Skip to main content

AdfsClient Class

As mentioned in a previous blog post, this class takes care of the interaction with the ADFS server.

Its main functionality is to request and decrypt SAML tokens from an ADFS server.

The class makes use of the .NET security token API, which in order to be used, it has to be configured. The easiest is to configure it through XML, in one of the application's .config files:

<system.identityModel.services>
  <federationConfiguration>
    <serviceCertificate>
      <certificateReference storeLocation="LocalMachine" storeName="My" x509FindType="FindByThumbprint"
        findValue="30 4e 10 91 73 fb 34 6a 90 19 f5 e7 d4 fa 2d 11 21 10 3e 3d"/>
    </serviceCertificate>
  </federationConfiguration>
</system.identityModel.services>

The configuration above allows us to use the predefined System.IdentityModel.Tokens.Saml2SecurityTokenHandler. I used this class to handle the reading (i.e. decrypting) and validating (i.e. extracting the claims) the token. If configured correctly, this class makes the entire token handling quite easy.

The configuration above refers to the SSL Certificate that must be installed on the machine running the AdfsClient, and basically configures a way of looking up the certificate by its thumbprint. This certificate is used to decrypt the encrypted SAML XML token, so it must contain a private key. This same certificate (only the public key) is configured in the ADFS Relying Party encryption panel and it is used by the ADFS server to encrypt the token when it's issued.

public const string SAML2_ASSERTION = "urn:oasis:names:tc:SAML:2.0:assertion";

private SecurityTokenHandlerCollection securityTokenHandlers;
private SecurityTokenHandlerCollection SecurityTokenHandlers
{
    get
    {
        if (securityTokenHandlers == null)
        {
            securityTokenHandlers = new SecurityTokenHandlerCollection(
                FederatedAuthentication.FederationConfiguration.IdentityConfiguration.SecurityTokenHandlers);
            for (int i = 0; i < securityTokenHandlers.Count; i++)
            {
                if (securityTokenHandlers[i] is Saml2SecurityTokenHandler)
                {
                    securityTokenHandlers[i] = new ValidatingSaml2SecurityTokenHandler
                    {
                        Configuration = securityTokenHandlers[0].Configuration
                    };
                }
            }
        }

        return securityTokenHandlers;
    }
}

public AdfsClient()
{
    IsInitialized = false;
}

public AdfsClient(string username, string password, string audienceUri, string stsEndpoint)
{
    IsInitialized = true;
    Username = username;
    Password = password;
    AudienceUri = audienceUri;
    StsEndpoint = stsEndpoint;
}

The constructors above are self explanatory, but they also initialize the current instance.

The method GetToken below, requests a token from the ADFS server, but only if there is no token already present in the internal cache. This is done in order to prevent requesting a new token for every single request. The cache key is constructed based off the user, password hash, audienceUri and STS endpoint.

A token is placed into cache for the duration that token is valid, as specified in the token itself.

public GenericXmlSecurityToken GetToken()
{
    if (!IsInitialized)
    {
        throw new AdfsClientException("AdfsClinet not initialized");
    }

    GenericXmlSecurityToken token;

    if (!cache.TryGet(CacheKey, out token))
    {
        WSHttpBinding binding = new WSHttpBinding();
        binding.Security.Message.ClientCredentialType = MessageCredentialType.UserName;
        binding.Security.Message.EstablishSecurityContext = false;
        binding.Security.Mode = SecurityMode.TransportWithMessageCredential;

        var endpoint = new EndpointAddress(StsEndpoint);

        using (var factory = new WSTrustChannelFactory(binding, endpoint))
        {
            factory.Credentials.UserName.UserName = Username;
            factory.Credentials.UserName.Password = Password;
            IWSTrustChannelContract channel = factory.CreateChannel();

            RequestSecurityToken request = new RequestSecurityToken
            {
                RequestType = RequestTypes.Issue,
                AppliesTo = new EndpointReference(AudienceUri),
                TokenType = SAML2_ASSERTION
            };

            token = (GenericXmlSecurityToken)channel.Issue(request);

            cache.Insert(CacheKey, token, token.ValidTo - token.ValidFrom);
        }
    }

    return token;
}

Next, method DecryptSaml2Token takes a string representation of the SAML token, as it was received from the ADFS server, and decodes it into a generic XML token and at the same time decrypts the encrypted part of the XML. This method is used during passive-authentication from the ADFS, namely in the previously explained SamlAuthenticationHandler.

The method uses a StringReader to identify where the token starts in the XML, and then uses the ReadToken method of the SecyrityTokenHandlers collection.

public Saml2SecurityToken DecryptSaml2Token(string tokenXml)
{
    using (StringReader stringReader = new StringReader(tokenXml))
    using (XmlReader reader = XmlReader.Create(stringReader))
    {
        reader.ReadToFollowing("EncryptedAssertion", SAML2_ASSERTION);
        return (Saml2SecurityToken)SecurityTokenHandlers.ReadToken(reader);
    }
}

The method DecryptToken below, decrypts a GenericXmlSecurityToken token and returns a SecurityToken, which represents a specific decrypted security token, but under a generic type. Since we know we are requesting SAML2 tokens from ADFS, it's safe to assume this token is in fact a Saml2SecurityToken that contains claims.

Also this method removes the object from cache, in case the decryption fails.

public SecurityToken DecryptToken(GenericXmlSecurityToken encryptedToken)
{
    try
    {
        var reader = new XmlNodeReader(encryptedToken.TokenXml);
        return SecurityTokenHandlers.ReadToken(reader);
    }
    catch (Exception e)
    {
        cache.Remove<object>(CacheKey);
        throw new AdfsClientException("Unable to decrypt token", e);
    }
}

Next, the method GetPrincipal reads the claims inside the token and extracts them in a collection of ClaimsIdentity objects by calling the ValidateToken method on the SecurityTokenHandlers collection.

It returns a ClaimsPrincipal object based off this claims.

public ClaimsPrincipal GetPrincipal(SecurityToken decryptedToken)
{
    try
    {
        ReadOnlyCollection<ClaimsIdentity> identities = SecurityTokenHandlers.ValidateToken(decryptedToken);
        return new ClaimsPrincipal(identities[0]);
    }
    catch (Exception e)
    {
        cache.Remove<object>(CacheKey);
        throw new AdfsClientException("Unable to validate token", e);
    }
}




Comments

Popular posts from this blog

Running sp_updatestats on AWS RDS database

Part of the maintenance tasks that I perform on a MSSQL Content Manager database is to run stored procedure sp_updatestats . exec sp_updatestats However, that is not supported on an AWS RDS instance. The error message below indicates that only the sa  account can perform this: Msg 15247 , Level 16 , State 1 , Procedure sp_updatestats, Line 15 [Batch Start Line 0 ] User does not have permission to perform this action. Instead there are several posts that suggest using UPDATE STATISTICS instead: https://dba.stackexchange.com/questions/145982/sp-updatestats-vs-update-statistics I stumbled upon the following post from 2008 (!!!), https://social.msdn.microsoft.com/Forums/sqlserver/en-US/186e3db0-fe37-4c31-b017-8e7c24d19697/spupdatestats-fails-to-run-with-permission-error-under-dbopriveleged-user , which describes a way to wrap the call to sp_updatestats and execute it under a different user: create procedure dbo.sp_updstats with execute as 'dbo' as

Content Delivery Monitoring in AWS with CloudWatch

This post describes a way of monitoring a Tridion 9 combined Deployer by sending the health checks into a custom metric in CloudWatch in AWS. The same approach can also be used for other Content Delivery services. Once the metric is available in CloudWatch, we can create alarms in case the service errors out or becomes unresponsive. The overall architecture is as follows: Content Delivery service sends heartbeat (or exposes HTTP endpoint) for monitoring Monitoring Agent checks heartbeat (or HTTP health check) regularly and stores health state AWS lambda function: runs regularly reads the health state from Monitoring Agent pushes custom metrics into CloudWatch I am running the Deployer ( installation docs ) and Monitoring Agent ( installation docs ) on a t2.medium EC2 instance running CentOS on which I also installed the Systems Manager Agent (SSM Agent) ( installation docs ). In my case I have a combined Deployer that I want to monitor. This consists of an Endpoint and a

SDL Web 8 - Content Delivery Microservices

Among the new features in SDL Web 8 there are the Content Delivery Microservices, namely: Audience Manager Content Deployer Contextual Image Delivery Discovery Service Dynamic Content Dynamic Linking Profiling and Personalization Metadata Query Taxonomy User Generated Content These microservices make up the Content Interaction Services and they expose the existing Content Delivery in-process APIs as RESTful services. They provide the server-side component in a Services-Oriented Architecture and act as data layer between the the web client and the Content Delivery Storage Layer. According to the SDL marketing, these microservices: Simplify upgrades, thus offering shorter time to value Modernize architecture, offering better separation between the web application and Tridion APIs Offer more flexibility with less downtime and improved scalability Improve quality, being self-running, contained and having less dependencies In technical words, these microservices