Database Access with Microsoft SQL Server with Active Directory authentication

Teleport can provide secure access to Microsoft SQL Server via the Teleport Database Service. This allows for fine-grained access control through Teleport's RBAC.

In this guide, you will:

1. Configure your Microsoft SQL Server database with Active Directory authentication.
2. Add the database to your Teleport cluster.
3. Connect to the database via Teleport.

This guide will focus on Amazon RDS for SQL Server using AWS-managed Active Directory authentication.

How it works

The Teleport Database Service joins the same Active Directory domain as the SQL Server database and uses the Kerberos protocol to authenticate with SQL Server. When a user connects to SQL Server via Teleport, the Database Service obtains a service ticket from Active Directory, then uses a long-term key for the database user to decrypt the ticket and connect to SQL Server. At that point, the Database Service forwards user traffic to the database.

• Self-Hosted
• Teleport Enterprise Cloud

Prerequisites

• A running Teleport cluster version 15.4.22 or above. If you want to get started with Teleport, sign up for a free trial or set up a demo environment.

• The tctl admin tool and tsh client tool.

  On Teleport Enterprise, you must use the Enterprise version of tctl, which you can download from your Teleport account workspace. Otherwise, visit Installation for instructions on downloading tctl and tsh for Teleport Community Edition.

• A SQL Server database with Active Directory authentication enabled.
• A SQL Server network listener configured with a Certificate using Subject Alternative Names
• A Windows machine joined to the same Active Directory domain as the database.
• A Linux node joined to the same Active Directory domain as the database. This guide will walk you through the joining steps if you don't have one.
• To check that you can connect to your Teleport cluster, sign in with tsh login, then verify that you can run tctl commands using your current credentials. tctl is supported on macOS and Linux machines. For example:

  tsh login --proxy=teleport.example.com --user=email@example.com
  tctl status
  Cluster  teleport.example.com
  Version  15.4.22
  CA pin   sha256:abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678

  If you can connect to the cluster and run the tctl status command, you can use your current credentials to run subsequent tctl commands from your workstation. If you host your own Teleport cluster, you can also run tctl commands on the computer that hosts the Teleport Auth Service for full permissions.

Step 1/7. Create a Teleport user

tctl users add \  --roles=access \  --db-users="*" \  --db-names="*" \  alice

tctl users add \  --roles=access,requester \  --db-users="*" \  --db-names="*" \  alice

For more detailed information about database access controls and how to restrict access see RBAC documentation.

Step 2/7. Join the Linux node to Active Directory

The Linux node where the Database Service will run must be joined to the same Active Directory domain as the SQL Server database.

Note that in order to be able to join, the Linux node must be able to resolve your Active Directory fully-qualified domain name. For example, for AWS-managed AD, use nameservers provided under "Networking details" on the directory's overview page.

Install necessary packages:

sudo apt-get update
sudo apt-get -y install sssd realmd krb5-user samba-common packagekit adcli

sudo yum -y update
sudo yum -y install sssd realmd krb5-workstation samba-common-tools

Edit /etc/krb5.conf to disable reverse DNS resolution and set the default realm. Make sure that the [realms] section contains your domain definition and has admin_server and kdc fields set pointing to the domain controllers:

[libdefaults]
default_realm = EXAMPLE.COM
rdns = false

[realms]
  EXAMPLE.COM = {
    kdc = example.com
    admin_server = example.com
  }

Join the realm:

sudo realm join -v -U admin@EXAMPLE.COM example.com
... * Successfully enrolled machine in realm

To confirm the node has joined the realm, use the realm list command:

sudo realm list
example.com  type: kerberos  realm-name: EXAMPLE.COM  domain-name: example.com  configured: kerberos-member  server-software: active-directory  client-software: sssd  ...

Step 3/7. Create keytab file

Teleport requires a keytab file to obtain Kerberos service tickets from your Active Directory for authentication with SQL Server. The easiest way to generate it is to use the adutil Linux CLI utility.

Install adutil on the Linux node you have joined to your Active Directory domain:

curl https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
sudo curl https://packages.microsoft.com/config/ubuntu/18.04/prod.list | sudo tee /etc/apt/sources.list.d/msprod.list
sudo apt-get update
sudo ACCEPT_EULA=Y apt-get install -y adutil

sudo wget -qO /etc/apt/trusted.gpg.d/microsoft.asc https://packages.microsoft.com/keys/microsoft.asc
sudo curl https://packages.microsoft.com/config/ubuntu/20.04/prod.list | sudo tee /etc/apt/sources.list.d/msprod.list
sudo apt-get update
sudo ACCEPT_EULA=Y apt-get install -y adutil

sudo curl -o /etc/yum.repos.d/msprod.repo https://packages.microsoft.com/config/rhel/8/prod.repo
sudo ACCEPT_EULA=Y yum install -y adutil

Log in to Active Directory using the kinit command:

kinit admin@EXAMPLE.COM

Use the adutil keytab create command to generate keytab entries for each Active Directory user that will be connecting to the SQL Server database:

adutil keytab create teleport.keytab alice
adutil keytab create teleport.keytab bob

You will be prompted to enter each user's password. All keytab entries will be merged into the same teleport.keytab file.

setspn -L alice

setspn -s user/alice alice

You can verify entries in the keytab file using klist command:

klist -ke teleport.keytab
Keytab name: FILE:teleport.keytabKVNO Principal---- --------------------------------------------------------------------------   5 alice@EXAMPLE.COM (aes256-cts-hmac-sha1-96)   2 bob@EXAMPLE.COM (aes256-cts-hmac-sha1-96)

Step 4/7. Set up the Teleport Database Service

The Database Service requires a valid join token to join your Teleport cluster. Run the following tctl command and save the token output in /tmp/token on the server that will run the Database Service:

tctl tokens add --type=db --format=text
abcd123-insecure-do-not-use-this

Install Teleport on your Linux server:

1. Assign edition to one of the following, depending on your Teleport edition:

   Edition	Value
   Teleport Enterprise Cloud	cloud
   Teleport Enterprise (Self-Hosted)	enterprise
   Teleport Community Edition	oss

2. Get the version of Teleport to install. If you have automatic agent updates enabled in your cluster, query the latest Teleport version that is compatible with the updater:

   TELEPORT_DOMAIN=example.teleport.com
   TELEPORT_VERSION="$(curl https://$TELEPORT_DOMAIN/v1/webapi/automaticupgrades/channel/default/version | sed 's/v//')"

   Otherwise, get the version of your Teleport cluster:

   TELEPORT_DOMAIN=example.teleport.com
   TELEPORT_VERSION="$(curl https://$TELEPORT_DOMAIN/v1/webapi/ping | jq -r '.server_version')"

3. Install Teleport on your Linux server:

   curl https://cdn.teleport.dev/install-v15.4.22.sh | bash -s ${TELEPORT_VERSION} edition

   The installation script detects the package manager on your Linux server and uses it to install Teleport binaries. To customize your installation, learn about the Teleport package repositories in the installation guide.

sudo teleport db configure create \  -o file \  --token=/tmp/token \  --proxy=teleport.example.com:443 \  --name=sqlserver \  --protocol=sqlserver \  --uri=sqlserver.example.com:1433 \  --ad-keytab-file=/path/to/teleport.keytab \  --ad-domain=EXAMPLE.COM \  --ad-spn=MSSQLSvc/sqlserver.example.com:1433 \  --labels=env=dev

sudo teleport db configure create \  -o file \  --token=/tmp/token \  --proxy=mytenant.teleport.sh:443 \  --name=sqlserver \  --protocol=sqlserver \  --uri=sqlserver.example.com:1433 \  --ad-keytab-file=/path/to/teleport.keytab \  --ad-domain=EXAMPLE.COM \  --ad-spn=MSSQLSvc/sqlserver.example.com:1433 \  --labels=env=dev

Provide Active Directory parameters:

Service Principal Name

You can use ldapsearch command to see the SPNs registered for your SQL Server. Typically, they take a form of MSSQLSvc/<name>.<ad-domain>:<port>.

For example, an AWS RDS SQL Server named sqlserver and joined to an AWS managed Active Directory domain EXAMPLE.COM will have the following SPNs registered:

ldapsearch -x -h example.com -D admin -W -b DC=example,DC=com servicePrincipalName
...
EC2AMAZ-4KN05DU, RDS, AWS Reserved, example.com
dn: CN=EC2AMAZ-4KN05DU,OU=RDS,OU=AWS Reserved,DC=example,DC=comservicePrincipalName: MSSQLSvc/sqlserver-rds.example.com:1433servicePrincipalName: MSSQLSvc/EC2AMAZ-4KN05DU.example.com:1433servicePrincipalName: MSSQLSvc/EC2AMAZ-4KN05DU.example.com...

Alternatively, you can look SPNs up in the Attribute Editor of the Active Directory Users and Computers dialog on your AD-joined Windows machine. The RDS SQL Server object typically resides under the AWS Reserved / RDS path:

Step 5/7. Start the Database Service

Configure the Teleport Database Service to start automatically when the host boots up by creating a systemd service for it. The instructions depend on how you installed the Teleport Database Service.

sudo systemctl enable teleport
sudo systemctl start teleport

sudo teleport install systemd -o /etc/systemd/system/teleport.service
sudo systemctl enable teleport
sudo systemctl start teleport

You can check the status of the Teleport Database Service with systemctl status teleport and view its logs with journalctl -fu teleport.

Step 6/7. Create SQL Server AD users

Connect to your SQL Server as an administrative account (e.g. sa) and create logins that will use Active Directory authentication:

master> CREATE LOGIN [EXAMPLE\alice] FROM WINDOWS WITH DEFAULT_DATABASE = [master], DEFAULT_LANGUAGE = [us_english];

Step 7/7. Connect

Log in to your Teleport cluster. Your SQL Server database should appear in the list of available databases:

tsh login --proxy=teleport.example.com --user=alice
tsh db ls
Name      Description         Labels
--------- ------------------- -------
sqlserver                     env=dev

tsh login --proxy=mytenant.teleport.sh --user=alice
tsh db ls
Name      Description         Labels
--------- ------------------- -------
sqlserver                     env=dev

To retrieve credentials for a database and connect to it:

tsh db connect --db-user=teleport sqlserver

tsh proxy db --db-user=teleport --tunnel sqlserver

To log out of the database and remove credentials:

tsh db logout sqlserver

Troubleshooting

Certificate error

If your tsh db connect error includes the following text, the certificate used by SQL Server is not a known Certificate Authority.

Error message: TLS Handshake failed: x509: certificate signed by unknown authority

To solve this, you can add the CA configuration to the database like the following:

  databases:
  - name: sqlserver
    protocol: sqlserver
    uri: sqlserver.example.com:1433
    ad:
      keytab_file: /path/to/teleport.keytab
      domain: EXAMPLE.COM
      spn: MSSQLSvc/sqlserver.example.com:1433
    static_labels:
      "env": "dev"
+   tls:
+     # Point it to your Database CA PEM certificate.
+     ca_cert_file: "rdsca.pem"
+     # If your database certificate has an empty CN filed, you must change
+     # the TLS mode to only verify the CA.
+     mode: verify-ca

If you’re unable to acquire the database CA, you can skip TLS verification by providing the configuration tls.mode: "insecure". However, we do not recommend skipping TLS verification in production environments.

Next steps

• Learn how to restrict access to certain users and databases.

• View the High Availability (HA) guide.

• Take a look at the YAML configuration reference.

• See the full CLI reference.

Further reading

• Manually join a Linux instance in the AWS documentation.
• Introduction to adutil in the Microsoft documentation.