
                    "InvalidPassword",
                    "en-US",
                    "Specified password is not valid for user '{0}'.",
                    userName);

                // create an exception with a vendor defined sub-code.
                throw new ServiceResultException(new ServiceResult(
                    StatusCodes.BadIdentityTokenRejected,
                    "InvalidPassword",
                    "http://opcfoundation.org/UA/Sample/",
                    new LocalizedText(info)));
            }
        }

        /// <summary>
        /// Verifies that a certificate user token is trusted.
        /// </summary>
        private void VerifyCertificate(X509Certificate2 certificate)
        {
            try
            {
                if (m_certificateValidator != null)
                {
                    m_certificateValidator.Validate(certificate);
                }
                else
                {
                    CertificateValidator.Validate(certificate);
                }
            }
            catch (Exception e)
            {
                TranslationInfo info;
                StatusCode result = StatusCodes.BadIdentityTokenRejected;
                ServiceResultException se = e as ServiceResultException;
                if (se != null && se.StatusCode == StatusCodes.BadCertificateUseNotAllowed)
                {
                    info = new TranslationInfo(
                        "InvalidCertificate",
                        "en-US",
                        "'{0}' is an invalid user certificate.",
                        certificate.Subject);

                    result = StatusCodes.BadIdentityTokenInvalid;
                }
                else
                {
                    // construct translation object with default text.
                    info = new TranslationInfo(
                        "UntrustedCertificate",
                        "en-US",
                        "'{0}' is not a trusted user certificate.",
                        certificate.Subject);
                }

                // create an exception with a vendor defined sub-code.
                throw new ServiceResultException(new ServiceResult(
                    result,
                    info.Key,
                    "http://opcfoundation.org/UA/Sample/",
                    new LocalizedText(info)));
            }
        }
        #endregion
        
        #region Private Fields
        private X509CertificateValidator m_certificateValidator;
        #endregion 
    }
}